Cardio Flashcards
Which of these leads are bipolar and unipolar
I, II, III = biopolar
aVR, aVL, aVF - unipolar
When does a U wave appear on an ECG
After the T wave - typically smaller then the T wave
What polarity (positive of negative) is on each corner of Einthoven’s triangle and what is the resulting direction of the deflection of a wave travelling towards that corner
LA - has negative and positive charge
RA - negative
LL - positive
Depolarisation towards positive = positive deflection
Depolarisations towards negative = negative deflection
What degrees does the heart need to be at to be in left axis deviation
When the QRS axis falls between -30 and -90 degrees
What direction to each of the limb leads travel in
Negative to positive
I : RA > LA
II : RA > LL
III : LA > LL
What is the primary cause of coronary artery disease
Athlerosclerosis
What are three common approaches to treatment of coronary artery disease
1) Lifestyle modifications
2) Medication - antiplatelet agents, statins, beta blockers
3) Revascularisation - stents, bypass grafting
What is the definition of heart failure
Impairment in the hearts ability to pump blood and is insufficient to meet the needs of the body
What are the two primary blood markers in heart failure and what do they each indicate
Troponin - usually found inside the cardiomyocytes, if this is present in the blood we know there is cardiac damage
BPN - this is created when the heart is working hard, so increases during cardiac stress. (>100ph/ml is considered positive and indicative of HF)
What is the difference in mechanism between heart failure with preserved ejection fraction and heart failure with reduced ejection fraction
HF with preserved EF - the heart is contracting normally but the volume of blood is very small. Because the proportion of the blood in and out is the same, the EF is preserved
HF with reduced EF - due to cardiomyocytes death so the heart isn’t contracting properly
What are the different treatment options for people with HF with preserved EF and those with HF with reduced EF
HF preserved EF - no treatment
HF reduced EF - medication, lifestyle changes or pacemakers
What is cardiac resynchronisation therapy
A 3 lead pacemaker is put into the RA, RV and LV to detect irregularities and provide shock if need be
What is restrictive cardiomyopathy and what pathological remodelling is usually associated with it
When the ventricle stiffen and cant fill with blood
Atrial enlargement is common
Infiltration of amyloids, sarcoidosis, too much iron, fibrosis and inherited metabolic disorders are all causes of what disease
Restrictive cardiomyopathy
What 3 blood markers will be present in a patient with restrictive cardiomyopathy
eosinophils, hemochromatosis, BNP
What is Left ventricular non-compaction and what other 2 pathologies can it cause
This occurs when the muscles in the LV don’t compact during development, leaving the muscle of the LV soft and spongy
Atrial enlargement
LBBB
What is Takotsubo Cardiomyopathy and what changes does it cause to the heart
Heart condition developed in response to an intense emotional or physical experience.
Ventricles change shape affecting it’s ability to pump blood
What is Desmoplakin Cardiomyopathy and what causes
This is a rare genetic disorder that is caused by dysfunctional desmosome complex.
Can result in repeated myocardial injury or infiltration of immune cells causing fibrosis
What are the mechanisms of bradycardia and tachycardia in channelopathies
Bradycardia - failure of impulse formation or conduction
Tachycardia - re-entry and mechanism of abnormal automaticity
What does Long QT syndrome effect, what are common symptoms and what is the primary treatment
K+ efflux
fainting, seizures
Medication (usually Na+ channel blockers or beta blockers)
What is the cause of Brugada syndrome
Mutation in voltage gated Na+ channel gene
What causes Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) and what are common treatments for this. What is a common pathological feature associated with CPVT
Inherited mutation of cardiac Ca2+ channels (RyR)
Treatment: beta blockers, antiarrhythmics
Arrythmias are common
What causes Arrhythmogenic cardiomyopathy and what cardiac pathologiy is commonly caused by this disease
Mutation of desmosome proteins
Can lead to HF - lack of desmosomes causes infiltration of fibroses leading to weakening of the heart muscle
1st degree AV block
Delay in the conduction of electrical signal from the atria to the ventricles.
Every impulse from the atria are conducted to the ventricle but at a slower speed
2nd degree AV block
type I - progressive delay in AV conduction until an impulse is blocked
type II - some atrial impulses are blocked without prior delay
3rd degree AV block
No conduction between the atria and ventricle
What are the different modes of treatment for AV block
type I - no treatment
type 2:1 - is symptomatic, medication
type 2:2/3 - pacemaker
What 5 things is acute inflammation characterised by
Redness - vasodilation increasing blood flow
Swelling
Increased permeability of capillaries
Migration of granulocytes and monocytes into the tissue
Activation of macrophages
BNP, tumour necrosis factor-alpha, transforming growth factor beta, growth differentiation factor 15 are all types of what
Cardiokines (heart immune molecules)
What is myocarditis and what are some non-infectious causes of this
Inflammation of the myocardium
idiopathic (no cause), rheumatic fever, cardiotoxic substances, systemic disease
What is pericarditis and what are some non-infectious causes of this
Inflammation of the pericardium
post MI pericarditis, radiation exposure
What is endocarditis
Inflammation of the lining of the heart and heart valves
What blood markers would you expect during general inflammation
Elevated WBC
Elevated RCB sedimentation rate
Elevated C-reactive protein (CRP)
What blood markers would you expect indicating damage to the heart, brain or muscle
Creatine phosphokinase (CPK)
Endothelial dysfunction is a hallmark of what
Several immune mediated pathologies (myocarditis, vasculitis, thyroiditis)
What type of cholesterol creates fatty streaks in atherosclerosis
LDL cholesterol
What are pericytes important for
Vascular formation, remodeling and function
What are cardiac tissue macrophages and what do they do and what do they secrete
Resident leukocytes activated by DAMPS
Release cytokines that initiate inflammatory cascades
Secrete proteolytic and inflammatory agents
What can activate pro-inflammatory responses
cellular injury and death
What is associated with arterial thrombotic conditions such as myocardial infarction and stroke
Hyperactive platelets
What are some extrinsic causes of bradycardia
hypothermia, hypothyroidism, antiarythmic drugs
What are some intrinsic causes to bradycardia
acute ischemia
infarction of the sinus note
ischemic heart disease
cardiomyopathy
myocarditis
In RBBB and LBBB what changes are their in the path of conduction
The conduction is travelling through the slow ventricular myocytes rather then the fast purkunjie fibres
What two divisions can LBBB be broken into
left anterior fascicular block (LAFB)
left posterior fascicular block (LPFB)
What conditions are commonly associated with RBBB
congenital cardiac disorders, pulmonary embolism, pulmonary hypertension
What conditions are commonly associated with LBBB
left ventricular disease, aortic stenosis, hypertension
What are the symptoms of CVD in men and woman
Men - burning chest pain, pressure in chest, pain in neck, jaw, shoulders
Woman - stabbing pain in chest, stomach pain
How does alcohol effect heart health
Increases blood pressure
Modifies NO generating system
Increases ROS
How does smoking effect cardiovascular health
Increases heart rate and blood pressure
Chemicals increase atherosclerotic changes
What are normal blood pressure ranges
120-129/80-84
What blood pressure range would be considered hypertension
140/90
What happens to our blood pressure during sleep
Systolic blood pressure drops 10% during sleep
During an exercise stress test what is happening in the heart that is causing symptoms to occur
Ischemia is causing symptoms like chest pain and breathlessnes
What is the Bruce Protocol preparation used for and what is it
It is used for patients before exercise stress testing
- no eating 4 hours before
- no caffeine or smoking 4 hours before
- must bring all medication to test
- no lotions, self tan, oils, ect on test area
During an exercise stress test, ST segment depression is usually driven by what
Hypoxic conditions lead to diminished ATP, decreasing the activating of ATP dependant processes. This includes the Na+/K+ATPase, in injured cells this isn’t working so there is no current during depolerisation.
What changes in ST interval would you need to see to stop an exercise stress test
ST depression up to 4mm
ST elevation up to 3mm
What is the effect of stenosis valves
stiffening of the valves restrict blood flow, increasing the workload on the chamber ejecting the blood
What is the value of the following on an ECG
1 small square
1 large square
5 large squares
1 small square = 1mm = 40ms
1 large square = 5mm = 200ms
5 large squares = 1second
What is the normal, bradycardic and tachycardic rate on an ECG
Normal: 600-100blm (3-5 large boxes)
Bradycardic: <60bpm (>5 large boxes)
Tachycardic: >100bpm (<3 large boxes)
Normal PR interval duration
120-200ms (3-5 small squares)
What is happening in the heart during the PR interval
Conduction through the AV node
Normal QRS complex duration
80-110 ms (<3 small boxes) measured in the lead where it is the biggest
Normal QT interval in men and woman
Men < 440ms
Woman < 460ms
What sort of pathologies are usually associated with QT changes
Channelopathies
Normal duration and amplitude of T waves
Duration: 120-200ms (3-5 small boxes)
Amplitude: <5mm in limb leads, <10mm in precordial leads
What are common causes of right ventricular hypertrophy
pulmonary hypertension, tricuspid stenosis, pulmonary embolism, chronic lung disease
What is the SA nodes intrinsic discharge rate
100bpm
What nervous system controls the SA node
Autonomic
What changes in normal sinus rhythm are seen in children and why
Their normal sinus rhythm is faster than adults due to having a smaller heart, decreased stroke volume, and decreased blood volume
What is happening during 2nd degree type 1 heart block
Malfunctioning AV node cells tend to progressively fatigue until they failue to conduct an impulse
What is happening to the conduction system during 2nd degree type 2 AV block
usually due to a failure of conduction at the level of the his-purkinjie system
What is causing the rhythm seen in 3rd degree heart block
Junctional or ventricular escape rhythms
What is happening during RBBB
LV is depolarised normally but the right ventricles only depolarise ones the left ventricular conduction crosses the septum so the right ventricles are delayed in depolarising
What is the conduction pathway in LAFB
Impulses are conducted to the LV via the posterior fascicle which inserts into the inferoseptal wall of the LV along its endocardial surface
How are junctional escape rhythms made
Pacemaker cells are found at various sites throughout the conducting system, with each site capable of independently sustaining the heart rhythm.
When do accelerated junctional rhythms occur
Accelerated junctional rhythm (AJR) occurs when the rate of an AV junctional pacemaker exceeds that of the sinus node. This situation arises when there is increased automaticity in the AV node coupled with decreased automaticity in the sinus node.
When do accelerated idioventricular rhythms occur
when the rate of an ectopic ventricular pacemaker exceeds that of the sinus node
What is atria flutter and what causes it
Atrial flutter is a rapid regular atrial rhythm due to small reentry circuit around the RA
What is atrial fibrillation
Completely disorganised atrial firing around 350-500bpm
What is the effect of atrial fibrillation on cardiac function
The loss of atrial systole means the 20% contribution the atria have to filling the ventricles is lost. So the ventricles aren’t filling fully, reduced cardiac output
What are the three main areas for treatment of atrial fibrillation
Rate control, anticoagulation and rhythm control
What drug is used in atrial fibrillation patients when treating rate control
Beta blockers
What are the clinical requirements a patient must meet before beginning anticoagulation therapy
CHA2S2-VASc must be >2
HAS-BLED > 3
If a patient is not suitable for anticoagulation therapy to treat atrial fibrillation, what is the alternative anticoagulation therapy technique that can be used
Left atrial appendage closure could be considered as this is the most likely site of clot formation
Where do focal atrial tachycardias originate from
Single ectopic focus within the atria but outside of the sinus node
What is happening in the heart to cause atrioventricular reentrant tachycardia
Additional connection between the atria and ventricles creates an assesory pathway. Impulses can conduct through this cause tachycardia.
What changes have occurred to the heart in Wolff-Parkinson-White syndrome
Congenital accessory pathway has formed. Because the accessory pathway lacks the intrinsic slowness of the AV node, ventricular depolarisation through the his-purkunjie system creates premature beats
How does atrioventricular re-entrant tachycardia differ from AV nodal re-entrant tachycardia
AVRT is due to a accessory pathway and reentry throughout the whole atria, whereas AVNRT is due to re-entry within the AV node only
How long does a ventricular tachycardia need to be going on for for it to be considered sustained
> 30 seconds
What are the typical treatments for recurrent ventricular tachycardia
Antiarrythmics, ICD, alblation
When does myocardial ischemia occur
When myocardial perfusion is disrupted and there is insufficient blood flow to the myocardium
What is Prinzmetal angina
angina due to spasms of the coronary arteries
Acute coronary syndrome
Describes a range of conditions related to sudden blood flow to the heart caused by acute rupture of a thrombus
What differentiates a STEMI and NSTEMI based on thrombus location
STEMI - if the thrombus is occluding a large artery
NSTEMI - if thrombus is occluding a small branch OR occlude and spontaneously repursues a large branch
Type 1 MI
Spontaneous MI related to ischemia due to primary coronary events such as plaque erosion and/or rupture
Type 2 MI
Secondary MI to ischemia due to either increased oxygen demand or decreased supply
Type 3 MI
sudden unexpected cardiac death often with symptoms suggestive of MI
Type 4 MI
MI associated with percutaneous coronary intervention (4a) or stent thrombosis (4b)
Type 5 MI
MI associated with surgery
What is MINOCA
acute myocardial infarction with angiographically no obstructive coronary artery disease or stenosis that is <50%
If a patient has elevated troponin levels and ischemic ECG changes what is their likely pathology
NSTEMI
What is the Sgarbossa Criteria used for
In patients with LBBB or ventricular paced rhythm MI diagnosis based on the ECG can be difficult so this criteria allows physiologists to differentiate the disorders
What is myocarditis
inflammation of the myocardium
What is pericarditis
Inflammation of the pericardium
What is a cardiac tamponade
medical emergency that takes place when abnormal amounts of fluid accumulate in the pericardial sac compressing the heart and leading to a decrease in cardiac output and shock
Normal concentration of K+ in the blood for the heart
3.5-5 mmol/L
What is Dextrocarida
rare congenital disorder where the heart is on the right side of the chest cavity
How do you calculate velocity of a ultrasound wave from frequency and wavelength
V=fλ
How many piezoelectric crystals are requires for continuous wave doppler ultrasound
2 - one transmission, one reception.
What type of ultrasound is used to measure velocity of blood flow
Continous wave doppler
In continuous doppler ultrasound, what is the effect on the trace if the fluid in the vessel is moving towards the probe
There is a positive shift
is continuous doppler able to have depth perception
No
How does continuous wave and pulsed wave doppler ultrasound differ
Both measure velocity of fluid, however pulsed wave doppler is able to measure blood flow at specific locations or depth
How many piezoelectric crystals are used in a pulsed doppler probe
1
What is pulse repetition frequency
number of pulses transmitted in one second
In pulsed wave doppler, what determines the interval between the transmission and reception of the ultrasound
The depth of the region of interest
Does continuous wave or pulsed wave doppler involve aliasing
Pulsed wave
Based on Nyquist Theorem, what does the sampling rate need to be to ensure no signal is lost in ultrasound
The sampling rate needs to be at least twice the highest frequency present in the signal
What are is one advantage and one disadvantage of continuous wave doppler
Accurately measures high velocity rates
Lack range resolution
What are is one advantage and one disadvantage of pulsed wave doppler
Ability to measure velocities at a specific location
Aliasing of velocities above Nyquist limit (so if there are frequencies returning to the probe that are higher then the Nyquist limit then these wont be recorded)
What is the parasternal long axis good at looking at
Shows intraventricular septum and inferior wall
Good for looking at mitral valve, aortic valves and thickness of LV
What is the parasternal short axis window good for seeing
Shows anatomy of aortic valve and its 3 leaflets
Can also see the pulmonary artery where pulsed doppler can be used to measure velocity through this
What is the apical 4 chamber view axis good for seeing
Shows 4 chambers of the heart
Can perform doppler on both tricuspid and mitral valve
What is the apical 5 chamber window good for seeing
This is apical 4 chamber view but with the apical valve in view.
Continuous wave doppler used to look at velocity of blood through aortic valve and LVOT
What can be seen on the apical 2 chamber axis
Left atrium and the inferior and anterior walls of the LV
What can be seen in the apical long axis window
Used to look at the left side of the heart
Can see the LA, LV and aortic valve
What can we see in the subcostal echo window
Good for seeing the pericardium
What can we see in the suprasternal notch view on echo
Aortic arch
what are the most common sized catheters used in the cath lab
JR4 and JR34
What are the 5 ideal parts of a catheter used in a cathlab
A short as possible
As rigid as possible
Long enough to reach the heart
Flexible
Narrow
If we were measuring aortic pressure in the cath lab and the pressure damped what does this indicate
The catheter has occluded the arteries, impeding perfusion
What is normal peak systolic pressure in LV
90-140mmHg
What normal end diastolic pressure of the LV
5-12mmHg
What does a left ventriculogram allow us to see
Provides assess to systolic function, degree of mitral valve motion abnormality and ventricular wall defects
In a healthy patient, what would be the pressure differences between the aorta and the LV during systole
There should no pressure gradient between the LV and aorta because the valve opens fully, allowing free flow of blood
What is normal systolic and diastolic aortic pressure
Systolic - 120mmHg
Diastolic - 70mmHg
What sort of catheter is used to calculate cardiac output
Swan-Ganz catheter
what is the normal cardiac output
4-8L/min
What is the normal cardiac index
2.4-4.2L/min/m^2
What is the equation for calculating the amount of oxygen consumed by the body
VO2 = 125 x body surface area
What is the cardiac output equation when using Ficks principle
CO = Oxygen consumption (Vo2) / Arteriovenous Oxygen Different
What is more accurate at measuring cardiac output, thermodilution or ficks method
Ficks method because it is based off actual blood concentrations of oxygen
What pathology would you not be able to perform an accurate thermodilution test of cardiac output
Patients with severe tricuspid regurgitation
What are intracardiac shunts
abnormal pathways for blood flow in the heart that form in additions to or in place of normal pathways
Ventricular septal defects, overriding aortic root, pulmonary stenosis, and right ventricular hypertrophy are all symptoms of what congenital heart disorder
Tetralogy of Fallot
When is it particularly important that the transducer is zeroed in the cathlab
When doing right heart pressure measurements because we are dealing with much smaller numbers
What can be the effect of catheter whip when measuring pressure in cathlab
The large waveforms caused by movement of the catheter can cause the measured pressure value to be inaccurate (underestimated or overestimated)
What is systemic vascular resistance
Resistance to blood flow by all the systemic vasculature, excusing the pulmonary vasculature
What is the effect of the RV when the pulmonary vascular resititance is high
An increase in vascular resistance means the RV needs to pump harder to move blood through the pulmonary valve. This can cause dilation of the RV
Normal RA pressure
2-6mmHg
Normal systolic and diastolic RV pressure
systolic - 15-25mmHg
diastolic - 0-8mmHg
Pulmonary artery pressure in systole and diastole
systolic - 15-30mmHg
diastolic - 8-15mmHg
Normal pulmonary wedge pressure
6-12mmHg
What pressure does the pulmonary artery need to be for someone to be considered to have pulmnoary hypertension
> 25mmHg
What pressure can you get through right heart catheratization that can estimate the LA pressure
By measuring the pressure in the pulmonary wedge you can use this to estimate the LA pressure
What parts of the heart does the right coronary sinus supply blood too
RA, RV and SA node
What areas of the heart does the Lcx and LAD supply blood too
Lcx - lateral wall of the left ventricle
LAD - left ventricle (diagonal branch purfuses the anterior wall, septal branch supplies the anterior septum)
What type of wire is used in cathlab
J wire
What percentage does a coronary artery need to be blocked to be considered flow limiting and requiring PCI
lesion that is >70% of the vessel diameter
What is FFR
This is a type of coronary flow study - the ratio of blood flow in a coronary artery in the presence of stenosis is compared with the flow in the same vessel in the theoretical absence of stenosis
What FFR values indicate a vessel is and isnt responsible for ischemia
FFR > 0.8 unlikely vessel is responsible for ischemia
FFR < 0.75 vessel is likely inducing ischemia
Patients with ischemia and no obstructive artery disease may have what pathology
Microvasculature dysfunction
What is intravascular ultrasound
A method of ultrasound where you are able to see cross sectional images of inside the arteries
What does OCT use to image the arteries
Infrared light
What coronary imaging method is able to differentiate between tissue characteristics
Optical coherence tomography (OCT)
If someone had a SYNTAX score of <23, would they be recommended for PCI or CABG
PCI
What is the principle goal of duel antiplatelet therapy following a PCI
prevention of stent thrombosis
What is defined as chronic total occlusion
100% occlusion of the coronary artery for a duration of greater than or equal to 3 months
What is a thrombectomy
It is a procedure used to remove a clot that has developed at the site of acute plaque rupture in MI
What is pericardiocentesis
Procedure to remove fluid from the pericardial sac
What are the three types of hypertension
- White coat hypertension - due to stress
- secondary hypertension - increase BP secondary to a known pathology
- Essential (primary) hypertension - more common and unknown cause
How do diuretics decrease hypertension and what is an example of one
Decrease Na+ absorption = increase water excretion = decrease blood volume
Thiazide
How do sympathetic blockers help hypertension
These bind to B1 receptors in the heart and bock vasocontriction.
How do ACE inhibitors work to reduce hypertention
These block the conversion of angiotensin 1 to angiotensin 2 so the renin-aldosterone system is suppressed and BP reduced
How does angiotensin II receptor antagonists work to reduce hypertension
Angiotensin 2 causes vasocontraction. By blocking this you are reducing constriction
How do Ca2+ channel blockers lower hypertension
Inhibit contraction of vascular smooth muscle to reduce peripheral resistance
How are Na+ channel blockers antiarrhythmic drugs
These block the sympathetic nervous system effect on the heart, slowing down the heart rate and reducing the atomicity of the heart muscle.
What is the effect on the refractory period of the myocardial action potential if strong and weak Na+ channel blockers are used, respectfully
Weak blockers - slightly reduce refractory period
Strong blockers - significantly decrease the time to depolarise but doesn’t change the refractory period
How do K+ channel blocker work as an antiarrhythmic
These make repolarisation last longer so contractions are prolongated
What is the class of drug used to treat heart failure and what is it’s mechanism of action
cardiac glycosides
stops the Na+/K+ pump pumping Na+ ut of the cell = increases contractility, slows heart rate and slow conduction velocity
What are the three types of drugs used to treat angina
Nitrates, b-blockers and Ca2+ channel blockers
What is the function of thrombolytics
Break down existing clots by breaking down fibrin
What do anticoagulants do
Inhibit formation and enlargement of existing blood clots but doesn’t dissolve existing clots
What is the mode of action of antiplatelets
Inhibit the step of platelet aggregation so no clot forms
When taking measurements in echo, should you measure from the inner and outer walls?
Inner
In what phase of the cardiac cycle must all measurements be taken from in echo
End of diastole
What phase of the cardiac cycle is the heart in when the mitral valve just opens and the aortic valve just closes
End systole
What is the position of the mitral valve at end diastole
Closed
What is a normal ejection fraction % and severe ejection fraction %
> 55%
Severe <35%
When you zoom into the aortic valve on parasternal long axis what three measurements would you take
SOV
STJ
PAA
Where in the aortic arch is the SOV located
The widest point above the aortic valve
When using M mode in parasternal long axis, what are you measuring
Measure the internal diameter of the LV
What are the names of the three aortic valve flaps
R - Right coronary cusp
N (bottom) - non coronary cusp
L - Left coronary cusp
What does TAPSE allow you to measure
Using M mode you can assess how well the RV is pumping
When using TAPSE, where does the M mode cursor need to cross through
The bottom of the RV and the angelus of the tricuspid valve
How do you interpret the results from TASPE
You can measure how much the RV is pumping by measuring the amplitude of the M mode waves in TAPSE
What is the normal TASPE measurement
> 1.7cm
What type of doppler is used to measure the velocity of the aortic valve in apical 5 chamber
Continous wave doppler
What type of doppler would you use to measure the velocity of the LVOT in apical 5 chamber
Pulsed wave doppler
What is the most commonly used technique for quantitative estimation of the LV systolic function
Transthoracic echocardiology (TTE)
What is stroke volume and its normal value
Volume of blood pumped from the ventricle per beat
70mls
What is cardiac output and its normal value and its equation
Amount of blood pumped out by the ventricle each minute
4900mls/5L
SVxHR = CO
What is the end diastolic volume and its normal value
volume of blood in the ‘full’ ventricle
120mls
What is end systolic volume and its normal value
volume of blood in the emptied ventricle
40mls
What is the equation for ejection fraction
(SV/EDV) x 100
SV = EDV-ESV
What is the Simpson method of Disc
To measure the volume of total left ventricle, it is sliced into discs apex down to mitral valve annulus into a series of discs
The diameter and thickness of each slice is then used to calculate the total LV volume.
How can accuracy be improved in the Simpsons method of disc
using diameters in 2 perpendicular planes (apical 4 and apical 2) so that the disc area is more defined.
What is a intra-aortic balloon pump and what does it do
Mechanical device that increases myocardial oxygen perfusion and indirectly increases cardiac output.
Inflates throughout diastole which pushes blood back towards the aortic root and increasing blood flow to the coronary arteries
What part of the aorta is a intra-aortic balloon pump located in
Descending aorta
What part of the ECG triggers the inflation of the intra-aortic balloon pump and which part of it triggers the deflation of the balloon
Inflation - midpoint of T wave
Deflation - dichrotic notch (peak of R wave).
What is the Impala and what does it do
This is a device inserted across the aortic valve that draws block from the LV and expels it directly into the ascending aorta, effectively offloading the hearts work
What is temporary pacing and when is it used
Electric shocks delivered to the ventricle to treat bradycardia or heart block.
Used in emergency situations before a more permanent solution can be done
During TAVI, is the old valve removed?
No it stays in the heart
What is TAVI
Transcatheter Aortic Valve Replacement/Insertion.
A new aortic valve is inserted in those who have severe aortic stenosis
What is Balloon Aortic Valvuloplasty and what does it do
This is a temporary treatment for people with aortic stenosis.
A balloon is inserted into the aortic valve and inflated multiple times to expand the opening and improve blood flow.
What three situations is ballon aortic valvuloplasty used
- bridge the gap for those wating for surgery
- Patients who are severely symptomatic but their AS is not urgent cardiac surgery
- In congenital disorders in children and younger adults as first line treatment
How long goes balloon aortic valvuloplasty tend to alleviate symptoms for
3-12 months
What is a mitral clip and what does it do
This is a small clip placed on the mitral valve that helps the mitral valve leaflets close better, reducing mitral regurgitation.
What is foramen ovule
This is a gap between the right and left atrium that is normal in fetal development and should close at birth
Explain the difference between these 4 types of atrial septum defects: secundum, primum, sinus venous and coronary sinus
Secundum - most common type. Occurs in middle of the septum
Primum - affects lower part of the septum
Sinus venous - affects upper part of the septum
Coronary sinus - rare, where the wall between the coronary singular and the left upper heart chamber is missing
What is the role of the left atrial appendage during atrial fibirllation
During atrial fibrillation, blood can pool in the left atrial appendage, increasing the risk of clot formation, leading to strokes.
A notched p wave usually is a result of pathology in what part of the heart? And what can contribute to this.
Due to left atrial enlargement.
The enlargement of the atria tends to be due to increased pressure in the LA. This can be causes my deformities in the Mitral valve
A hyperacute/peaked p wave usually is a result of pathology in what part of the heart? And what can contribute to this.
Enlargement of right atrium
Due from an increased in right atrial pressure. Can be due too tricuspid valve deformities or pulmonary hypertension
Why are the AV node cells unable to conduct, cause Mobitz Type 2 AV block
They are in their absolute refractory period
What is the normal beats per minute of the SA node, AV node and bundle of his
SA node 60-100bpm
AV node 40-60bpm
Bundle of His 20-40bpm
What are some indications for pacing treatment
Symptomatic sinus bradycardia
Sinus node dysfunction
Sinus arrest/sinoatrial block
AV block
What is the battery status at the input time of the pacemaker and what does this decline to when the pacemaker needs replacing
Input = 3.2V
End of service = 2.8V
What 4 things is pacemaker battery longevity affected by
Pulse amplitude
Pulse width
Battery capacity
Pacing percentage
How does a pacemaker battery decline over time
For the first few years there is very little decline in battery, however there is a sudden decrease towards the end of service
When will a pacemaker deliver a pace
If the interval is timed out (there is no intrinsic beat within a set time frame) then the pacemaker will send a beat
What factors make up the output of the pacemaker
Pacing impulse - made up of pulse amplitude and pulse width
What is the safety margin for a lacemaker lead in relation to pulse amplitude
Safety margin of a lead is twice the threshold pulse amplitude
(if threshold is 1mV at 0.4s, output should be 2mV at 0.4s)
What is threshold in regards to pacemakers
minimum energy required to consistently elicit a myocardial depolarization
What 4 factors will affect the threshold of a pacemaker
Antiarrhythmics
Myocardial infarction
Hyperkalemia
Severe acidosis or alkalosis
What is the current of injury in pacemakers
When a pacemaker lead is screwed into the myocardium this causes injury to this part of the muscle.
This is seen as S-T elevation on the ECG
What do pacemaker leads contain to reduce current of injury
Steroid dexamethasone is at the top of the leads to reduce the inflammation at the site of injury
What is slew rate of a pacemaker and what is the normal slew rate for atria and ventricles, respectfully
Slew rate is the change in electrical potential (voltage) overtime
Atria = >0.5V/s
Ventrical = >0.75V/s
What does the strength duration curve for a pacemaker tell us
This tells us the quantity of charge/voltage required from the pacemaker to cause a myocardial contraction in the heart
What is rheobase in regards to the strength duration curve of a pacemaker and after what duration should this be reached usually
The minimum intensity required to stimulate a muscle at infinite duration
Rheobase should be reaches 1-2ms after the pulse
What value can you use to estimate the most efficient pacemaker pulse duration
Chronaxie Time - this is double the rheobase number
How do pacemakers sense cardiac depolarisation
Measuring changes in electrical potential of myocardial cells between the anode and cathode
In pacemaker lead sensitivity, what parts of the ECG do you want to ensure the pacemaker is sensing in both atrial sensing and ventricle sensing, respectfully
When sensing atria - want it to only detect P waves
When sensing ventricles - want it to only detect the R wave
Sensitivity should be half the value of the wave you want to see
To make a pacemaker less sensitive, what must you do to the sensitivity value and what is the effect of this
Must increase the sensitivity value (make the fence taller)
This will mean the pacemaker will see less activity, and will pace more then necessary
To make a pacemaker more sensitive, what must you do to the sensitivity value and what is the effect of this
Must lower the sensitivity value (make fence shorter)
This could cause the pacemaker to double count the waves, thinking it is an arrythmias
What faults to the pacemaker leads will cause an decrease and increase in impedance, respectfully
Insulation break = low impedance (<300 ohms)
Lead fracture - high impedance (1200 ohms)
What three things is sensing accuracy affected by in a pacemaker
Pacemaker circuit (lead integrity)
Electrode placement in the heart
Lead polarity
What is the Ab marker channel on a pacemaker
Atrial Blanked Event - a period of time in which the pacemaker sense amplifiers are off and the pacemaker does not sense anything
What does AR marker on a pacemaker mean
Atrial Refractory Event = a period of time in which sensed events are seen but ignored due to timing purposes
What does VR marker on pacemaker mean
Ventricular Refractory Event
What sort of filter and what bandwidth quantities are used in a pacemaker
Band pass filter used - 20-40Hz are sensed
What is the timing circuitry made of in a pacemaker
Crystal oscillator
What is a bipolar lead configuration of a pacemaker
The lead has both the anode and cathode at the tip of the lead
In bipolar pacemakers, what electrode is doing the pacing
Cathode
In a unipolar pacemaker where are the anode and cathode loacted
Anode in pacemaker box
Cathode at tip of lead
Which type of pacemaker is less susceptible to oversensing of non-cardiac signals
Bipolar
What type of pacemaker has a smaller lead diameter
Unipolar
What are the two ways pacemaker leads can be implanted
Intracardially - within the heart
Epicardial - sutured to the outside of the heart
What is the difference between an active and passive transvenous pacemaker lead
Active - helix is screwed into the endocardial tissue
Passive - lodged into the trabeculae of the apex
What is the most commonly used transvenous pacemaker lead and where can this be positioned in the heart
Active fixation lead - these can be screwed into anywhere of the heart
VVI Pacemaker Mode
- What chambers are paced
- What chamber are sensed
- When is pacing inhibited
- What patients is this used in
Pace ventricles
Sense ventricle
When intrinsic QRS is sensed, pacing inhibited
Used in patients with chronic AF or those whose ventricular rate is very slow (heart block)
AAI Pacemaker Mode
- What chambers are paced
- What chamber are sensed
- When is pacing inhibited
- What patients is this used in
Pace atrium
Sense atrium
When intrinsic P wave is sensed, pacing inhibited
Sick sinus node syndrome patients. But normally apart of duel pacing.
DDD Pacemaker Mode
- What chambers are paced
- What chamber are sensed
- What patients is this used in
Pace both A and V
Sense both A and V
Used to maintain AV synchrony between A and V. Most commonly used in high grade AV block
How do you calculate the rate of pacemaker when knowing the interval
60,000 / interval = rate (bpm)
How do you calculate the interval of pacemaker when knowing the rate
60,000 / rate = interval (ms)
What is the lower rate interval in pacemakers
Lowest rate the pacemaker will pace at if no intrinsic event is sensed
When is the lower rate interval of a pacemaker reset
If an intrinsic event is sensed, it resets the lower rate interval and if no intrinsic events are sensed, the pacemaker will pace
What is a pacemakers response to exercise
A pacemaker will increase its rate of pacing to exercise if the patient does not increase their intrinsic rate
What is VOO and AOO pacing
VOO is permanently pacing the ventricle
AOO is permanelty pacing the atrium
What is loss of capture in pacemakers
When the pacemaker paces but there is no response from the myocardium
What are three possible reasons for loss of capture in a pacemaker
Increased pacing output (has the threshold increased)
Lead dislodged and not in contact with myocardium
Lead fracture
What occurs if the pacemaker is under sensing
This will result in the pacemaker not sensing the intrinsic beats of the heart, so it will pace at the lower rate of the device. This is overpaced.
What occurs is the pacemaker is oversensing
This will result in under pacing - the pacemaker is sensing too much and resetting the timed interval, potentially leading to it not pacing when it needs to
What setting do you change to help reverse undersensing
Want to make the pacemaker more sensitive by decreasing the sensitivity value
What settings do you change if the pacemaker is oversensing
Make pacemaker less sensitive by increasing the sensitvity value
What is the main indication for duel pacemaker
AV block
In a duel pacemaker, what events mark the beginning and end of the lower rate interval
Lower rate interval begins with AS/AP. This then is reset if there is another AS/AP
In duel chamber pacemakers, when does a pace AV delay occur and when does a sensed AV delay occur
Paced AV delay - occurs after an AP event
Sensed AV delay - occurs after an AS event
What two pacemaker markers usually make up a AV delay in duel chamber pacemaker
usually a AV delay will consist of a AB (atrial blanking period) then a AV (atrial refractory period) before the QRS
What is the difference in time between a paced AV delay and a sensed AV delay in duel chamber pacemakers
PAV delay is usually programmed 30ms longer then the SAV delay to allow conduction of the paced atrial beat to reach the left atrium
In what phase of the ECG is the atrial refractory in duel chamber pacemakers
From the beginning of the P wave to the beginning of the QRS
In duel chamber pacemakers, what is the post ventricular atrial blanking (PVAB) and when does it occur
Time period too prevent sensing of the ventricular signal on the atrial channel
Occurs for the QRS and T wave
In duel chamber pacemakers, what is the post ventricular atrial refractory period (PVARP) and when does it occur
Time period to prevent oversensing of retrograde P waves
Occurs from beginning of QRS to halfway through T wave
In duel chamber pacemakers, what is the total atrial refractory period (TARP) and when does it occur
This is the total refractory period of the atrial channel
TARP is made up of the sensed AV delay (P wave - QRS) and the PVARP (QRS - end of T wave)
In total TARP covers from the beginning of the P wave to the end of the T wave
In duel chamber pacemakers, what is the post atrial ventricular blanking (PAVB) and when does it occur
Timing interval to prevent ventricular oversensing to a paced atrial beat
This occurs after the P wave
In duel chamber pacemakers, what is the ventricular blanking period (VB) and when does it occur
Prevents the ventricle from oversensing the ventricular paved signal or the already depolarising ventricle
Occurs during the QRS
In duel chamber pacemakers, what is the ventricular refractory period (VRP) and when does it occur
Period where sensed events are ignored after the ventricular depolerisation
Occurs from beginning of QRS to end of T wave
If a ventricular channel was oversensing T waves, what setting could you change
Extend the ventricular refractory period (VRP)
What is the upper rate interval in a pacemaker
The maximum rate the ventricle can be paced in response to sensed atrial activity
Why is the upper rate interval in duel pacemakers
The ventricle will increase in pacing if the atria have increased in intrinsic activity. However, we don’t want the ventricle continue to increase infinitely with the atria. The upper rate interval allows there to be a maximum rate at which is will increase the ventricle pacing.
What happens to AV syncrony once the upper rate interval is met in duel pacemaker
AV synchrony wont be maintained
What is the upper sensor rate in duel pacemaker
This sensor rate can drive up atrial rate is the SA node isnt working/is lazy
In a duel pacemaker what happens is the atrial rate goes over the upper tracking rate
The venticle is still limited to the upper tracking rate and will not continue to rise with the atria
When the atria are beating faster then the upper tracking rate, what is the first behaviour the ventricles will exhibit
Wenckebach Behaviour
Explain how Wenckebach behaviour occurs in duel chamber pacemakers
When the atrial are beating faster then the upper tracking rate, Wenckebach behaviour is the first to occur in the ventricle
The AV delay progressively gets longer until a P wave falls into the PVARP. This means the P wave isn’t sensed so the ventricle wont beat. There is a skipped ventricular pace.
When does 2:1 behaviour occur in duel pacemakers and why
Occurs when the atria is beating above the upper tracking rate
Every second P wave falls into the PVAVRP. These refractory P waves are no sensed by the ventricle so no VP is delivered.
How do you calculate the rate at which 2:1 behaviour will occur in duel pacemakers
rate at which 2:1 will occur = 60,000 / TARP
How would you increase 2:1 block rate
You would shorten TARP
Do this but either shortening PVARP or SAV delay
Why do yo want a relatively high 2:1 block rate
You don’t want 2:1 behaviour to occur immediately as the atria exceed the upper tracking rate. You want there to be wenckebach first
When is it desirable to decrease the RV pacing
In patients with intact AV node or 1 degree AVB or high grade AVB
What is the pacing algorithm used for reduced RV pacing in Medtronic devices
AAI-DDD
What is occurring in the pacemaker in AAI-DDD algorithm
The pacemaker is constantly pacing the atrium, but it is able to sense if there is loss of AV conduction and then switch into DD mode and pace the ventricle
What changes in the Av delay are seen in pacemakers reducing RV pacing
They extend the AV delay to allow AV conduction to be seen if there is any.
If there isnt any sensed then it will switch to DDD and pace the ventricle
In what patients is rate response used in duel pacemakers
Patients that are chronotropic incompetence (their heart cant increase in rate with metabolic demand)
Patients with sinus node dysfunction and chronic AF
What is the mode switch rate for pacemakers
171 bpm
When would the mode of a DDD pacemaker switch
If the atrial rate exceeded the mode switch rate - this usually occurs during AF and atrial flutter
Once the atrial rate exceeds the mode switch rate, what mode does the pacemaker switch into.
What rate is the ventricle paced at in this new mode
Switched from DDDR to DDIR (non-tracking mode)
Ventricle is paces at the lower rate or the sensor rate (which ever is highest)
Why is mode switching important for patient symptoms
If the pacemaker didn’t switch modes when atrial rate increased, it would continue to increase ventricular rate. Fast ventricular pacing can make a patient very symptomatic
When does pacemaker mediated tachycardia occur
When there is loss of AV conductions and triggers retrograde conduction (V-A) and causes rapid ventricular pacing
How do we terminate pacemaker mediated tachycardia
We want the retrograde P wave to fall under a refractory period (PVARP). The pacemkaer can extend the PVARP period for one beat to break the cycle
What do we have to be careful of if we are increasing the PVARP permanently to avoid pacemaker tachycardia
By increasing PVARP you are increasing TARP which can increase in a decrease in rate of 2:1 behaviour
What is pacemaker syndrome
An assortment of symptoms related to the adverse hemodynamic impacts from the loss of the AV syncrony
What usuallly causes pacemaker syndrome
Atria contracting against closed AV valves
What are two symptoms of pacemaker syndrome
Neck palpitation and dizziness
What is the approach to managing pacemaker syndromes
to restore AV synchrony using a duel chamber pacemaker instead of a single chamber
How are the pacemaker leads usually implanted
Via the subclavian, cehalial or axillary vein which advances to the SVC and down the RA/RV
What changes could be expected to see in the oxygen saturation and blood pressure upon insertion of a pacemaker leads in EP lab
Blood pressure can drop and oxygen saturations can drop
What are the 7 elements that are checked in a pacemaker follow up
PBL-STOP
Presenting rythum/rate
Battery status
Lead status
Sensing
Threshold
Observation
Programming
What should the sensing quantities be for the P and R wave respectfully
P wave > 1.5mV
R wave > 5mV
Where is an ICD implanted
Prepectoral Pocket
What patients are ICDs implanted in
Patients with high risk of sudden cardiac death, usually via ventricular arrythmias
What heart chambers are ICD leads in
Single lead CIS - in right venticle
Duel lead CID - in RV and SVC
What is the voltage of the shock delivered by an ICD
40J, 80V
How long will the capacitor hold the charge for a shock for in an ICD before it needs to be recharged
15 seconds
How are ICD leads different to pacemaker leads
ICD leads, unlike pacemaker leads, are delivering a shock
Can you defib someone with an ICD
Yes, the pads just cant be over the ICD
What configuration of leads are used in pacemaking and ICD
IS-1
What is the difference between DF1 and DF3 ICD leads and which one is used most commonly
DF1 - multiple leads come out of the main lead
DF4 - all components are in one lead (mostly used)
What shock configuration is used in ICD these days
Single coil ICD leads with RV coil to can
In relation to heart rhythm, when is a VT shock always delivered by an ICD
VT shock is always synced up with the R wave to ensure the heart return to synchronous rhythm
What is the difference between VT and VF sensing in ICD
VT tends to be monomorphic and regular so the ICD can detect this is it exceeds the maximum rate intervals
VF tends to be polymorphic and irregular, so it is likely to be under sensed on intervals alone. The ICD instead uses intervals (NID) and rate to detect VF
What is auto adjusting sensitivity in regards to a ICD
The ICD resets its sensitivity threshold at each R wave based off the preceding R wave
Why cant ICDs ever be configured in unipolar
They would be too sensitive to noise and innaproporately shock
What two configurations can an ICD be put in
True bipolar - tip to ring (used commonly)
Integrated bipolar - tip to RV coil (larger sensing circuit that can cause oversensing)
What are the 4 channels on a ICD display
Leadless ECG - coil to can
Far field channel (shock channel) - Can to RV
Near field channel (sensing channel) - Top to ring
Marker channel - shows how the device is working
Following a ICD shock for VF, what will the ICD continue to monitor for a short time afterwards
The device will continue to count the intervals between R waves and monitor the rate to ensure another VF episode is detected immediately is there is another one
What is atrial tachycardia pacing (ATP)
Sequence of pacing pulses faster then the arrythmia occurring to excite the excitable gap in the VT circuit
How quick is the pacing in atrial tachycatia pacing in ICD
20-30ms
What is burst atrial tachycardia pacing (ATP)
Sequence of pacing pulses with fixed coupling intervals
What is ramp atrial tachycardia pacing (ATP)
Sequence of pacing pulses with auto-decremental values so the coupling interval get progressively shortened
What is a risk associated with ramp ATP in ICDs
It can accelerate the VT into a VF
What is the timeline of ATP therapy to treat VT in an ICD
First therapy is burst ATP
Second therapy is ramp ATP
Third - Sixth is a shock
What will the SVT and VT morphologies look like in compared to normal sinus rhythm
SVT will match normal sinus rhythm morphology as it originates from the atrium
VT will look different as VT originates from the ventricle
How much do SVT and VT morphologies have to match sinus rhythm to be considered normal VT
Morphologies have to match by 70% or more
What channel in the ICD is responsible for collecting morphology template and comparing it to the VT rhythm
Far field channel (RV coil to can)
How does onset help differentiate between VT and sinus tachycardia in an ICD
VT routinely starts with a sudden onset whereas sinus tachycardia would be more gradual
How can stability be used in ICD
Stability can be used to differentiate between atrial fibrillation and VT on the basis that the AF is irregular and monomorphic VT is stable
How is stability set on an ICD
There can be a set value of variation between the R-R interval that can be allowed. Once this is exceeded, the ICD will class the rhythm as AF
What percentage of shocks from ICDs are inapproproate
30%
What conditions do we want to try minimise VT shocks occuring in to minimise the amount of inapproporate shocks in an ICD
We want to minimise shocks in non-sustained VT that will self terminate or that could terminate with ATP
What are some reasons inapproporaite shocks can occur in ICD
Atrial Fibrillation
Atrial Tachycardia
SVT
Sinus Tachycardia
Lead Failure
How can AF cause an ICD to sense it as a VT/VF
AF that is rapidly conducted to the ventricles can be extreamly fast and enter the VT/VF zone which may cause an inapproporate shock
What patients are at risk for T wave oversensing
Those with brugada syndrome or long QT syndrome
What two things can we adjust to avoid T wave oversensing
Increase ventricular sensitivity or turn on auto-adjusting sensitivity
What is the Frank Starling compensatory in heart failure
In normal conditions - stroke volume increases and the end diastolic volume increases, causing strain on the cardiac wall forcing the muscles to contract more forcefully
In HF - the contractility is unable to increase with this demand and the left ventricle will become dilated
What is the neurohormonal alteration compensatory mechanisms in HF
Increase in SNS nervous system leads to an increase in HR, contractility and vasoconstriction.
Renin-aldosterone system overactive and causes fluid retention
What is the role of BNP in blood
Helps blood circulate around the body
What are some lifestyle modifications to treat HF
Na+ restriction, appropriate fluid intake, exercise, smoking cessation, weight loss
What is ventricular dyssynchrony
When there is late activation of the lateral region of the LV in respect to the activation of the septum
What are the mechanical, structural and electrical causes of ventricular desynchrony
Mechanical - regional wall abnormalities
Structural - disruption of the myocardial collagen matrix
Electrical - conduction delay
What is the best predictor for optimal CRT response in an ECG
QRS width > 130ms
What is the aim of CRT
Cardiac device that attempts to normalise the timing of the activation of the left and right ventricle or lateral wall and septum to improve desynchrony seen in LBBB
How does LBBB occur as a result to HF
In HF the left ventricle dilates, this can cause LBBB where the RV contracts before the LV
Where are the leads placed in the heart in CRT
1 lead in RA, one lead in RV, one lead in LV implanted through the coronary sinus
What is the coronary sinus
A branch that is accessed from the bottom of the RA
Why does the left ventricular lead in CRT aim for the lateral wall of the LV
The lateral wall is the latest point of activation of the LV so by activating this we can cover the whole LV with stimulus to reduce the dysynchrony
What are some positive outcomes of CRT
LV and RV are synchronised - narrowing QRS
LV septal and free wall synchronised, improving LV contraction
Improves EF
Improves HF symptoms
What is the main configuration of LV lead in CRT and what is the benifit of this
IS4 - quadripolar
Having a large range of vectors helps capture the whole LV when it is pacing
What is the ideal impedance for pacing devices
500-1000 ohms
What configuration of the LV lead in CRT has been used hisotrically and when would it be used in patients today
IS-1 - bipolar
Used when patients vessels are very small
What is Optivol in CRT
Feature on Medtronic devices that measures transthoracic impendence - as fluid increases in the lungs, Optivol increases and transthoracic impedance decreases
Besides from the LV, where are two other locations that pacing can occur in CRT
His Bundle and Left Bundle
Where are the leads implanted in Left Bundle Pacing CRT
Lead is implanted slightly distal to the His Bundle and is screwed deep into the LV septum, ideally to capture the left bundle branch
Where is a leadless pacemaker implanted
Directly into the RV from the femoral vein
When are leadless pacemakers used
In patients with occluded veins as they are prone to pocket infections
What is a subcutaneous ICD
Where the leads are implanted under the muscle and the leads run from the can to the left side of the atrium
What shocks is a subcutaneou ICD able to deliver and not able to deliver
It can give shocks for VT/VF but cant deliver ATP or bradycardia support pacing
What is the effect of holding a magnet over an ICD
This will temporality suspend tachycardia detection so no shocks will be delivered
What are indications for EP study
Patients with palpitations, dizziness and syncope
What is the aim of a EP study
See what the cause of the arrythmia is or to induce an arrythmia
What is the bachman bundle
The conduction path between the SA node and LA
What phase of the action potential is accelerating to cause abnormal automaticity
Phase 4 (resting phase)
Atrial tachycardia, reperfusion VT, ischemic VT and fascicular VT are die to what tope of arrythmia mechanisms
Abnormal Automaticity
Atrial tachycardia, AVNRT, atrial fultter, VT scar mediated and idopathic VT are due to what mechanism of arrythmia
Re-entry
What is the most common mechanims of tacyarrythmia
Re-entry
Atrial tachycardia, RVOT and LOT are caused by what mechanism of arrythmia
Triggered activity
What is occuring on the ionic level in absnormal automicity arrythmias
Leakage of positive ions into the cardiac cell leading to late phase 3 or early phase 4 of the AP
What is the arrythmia mechanism of torte de poides
Triggered activity
How is the heart accsess in EP study via the femoral vein
Femoral vein > RA > coronary sinus > RV
How many catheters are used in EP study
4
What type of catheter is used during EP study in the high right atrium and where should the tip be located
Quadripolar catheter
Tip should be on the lateral wall
What type of catheter is used during EP study in the right ventricular apex and where should the tip be located
Quadripolar catheter
Tip as close as possible to the RV apex
What type of catheter is used during EP study in the coronary sinus and where should the tip be located
Octapolar catheter
Located along mitral valve annulus
What type of catheter is used during EP study in the His bundle and where should the tip be located
Hexapolar Catheter
Top is straddling the tricuspid annulus
What is the normal sweep speed in EP study
100ms
What is the IEGMS showing in an EP study
This represents the local electrical activity of the groups of cells in contact with the catheter giving infoamtion on the local electricla acticity
What is the PA interval on IEGMS and what is a normal duration for this
PA interval measure’s from the onset of P wave to the rapid defelction of the A wave on the his-bundle catheter
25-50ms
What is the AH interval on IEGMS and what is a normal duration for this
Measures the his bundle catheter from A signal to onset of H signal
50-125ms
What is the HV interval on IEGMS and what is a normal duration for this
measures the onset of the Hi deflection to the earliest ventricular activation on any channel
35-55ms
What pacing algorithyms are used in the atrium and ventricles, respectfully, in EP study
VOO in vetricle
AOO in atrium
What is pacing drive train in EP study
series of -10 fixed stimuli at a constant rate, refered to as S1
What is pacing drive train with premature extra stimuli in EP study
Consists of introducing one or more premature stimuli (S2) for a short train impulses (S1)
What is the funtional refractory period
The period of time when an action potential cannot be initated by a normal pacing stimulus
What is the effective refractory period
The longest coupling interval that faults to capture the tissue (S1-S2)
What is the wencheback interval in EP study
The longest cycle length that does not result in 1:1 conduction during constant pacing
What is decremental atrial pacing in EP studies, how it is performed and what does it reveal
This assesses the function of the AV node
Method: pace at a cycle length shorter then the sinus cycle then gradually decrease the cycle length.
The cycle lenght at which a beat is skipped is the wenchback cycle legnth
What is the purpose of atrial extra stimulus pacing in EP study
induce arrhythmias and out the AV nodal refractory period
In atrial extrastimulus pacing in Ep study, what happens to the interval lengths as the conducting intervals decreased
As the conducting intervals decrease, the conduction velcoity through the AV node progressively decreases and the AH interval progressively lengthens
How is atrial extrastimulus pacing performed in EP study
Giving a drive train at fiixing intervals progressively decreasing until AV refractory period occurs
What does decremental ventricular pacing reveal in EP study
How the atria and ventricles are electriclaly connected as well as AV nodal regractory period
What would how up during pacing manoeuvres in an EP study if AVNRT was present
AH jump and slow pathways
What is sinus node recovery time
The interval between the last paced atrial depolarisation and the first spontaneous atrial depolarisation resulting from the SA node
What is the normal sinus node recovery time
<1500ms
What is an abnormal CSNRT in EP study
> 525ms
What is corrected sinus node recovery time and how is it calculated in EP study
CSNRT is the difference between the baseline cycle legnth of the SA node and the SNRT when the atria is pacing in overdrive
CSNRT = SNRT - SA node baseline
How is SNRT measured in EP study
This is the time taken for the sinus rhythm to resume after 30 seconds of overdrive atrial pacing at several cycle lengths
If there is AV block above the His bundle what changes would be observed in an EP study
Prolongation of AH interval
If there was a AV block below the His bundle what changes would be seen in an EP study
HV interval block
What length of HV block needs to be seen in an EP study to indicate pacemaker implantation
> 100ms would suggest a permentnt pacemaker
What is the normal impedance of a RF ablation catheter
100-150 ohms
If the impedance of a RF ablation catheter in an EP lab goes down to 0 what does this mean
The cathather is in contact with the tissue
What does it mean if the impedance of a RF apblation catheter increases too high
This could mean you are burning tissue that doesnt need to be burnt
What are the two possible pathways of AVNRT
Beta - fast pathway with long refractory period
Alpha - slow pathway with short refractory period
What pathways, fast or slow, does a conduction usually travel down in sinus ryhtum
Fast pathwya
When a PAC arrives at the atria, what conduction pathway, fast or slow, does it travel down to reach the his bundle
Slow pathway - this is because the fast pathway is still in its long refractory period but because of the short refractory period of the slow pathway it will be able to travel down there
In regards to the refractory periods of the AV conductio pathways, under what situation would a PAC travel down the fast pathway
If the fast pathway recovers in time the PAC that is travelleing down the short pathway could conduct retrogradly up the fast pathway
How does AVNRT look on the EP study screen
The atrial and ventricle electrical signals will line up as they are being activated at the same time
What is the treatment of AVNRT in EP study
RF ablation of the short pathway
A sudden abrupt prolongation of the AH interal signal in the EP study tells you what
The signal has moved from the fast pathway to the slow pathway
What length of prolongation of the AH interval in the EP study is indicative of the conduction pathway now going down the short pathway and not the fast pathway
> 50ms
What type of accessory pathway has developed in AVRY
A accessory pathway in the form of muscle connection between the atrium and ventricle which means this can bypass the AV node and cause preexcitation of the ventricles
Orthodromic AVRT
Anterograde conduction through AV node
Antidromic AVRT
Retroradde conduiton through AV node
What is the most common form of accessory pathway in AVRT and i what direction do signals travel through this
Concealed ventricular preexcitation
Can only conduct retrogradely
How do they know where they will ablate to treat AVRT
The earliest electrical signal seen on the EP screen is where they abalte
What temperature is AVRT ablation done at
60 degrees
Where specifically in the RA does atrial flutter usually originate from
Cavotricusptid isthmus (CTI) - located between the inferior vena cava ostium and the tricuspid valve
What direction is CTI dependant flutter (typical flutter) moving in
Couterclockwise
What temperature is used in atrial flutter ablation
80 degrees
Following atrial flutter ablation, what signals would be indicative of unsucsessful ablation
Signals from the Halo catheter should be the last to activate - if this is not the case then the signal is breaking through the CTI still
Once you have ablated a clockwise atrial flutter what should you do
pace from distal halo catheter 102 and measure the proximal CS7-8
If the CTI is fully blocked by atrial flutter ablation what should the Distal Halo 1-2 and CS7-8 be in relation to each other
They should be the exact same if the CTI is fully blocked
Where is atrial fibrillation commonly located
Pulmonary veins
What is the treatment for atria fibrillation in EP study
Pulmonary Vein Isolate (PVI)
What is pulmonary vein isolate (PVI)
Pulmonary veins are electrically isolated from the body of the LA using ablation
What method is most commonly used for PVI
WACA
How do you test if atrial fibrillation ablation was sucsessful
Pace from the ablation catheter in the pulmonary veins - there is no capture on the heart signal then it is sufficnetly blocked
When is fast anatomical mapping (FAM) used in the EP study
Used to map the LA and 4 pulmonary veins in preapration for a PVI
On a FAM, what colour indicates scar tissue/ablated tissue and what colour represents healthy tissue
Ablated tissue - red
Health tissue - purple
What is the last resort ablation for atrial fibirllation
AV node ablation
Why is AV node ablation the last resort for treatment of atrial fibirlation
Ablating the AV node will give the patient complete heart block, making them pacemkaer dependant
When do you choose to ablate when someone has a PVC
Most people have isolated PVCs but they are infrequent so dont require ablation
20,000 PVC’s a day would indicate a ablation
What types of ventricular tachycardia is the only type that can be treated with ablation
Monomorphic
What is the most common form of monomorphic VT
Re-entry VT
What is activation mapping used for in EP lab
used to record the electrical signal sequence during the VT - showing where to alblate
What is entrainment mapping used for in EP study
Used to prove the location of the catheter is close to the VT circuit
How do you perform a post pacing interval (PPI) following a VT ablation
Measured from the last pacing stimuli to the next electrical acitivty seen on the ablation catheter tip
What do you want the PPI to be following successful VT ablation
PPI should be equal to or with (less than 10-30ms) of the tachy cycle length
