CV Flashcards
Why do we have to see the same waveform 12 times on a standard ECG?
The 12 leads provide important spatial information about the heart
They all view the electrical activity of the heart from a different position
allows you to localise pathology to a particular heart region
What is the normal cardiac axis?
-30 to +90
(2pm - 6pm)
Most positive deflection in lead II
most negative deflection in aVR
If leads I and II are positive, the axis is normal
What can left axis deviation suggest?
conduction abnormality
What can right axis deviation suggest?
pulmonary embolus/congenital heart defect
If the right ventricle becomes hypertrophied, it has more effect on the QRS complex than the left ventricle, and the average depolarization wave – the axis – will swing towards the right
What would you see in left axis deviation?
overall electrical activity becomes distorted to the left
between -30° and -90°
positive lead I and aVL
negative lead II and III
What would you see in right axis deviation?
overall direction of electrical activity is distorted to the right
between +90º and +180º
Negative QRS in lead I, positive in aVF
What is the ECG paper speed?
25 mm/s
How many large squares would you find in a second on ECG?
5 (one square = 0.2s)
First degree heart block
slowing in AV nodal conduction
prolonged PR interval
second degree heart block
intermittent failure of AV nodal conduction
two types:
1) Mobitz I: PR interval steadily increases until a QRS complex is missed. the pattern resets
2) Mobitz II: regular skipping of QRS. e.g. P – QRS – P – P – QRS (this is 2:1). Most beats are normal but there is occasionally atrial depolarisation without ventricular depolarisation.
third degree heart block
complete failure of AV nodal conduction
No impulse conduction from atria to ventricles. No relationship between P:QRS.
ventricles are excited by a slow ‘escape rhythm’, from a depolarizing focus below the AV node
Which ECG leads are inferior?
II, III and aVF
Which ECG leads are anterior?
V1-V4
Which ECG leads are lateral?
I, aVL, V5, V6
What is an ECG lead?
imaginary line between 2 ECG electrodes.
Each lead provides a different view of the electrical activity of the heart
Which plane are the limb leads in?
Coronal
Which plane are the chest leads in?
Transverse
Which lead usually provides the rhythm strip on an ECG?
Lead II
What’s the normal range of the PR interval?
<1 large square
<200ms
What’s the normal range of the QRS complexl?
< 3 small squares
< 120ms
sinus rhythm
normal heart rhythm, starts in the sinoatrial node
Rhythm = activation sequence of the heart
What does a narrow QRS indicate?
that the rhythm is arising from the AVN or above
i.e. the rhythm is using the specialized conducting system (His-Purkinje system) to depolarize the ventricles (the fast route to depolarize all ventricular muscle in a short period of time)
What is heart failure?
failure of cardiac output to meet the physiological demands of the body
Name 4 causes of heart failure
MI
hypertension
toxins (alcohol, chemotherapy)
valve disease
what is systolic heart failure?
heart failure with reduced ejection fraction. inability of the ventricle to contract normally
Usually has a coronary cause
Affects younger male patients
what is diastolic heart failure?
heart failure with preserved ejection fraction
Inability of the ventricle to relax and fill normally, causing increased filling pressures
older
more often female
hypertensive aetiology
How do compensatory changes lead to heart failure?
haemodynamic changes cause compensatory changes in the heart and cardiovascular system
these physiological changes occur to maintain cardiac output and peripheral perfusion
chronic activation increases cardiac workload, causing progressive damage
as heart failure progresses, these mechanisms are overwhelmed and become pathological
What neurohumoral adjustments are seen in heart failure?
ischaemic injury causes decreased efficiency of the heart –> perceived hypotension
neurohumoral adjustments act to maintain arterial pressure and perfusion of vital organs
Noradrenaline increases cardiac contractility and peripheral vasoconstriction
RAAS (activated by reduced renal perfusion) increases blood volume -> fluid overload
What is the significance of BNP in heart failure?
distinguishes HF from other forms of dyspnoea
secreted by the ventricles in response to myocardial wall stress
Levels are increased in patients with heart failure, and levels correlate with the severity of heart failure
Low BNP excludes heart failure
Treatment of hear failure (reduced ejection fraction)
1) start with a beta blocker/ACEi (ARB if intolerant)
2) with ongoing symptoms, add a MR antagonist
3) sacubitril/valsartan (stop ACEi)
4) devices/ivabradine
5) digoxin
6) LVAD or transplant
What is the most evidence-based therapy in heart failure?
Beta-blockers
Mechanism of action: sacubitril
inhibits neprilysin, an enzyme that breaks down natriuretic peptides
this increases the number of natriuretic peptides in the body
this increases natriuresis
LCZ696
contains bothan ARB (valsartan) and a neprilysin inhibitor
blocks the unwanted effects of ANG-II and upregulates the beneficial system (natriuretic peptides)
What is an implantable cardioverter-defibrillator (ICD)
a device implantable inside the body
able to perform cardioversion, defibrillation, and pacing of the heart
ivabradine
selectively inhibits the pacemaker If current
Blocking this channel reduces cardiac pacemaker activity
This slows heart rate at the SAN
How would you manage inadequately perfused patients?
give them positive inotropes
e.g. adrenaline/dopamine
How would you manage congested patients?
treat the fluid overload with diuretics
NYHF classification
I - No symptoms and no limitation in ordinary physical activity
II - dyspnoea during normal activities but comfortable at rest
III- dyspnoea limits normal activities
IV - dyspnoea at rest, essentially bedbound
CXR signs in LV failure
remember: ABCDE
A = alveolar oedema (perihilar - bat's wings) B = kerley B lines (interstitial oedema) C = cardiomegaly D = dilated upper lobe vessels E = pleural Effusion
Infective endocarditis
Infection of endocardium
Results in formation of a vegetation - a mass of platelets, fibrin, microorganisms, and inflammatory cells
Results in damage to cusp of valves
Which valve is most commonly affected by infective endocarditis?
mitral valve
Which valve is most commonly affected by IE in PWIDs?
tricuspid
causes:
(1) particulate-induced endothelial damage to right-sided valves
(2) increased bacterial loads in these patients
(3) direct physiologic effects of the injected drugs
(4) deficient immune response caused by IVDU
Classification of infective endocarditis
1) Native valve endocarditis (NVE) = most common type
2) Endocarditis in PWIDs
3) Prosthetic valve endocarditis (PVE)
What is the most common cause of infective endocarditis in PWIDs?
staph aureus
What is the most common cause of infective endocarditis in native valve endocarditis?
Strep viridans
presents more indolently, causing Subacute disease
What is the most common cause of infective endocarditis in prosthetic valve endocarditis?
CoNS
remember: CoNS because a prosthetic valve is a con
List some risk factors for infective endocarditis
underlying valve abnormalities (aortic stenosis/mitral valve prolapse)
IVDU
Rheumatic heart disease
Dental work
Acute infective endocarditis
patient presents very unwell
progressive valve destruction
metastatic infection developing rapidly → i.e. septic emboli
commonly caused by S. aureus
Subacute infective endocarditis
presents indolently over weeks to months in an insidious manner
rarely leads to metastatic infection
commonly caused by Strep. viridans
What is the most common cause of IE
Strep. viridans
What should you be worried about in a patient who has Fever + murmur?
Fever + murmur = IE until proven otherwise
what embolic events can occur in infective endocarditis?
Small emboli:
- Petechiae
- Splinter haemorrhages
- Haematuria
Large emboli:
- CVA
- Renal infarction
Right sided endocarditis (in PWID)
-Septic pulmonary emboli
What are possible long term effects of infective endocarditis?
can be categorised into immunological damage and direct tissue damage
Immunological reaction:
- Splenomegaly
- Nephritis
- Vasculitic lesions of skin & eye
- Clubbing
Tissue damage:
- Valve destruction
- Valve abscess
What are 3 cases in which you should be suspicious of infective endocarditis?
1) patients with S.aureus bacteraemia
2) Any PWID with a positive blood culture
3) patients with prosthetic valves and positive blood cultures
How should you investigate infective endocarditis?
1) blood culture
2) echocardiography (transthoracic)
What are the guidelines for blood cultures in suspected infective endocarditis?
- 3 sets of blood cultures of 10ml in each bottle (20ml total)
- different peripheral sites
- before antibiotic administration
- aseptic technique crucial
What are the Duke criteria?
used to diagnose infective endocarditis
Major criteria:
- Typical organism in 2 separate blood cultures
- Positive echocardiogram or new valve regurgitation
Minor: FIIVE
- Fever >38 ̊C
- IVDU or other predisposition (heart condition)
- Immunological phenomena (eg. oslers nodes)
- Vascular phenomena (eg. septic emboli)
- positive blood culture
How many of the Duke criteria do you need to be diagnosed with IE?
Definite IE is defined as:
- 2 major
- 1 major + 3 minor
- 5 minor
What are 3 Indications for surgical intervention in IE?
1) Heart Failure
2) Uncontrolled Infection
3) prevention of embolism
How long will antimicrobial therapy be given for in IE?
4 weeks for NVE
6 weeks for PVE
What antibiotics would you use to treat IE caused by streptococcus species?
high doses of benzyl penicillin plus gentamicin
give IV
What antibiotics would you use to treat IE caused by enterococcus species?
amoxicillin or vancomycin +/- gentamicin
give IV
should you avoid beta blockers in patients with AF?
no
beta blockers work at the AV node to slow conduction
they are first line for rate management in AF
What do blunted costophrenic angles indicate?
pleural effusion
What is the difference between transudate and exudate?
Transudate is fluid pushed through the capillary due to high pressure within the capillary.
Exudate is fluid that leaks around the cells of the capillaries caused by inflammation. (Higher protein content)
Name three causes of transudate
LVF, Cirrhosis, Nephrotic syndrome
Name three causes of exudate
PE, Bacterial Infection, Bronchial Cancer
What is the difference between interstitial oedema and alveolar oedema?
interstitial oedema - occurs at lower pulmonary venous pressures. Fluid collects in interlobar fissures and septa (Kerley B lines)
alveolar oedema - occurs at higher pressures (>30 mm Hg). Causes areas of consolidation and mottling of the lung fields, and pleural effusion.
Continued fluid leakage into the interstitium, which cannot be compensated by lymphatic drainage.
Interstitium is overloaded and the fluid has nowhere else to go
Causes spill of fluid from interstitium into alveoli (alveolar oedema) and leakage into the pleural space (pleural effusion).
symptoms of MI
Crushing central chest pain Back pain Jaw pain – lower jaw Indigestion Sweatiness, clamminess Shortness of breath
Possible signs of MI
Tachycardia (HR > 100bpm) Distressed patient crackles/ raised JVP Low BP Sweaty, clammy Arrhythmia
What is troponin?
marker of cardiac necrosis
definition of MI
Any elevation in troponin in clinical setting consistent with myocardial ischaemia.
E.g. chest pain, breathlessness, etc.
Type 1 Spontaneous MI
due to a primary coronary event
e.g. coronary artery plaque rupture and formation of thrombus
Chest pain, ECG changes, raised troponin
Type 2 MI
Increased oxygen demand or decreased oxygen supply
Not a primary problem in the coronary arteries
Troponin increases due to another cause of heart stress
e.g. PE, Heart failure, sepsis, anaemia, arrhythmias, hypertension, or hypotension
Type 3 MI
sudden cardiac death
Type 4 MI
Iatrogenic
4a MI associated with percutaneous coronary intervention
4b MI Stent thrombosis
Type 5 MI
Iatrogenic
associated with CABG
What should you suspect in a patient who is Breathless with high troponin levels?
PE
Name 3 causes of Chronic elevation of troponin
renal failure (reduced excretion)
infiltrative cardiomyopathies, e.g. sarcoidosis
chronic heart failure
What is unstable angina?
An acute coronary event without a rise in troponin
What ECG findings do you expect in a Posterior infarct?
Location of the infarct means that an ST elevation is not seen
There are no ECG leads directly over the back of the heart
Can be diagnosed by looking for reciprocal ST elevation
What is the significance of Left bundle branch block in MI?
NEw - can indicate infarction
old - can obscure ST elevation on ECG
What is the general pattern of ECG manifestation of ischaemia?
1) ST elevation
2) pathological Q wave
3) T wave inversion
4) normalisation with persistent Q wave
other factors
- change in heart axis
- broad QRS complex
- ST depression
Which artery is likely to be blocked with ST elevation in the anterior leads?
LAD
Which artery is likely to be blocked with ST elevation in the lateral leads?
left circumflex artery
Which artery is likely to be blocked with ST elevation in the inferior leads?
right coronary artery
Which leads will show reciprocal ST depression when there is ST elevation in anterior leads?
reciprocal ST depression in inferior leads
What does ST elevation in aVR indicate?
occlusion of the left main coronary artery
Which leads will show reciprocal ST depression when there is ST elevation in lateral leads?
reciprocal ST depression in inferior leads
Which leads will show reciprocal ST depression when there is ST elevation in the inferior leads?
‘Reciprocal’ ST depression in high lateral leads (I and aVL)
Which leads will show a STEMI with right coronary artery occlusion?
inferior leads (II, III, and aVF)
What kind of STEMI doesn’t cause ST elevation?
posterior wall infarction
you would see anterior ST depression