arrhythmias Flashcards
What are the causes of arrhythmias
Cardiac: ACS/ischaemia, HF, mitral valve disease, myocarditis, pericarditis, accessory pathways (e.g. WPW)
Non-cardiac: Electrolytes, drugs, thyrotoxicosis, anaemia
what are the 3 mechanisms behind the formation of arrhythmias
Ectopic re-entry loops
delayed depolarisation
state the different categories of arrhythmias
Brady - sinus, sick sinus, heart block
Tachy _ broad (from ventricles or SVT), narrow (down bundle of his)
define bradycardias
Heart rate <50bpm
what are the different types/ causes of bradycardias - briefly explain each one
Sinus Brady - naturally slow, Bblockers, hypothyroid, Raised ICP, MI (SAN damage)
Sick sinus - slow followed by bouts of tachy - widespread disease of the atria not just SAN
heart block: - caused by fibrosis e.g. ischaemia, haemochromatosis
1st degree - AVN delayed but still conducts each P
2nd degree type 1 - progressive delay in AVN (P-R interval) until one QRS complex is missed following P wave
2nd degree type 2 - AVN not delayed but misses conduction every 2nd or 3rd beat
3rd degree - no relationship between P wave and QRS complexes, AVN does not work at all
define narrow complex tachycardia
HR>100 with a QRS complex <120ms (3 small squares)
explain the different causes of narrow complex tachycardias
- sinus tachy - stress, fever, pregnancy, thyrotoxicosis
- AF
- Flutter
- multi-focal atrial ectopics - numerous ectopic within atria, associated with COPD
- AVNRT (re-entry through from ventricles to atria via AVN)
- AVRT (re-entry through from ventricles to atria via other way than AVN e.g. WPW orthodromic)
define broad complex tachycardias
HR>100, QRS>120ms
explain the different types of broad complex tachycardias
- VT - Depolarisation coming from within the ventricles themselves at an increased rate
- SVT - depolarisation comes from above the ventricles but not down natural pathway (e.g. bundle of his)
types: - aberrancy - with increased rate one of the BB turns itself off (not present at rest)
- pre-existing BBB - broad as only one BB conducting
- accessory pathways - new pathway between atria and ventricles e.g. WPW antidromic
how do people with arrhythmias present?
Palpitations chest pain exercise intolerance syncope asymptomatic anxiety signs of HF
what investigations would you suggest for someone presenting with palpitations or syncope?
Bloods - FBC (anaemia), U&E (K+, Mg, Ca), TFT (Hyper)
ECG / ambulatory
ECHO - heart stretch and mitral valve
Exercise stress test
how is sick sinus syndrome treated?
treat when <40bpm or symptomatic
Give IV atropine to block M2 receptors to speed heart or IV isophrenaline which stimulates B1 so speed heart
Pacemaker inserted (to treat brady)
B blockers to slow heart (blocks remaining ectopics)
when is sick sinus syndrome NOT treated?
when HR >40bpm and asymptomatic
what are the causes of heart block?
ischaemia, fibrosis (SLE, RA), haemochromotosis, pharma e.g. b blockers, CABG (also aortic valve replacement - damaged in tavi)
when does heart block require pacing?
When 2nd degree type 2 or 3rd degree
3rd degree requires pacing as ventricular rates are slow and unreliable (type 2 likely to develop into type 3 and why it needs replacing)
what drugs can aid in heart block?
Atropine (for transient heart block)
adrenaline
describe ECG changes seen in wolf Parkinson white
Delta waves present (slow rise R)
P-R interval shortened as depolarisation begins through the accessory pathway whilst AVN hold conduction
explain why WPW can be both broad and narrow complex tachycardia
Both are re-entry loop (does not always happen in WPW, only when cause of tachy)
Broad as can have accessory route which does not follow the usual pathway (bundle of his) then back up AVN
Narrow as down the normal pathway AVN then back up to atria through the accessory route
describe steps in managing a narrow complex tachycardia
A-E, IV access and give o2, call help
if unstable straight to DC cardioversion
if stable: try Valsalva manoeuvre, carotid massage
if unsuccessful try pharma: give adenosine 6mg up to 25mg to block AVN (rhythm)
treat underlying rhythm with fleccanide or B blockers
in long term ablate accessory pathway - or treat with flecanide long term
how does adenosine help narrow complex tachycardia?
blocks AVN
dosage of 6mg up to 25mg
what are side effects of adenosine ?
bronchospasm
impending doom
chest pain
flushing
how does flecanide help narrow complex tachycardia
voltage gated Na channel blocker
slows down action potential - prevents excitability of myocytes (can also slow AVN)
how is a broad complex tachycardia treated?
A-E, peripheral IV access, O2, call for help
unstable patient - straight to DC cardiovert
then begin amiodarone
stable patient:
give controlled o2 therapy, correct electrolytes, give IV amiodarone, continue ECG monitoring
for all long term:
continue amiodarone for 7 days
long term bisoprolol
consider implanting automatic cardiac defibrillator
what ECG changes are found in VT?
Concordance - every ECG lead has same deflection in QRS (either up or down)
Capture beats and fusion beats - narrower than usual ventricular QRS
What is AF?
atria chaotically fibrillate instead of contracting - unsynchronised myocyte contraction
originates in left atria usually
explain ECG changes associated with AF
absent P waves with wobbly baseline
QRS is irregularly irregular
tachycardia sometimes
what are the causes of AF?
Mnemonic = MITRAL
mitral valve disease
IHD/HTN
thyroid disease
rheumatic fever
alcohol excess / metabolic disturbance (K+)
lung disease (P.E, pneumonia), LV hypertrophy
what are the complications of AF?
Ventricular tachy (SVT) - AVN increases responsiveness so high rate of depolarisation reaches ventricles
reduced CO - partly due to SVT, and atria do not contract so less filling
Thromboembolism - stasis (esp atrial appendices) leads to thrombi formation which can lead to:
- stroke
- mesenteric infarct
- limb ischaemia
describe the symptoms of AF
Direct - asymptomatic, chest pain/palpitations, irregularly irregular pulse
indirect - (related to cause)
- valve disease = breathless, murmur
- HF = hepatomegaly, raised JVP, decreased BP
- thyroid = goitre
- infection = fever
what investigations would you carry out in someone with AF?
bloods - FBC, U&E, TFTs, troponin, BNP
ECG
ECHO - valve disease, stretch
what is atrial flutter?
ectopic atrial beats cause re-entry circuit in the atria
atrial myocytes conduct in synchrony but at an increased rate without rest
atrial rate at approx. 300bpm
describe ECG changes seen in atrial flutter
lots of P waves very close to one another = saw tooth
get a pattern of P to QRS that can be 2:1, 3:1 or 4:1 etc
what are the causes of atrial flutter?
ischaemia
HTN
cardiomyopathy
heart valve abnormalities
what are signs/symptoms of atrial flutter?
palpitations - flutter feeling in the chest SoB syncope raised JVP anxiety tachycardia
what are the complications of atrial flutter?
relatively benign condition
strain on heart from tachy
clot formation risk
how is acute unstable AF managed?
ABCDE
Do tests and keep ECG monitoring on throughout
start treating the cause
Emergency DC cardioversion
(do not worry about starting anticoagulation before, although heparin should be started)
how is acute stable AF managed that occurred less than 48 hours ago managed?
Can wait a few hours to see if spontaneously resolves (70% of cases)
rate control - verapamil/bisoprolol
Rhythm control - electrical or pharma:
- no IHD then amiodarone or flecanide
- amiodarone if evidence of structural/IHD
when starting rhythm control also start heparin due to risk of coagulation
how is acute stable AF that occurred more than 48 hours ago managed?
- Rate control only
- delay rhythm control until anticoagulation has occurred for 4 weeks prior to cardioverting - INR >2
- Can check atrial appendices for thrombi via trans-oesophageal USS
- continue anticoag at least 4 weeks post-cardioversion and then monitor for need of long term anticoagulation using CHADsVaSc
describe management of chronic AF
Rate control - b blocker/Ca channel locker usually 1st line
Digoxin considered if congestive HF
Rhythm control - Sotalol first line
amiodarone/flecanide (preferred in paroxysmal, young and symptomatic AF - can do pill in pocket approach)
Anticoagulation - warfarin/NOAC offered
Catheter ablation and pacing - ablate AVN and insert ventricular pacemaker
what is cardioversion and compare the different types?
intention to put heart back into sinus rhythm
- electrical = DC cardioversion
can be attempted up to 12 months of AF onset
- Pharma = amiodarone, flecanide
less successful but no need for sedation
what are the contraindications to cardioversions
AF >1year
AF likely to reoccur e.g. cause still there or structural
Cardioversion already failed no of times
Anticoag is contraindicated
define paroxysmal, persistent and permanent AF
Paroxysmal = most common, terminates 1-7days
persistent = >7days
Permanent = >1 year
what is the CHADSVAS score
risk of thromboembolitic event C = CCF (1) H = HTN (1) A2 = >65 (1), >75 (2) D = Diabetes (1) S2 = Stroke/TIA/Thrombus (2) Va = Vascular disease (1) Sc = Sex female (1)
what is HASBLED?
risk likelihood of bleeding: H = HTN A = abnormal liver/renal function S = Stroke B = Bleeding L = labile INR E = Elderly D = drugs/alcohol score of >3 = high risk of bleeding
what other way can the risk of stroke in AF be reduced other than anticoagulation?
surgically remove the atrial appendices as 90% clots form there
where do AF and flutter originate?
AF = left atria from smooth muscle of pulmonary veins
flutter = right atrium
how can you tell if there is left axis deviation or right axis deviation on ECG?
left axis deviation = aVL > I
right axis deviation = III > aVF
what are the causes of left and right axis deviation?
hypertrophy or conduction defects such as WPW, hemi-blocks
what is p mitrale?
Bifid P waves
caused by left atrial hypertrophy as a result of HTN, or mitral valve disease
what is p pulmonale?
Peaked P waves
anything causing right atrial hypertrophy
COPD, CHD, tricuspid stenosis, pulmonary HTN
what is the normal PR interval?
120-200ms
what are the causes of tall and wide QRS complex?
tall = ventricular hypertrophy
wide = BBB, ventricular ectopics, WPW
what causes ST elevation?
MI, pericarditis (concave + widespread over all leads)
what causes ST depression and how can ST depression be defined?
Ischaemia
defined as:
- >1mm in 2 consecutive limb leads
- >2mm in 2 consecutive chest leads
when is a T wave inverted?
NSTEMI
when is a T wave tall?
Hyperkalaemia or MI
when do we see U waves?
Hypokalaemia
How do you treat WPW?
Flecanide to control arrhythmias
or ablate the accessory pathway
What is the Valsalva manoeuvre?
strain and hold breath in supine position
on release of strain the vagal activity should reduce
how do you treat atrial multi-focals (ectopics)
often due to COPD - hypoxia and hypercapnia
correct this and ectopics will correct
What is the difference between Defibrillation and Cardioversion
Defibrillation = non-synchronised random administration of shock (given any time in cardiac cycle - emergency)
Cardioversion = synchronised administration of shock (given at certain point in cycle e.g. after QRS to shock heart back into normal rhythm)
What are the indications for defibrillation?
Emergencies:
- Pulseless VT
- VF
what are the indications for electrical cardioversion?
- SVT
- AF
- VT with a pulse
Do defibrillation and electrical cardioversion require sedation?
Defibrillation = with or without, done in emergency setting
Cardioversion = almost always sedated first
