Arrhythmia/channelopathies Flashcards
What are the three most common exacerbators of AF?
Obesity
OSA (but less convincing evidence that managing OSA helps AF)
Alcohol
What is the commonest non-ischemic cause of SCD in young?
Hypertrophic cardiomyopathy
90% of SCD are due to ischemic heart disease
What is the most common rhythm in SCD?
Ventricular fibrillation
Anti-arrhythmic drugs are not beneficial in preventing SCD
What are the indications for ICD?
- Resuscitated VT/VF cardiac arrest (not due to reversible cause)
- VT sustained or symptomatic, not ablatable and failed anti-arrhythmic or LVEF <40%
- Hereditary cardiac conditions (primary and secondary prevention)
- Hypertrophic cardiomyopathy
- Long QT syndrome
- Arrhythmogenic right ventricular dysplasia (ARVD)
- Brugada syndrome - Others - at least 1 month post-MI and LVEF <30%, CHF with LVEF <35%
NOT RECOMMENDED in non-ischemic cardiomyopathy with LVEF <35% (except young people)
What are the predictors of sudden cardiac death in hypertrophic cardiomyopathy?
Resuscitated cardiac arrest (12%) Early symptom onset (6%) Family hx of SCD (esp >1) (6%) VT on Holter (6%) Syncope Septal hypertrophy >30mm Exertional hypotension/ischemia Specific mutations - Myosin R403Q, troponin T
What is the normal QTc interval?
Men - up to 430ms
Women - up to 450ms
What is the channelopathy associated with congenital LQTS?
LQT1 (commonest) - affect K channel (underactive), triggered by exercise (68%) and emotional stress (14%). Associated with Jervell-Lange-Nielsen syndrome with bilateral sensorineural hearing loss
LQT2 - affect K channel (underactive), triggered by emotional stress (49%) and exercise (29%)
LQT3 - affect Na channel (overactive), triggered by sleep/bradycardia
LQT3 event rate is lowest but more malignant
What are the risk factors for syncope/SCD in LQTS?
QTc >500 (esp >600) Prior syncope or resuscitated cardiac arrest Family history of SCD LQT3 in males LQT2 in females Deafness T wave alternans Infant<1yo/neonates
What are the QT prolonging drugs?
Anti-arrhythmics - Class 1 (Procainamide, Flecainide, Lidocaine) and Class 3 (Amiodarone, Sotalol)
Anti-depressant - TCA, SSRI, MAO inhibitor
Antibiotics - Erythromycin, Cotrimoxazole
Antifungal -conazoles
Anti-pychotics - Haloperidol, Lithium, Phenothiazine
Terfenadine, Astemizole, Diphenhydramine
Catecholamines
Diuretic (K wasting)
Methadone
Anti-arrhythmic drug classes
Class 1 - block Na channel (Procainamide, Lidocaine, Flecainide)
Class 2 - beta blocker (block adrenergic receptor)
Class 3 - block K channel (Amiodarone, Sotalol)
Class 4 - calcium channel blocker (Verapamil, Diltiazem)
Class 5 - other or unknown mechanism
Strong risk factors for stroke in the context of AF
Age - scores 2 points
Previous stroke/TIA/thromboembolism - scores 2 points
But if you have valvular heart disease e.g. mitral stenosis - risk of stroke is 20x higher compared to non-valvular 4x
CHA2DS2VASc
CHF HTN Age ≥75 - 2 points Diabetes Stroke/TIA/thromboembolism - 2 points Vascular disease Age 65-74 - 1 point Sex (female)
Maximum score you can get is 9
If ≥2 anticoagulation indicated
If score 1 anticoagulation still probably superior to Aspirin (but except when 1 point only due to female sex without other risk factor)
When do you use NOAC vs Warfarin?
NOAC is superior to Warfarin in non-valvular AF (bleeding risk was similar, less fatal/intracranial bleeding, lower mortality)
When should you use rhythm control for AF?
In young pt usually fit and well and AF onset <48hrs
Flecainide - use if no underlying structural heart disease/CAD, effective in short duration <24hr AF
Amiodarone - can be used in presence of structural heart disease
Cardioversion (DCCV) indicated in haemodynamic instability - severe acute HF, hypotension
Symptomatic persistent AF can be cardioverted but need anticoagulation prior (should be therapeutically anticoagulated for at least 4 weeks
NOTE: AFFIRM study comparing rhythm vs rate control showed no reduction in mortality, higher hospitalisation, no reduction in stroke with rhythm control approach
What is the commonest Long QT syndrome?
LQT1 type is commonest - mutation in K channel KVLQT1/KCNQ1 (underactive)
Triggered by exercise (64%) and emotional stress (14%)
Associated with Jervell-Lange-Nielsen syndrome - bilateral sensorineural hearing loss
Amount of repolarising current reduced leading to increased action potential duration. Myocyte refractory phase lengthened.
What are the features of LQT3?
Mutation in Na channel (SCN5A) - becomes overactive
Slow inactivation of sodium channel results in prolonged Na influx during depolarisation
Can be triggered by bradycardia/sleep - don’t use B-blocker in LQT3
What are the HIGH risk factors for SCD in LQTS?
QTc >500 (especially >600)
LQT1, LQT2, male sex LQT3
What is the treatment for LQTS?
Beta blockers first line in LQT1 and LQT2 types (NOT in LQT3) - Propranolol or Nadolol preferred (they reduce syncope and SCD)
Avoid QT prolonging meds, correct electrolyte imbalance
ICD for primary vs secondary prevention
Family history alone is not an indication of ICD. Not everyone with congenital LQTS have ICD
What is Andersen Tawil Syndrome?
It is LQT7 affecting K channel (KCNJ2 mutation) - autosomal dominant
QT can be prolonged or normal
Can get ventricular arrhythmia - rarely fatal
Periodic paralysis - potassium responsive
Dysmorphic features - hyperteleorism, short stature, micrognathia, broad forehead, scoliosis
What are the features of Brugada syndrome?
Na channel mutation - same as LQT3 but here Na channel is underactive
Autosomal dominant inheritance, common in young south east asian males
Right precordial (pseudo RBBB) ST elevation on ECG - typically V1, V2
Sudden death, VF - especially during sleep
Increased risk of atrial arrhythmia mainly AF
Exacerbating factors are fever, class 1 anti-arrhythmic drugs e.g. Flecainide
Treatment with ICD
All 1st degree relatives should be tested with ECG
Type 1 pattern - coved type ST, T wave negative
Type 2 pattern - saddle back ST, T wave positive or biphasic
What are the features of arrhythmogenic right ventricular dysplasia?
Inherited myocardial disease associated with paroxysmal ventricular arrhythmia and SCD (2nd most common cause of SCD after HCM in young)
ECG - Epilson wave (small positive deflection at the end of QRS complex, this is most specific finding), T wave inversion in V1-V3, localised QRS widening V1-V3
What is catecholamine induced polymorphic VT?
Exercise or emotion induced ventricular arrhythmia - symptoms generally develop <20yo, high mortality 30-50%
Normal QT interval
Most common mutation is Ryanodine receptor mutation (found in myocardial sarcoplasmic reticulum) - autosomal dominant
Rare mutation is Calsequestrin CASQ2 - autosomal recessive
Both mutations act by inducing diastolic calcium release from the sarcoplasmic reticulum —> resulting in intracellular calcium overload —> delayed afterdepolarisation and triggered activity
Treatment with ICD, beta blockers
Genetic testing for any patient suspected of having CPVT and all relatives where a pathological mutation identified
What are the non-selective beta blockers (both B1 and B2)?
Propranolol
Carvedilol - also alpha blocking
Labetalol - also alpha blocking
Nadolol
What are the selective beta blockers (cardioselective, B1)?
Atenolol Bisoprolol Metoprolol Celiprolol Esmolol Nebivolol
