Cardiac Conditions that Cause Sudden Death Flashcards
Define sudden cardiac death
Event that is non-traumatic, non-violent, unexpected and resulting from sudden cardiac arrest within 6hrs of previously witnessed normal health
Is Brugada syndrome a channelopathy or cardiomyopathy?
Channelopathy
What is a channelopathy?
Ion current imbalance + development of early/late depolarizations
What is a cardiomyopathy?
Arrhythmogenesis related to scar/electrical barrier formation and subsequent re-entry
Are channelopathies normal or abnormal at screening?
Often normal
Are cardiomyopathies normal or abnormal at screening?
Often abnormal
What are the mechanisms of arrhythmia?
Automaticity - thing that keeps node firing
Trigger
Re-entry e.g. scar
When do ‘after depolarizations’ occur?
interrupt phase 2,3 or 4 of cardiac action potential
What do after depolarizations lead to?
Triggered activity - sustained cardiac arrhythmia e.g. fibrillation
When do early after depolarizations occur?
During phase 2 or 3
What happens during phase 4 of the cardiac action potential?
Repolarization phase
Ventricular myocyte at rest
K+ channels open
Resting membrane potential = -90mV
What happens during phase 0 of the cardiac action potential and why?
Fast Na+ influx
Depolarization
What happens during phase 1 of the action potential cardiac cycle?
Closure of Na+ channels and transient K+ efflux
What happens during phase 2 of the action potential cycle?
Ca++ influx
Plateau
What happens during phase 3 of the cardiac action potential cycle?
Closure of Ca++ channels and K+ efflux
Rapid repolarization
What type of activity do after depolarizations lead to?
Triggered activity - sustained cardiac arrhythmia
What causes an early after depolarization?
Increase in the frequencyof abortive action potentials before normal repolarization is complete
Why might phase 2 be interrupted by an early afterdepolarization?
Augmented opening of Ca2+ channels
Why might phase 3 be interrupted by an early afterdepolarization?
Opening of Na2+ channels
What do early afterdepolarizations cause?
Torsades de Pointes
What is Torsades de Pointes?
Specific form of VT in patients with long QT syndrome.
What might Torsades de Pointes look like on ECG?
Rapid, irregular QRS complexes
What can cause early afterdepolarizations?
Hypokalemia
Drugs that prolong QT interval
Are the vast majority of cardiac conditions dominantly or recessively inherited?
Dominantly
When do delayed afterdepolarizations occur?
Phase 4 after repolarization complete but before another action potential would normally occur
What causes delayed afterdepolarizations?
Elevated cytosolic Ca2+ concentrations
What drug toxicity can cause elevated cytosolic Ca2+ concentrations?
Digoxin
What causes the delayed afterdepolarization?
Overload of sarcoplasmic reticulum causes spontaeous Ca2+ release after repolarization
Causes relased Ca2_ to exit cell through 2Na+/2Ca2+ exchanger
Results in net depolarizing current
Bidirectional ventricular tachycardia is a classical feature of what afterdepolarization?
Delayed afterdepolarization
also catecholaminergic polymorphic ventricular tachycardia/CPVT
What causes QT prolongation?
Less repolarising current prolongs APD (action potential duration)
OR
More depolarising current prolongs APD
Polymorphic VT is triggered by what in congenital LQTS?
Adrenergic stimulation
What is the name of the autosomol dominant congenital LQT syndrome that causes isolated LQT?
Romano-Ward syndrome
What is Jervell and Lange-Nielsen-syndrome?
Is it autosomal dominant or recessive?
Long QT syndrome associated with deafness
Autosomal recessive
Are you likely to die from LQT syndrome?
No
What is the treatment for long QT syndrome?
Beta blockers
What should people with LQTS1 avoid?
Strenuous swimming