Bidirectional VT before degenerating into VF (leaky ryanodine receptor disease) or digoxin toxicity
AD - young - exercise triggered arrhythmias in the setting of a structural normal heart which feels like type I QT prolongation but not
present. Resting ECG normal. Diagnostic Gold Standard is treadmill stress test.
CPVT
Ca induced calcium release (CICR) leaky ryanodine receptors RyR2
Not with Ca receptors on cell membrane but RyR2 on SR that release Ca. Diastolic overload of intracellular Ca
Mainstay therapy is BB. Many reports of ICD storm where shock releases catecholamines triggers VT again and many shocks ensue.
Failure to rescue CPVT patients despite ICD.

Flecainide besides its Na channel blocker activity is a potent Ryanodine receptor stabilizer, it decreases the leak in Rya
receptors
. Left Cardiac sympathetic denervation?

Whenever young adult with normal ECG normal echo and PVCs/VT induced by exercise with beat-to-beat variability: think CPVT