AMPK Methods and Protocols

In younger patients (below 35 years), SCD usually arises due to

very rapid anterograde conduction of a supraventricular arrhythmia

(e.g., atrial fibrillation) directly over an accessory pathway—i.e.,

pre-excited supraventricular arrhythmia—which may degenerate

into a lethal ventricular arrhythmia [29]. In older patients (over

35–40 years), SCD is thought to more frequently reflect the sudden

onset of complete heart block or asystole resulting in hemodynamic

collapse. It is possible that other pathogenic mechanisms may be

involved in cases with particularly massive cardiac

hypertrophy [24].

5.2 Clinical
Electrophysiology

5.2.1 Atrial Arrhythmia

Symptoms caused by atrial tachyarrhythmias usually commence

between the end of adolescence and the third decade of life.

Indeed, paroxysmal atrial flutter and fibrillation are responsible

for most symptomatic cases among young adults. The resulting

ventricular heart rate may be very rapid in the setting of conduction

over an associated accessory pathway with short refractory period

and can result in SCD (Fig.9). Fatal thromboembolic stroke in

Fig. 8Typical presenting ECG features associated with a pathogenic mutation inPRKAG2. 12-lead ECG of a
26-year-old male Arg302GlnPRKAG2mutation carrier with a history of paroxysmal atrial fibrillation and
syncope. It demonstrates sinus bradycardia, atrial ectopy, and ventricular pre-excitation with a pattern
suggestive of a left-sided accessory pathway with a very short PR interval which does not increase during
the atrial extrasystole

PRKAG2 syndrome 601