Table 1.

Typical ECG features in patients with EA. Modified from the 2014 PACES/HRS consensus statement on the recognition and management of arrhythmias in adult congenital heart disease [14].

Rhythm	Normal sinus rhythm Possible ectopic atrial rhythm Supraventricular tachycardia Atrial fibrillation; intra-atrial reentrant tachycardia (40%)
PR interval	Usually long (1st degree AVB) Short with WPW
QRS axis	Normal Left axis deviation
QRS configuration	Low-amplitude multiphasic atypical right bundle branch block (RBBB) If no RBBB present, consider right sided pathway
Atrial enlargement	Common, with Himalayan p waves
Ventricular hypertrophy	None; diminutive RV
Unique features	Accessory pathway common Q waves present in inferior (II, III, avF) and anterior (V1–V4) leads
Wide complex tachyarrhythmias	Multiple APs have a higher probability of antidromic reciprocating tachycardia Ventricular tachycardias likely a late cause of SCD