The 12 lead ECG during sinus rhythm (panel A) in a patient with enhanced atrioventricular nodal conduction (EAVNC). The ECG shows a normal PR interval and QRS complex without evidence of preexcitation. During atrial fibrillation (AF) (panel B), there is a rapid ventricular response of up to 270 beats/min, a result of EAVNC and a short AV nodal refractory period.
