Puzzle 2009 02 Answer

Answer

The interpretation of the ECG is rather straightforward. The ventricular rhythm is slow (≤40 beats/ min) and at first glance one may consider this to result from a slow sinus rhythm. In fact, the sinus rhythm is 80 beats/min and 2:1 atrioventricular conduction is present. In the extremity leads the second P wave may be mistaken for a U wave, but in particular in lead V1 the second, blocked P wave is clearly visible. Conduction through the ventricles occurs with a right bundle branch block. Repolarisation is normal. Hence, this ECG is characterised by significant conduction abnormalities, i.e. second-degree AV block and right bundle branch block. Therefore, the most likely reason for her syncopes is a bradycardia and pacemaker therapy seems warranted.