Electrophysiology

There is no conduction down the right bundle branch. However, the septum is depolarized from the left side as usual causing an R wave in the right ventricular lead (V1) and a small Q in the left ventricular lead (V6). Excitation only spreads on its normal pathway to the left ventricle and this causes an S in V1 and an R in V6. There is delayed excitation of the right ventricle and therefore this depolarizes after the left. This causes a second R wave in V1, and a wide S wave in V6.

Reference

1. Surawicz B et al. American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology. American College of Cardiology Foundation. Heart Rhythm Society. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part III: intraventricular conduction disturbances: a scientific statement from the American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart Rhythm Society. Endorsed by the International Society for Computerized Electrocardiology. J Am Coll Cardiol. 2009 Mar 17;53(11):976-81