In a “normal” electrocardiogram (ECG), the transition of the QRS axis in the precordial leads occurs between leads V 3 and V 4 (i.e., there is a dominant S in V 3 and a dominant R in V 4).

PERHAPS they are running against the clock? R. A. Cotmore, Mansfield, Notts. BECAUSE of the effect of the Earth's rotation, an athlete running anti-clockwise will have a slight advantage, resulting in ...