Biatrial enlargement in biventricular HCM
P waves in lead II has a duration of 120 msec and amplitude of 0.3 mV, suggesting biatrial overload. The pattern is that of P mitrale or an M shaped P wave. P wave in V1 has a sharp upstroke of 0.2 mV indicating right atrial overload and deep and wide negative deflection indicating left atrial overload. This biatrial overload has occurred because of biventricular hypertrophic cardiomyopathy which produces diastolic dysfunction of both ventricles and consequent atrial enlargement. The prominent biphasic deflections in mid precordial leads going beyond the recording strip is indicative of biventricular hypertrophy. The deep and wide Q wave in V6 is due to the septal hypertrophy.