P mitrale and right ventricular hypertrophy
P mitrale of left atrial enlargement is manifest as broad notched (M shaped) p wave in lead II, classically seen in mitral stenosis. The broad negative P wave in V1 is also indicative of left atrial overload. qR pattern in V1 with T wave inversions in anterior leads is suggestive of right ventricular hypertrophy. The axis appears to be in the north-west or indeterminate region, which could be a manifestation of extreme right axis deviation due to right ventricular hypertrophy as a consequence of pulmonary hypertension in mitral stenosis. T waves in V5 and V6 are unusually tall. Lead II rhythm strip at the bottom of the tracing documents a normal sinus rhythm, which can anytime degenerate into atrial fibrillation in this case with gross left atrial overload. Such degeneration into atrial fibrillation can cause rapid initial deterioration in clinical status, sometimes presenting as pulmonary edema. Patients with severe pulmonary hypertension due to obliteration of pulmonary vascular bed can be sometimes be protected from pulmonary edema as the right ventricular output is restricted to certain extend, which could also be due to right ventricular dysfunction and associated tricuspid regurgitation.