Electrical and mechanical aspects of left atrial activity.

The relation between abnormalities of the P wave of the electrocardiogram and the left ventricular filling pattern as shown by apex cardiography has been investigated in 76 subjects with either normal hearts or hypertensive/ischaemic heart disease. Deteriorating left ventricular function, as shown by apex cardiography, was associated with increasing negativity of the P wave 'terminal force' in lead Vi. There was a significant association between the amplitude of the 'a' wave of apex displacement and the P wave 'terminal force' in patients without a pathological third heart sound.