Prolonged atrio-ventricular conduction and aortic insufficiency.

The haemodynamic and electrocardiographic data of 10 patients with aortic insufficiency were reviewed. None of them had received a digitalis preparation, and all had a significantly longer P-R interval than 10 similarly studied normal patients (mean P-R 0·213 and 0·153 second respectively, p<0·001) thus corroborating previous reports of the association of atrio-ventricular conduction delay and aortic insufficiency. Left ventricular end-diastolic pressure was approximately the same or higher than pulmonary artery systolic pressure in three patients and higher than pulmonary artery end-diastolic pressure in seven patients. An analysis of the timing of atrio-ventricular events suggested that an earlier atrial systole (due to P-R prolongation) enabled an increment of forward flow which would otherwise be precluded by the premature closure of the mitral valve associated with aortic insufficiency. Due to the advantageous timing, left atrial and therefore right heart pressures were lower, thus tending to protect the pulmonary vascular bed.