About Video

This recording is taken from the apex area of a young patient. In this recording the S1 intensity is clearly varying. Sometimes it fades out completely replaced merely by a short faint noise of a systolic murmur. In some cycles however the intensity is quite good. The patient had a varying intensity of S1 due to changes in the intensity of M1 caused by varying PR intervals. The patient in fact had congenital complete atrio-ventricular block with essentially a junctional pacemaker driving the ventricles with P waves independent of the ventricular depolarizations. The PR interval was varying in a haphazard manner due to the atrio-ventricular dissociation caused by the A-V block. The varying PR intervals lead to the varying intensity of the M1, the short PR interval producing the loud S1 and the long PR interval producing the soft S1 with variations in between.