Systolic atrial sounds during atrioventricular dissociation: the "wandering" fourth heart sound.

The fourth heart sound consists of low frequency vibrations which are heard in presystole during sinus rhythm. Fourth heart sounds have been described during various phases of diastole in subjects with ventricular pacemakers, by virtue of complete atrioventricular dissociation and/or block.’ Although such sounds are commonly heard during diastole, there has not been adequate emphasis on their occurrence during systole. We describe here the phonocardiograms recorded from patients with right ventricular pacemakers in whom audible fourth heart sounds were heard and recorded during systole. *From The Institute for Cardiovascular Diseases, Good Samaritan Hospital, Phoenix. Supported in part by the Nichols’ MemorialFund. Reprint requests: Dr. Benchimol, Good Samaritan Hospital, Phoenix 85006 Figure 1 shows the simultaneously recorded phonocardiograms, external femoral arterial pulse tracing and electrocardiogram from an 82-year-old patient with a right ventricular pacemaker. The electrocardiogram demonstrates sinus bradycardia (rate, 45/mm), atrioventricular dissociation and a pacemaker-induced ventricular rhythm at a rate of 65/mm. Prominent fourth heart sounds can be seen throughout the tracing, which are recorded during diastole and systole. The most prominent fourth heart sound on the record occurs during late systole and follows the second P wave of the electrocardiogram. Figure 2 shows the simultaneously recorded phonocardiograms, jugular venous pulse tracing and lead 2 of the electrocardiogram in a 68-yearold woman with sinus rhythm, complete heart block and a pacemaker-induced ventricular rhythm. Here,