Delayed timing of heart and arterial sounds in patients with implanted pacemakers.

We have recorded the timing of the heart sounds and the arterial sounds with reference to the onset of each cardiac cycle in 16 patients before and after implantation of a pacemaker prosthesis, and in an additional 18 patients after pacemaker implantation only. The interval between the QRS complex and the Korotkoff sound at diastolic pressure (QKd) is markedly prolonged, from 206 to 294 msec., a change corresponding to 10 standard errors of the mean difference. Likewise, the Q-Korotkoff interval at systolic pressure (QKs) is prolonged from 329 to 414 msec. The interval between the QRS complex and the onset of the first sound (S1) is prolonged by approximately 90 msec., whereas the interval between the QRS and the second heart sound (S2) is prolonged by 70 msec. We noted an associated increase in heart rate, a slight decrease in systolic pressure, an increase in diastolic pressure, a decrease in pulse pressure, and a slight decrease in the deltaP/deltat at the brachial artery measured indirectly and noninvasively.