Effect of Changes in Ventricular Rate on Forearm Blood Flow and Systemic Arterial Pressure in Patients with Artificial Pacemakers

Abstract

The effect of sudden changes in heart rate at rest on forearm blood flow, using strain-gauge plethysmography, and brachial arterial pressure was studied in six patients being maintained with external pacemaking for complete heart block. Heart rate was changed suddenly from a slow idioventricular to a normal rate of 70 beats/min, from 70 to 150 beats/min, from slow idioventricular to 150 beats/min suddenly, and from 150 to a slow pacemaker-induced or idioventricular rhythm also suddenly. Sudden changes in heart rate caused only small and non-significant changes in forearm blood flow when measured immediately after and within approximately one minute of the rate change. Forearm pulse volume decreased in all patients and arterial pulse pressure decreased in all but one patient immediately afer sudden increases in ventricular rate. A sudden decrease in ventricular rate caused immediate increases in forearm pulse volume and arterial pulse pressure. In each instance, these changes occurred from one beat to the next and could be related to the diastolic filling time. It is concluded that following sudden changes in heart rate over a wide range forearm blood is relatively constant, whereas forearm pulse volume changes in proportion to diastolic filling time. During these circumstances changes in forearm pulse volume presumably reflect changes in left ventricular stroke output, and these changes appear to occur from one beat to the next.

Key Words:

• Artificial pacemaker
• blood pressure
• forearm blood flow
• forearm pulse volume
• heart rate
• pulse pressure
• stroke volume