Independent effects of heart rate and exercise on left ventricular wall movement measured by reflected ultrasound

Abstract

Movement of the posterior wall of the left ventricle was assessed using an ultrasound technique in 11 normal subjects at rest and immediately after maximal erect exercise. Maximal posterior wall velocity was measured as the maximal slope of the wall movement from the end-diastolic position to the end-systolic position, and posterior wall excursion was measured as the maximal amplitude of movement anteriorly. Maximum posterior wall velocity increased from a mean of 37 mm/sec at rest to 96 mm/sec after exercise ( P < 0.001), and posterior wall excursion increased from 4.00 mm at rest to 6.8 mm after exercise ( P < 0.001). The effect of heart rate alone on posterior wall movement was evaluated using the technique of atrial pacing. Increasing the heart rate in 6 patients resulted in a reduction in both posterior wall velocity and excursion. At identical heart rates in 5 patients there was a significant increase in both posterior wall velocity and excursion during exercise compared to atrial pacing. It is suggested that changes in posterior wall movement reflect alterations in left ventricular function independent of heart rate, and that these changes can be measured by reflected ultrasound.