AJP - Heart and Circulatory Physiology, Vol 251, Issue 4 834-H840, Copyright © 1986 by American Physiological Society
Effects of verapamil on regional myocardial diastolic function in pacing-induced ischemia in dogs
P. D. Bourdillon, W. J. Paulus, T. Serizawa and W. Grossman
The upward shift in the left ventricular diastolic pressure-volume
relationship during pacing-induced angina may be related to increased
cytosolic calcium availability with persistent contractile element
interaction in diastole. To assess the influence of calcium channel
blockade on these changes in diastolic function, we studied the effects of
verapamil in dogs with 90% stenoses of the left anterior descending and
circumflex coronary arteries. Ultrasonic crystals were implanted in the
myocardium to monitor anterior wall and lateral wall segment length. Left
ventricular pressure was measured with a micromanometer catheter. The left
atrium was paced at a rate 1.5 times that of the resting heart rate for 3
min. An upward shift of the left ventricular diastolic pressure-segment
length relationship developed after pacing tachycardia, with a rise in the
left ventricular end-diastolic pressure (LVEDP) from 4.7 +/- 1.2 to 14.3
+/- 2.2 mmHg (P less than 0.01, n = 13), and pressure was higher at any
segment length throughout diastole. Increases in end-diastolic segment
length were small (12.3 +/- 1.9 to 12.7 +/- 2.0 mm for the anterior wall, P
less than 0.05; 15.1 +/- 1.4 to 16.4 +/- 1.5 mm for the lateral wall, P
less than 0.01). Pretreatment with verapamil (0.08 mg/kg iv) did not reduce
this upward shift: LVEDP rose from 6 +/- 1 to 16 +/- 1 mmHg (P less than
0.01, n = 7) and there were similar small increases in end-diastolic
segment length.(ABSTRACT TRUNCATED AT 250 WORDS)
