M. Sakuma et al., EFFECTS OF CHANGES IN AFTERLOAD ON REGIONAL WALL-MOTION IN ACUTE ISCHEMIC CANINE HEART, Tohoku Journal of Experimental Medicine, 169(1), 1993, pp. 31-41
The aim of the present study was to examine effects of changes in afte
rload on regional myocardial motion in acute ischemia. Ischemic and no
n-ischemic segment lengths of the left ventricular free wall were meas
ured by miniature ultrasonic gauges in eleven open chest dogs with the
pericardium preserved. In a stable state after left anterior descendi
ng coronary artery occlusion, peak left ventricular pressure was varie
d by the infusion of angiotensin II (n = 8) and sodium nitroprusside (
n = 8). To exclude effects of preload on the responses, end-diastolic
lengths of the non-ischemic region before and during infusion of each
drug were matched with vena caval occlusion. When peak left ventricula
r pressure elevated from 113 +/- 2 (mean +/- S.E.)mmHg to 145 +/- 6, i
n isovolumetric contraction phase, degree of active shortening in the
non-ischemic region and that of paradoxical expansion of the ischemic
region did not change. In ejection phase, active shortening of the non
-ischemic region decreased from 1.38 +/- 0.11 mm to 1.06 +/- 0.10 but
that of the ischemic region remained unchanged. Stroke volume decrease
d from 14.5 +/- 1.3 ml to 10.8 +/- 1.0. When peak left ventricular pre
ssure decreased from 111 +/- 4 mmHg to 101 +/- 6, in isovolumetric con
traction phase, active shortening of the non-ischemic region decreased
from 0.90 +/- 0.13 mm to 0.76 +/- 0.15 and paradoxical expansion of t
he ischemic region reduced from - 0.95 +/- 0.11 mm to - 0.80 +/- 0.11.
In ejection phase, shortening of the non-ischemic region increased fr
om 1.05 +/- 0.13 mm to 1.31 +/- 0.15 but that of the ischemic region d
id not change. Stroke volume increased from 11.5 +/- 1.3 ml to 14.0 +/
- 1.4. These results indicate that in acute isehemia, changes in isovo
lumetric shortening of the non-ischemic region and paradoxical expansi
on of ischemic region are related with each other in isovolumetric con
traction phase when afterload is altered and suggest that stroke volum
e is affected by the shortening of ejection phase in the non-ischemic
region.