Modification of regional myocardial performance caused by blood withdrawal and infusion in acute ischaemic canine heart

Abstract

The effect of changes in preload on regional myocardial motion in acute ischaemia was examined by miniature ultrasonic gauges after left anterior descending coronary artery occlusion in eight open chest dogs with the pericardium preserved. Left ventricular end-diastolic pressure was varied by blood withdrawal and infusion. When preload changed, isovolumetric shortening in the non-ischaemic region was inversely related to that in the ischaemic region. When preload decreased, stroke volume decreased and was accompanied by a decrease in end-diastolic length and ejection shortening in the non-ischaemic region together with an increase in isovolumetric bulging in the ischaemic region. When preload increased, these variables changed in opposite directions. These results indicate that in acute ischaemia: (1) changes in isovolumetric shortening in the non-ischaemic and ischaemic regions were related with each other when the level of volume expansion varied, and suggest that; (2) stroke volume is affected by end-diastolic length, ejection shortening in the non-ischaemic region and isovolumetric bulging in the ischemic region.

Effects of Tachycardia on Regional Wall Motion in Acute Ischemic Canine Heart

“…These results seem to differ from those of the previous reports (Akaishi et al 1985;Noma et al 1988a, b;Ishikawa et al 1993;Sakuma et al 1993) which showed that the increase of the isovolumetric shortening in the non-ischemic region reflected the increase of the isovolumetric bulging in the ischemic region, both in the preload change and in the afterload change. The changes of the end-diastolic relations between the non-ischemic and ischemic regions partly affected the relationship between these two regions in the isovolumetric phase.…”

“…The period from end-diastole to aortic valve opening was determined as the isovolumic contraction phase, and the period from aortic valve opening to end-systole as the ejection phase. For comparison of the segment lengths in the ischemic and the non-ischemic regions, each measured value was normalized with the end-diastolic length of control being 10 mm (Shirato et al 1978;Ishikawa et al 1993). Total systolic shortening equals end-diastolic length minus end-systolic length.…”

“…In regional ischemic heart, the effects of changes in preload, afterload and contractile state on regional wall motion have been reported (Akaishi et al 1985;Lew and Ban-Hayashi 1985;Noma et al 1988a, b;Ishikawa et al 1993;Sakuma et al 1993). It has been shown that the degree of isovolumetric shortening in the non-ischemic region reflects the degree of paradoxical systolic expansion in the ischemic myocardium.…”

“…When the heart rate increased, the end-diastolic length (preload) were decreased but, at least, the left ventricular pressure at the timing of aortic valve opening (afterload) was not decreased. On the basis of previously reported data on the effect of preload and afterload (Lew and Ban-Hayashi 1985;Ishikawa et al 1993;Sakuma et al 1993), tachycardia may precede the increase of the shortening in the non-ischemic region during the isovolumetric shortening phase. However, differing from this estimation, the shortening of the nonischemic region showed no significant change with the increase in heart rate.…”

“…On the other hand, the increase in the bulging in the ischemic region with the increase in heart rate can be partly explained by the reduction of the end-diastolic length (Ishikawa et al 1993). In the isovolumetric contraction phase, the increment of the shortening in the non-ischemic region has been explained by the augmentation of bulging in the ischemic region that is increased when the preload is decreased or the afterload increased (Lew and Ban-Hayashi 1985;Noma et al 1988a;Ishikawa et al 1993;Sakuma et al 1993). But when the heart rate increased, the increase of the bulging in the ischemic region was not accompanied by shortening in the non-ischemic region.…”