The effect of hypothermic intermittent aortic cross-clamping (ACC) on myocardial metabolism in dogs on cardiopulmonary bypass (CPB)

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MYOCAP.DIAL PROTECTION IN OPEN-HEART SURGERY: COMPARISON OF THE EFFICIENCY OF CHEMICAL CARDIOPLEGIA VS INTERMITTENT ISCHEMIA PLUS REPERFIJSION. J. Schaper, U. Schmidt, H. Scheld, F. Hehrlein, Max-Planck-Institute, Bad Nauheim; Department of Cardiovascular Surgery, University Giessen, Federal Republic of Germany. Myocardial protection (MP) during heart surgery, though continuously improved, is not yet perfect, and new methods are constantly investigated. A standardized ultrastructural evaluation of cardiac biopsies (B) was used for the differentiation of ischemic injury (I) after induced cardiac arrest in 120 patients (pts) undergoing coronary bypass surgery (ACVB). HP was achieved by cardioplegia (C) according to BretSchneider (30 pts), Bleese (30 pts) or the St. Thomas Hospital solution (30 pts) and in 30 pts by ventricular fibrillation and intermittent ischemic intervals (I I) followed by coronary reperfusion (rep). General and topical hypothermia were identical in all pts. Number of ACVBs varied from 2-8, time of cardiac arrest or I I ranged from 20-105 min. Chemical C produced, by ultrastructural criteria, subcellular I of moderate degree which increased with ischemic time. I I plus rep produced ischemic I of greater and unpredictable severity; intracellular edema of myocytes and capillary end&helium was excessive; damage was unrelated to ischemic time or n of ACVBs. Conclusion: Chemical C provides satisfactory MP, I I plus rep cause very severe ischemic damage and extreme myocardial edema, and may not be recommended for MP during cardiac surgery.

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DIFFERENCES CARDIDPLEGIA. Departments

IN ELECTRICAL J.S. Juggi, of Physiology

AND P. and

MECHANICAL Braveny, Cardiology,

H.J.

RECOVERY FROM ISCHEMIC HEART ARREST AND Shuhaiber, A.M. Yousof, G. Telahoun, Faculty of Medicine, Kuwait University,Kutit

The course of recovery of heart activity (assessed by heart rate, A-V conduction time, monophasic action potentials, contractile force and perfusion rate) from cold ischemic arrest was studied on isoiated perfused rat hearts. The effect of control ischemia (2 min perfusion at 2DoC prior to stop)was compared with various cardioplegic -protective formulations based on high K+ content. During control ischemia the heart activity extinguished only gradually: action potentials were biphasic, A-V conduction extremely prolonged and contractions slow and relatively strong. Upon reperfusion (3pC) the recovery of electrical activity was almost instantaneous and normalized within 2 min.whereas,the contractile force remained substantially depressed In contrast, K+- rich solutions stopped the heart within several cycles; recovery was greatly delayed and transitorily associated with severe arrhythmias(A-V block, repetitive depolarizations during prolonged plateau, ventricular fibrillation). Neverthless, the action potentials as well as the contractile force virtually normalized in ID-15 min. High concentrations of glucose and calcium antagonists further improved the recovery from ischemic arrest. The data indicate that the electrical and mechanical activity do not recover in parallel, and obviously on different conditions. (Supported by Kuwait University MY-007 Research Grant.)

309THE EFFECr OF HYPOTHEKIUC INTEFu+ITTENT AORTIC CROSS-CLAiiING (ACC) ON ,$YOCAHDIAL j$E'lXBOLISM IN DOGS ON CARDIOPULriONARY BYPASS (CPB). F.H. van der Veen, G.J. van der Vusse, T. van der Nagel, P. Willemsen and W.A. Coumans. Departments of Physiology, University of Limburg, Maastricht, the Netherlands. Hypothermic (25'C) intermittent ACC is widely used during aorta-coronary bypass surgery. We have examined the effect of repetitive ischemia and reperfusion on cardiac metabolism in a dog model (~12). Four periods of ischemia (10 min) and reperfusion (15 min) were applied. At the end of each period of ischemia myocardial tissue content of ATP and Creatine phosphate (CP) had decreased by 22 and 61% respectively, and inorganic phosphate (Pi) raised by 550% (median values). There was no consistent change for glycogen. During 15 min of reperfusion the tissue contents of these variables turned back to normal pre-ischemic values. Although Lactate, pi and K+ were released from the heart in measurable amounts during the initial phase of each reperfusion period, the total quantity released reflected only a minor part Of the content present in the heart at the end of the ischemic period.-Fe c_opamption of oxygen was high in the immediate reperfusion phase