IMPORTANCE OF SEVERITY OF CORONARY-ARTERY DISEASE FOR THE TOLERANCE TO NORMOVOLEMIC HEMODILUTION - COMPARISON OF SINGLE-VESSEL VERSUS MULTIVESSEL STENOSES IN A CANINE MODEL

The response of global cardiovascular and regional myocardial function (as seen with sonomicrometry) to continuous, progressive hemodilution (Dextran 70) was compared in dogs with proximal circumflex coronary a rtery stenosis and dogs with proximal circumflex coronary artery and p roximal left anterior descending artery stenoses. Hemodilution-induced failure, defined as greater than 50% loss in function or death of the animal, was determined for systolic shortening in the circumflex coro nary artery and left anterior descending artery territories, mean arte rial pressure, and maximum left ventricular rate of pressure rise. Tim e to failure was compared between groups by log-rank tests. Systolic s hortening of the circumflex coronary artery failed at a similar median time point in both groups (30 minutes in the group with single-vessel stenosis and hemodilution versus 40 minutes in the group with multive ssel stenosis and hemodilution). Systolic shortening of the left anter ior descending artery (80 versus 50 minutes), mean arterial pressure ( 70 versus 50 minutes), and maximum left ventricular rate of pressure r ise (70 versus 40 minutes), however, failed significantly later (p < 0 .01) in animals with single circumflex coronary artery stenosis, A mar ked increase (+50%) in systolic shortening of the left anterior descen ding artery was observed during hemodilution only in the circumflex co ronary artery stenosis group. The better hemodilution tolerance in the circumflex coronary artery stenosis group may be explained by the com pensatory increase in myocardial contractile function in non-coronary flow-compromised myocardium, which seems to be crucial for global card iovascular stability during hemodilution in the presence of coronary s tenoses.