Improved myocardial performance after aortic cross clamping by combining pharmacologic arrest with topical...

In 22 dogs, we compared the protective effects of combining topical hypothermia and cardioplegia to those of either technique alone on myocardial flow, distribution, metabolism, compliance, and performance after 1 hour of aortic cross clamping. Topical hypothermia alone caused redistribution of coronary flow away from the subendocardium (endocardial/epicardial flow fell from 1.13 to 0.77) and reduced left ventricular compliance and performance severely (48% depression of ventricular function). Cardioplegia alone caused redistribution of flow toward the subendocardium (endocardial/epicardial flow increased to 1.4) and decreased compliance and function moderately (31% depression). In contrast, combined topical hypothermia and cardioplegia caused no significant change in left ventricular flow distribution, compliance, or performance. We concluded that the normal heart can be cross clamped safely for up to 60 minutes (no myocardial depression) only when cardioplegia and topical hypothermia are used in combination (P less than 0.01).