Topical cardiac hypothermia for myocardial preservation

We compared moderate (29° C.) and profound (5° C.) (ice chips) cardiac hypothermia for myocardial preservation during aortic cross-clamping for 30 or 60 minutes in a canine right heart bypass preparation. Ventricular function deteriorated significantly at 29° C. but not at 5° C. Maximum dp/dt declined only after 60 minutes of ischemia at 29° C, and Vmaxdecreased after one hour at either temperature. Lactate and pyruvate washout were greater after 29° C., and pyruvate production persisted after 60 minutes of ischemia at 29° C. Reactive hyperemia was greater after 30 minutes of ischemia at 29° C. Reactive hyperemia was greater after 30 minutes of ischemia at 29° C., and total coronary flow remained elevated after 60 minutes of ischemia at 29° C. Coronary flow distribution was not altered by hypothermia. Ultrastructural changes were primarily time dependent and not temperature dependent. Ice-induced subepicardial injury was not evident in the ultrastructure or by flow distribution. Sixty minutes of profound topical cardiac hypothermia is moderately well tolerated by the canine heart, but functional and structural alterations are evident.