St. Thomas' Hospital cardioplegia for myocardial preservation during prolonged aortic cross-clamping

The effectiveness of St. Thomas' Hospital cardioplegia for myocardial preservation during prolonged aortic cross-clamping was analyzed in a clinical series of 100 consecutive cardiac surgical patients identified as having aortic cross-clamp times greater than 120 minutes. Hospital mortality from all causes was 8%, but only one of these 8 patients succumbed from immediate primary failure of the myocardial preservation protocol. Severe but reversible low cardiac output syndrome occurred in 5 patients, and in 4 of them there had obviously been a primary failure in cardiac protection. Peri-operative, clinically "silent" myocardial infarction could be demonstrated in retrospect by electrocardiographic criteria in 3 other patients. Post-operative complications occurred in 26 patients, many of them having several complications at the same time. Paired left ventricular and right ventricular prebypass and post-bypass biopsies processed for cytochemical and biophysical investigation were available from one third of the patients. Only 2 cases showed a severe deterioration. There was lack of correlation between the duration of aortic occlusion and operative mortality rate, incidence of peri-operative infarction, and occurrence of low cardiac output syndrome post-operatively. The results thus indicate that St. Thomas' Hospital cardioplegia is a very effective means of myocardial protection during prolonged periods of aortic cross-clamping.