Long-term survival rates after prolonged aortic cross-clamping with St. Thomas' Hospital cardioplegia.

Prolonged aortic cross-clamping (in excess of 120 min) was necessary in 154 cardiac surgical patients. St. Thomas' Hospital cardioplegia was used for myocardial preservation. Quantitative polarization microscopy enabling quantitative birefringence measurements to assess the change in birefringence of the muscle fibres in response to the addition of buffer containing ATP and calcium (i.e. myocardial contractility) was used to detect whether there had been any deterioration in right or left ventricular myocardium during the bypass period. 30 day survival was 90%, long-term (60 months) survival was 80%. In single valve replacements, patients with aortic valvular replacement had 100% survival up to 92 months, whereas patients with mitral valvular replacement had survival rates of 83% after 12 months and 27% after 60 months. Survival rates after 60 months were 89% for coronary artery bypass grafting, 80% for multiple valve replacements, and 74% for combined valvular and coronary artery bypass grafting surgery. Quantitative birefringence assessment of function showed that in the surviving patients 5% had functional deterioration during bypass whereas in the non-surviving patients 70% had functional deterioration. It may be concluded that after cardiac surgery necessitating prolonged aortic cross-clamping--once the initial operative problems are overcome--reasonable long-term results can be obtained by using St. Thomas' Hospital cardioplegia.