Induced Ischemic Arrest of the Heart: Metabolic Considerations

Normothermic ischemic arrest of the heart as an adjunct to open-heart surgery has gained widespread clinical acceptance. This form of arrest, achieved by simply cross-clamping the ascending aorta to eliminate coronary perfusion, is convenient in that it provides a bloodless operative field and a relaxed myocardium. The upper limit ofthe safe period of such ischemia is generally considered to be in the range of 30 to 45 minutes. 1 Clinical experience has revealed that, in some cases, it is possible to exceed these limits with relative impunity. However, about half of the deaths during cardiac surgery and in the early post-operative period are associated with some degree of ischemic necrosis of the inner third of the myocardium, the characteristic lesion of prolonged ischemic arrest of the total heart. 2 , 3 • Safety in elective arrest of the heart thus becomes a problem of great importance in cardiac surgery.