Cardioplegia: the protection of the myocardium during open heart surgery: a review.

Cold chemical cardioplegia is currently the method of choice for providing a still, relaxed and unobstructed operating field during open heart surgery. This procedure involves aortic cross clamping, with the resulting tissue ischemia being modified by coronary infusion of cold chemical solutions, together with the application of topical hypothermia. This paper defines some of the detrimental cellular changes which occur as a result of the induced ischemia, and considers the mechanisms by which cardioplegia can afford extensive protection. Three components of protection are defined and discussed: firstly, energy conservation through the rapid induction of diastolic arrest; secondly, slowing metabolic and degenerative processes through the use of hypothermia; thirdly, selective prevention or reversal of various unfavourable ischemic changes. On the basis of these three components, it is possible to derive a number of guide lines for the formulation and use of safe and effective cardioplegic solutions.