The prevention of myocardial ischaemia by the method of profound selective myocardial hypothermia during open heart surgery.

A new method of myocardial protection, profound selective myocardial hypothermia has been employed in order to avoid the effects of cardiac ischaemia during aortic cross clamping in the course of operations undertaken under extracorporeal circulation. It consists of the irrigation of the aortic root immediately after cross clamping with 4 liters of Ringer Lactate at 4 degrees C which perfuses the entire coronary bed and induces complete uniform profound coling of the intrapericardial mass to a temperature of approximately 10 degrees C with resultant flat electrocardiogram and cessation of all electrical activity of the myocardium. This inactivity remains complete until the aorta is unclamped permitting reoxygenation and rewarming of the heart with resumption of its function. This method has been used in the course of 250 cardiac procedures involving the use of extracorporal circulation including 177 valve replacements, either aortic or mitral and aortic, 54 saphenous vein bypass procedures, either simple or with valve replacement and 19 other assorted procedures including cardiac transplantation and complex congenital malformations. Thermal, electrocardiographic, hemodynamic, histologic, histochemical and enzymatic observations have proven the minimal significance of the ischemic lesions produced in hearts protected in this manner. The total mortality was 6.4% which proves the value of this method and its superiority over the 2 techniques most often used at the present time, coronary perfusion or topical myocardial hypothermia according to Shumway's method.