Myocardial Performance Early After Aorto-Coronary Bypass Surgery Cardioplegic Arrest Versus Coronary Perfusion

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Abstract
Haemodynamic adaptation was studied during the first 10 h after aorto‐coronary bypass surgery. In a control group of 12 patients the heart was fibrillating and perfused during cardiopulmonary bypass (at 30°C), and in 11 patients cold cardioplegic arrest was used. The first 4–5 h were characterized by rewarming, with increasing oesophageal temperature, cutaneous vasoconstriction and elevated systemic vascular resistance (SVR). A phase of vasodilation followed. In the control group the oxygen uptake index increased by 57% during rewarming, but the cardiac index (CI) was constant (about 2.8 1 min‐1 m‐2). The arterio‐venous oxygen content difference (AVDo2) therefore increased (max. 3.0 mmol 1‐‐1). The postoperative left ventricular performance was better and the serum levels of aspartate aminotransferase (ASAT) during the first 2 days postoperatively were lower in the cardioplegic patients than in the controls, indicating more efficient myocardial preservation. In the cardioplegic‐hypothermic group, CI was constant at about 3.2 1′min‐1 m‐2 (significantly higher than in the control group) and AVDo2 remained normal during the rewarming period. The heart rate was lower initially in the cardioplegic patients than in the controls, implying a favourable influence on myocardial oxygen consumption. The better myocardial function in the cardioplegic‐hypothermic group was associated with an only moderately increased SVR. This suggests that the elevated SVR in the control group could have been due to myocardial depression.