Circulatory Adaptation after Mitral Valve Replacement: A Clinical Study Peroperatively and in the Early Postoperative Period

Abstract

The myocardial function and the central and peripheral circulation were studied in a group of 7 patients after mitral valve surgery. The postoperative clinical course was similar in all patients. Peroperatively, after termination of bypass, the blood pressure was low. The total peripheral vascular resistance (TPR) and pulmonary vascular resistance (PVR) were normal. Cardiac output (CO) and stroke volume (SV) were low. Immediately following the operation there was a period with an elevated mean arterial pressure (Pa,m), a raised TPR and a somewhat raised PVR. CO and SV were essentially unchanged. The heart rate was increased. In this phase the oesophageal temperature was rising and 2 patients were shivering. This was followed by a period with decreasing Pa,m and TPR, but essentially no change in CO and SV. VO₂ tended to be lower in this phase than previously, despite a continuous increase in oesophageal temperature. About 5 hours postoperatively, the oesophageal temperature had reached its peak and this was followed by a period of progressive peripheral warming with peripheral cutaneous vasodilatation, during which CO and SV increased, while the heart rate decreased, after which the circulation became stable. The left and right ventricular function, expressed as the relation between LVSWI and mean left atrial pressure (Pla,m), and RVSWI and mean right atrial pressure (Pra,m), respectively, varied in the postoperative period and tended to improve at the time of peripheral warming. Postoperative circulatory adaptation, characterized by an initial period of increased systemic vascular resistance followed by a period of systemic vasodilatation and then peripheral warming with stabilization of the circulation, seemed to be the common pattern of reaction in these patients after mitral valve replacement.