Changes of cardiac performance in renal failure

Clinical and experimental studies were carried out in order to evaluate the role of myocardial dysfunction in the genesis of circulatory congestion associated with renal failure. Among the patients with chronic renal failure, those with circulatory congestion had greater blood volume and higher venous pressure while lower cardiac index and stroke work index than those without circulatory congestion. After peritoneal dialysis, although blood volume and venous pressure decreased in both groups, cardiac index increased in the former while it decreased in the latter group. In 15 dogs, acute renal failure was produced by ligating both ureters. As uremia developed, blood volume and left ventricular end-diastolic pressure increased with or without an increase in cardiac index. The depression of ventricular function curve was evident in all the dogs. The peritoneal dialysis performed at this stage resulted in a prompt recovery of left ventricular end-diastolic pressure with minimum change in cardiac index. The measurement of dp/dt/IIT also indicated a depression of myocardial contractility at uremic stage and its recovery after dialysis. We conclude that impairment of myocardial function is implicated in the development of circulatory congestion in renal failure.

Influence of changes in heart rate, aortic pressure and flow rate upon experimental coronary insufficiency

This study was designed to evaluate the role of heart rate, aortic pressure, and aortic flow in the development of coronary insufficiency following acute coronary stenosis. In dogs, each of these parameters was controlled at a predetermined level while the left anterior descending coronary artery was constricted with a small screw clamp. The critical coronary pressure (CCP), i.e. the pressure below which a rise of left atrial pressure could be detected, was determined at various levels of hemodynamic load. Increases in aortic pressure, elevation of the heart rate and an increase in aortic flow rate were all associated with an elevation of the CCP and an increase in tension-time index (TTI). The changes in CCP were most striking when TTI was increased by aortic flow rate change. These findings suggest that with high aortic pressure, further constriction of coronary artery is required to precipitate coronary insufficiency, that the level of pacing required to induce coronary insufficiency is a useful index in assessing the degree of coronary stenosis, and that an augmentation of aortic flow rate is an important factor in the initiation of coronary insufficiency.