Non-invasive monitoring of cardiac function during haemodialysis

The cardiac function during haemodialysis has been studied using a non-invasive method in a prospective investigation of 7 elderly patients, all of whom had an enlarged heart on the chest X-ray and in all of whom experience had shown that a fall in blood pressure developed during haemodialysis. The cardiac output was determined by impedance cardiography and showed no significant changes during dialysis. A significant rise was observed in the heart rate and this was found to reach a maximum during the periods in which the blood pressure was lowest. Left ventricular function was evaluated from the systolic time intervals, PEP/LVET (PEP = pre-ejection period and LVET = left ventricular ejection time) and the noninvasive contraction index BP diastolic/PEP. The electromechanical systole (QS2), LVET and the non-invasive contraction index all decreased significantly during dialysis, while PEP and PEP/LVET were significantly increased. All the changes were most pronounced at the time when the blood pressure was lowest. It is concluded from the investigation that the cause of the fall in blood pressure during haemodialysis of elderly patients with impaired cardiac function may be ascribed to transient reduction in left ventricular performance.