Prior studies of the effect of hemodialysis on left ventricular function have not distinguished between the removal of uremic toxins and the change in cardiac filling volume. To separate these effects, left ventricular function was examined by serial echocardiography in five stable hemodialysis patients before and after three different dialysis procedures: (a) hemodialysis with volume loss, (b) ultrafiltration (volume loss only), and (c) hemodialysis without volume loss. The patients were similarly studied under control conditions and after increased (5° of head-down tilt for 90 min) and decreased (lower body negative pressure) cardiac filling volume. After hemodialysis with volume loss, end-diastolic volume (EDV) decreased from 167 to 128 ml (P < 0.001) and end-diastolic volume (ESV) decreased from 97 to 51 ml (P < 0.001) without a change in stroke volume (SV). Ejection fraction increased from 42 to 52% (P < 0.001) and mean velocity of circumferential fiber shortening (VCF) increased from 0.61 to 1.04 circumferences (circ)/s (P < 0.001). After ultrafiltration, EDV decreased from 167 ml to 124 ml (P < 0.001) and SV from 73 ml to 39 ml (P < 0.001), without significant changes in ESV or VCF. In contrast to the maneuvers in which volume loss occurred, after hemodialysis without volume loss ESV decreased from 95 to 66 ml (P < 0.001) and SV increased from 74 ml to 97 ml (P < 0.001) without changes in EDV. EF increased from 44 to 59% (P < 0.001) and VCF increased from 0.64 to 1.26 circ/s (P < 0.001). Ventricular function curves plotted from data obtained under conditions of altered cardiac filling volume before and after the three dialysis maneuvers demonstrate that ultrafiltration produced a pure Frank-Starling effect, while hemodialysis with or without volume loss produced a shift in the ventricular function curves, which demonstrated an increase in the contractile state of the left ventricle. The changes in left ventricular function produced by regular hemodialysis are the combined effects of a decrease in EDV and an increase in the contractile state of the left ventricle.
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