Cardiovascular response to orthostatic tilt in patients with severe congestive heart failure.

Baroreflex mediated haemodynamic responses and aortic pulsatile stretch were studied in patients with congestive heart failure due to ischaemia. Seven patients with severe congestive heart failure (baseline angiographic ejection fraction 21(3)% (mean(SEM); left ventricular end diastolic volume and pressure 351(43) ml and 22(3) mmHg respectively) were compared with seven control subjects whose angiographic ejection fraction was 74(3)%. Passive 45 degrees upright tilt was used to unload baroreceptors. Aortic pulsatile stretch (pulsatile distension as percentage of diastolic diameter) was calculated from echocardiographic measurements of aortic diameters. Upright tilt caused a significant decrease in cardiac filling pressures in patients with congestive heart failure, as in control subjects. During tilt control subjects had substantially increased systemic vascular resistance and heart rate and decreased stroke volume, but arterial pressure, cardiac index, and aortic pulsatile stretch were maintained constant. Patients with congestive heart failure developed peripheral vasodilatation, had no increase in heart rate, and failed to maintain arterial mean and systolic pressures in the tilted position. They had, however, maintained a constant pulse pressure and increased cardiac index, stroke volume, and aortic pulsatile stretch. The response to upright tilt in patients with congestive heart failure may be explained by faulty sympathetic reflexes, causing vasodilatation and hypotension rather than vasoconstriction, and a rise in stroke volume due to the decrease in afterload.