Effect of experimental heart failure on peripheral sympathetic vasoconstriction

To investigate whether heart failure impairs peripheral sympathetic vasoconstriction, hindlimb vascular responses to lumbar chain stimulation (0.5-20 Hz) were studied in normal dogs and in dogs with chronic heart failure produced by rapid ventricular pacing. At lumbar chain stimulation rates of 0.5-3 Hz, hindlimb vascular responses were comparable in both groups. However, at stimulation rates of 5-20 Hz, vascular responses were significantly attenuated in the dogs with heart failure. Vascular responses to norepinephrine (0.1, 1, and 10 micrograms/min) were not altered. These findings suggest that chronic heart failure results in impaired sympathetic vasoconstriction, probably because of reduced neurotransmitter release. This abnormality may interfere with the capacity of the failing circulation to compensate for a low cardiac output and thereby intensify the severity of heart failure.