Arterial baroreceptor control of peripheral vascular resistance in experimental heart failure.

Heart failure is known to impair arterial baroreceptor control of heart rate. To determine if baroreceptor control of peripheral vascular resistance is also impaired, heart rate and hind limb vascular responses to phenylephrine and nitroglycerin administration were compared in control dogs and in dogs with heart failure produced by chronic rapid ventricular pacing. Baroreflex control of the heart rate was depressed in the dogs with heart failure, as evidenced by a reduced slope of the blood pressure-to-heart rate relationship (controls: -2.5 +/- 0.3 beats/mm Hg versus heart failure: -1.5 +/- 0.2 beats/mm Hg [(p less than 0.04)]). Arterial blood pressure in the dogs with heart failure was also reduced (controls: 90 +/- 3 mm Hg versus heart failure: 75 +/- 3 mm Hg [(p less than 0.01)]). Nevertheless, dogs with heart failure exhibited normal slopes of the blood pressure versus hind limb vascular resistance relationship (controls: -2.4 +/- 0.4 units/mm Hg versus heart failure: -2.9 +/- 0.5 units/mm Hg [(p = NS)]), consistent with preserved baroreflex control of the peripheral vasculature. These data suggest that heart failure impairs arterial baroreflex control of heart rate and lowers the baroreflex pressure operating range but does not alter baroreflex control of peripheral resistance.