The effect of systemic blood pressure on cardio-vascular reflexes in elderly subjects

The evidence for impairment of cardiovascular reflexes by hypertension in elderly subjects is mixed. This study tested the hypothesis that baroreceptor- and non-baroreceptor-mediated responses in elderly subjects differed with hypertension. 54 elderly subjects were studied: 16 with combined hypertension (CT) (blood pressure 184 +/- 4/102 +/- 2 mmHg), 16 with isolated systolic hypertension (180 +/- 3/85 +/- 1 mmHg) and 22 normotensives (NT) (138 +/- 2/76 +/- 1 mmHg). All subjects performed isometric exercise with a handgrip dynamometer. Heart rate (HR), blood pressure and forearm vascular resistance (FVR) responses were then studied to 60 degrees head-up tilt and the cold face stimulus. Baseline FVR, and the response to isometric handgrip, were similar in all groups. Subjects with isolated systolic hypertension manifested greater increases in FVR with tilt (P<0.001), whilst the HR increment was greater in the NT group (P<0.001). Blood pressure changes with tilt were similar in the three groups. With the cold face stimulus (CFS) a rise in FVR of approximately 30% was seen in all groups and blood pressure rose modestly, with the largest increases being seen in the combined hypertensives. This study in elderly subjects indicates significant differences with hypertension in the response to tilt, with an impaired baroreceptor-cardiac reflex being compensated by an augmented baroreceptor-vascular response.