The effect of nifedipine on arterial pressure and reflex cardiac control.

Abstract

Nine patients with untreated essential hypertension (mean casual blood pressure 173/109 +/- 14/7 mm Hg) (+/- SD) were studied in the control state and after 16 weeks of treatment with nifedipine, 10 mg orally every 8 hours. Direct arterial blood pressure monitored continuously over 24 hours showed that nifedipine significantly reduced systolic and diastolic blood pressure throughout the day and the night. The variability of blood pressure was not altered by nifedipine therapy. There was no significant change in heart rate after nifedipine therapy. Chronic nifedipine therapy increased forearm blood flow and decreased forearm vascular resistance, consistent with its action as a vasodilator. The absolute blood pressure responses to tilt, handgrip and cold were reduced, but the percent increase in pressure was not altered by therapy. Plasma renin activity was not altered by chronic nifedipine therapy. At each study, the sensitivity and setting of the baroreflex response to i.v. phenylephrine was measured. After chronic nifedipine therapy there was resetting of the sinoaortic baroreflex and an increase in its sensitivity. Successful control of blood pressure with nifedipine led to a significant reduction in the left ventricular mass index.

The effects of acute and chronic dihydropyridine calcium antagonist therapy on baroreflex sensitivity: a re-analysis using the sequence method

“…We have re-analysed previously published data from our department [1][2][3] on patients given calcium antagonists both acutely and chronically, to determine the influence of dihydropyridine therapy on continuous, spontaneous 24-h baroreflex sensitivity (BRS). Despite having been used routinely in the treatment of hypertension and ischaemic heart disease for 20 years, the safety of calcium antagonists has recently been called into question.…”

“…8 BRS is impaired in hypertension, but the influence of chronic dihydropyridine therapy on BRS is unclear and the results of previous studies on the effects of calcium antagonists have been inconsistent. [1][2][3]9 Patients and methods Twenty-three patients were included in this reanalysis. Ten were studied after an acute dose of a dihydropyridine calcium antagonist and 21 after chronic therapy.…”

Baroreflex sensitivity changes with calcium antagonist therapy in elderly subjects with isolated systolic hypertension

“…45 Although it is unlikely that left ventricular mass would be altered to any great extent by 6 weeks of antihypertensive treatment, previous studies in younger subjects with moderate combined hypertension have found left ventricular mass to be significantly reduced after only 16 weeks of nifedipine therapy, so some alteration cannot be entirely discounted. 13 The tilt test examines the integrated response of the cardiovascular system to orthostatic stress and does not discriminate between arterial high-pressure baroreflex responses and those evoked by the cardiopulmonary low-pressure receptors that are stimulated by pooling of blood in the lower limbs. Although the two responses can be separated to an extent by use of low and high-level lower body negative pressure, 46 passive tilt has the advantage of simulating the stresses to which the cardiovascular system is subjected during normal activities and when the drug is used in clinical practice.…”

“…7,8 Several studies have addressed the issue of the modification of arterial baroreceptor-cardiac reflex sensitivity (BRS) with antihypertensive treatment in young and elderly subjects, predominantly with either angiotensin-converting enzyme inhibitors [9][10][11][12] or with calcium channel blocking drugs. [12][13][14][15][16][17] The basis for the observed increases in BRS with treatment, although not seen in every study, 17 is thought to be an increase in large artery compliance permitting resetting of baroreflexes. On this basis it could be proposed that elderly subjects with isolated systolic hypertension (ISH), who represent over half of all elderly hypertensives 18 and who have demonstrable reductions in large artery compliance when compared to their peers with combined hypertension [19][20][21] (usually attributed to more advanced arteriosclerosis), may not respond with the same alterations in BRS with treatment as have been described in younger subjects.…”

“…On this basis it could be proposed that elderly subjects with isolated systolic hypertension (ISH), who represent over half of all elderly hypertensives 18 and who have demonstrable reductions in large artery compliance when compared to their peers with combined hypertension [19][20][21] (usually attributed to more advanced arteriosclerosis), may not respond with the same alterations in BRS with treatment as have been described in younger subjects. 13,14 This may lead to impaired cardiovascular homeostasis and practical therapeutic problems such as orthostatic intolerance. 22 Conversely, an increase in BRS may lead to improved cardiovascular reflex responses and reduced BP variability.…”