Effect of calcium antagonists on ambulatory blood pressure and its variations

Our previous studies have shown that blood pressure variability is not linked to activity of the adrenergic nervous system but that a small part of the variation is due to vagal nervous tone. The present work investigates whether myogenic activity of blood vessels could be responsible for the blood pressure variations. To test this hypothesis, variability was measured before and after administration of nifedipine, known to decrease spontaneous vascular contractions. In 17 patients with moderate essential hypertension, blood pressure was measured every 30 min for 12 h with a device recording Korotkoff's sounds on tape. Blood pressure variability was defined as the standard deviation of the mean of all readings. Placebo, nifedipine (20 mg b.i.d. in a slow-release formulation) alone and in combination with atenolol (50 mg b.i.d.), and atenolol alone were given double-blind for 3 weeks each. At the end of each period, a 12 h blood pressure profile was recorded. Systolic blood pressure significantly decreased with any of the drugs used; the combination of nifedipine and atenolol caused a greater decrease than that of any of the drugs alone. Diastolic blood pressure only decreased with the combination of nifedipine and atenolol. Nifedipine did not cause significant changes in systolic or diastolic variability; a small but nonsignificant decrease in diastolic variability was seen with atenolol and the combination of atenolol and nifedipine. The present data do not support the hypothesis that blood pressure variability is linked to myogenic vascular activity because no decrease in blood pressure variability was seen with nifedipine.