Relationship of Blood Pressure to Heart Rate in Isolated Systolic Hypertension

BACKGROUND: Patients with isolated systolic hypertension (ISH) have been noted to be less responsive to β-blockers than patients with essential hypertension (HTN). The purpose of this study was to determine the relationship between blood pressure (BP) and heart rate in ISH. METHODS: A total of 619 patients underwent 24-hour ambulatory BP monitoring. Patients were grouped as normal, HTN, or ISH. Clinical characteristics, mean BPs, and mean heart rate were compared between the groups. RESULTS: Two hundred seventy-one patients had normal BP, 98 had HTN, and 90 had ISH. Antihypertensives were used in 37% with normal BP, 51% with HTN, and 58% with ISH. The pulse pressure was highest for ISH (67 [10] mm Hg), followed by HTN (59 [12] mm Hg) and normal BP (49 [7] mm Hg; P < 0.0001). Heart rate in ISH was 71 [10] beats per minute; slower than that for normal BP (73 [11] beats per minute; P = 0.0464) and HTN (78 [12] beats per minute; P < 0.0001).There was a positive relationship between diastolic BP and heart rate. In ISH, there was a negative relationship between systolic BP and heart rate (slope = -0.18; r = 0.24; P = 0.0209) and a positive relationship between diastolic BP and heart rate (slope = 0.19; r = 0.33; P = 0.0015). CONCLUSIONS: The noted relationship of heart rate to systolic BP and pulse pressure may in part explain the lower efficacy of β-blockers in patients with ISH. The rate-lowering effects of these medications may result in an increase in systolic and pulse pressures.