EFFECTS OF HEART RATE ON ARTERIAL COMPLIANCE IN MEN

Abstract

1. Arterial compliance is a major determinant of left ventricular afterload. In keeping with earlier experimental data obtained in isolated arterial segments, it has recently been shown in the rat that arterial compliance decreases with an increase in heart rate (HR) induced by atrial pacing. 2. To elucidate the potential relevance of this effect in humans, we investigated nine male volunteers (age 20–30 years; mean 26 years). Systemic arterial compliance (SAC) was measured with the diastolic area method and carotid-to-femoral and femoral-to-dorsalis pedis pulse wave velocities (PWV) were measured to determine regional changes in compliance. Heart rate was first lowered with intravenous metoprolol to 56±2 b.p.m. and then increased by transoesophageal atrial pacing to 80 and 100 b.p.m. 3. Increasing HR from 56±2 to 80 b.p.m. by pacing increased mean arterial pressure (MAP) from 78±2 to 98±1 mmHg (P < 0.001) and then to 102±2 mmHg (P = NS). Systemic arterial compliance fell from 0.48±0.06 to 0.33±0.04 arbitrary compliance units (ACU; P < 0.01), carotid-to-femoral PWV increased from 6.1±0.3 to 6.8±0.4 m/s (P < 0.001) and femoral-to-dorsalis pedis PWV increased from 8.9±0.4 to 10.1±0.5 m/s (P < 0.001). Pacing at 100 b.p.m did not change MAP, but did lead to a further decrease in SAC (to 0.24±0.03 ACU; P < 0.05) and further increases in carotid-to-femoral (7.3±0.4 m/s; P = NS) and femoral-to-dorsalis pedis PWV (11.3±0.4 m/s; P < 0.001). 4. We conclude that systemic, central and peripheral compliances decrease in vivo with an increase in HR induced by atrial pacing.