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Effects of heart rate on arterial compliance in men
Y L Liang1, C D Gatzka, X J Du
1Alfred and Baker Medical Unit, Baker Medical Research Institute, Australia.
Insights
Systemic arterial compliance decreases with increased heart rate in humans. This study in male volunteers shows reduced arterial compliance and increased pulse wave velocity when heart rate is elevated via atrial pacing.
Area of Science:
- Cardiovascular Physiology
- Arterial Mechanics
- Hemodynamics
Background:
- Arterial compliance is a critical determinant of left ventricular afterload.
- Previous studies in rats indicated that arterial compliance decreases with elevated heart rate (HR).
- The relevance of this phenomenon in humans required further investigation.
Purpose of the Study:
- To investigate the effect of increased heart rate on systemic arterial compliance in human subjects.
- To determine regional changes in arterial compliance using pulse wave velocity measurements.
Main Methods:
- Nine healthy male volunteers (age 20-30 years) participated.
- Systemic arterial compliance (SAC) was measured using the diastolic area method.
- Carotid-to-femoral and femoral-to-dorsalis pedis pulse wave velocities (PWV) were assessed.
- Heart rate was manipulated using intravenous metoprolol and transesophageal atrial pacing (56, 80, and 100 b.p.m.).
Main Results:
- Increasing HR from 56 to 80 b.p.m. significantly increased mean arterial pressure (MAP) and decreased SAC (0.48 to 0.33 ACU).
- Both carotid-femoral and femoral-dorsalis pedis PWV increased significantly with elevated HR.
- Further HR increase to 100 b.p.m. led to a further decrease in SAC (0.24 ACU) and increased PWV, without significant MAP changes.
Conclusions:
- Systemic, central, and peripheral arterial compliances decrease in vivo with an increase in heart rate induced by atrial pacing in humans.
- These findings highlight the dynamic relationship between heart rate and arterial properties, impacting cardiovascular load.
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.