Total Arterial Compliance in Ambulatory Hypertension During Selective β1-Adrenergic Receptor Blockade and Angiotensin-Converting Enzyme Inhibition

Aortic root flow and pressure estimates were obtained noninvasively with Doppler echocardiography and calibrated subclavian artery pulse tracing in 30 subjects with ambulatory hypertension in a randomized, crossover study with 4 weeks' treatment and washout periods. Total arterial compliance, assessed by use of a three-element Windkessel model of the arterial tree, increased 42% with atenolol (50-100 mg once daily), and 7% (p = NS) with captopril (25-50 mg twice daily). Atenolol reduced mean arterial pressure by 15%, heart rate by 22%, and cardiac output by 14%, and increased acceleration time of aortic root flow by 17% and stroke volume and ejection time each by 11%. Captopril reduced mean arterial pressure and total peripheral resistance each by 7%. Acceleration time of aortic root flow, ejection time, heart rate, stroke volume, and cardiac output were not significantly changed by captopril. We conclude that total arterial compliance, at the operational blood pressure, increases during selective beta1-adrenergic receptor blockade in subjects with ambulatory hypertension. Although the main mechanism may be a reduction in mean arterial pressure, it should be considered whether reduced heart rate may play an additional role. The nonsignificant increase in total arterial compliance during angiotensin-converting enzyme inhibition may primarily be a consequence of a modest reduction of the mean arterial pressure.