Physiological Evaluation of Beta-Blockers versus Vasodilator Treatment in Hypertensive Patients by Cardiopulmonary and Bioimpedance Cardiography Exercise Tests

Objective: To evaluate and compare the physiological antihypertensive effect of beta-blockers vs. vasodilators by cardiopulmonary exercise test (CPET) and by bioimpedance hemodynamic cardiography (ICG).
Design and Methods: 42 pts, 24 males and 18 females, were divided into two groups:
A)16 lone hypertensive pts treated only with vasodilator agents.
B)26 lone hypertensive pts treated only with beta-blocking agents.
A CPET and a bioimpedance cardiogragpy were performed in all the pts while taking their medications.
The following CPET indices were measured during exercise: HR, BP, O2-consumption(VO2),
O2-pulse(O2P), Ventilatory anaerobic threshold(VAT), and Respiratory exchange ratio(RER). The bioimpedance parameters were: HR, BP, Cardiac output (CO) and index, Stroke volume (SV) and index, Systemic vascular resistance (SVR) and index, and Left cardiac work (LCW) and index. The two tests were performed within two weeks apart.
Peak values of the cardiopulmonary indices were compared among the two groups, as well as the bioimpedance parameters, for each index separately, and P values less than 0.05 were considered statistically significant.
Results: The following table summarized the CPET results:
Group N age peak-HR* peak-VO2* peak-O2P* VAT(%VO2-max) peak-RER
A 16 58+/-13 90+/-8# 96+/-9# 108+/-13# 55+/-8# 1.17+/-0.12
B 26 59+/-10 69+/-12& 69+/-11& 102+/-33# 43+/-9& 1.17+/-0.1
*Expressed by % related to normal predicted values.
Statistically significant: # vs & or $; & vs $.
Significant hemodynamic differences between group A vs. B were observed as well:
CO – 4.5 L/min+-0.8 vs. 5.6+-0.9 (p<0.05); SV – 64 ml+-8 vs. 76+-9 (p<0.05);
SVR – 1572+-381u vs. 1150+-355u (p<0.05) and LCW – 4.7+-0.9u vs. 6+-1u (p<0.05).
Conclusions: A significant physiological disadvantage was shown in the treatment of beta-blockers compared to vasodilators in pts with lone hypertension by both, the CPET and the bioimpedance hemodynamic cardiography. It is suggested that the negative inotropic and chronotropic effects of beta-blockers cause reduction of CO which increase SVR and afterload, which further reduce CO.