Noninvasive Evaluations of Cardiocirculatory Responses to Graded Exercise Using a Sitting Bicycle Ergometer

(2) Hemodynamic Response to Graded Exercise in Essential Hypertension

Abstract

Essential hypertension is an unknown disorder affecting the normal regulation of blood pressure at rest and under the stress of exercise. In this study the hemodynamic response to graded exercise using a sitting bicycle ergometer was evaluated in 59 men with essential hypertension and 37 normotensives by systolic time intervals and Minnesota impedance cardiograph. The hypertensive patients were divided into three groups; group I comprised 18 subjects with labile hypertension; group II, 20 uncomplicated fixed hypertensive subjects with diastolic blood pressure over 90mmHg; group III, 21 hypertensive sujects with left ventricular hypertrophy. The age of hypertensive group covered from 23 to 58 years old. All the hemodynamic changes of those were compared to the age-matched normotensives.
After resting recordings at recumbency, the subects exercised twice with a resting period of 10 minutes in between; first at 50 watts for 5 minutes and at 100 or 125 watts. Continuous respiroventilatory recordings were performed simultaneously.
At rest group I was characterized by a significant increase of oxygen uptake and heart rate, shortened QS₂I and LVETI and normal PEP, while group II and III showed prolonged PEP and shortened LVETI. In addition decreased PTT was shown in group II and III.
Maximal heart rate of group I in exercise was higher than the others. Group III showed the lowest maximal heart rate in exercise, while the systolic blood pressure showed a greater increase. Immediately after mild exercise the percent increment of cardiac output and stroke volume and the decrement of total peripheral resistance were significantly smaller in group I and greater in group II than control, but the circulatory response to higher load of exercise did not differ between group I and control. However the recovery of the cardiovascular values were rapid in group I. LVETI after exercise showed a decrease in group I, but remained unchanged or increased in group II. On the other hand in group III, the increase of cardiac output and stroke volume were less than in group II, although the decrease of total peripehral resistance was not significant. Moreover the prolongation of QS₂I and PEP immediately after exercise were most prominent in group III.
These findings indicate that in response to exercise: (1) in group I, enhanced myocardial contractility and increased afteroad with exercise are found to be mediated by increased sympathetic stimulation, (2) in group II, augmented myocardial contractility in exercise, probably adapted to increased preload, higher blood pressure elevation and so on, is suggested to be more dominant, (3) group III indicates the presence of depressed myocardial contractility and restrictive vascular changes.