EFFECTS OF BETA-BLOCKADE ON THE RELATION BETWEEN HEART-RATE AND VENTRICULAR DIASTOLIC PERFUSION TIME DURING EXERCISE IN SYSTEMIC HYPERTENSION

It is well known that cardiovascular response to exercise involves sympathetic stimulation of the heart and peripheral vessels and that β blockade interferes with adrenergic response during exercise. When a decrease in heart rate is prevented by atrial pacing, regional myocardial function and blood flow in ischemic areas tend to be more depressed after β blockade, suggesting that β blockade could unmask an α2 adrenergic vasoconstriction, worsening regional blood flow and function.1 An alternative hypothesis might be that β blockade modifies the relation between diastolic time and heart rate. In fact, there is also some evidence that β blockade impairs the postexercise diastolic time in patients with coronary artery disease.2 However, this effect is not clearly explained, since ischemia alone could interfere with diastole duration.3,4 Moreover, the effect of β blockade on diastolic time during exercise is still unknown. This study investigates the effects of β blockade on diastolic time during exercise in hypertensive patients without stress-induced myocardial ischemia. © 1991.