[Modification of sympathetic hyperactivity by drugs. Short-term pharmacologic experiments using parasympathomimetics and beta-receptor blockaders in humans]

Disparate hemodynamic responses to mental challenge after antihypertensive therapy with beta blockers and calcium entry blockers

The hemodynamic response to mental challenge was studied in 40 male outpatients with mild essential hypertension. The patients were treated randomly either with a beta adrenoreceptor blocker (oxprenolol) or with a calcium entry blocker (nitrendipine). Cardiovascular reactivity was evaluated with two different mental arithmetic tasks before and six months after treatment by continuously measuring systolic and diastolic pressure (ultrasonic Doppler device), heart rate (electrocardiography), and stoke volume (impedance cardiography). Patients in both treatment groups had equal decreases in arterial pressure and the same pressures at rest. In patients receiving calcium entry blockers, mental challenge provoked an increase in stroke volume and a decrease in total peripheral resistance similar to results in the pretreatment phase. In contrast, beta adrenoreceptor blockade reversed the hemodynamic response pattern to a distinct decrease in stroke volume (p less than or equal to 0.05) and an increase in total peripheral resistance (p less than or equal to 0.05). In addition, an attenuated heart rate response (p less than or equal to 0.01) and a larger increase in diastolic pressure (p less than or equal to 0.01) were found in the beta blocker group compared with the calcium entry blocker group. Although beta blockers and calcium blockers produce equal decreases in arterial pressure, beta blockers evoke an abnormal hemodynamic response to mental challenge, whereas calcium entry blockers preserve the physiologic reactivity pattern of the untreated state.