Copyright © 1983 by the European Society of Cardiology.
© 1983, by the European Society of Cardiology
Haemodynamic effects of intravenous labetalol in hypertensive patients with obstructive coronary heart disease complicated by acute myocardial infarction of recent origin
Rehabilitationszentrum Felbring der PV Arb, Wissenschaflliche Forsehungsstelle der l. Med. Univ. Klinik Wien A-2723 Muthmannsdorf, Austraia
Received 21 January 1982; revised 31 December 1982; .
Requests for reprints to Dr Mulac.
Abstract
The haemodynamic effects of 50 mg labetalol given intravenously were measured at rest, at the peak period during exercise, and 10 min after exercise in 12 patients (mean age 51.2 years) with long standing hypertension (systolic pressure > 160 mm Hg, diastolic pressure > 95 mm Hg) with a history of acute myocardial infarction. All studies were carried out at least 3 months after myocardial infarction. All patients had a positive exercise test with symptoms of angina at the time measurements were made. At rest labetalol lowered mean systolic pressure from 187 mm Hg to 166 mm Hg, and mean diastolic pressure from 90 mm Hg to 82 mm Hg, and there was little change in heart rate, cardiac index, or pulmonary artery and capillary pressure, but stroke work index was lower (P<0.005). At the peak exercise period labetalol reduced the mean systolic pressure from 244 mm Hg to 201 mm Hg, and the mean diastolic pressure from 106 mm Hg to 95 mm Hg, and the mean heart rate from 108/min to 96/min. The cardiac index was also significantly reduced (P<0.001). Ten minutes after exercise, mean systolic and mean diastolic pressures were lower than control values, pulmonary capillary pressure was significantly reduced (P < 0.005), as were stroke work index (P < 0.001), and total peripheral resistance (P < 0.05). Labetalol also reduced the degree of ST segment displacement and the incidence and severity of anginal symptoms during exercise. The results indicate that labetalol improves haemodynamics especially under stress, and improves the patho-physiological mechanism of myocardial ischaemia. The alpha and beta blocking effects of labetalol are balanced in such a way, that, during and following exercise, the haemodynamic benefits of beta blockade outweigh the unfavourable effects, because these are diminished by the concomitant minor degree of alpha blockade.
Key Words: Labetalol • hypertension • coronary heart disease • myocardial infarction