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Haemodynamic effects of intravenous beta-blocking drugs in coronary heart disease
Insights
Intravenous beta-blocking drugs impact cardiac function differently based on their properties. Drugs with intrinsic sympathomimetic activity cause less depression of left ventricular pumping function in myocardial infarction patients.
Area of Science:
- Cardiology
- Pharmacology
Background:
- Intravenous beta-blocking drugs are increasingly used in early myocardial infarction.
- Comparative hemodynamic effects of these drugs with varying ancillary properties are not well understood.
Purpose of the Study:
- To compare the hemodynamic effects of intravenous beta-blocking drugs with different pharmacological properties in patients with coronary heart disease and acute myocardial infarction.
Main Methods:
- The study assessed the dose-response relationship of intravenous beta-blocking drugs on left ventricular pumping function.
- Hemodynamic effects were evaluated in patients with stable coronary heart disease and acute myocardial infarction.
Main Results:
- All intravenous beta-blocking drugs reduced left ventricular pumping function in a dose-dependent manner.
- Drugs with intrinsic sympathomimetic activity caused less depression of left ventricular pumping function.
- This effect is attributed to increased myocardial contractility and reduced afterload via beta-adrenoceptor stimulation.
- A similar, though less pronounced, separation was observed in acute myocardial infarction patients.
Conclusions:
- Intrinsic sympathomimetic activity in beta-blocking drugs may offer hemodynamic advantages by preserving left ventricular function.
- The clinical benefit of these hemodynamic advantages in patients requires further confirmation through formal clinical trials.
Abstract:
Intravenous beta-blocking drugs are being increasingly used in early myocardial infarction but little is known of the comparative haemodynamic effects of drugs with different ancillary pharmacological properties. In patients with stable coronary heart disease all intravenous beta-blocking drugs reduce left ventricular pumping function in a dose-response fashion. The reduction in cardiac mechanical activity is directly related to the dose and inversely related to the degree of intrinsic sympathomimetic activity possessed by each drug; it is independent of the property of 'cardioselectivity'. The lesser depression of left ventricular pumping performance after beta-blocking drugs with intrinsic sympathomimetic activity is probably due to two primary pharmacodynamic effects: a) increased myocardial contractile activity due to stimulation of post-synaptic beta 1- and presynaptic beta 2-adrenoceptors in the sinus node and ventricular myocardium; b) reduction in left ventricular afterload consequent upon the fall in systemic vascular resistance resulting from stimulation of vasodilator beta 2-adrenoceptors in peripheral resistance vessels. A similar but less marked haemodynamic separation of beta-blocking drugs with and without intrinsic sympathomimetic activity is observed in patients with acute myocardial infarction. The quantitative difference in the haemodynamic effects of intravenous beta-blocking drugs in angina pectoris compared to their effects in acute myocardial infarction is probably due to the higher level of sympathetic stimulation and sensitivity to beta-blockade in the latter. It has yet to be shown by formal clinical trial that the haemodynamic advantages attributable to the possession of intrinsic sympathomimetic activity by a beta-blocking drug are translated into clinical benefit.