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[Effects of selective beta adrenergic block on myocardial contractility. Relative role of negative inotropic and
Abstract:
Left ventricular function was studied in 15 patients both before and after intravenous administration of Practolol (an agent blocking selectively the heart beta-adrenergic receptors (beta 1)), while the heart rate was constant by right atrial pacing. The negative inotropic effect linked to the negative chronotropic effect of the beta-adrenergic blockage, represented approximately one quarter of the overall depression of the contractility. Right atrial pacing determined a decrease of the left ventricular end-diastolic pressure and an increase of the pacing rate by 20% above the spontaneous heart rate, after administration of 30 mg of Practolol, brought the contractility back to its control level.
Insights
Practolol (beta 1 blocker) reduced heart contractility, but pacing normalized function. This study clarifies beta-blocker effects on left ventricular function.
Area of Science:
- Cardiology
- Pharmacology
Context:
- Investigating the effects of beta-adrenergic receptor antagonists on cardiac function.
- Assessing the interplay between chronotropy and inotropy in the heart.
Purpose:
- To evaluate the impact of selective beta 1-adrenergic blockade with Practolol on left ventricular function.
- To determine the extent to which negative chronotropic effects contribute to the overall negative inotropic impact of beta-blockers.
Summary:
- Left ventricular function was assessed in 15 patients before and after Practolol administration, with heart rate controlled by atrial pacing.
- The study found that the negative inotropic effect of beta-adrenergic blockade accounted for approximately one-quarter of the total contractility depression.
- Increasing the pacing rate by 20% above the spontaneous heart rate, following Practolol administration, restored contractility to baseline levels.
Impact:
- Provides insights into the mechanisms underlying beta-blocker-induced cardiac depression.
- Demonstrates the potential of heart rate manipulation to counteract negative inotropic effects of beta-blockers.
- Contributes to understanding the management of cardiac function during beta-adrenergic blockade.