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Hemodynamic effects of atrial pacing and prenalterol infusion in patients taking beta-adrenergic blocking drugs
Insights
Prenalterol, a beta-adrenergic agonist, enhanced cardiac function in patients with coronary artery disease under beta-blockade. The drug improved heart contractility and ejection fraction, with effects related to blockade levels.
Area of Science:
- Cardiology
- Pharmacology
Background:
- Coronary artery disease (CAD) poses significant cardiovascular risks.
- Beta-adrenergic agonists are used to modulate cardiac function.
- Assessing drug efficacy during existing beta-blockade is crucial for patient management.
Purpose of the Study:
- To evaluate the inotropic and chronotropic effects of prenalterol in patients with CAD.
- To determine the dose-response relationship of prenalterol during chronic beta-adrenergic blockade.
- To assess the impact of prenalterol on left ventricular function and hemodynamics.
Main Methods:
- Nine patients with angiographically confirmed CAD were studied.
- Prenalterol was administered in incremental doses (2.5, 5.0, 7.5 mg) during chronic beta-blockade.
- Cardiac function was assessed using heart rate, left ventricular dP/dt max, pulmonary artery wedge pressure, and left ventricular cineangiography.
Main Results:
- Prenalterol increased heart rate and left ventricular dP/dt max in a dose-dependent manner.
- Pulmonary artery wedge pressure decreased significantly.
- Independent of heart rate changes, prenalterol demonstrated a significant inotropic effect, increasing left ventricular dP/dt max.
- Ejection fraction increased significantly (0.73 to 0.83).
Conclusions:
- Prenalterol exhibits potent inotropic effects in patients with CAD, even under beta-adrenergic blockade.
- The drug's efficacy is dose-related and influenced by the degree of beta-blockade.
- Prenalterol may be a valuable therapeutic option for improving cardiac function in specific patient populations.
Abstract:
Prenalterol, a beta-adrenergic agonist, was given to nine patients with angiographically proved coronary artery disease. Subjects were studied during chronic beta-adrenergic blockade. The adequacy of blockade was assessed by the exercise heart rate response and by plasma concentrations of blocking agents. After incremental doses of 2.5 mg, 5.0 mg and 7.5 mg of prenalterol, heart rate was increased by 20%, 24% and 38%, respectively, and left ventricular dP/dt max by 55%, 73% and 61%, respectively. Systolic and diastolic blood pressures did not change significantly; pulmonary artery wedge pressure fell from 10 +/- 0.5 mm Hg to 7.1 +/- 0.9 and 6.7 +/- 0.7 mm Hg after 2.5 mg and 5.0 mg, respectively (p less than 0.01 for both). The net inotropic response to prenalterol was assessed, independent of the chronotropic response, using incremental atrial pacing before and after drug infusion. At identical heart rates, left ventricular dP/dt max increased by 40%, 49% and 48% after 2.5 mg, 5.0 mg and 7.5 mg, respectively. Left ventricular cineangiography before and after infusion showed an increase in ejection fraction from 0.73 +/- 0.02 to 0.83 +/- 0.03 (p less than 0.001). Plasma prenalterol concentration estimations demonstrated a clear, dose-related inotropic response, the level of response in each patient being largely determined by the degree of beta-adrenergic blockade at the time of the study.