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Effect of timolol maleate on pacing induced myocardial ischaemia
Insights
Timolol maleate improved exercise tolerance in patients with coronary artery disease by reducing heart rate and myocardial contractility. This beta-blocker therapy enhanced myocardial metabolism and increased tolerance to pacing stress.
Area of Science:
- Cardiology
- Pharmacology
Background:
- Coronary artery disease (CAD) poses significant challenges to myocardial function and exercise capacity.
- Understanding the hemodynamic and metabolic effects of beta-blockers like timolol maleate is crucial for managing CAD patients.
Purpose of the Study:
- To evaluate the impact of intravenous timolol maleate on coronary and systemic hemodynamics.
- To assess changes in myocardial metabolism and plasma catecholamine levels during stress in CAD patients.
- To determine the clinical efficacy of timolol maleate in improving exercise tolerance.
Main Methods:
- Ten patients with confirmed coronary artery disease underwent rapid atrial pacing to induce angina.
- Hemodynamic parameters, myocardial metabolism (lactate exchange), and plasma catecholamines were measured before and after intravenous timolol maleate administration.
Main Results:
- Timolol maleate reduced resting and pacing cardiac output and resting heart rate, without affecting arterial blood pressure.
- Left ventricular stroke work index decreased during pacing; coronary sinus blood flow remained unchanged.
- Nine out of ten patients showed clinical improvement, with a prolonged mean pacing time to angina, suggesting increased tolerance to stress.
Conclusions:
- Intravenous timolol maleate enhances tolerance to atrial pacing stress in patients with coronary artery disease.
- The observed improvement is attributed to reduced myocardial contractility and decreased lipolysis, leading to better myocardial metabolism.
- Timolol maleate demonstrates potential as a therapeutic agent for improving exercise capacity in CAD patients.
Abstract:
The effects of timolol maleate administered intravenously on coronary and systemic haemodynamics, myocardial metabolism, and plasma catecholamine concentrations were assessed in 10 patients with confirmed coronary artery disease. Rapid atrial pacing to the onset of angina was performed in all patients. Timolol reduced cardiac output at rest and during pacing and reduced resting heart rate but did not affect arterial blood pressure. Left ventricular stroke work index fell during pacing. Coronary sinus blood flow was unchanged, but pulmonary artery diastolic pressure rose after timolol. The drug produced clinical improvement in nine of the 10 patients with prolongation of the mean pacing time to angina. There was evidence of improved myocardial metabolism with a change from production to extraction of lactate: Arterial noradrenaline concentrations at rest rose after timolol. In these patients with coronary artery disease timolol produced an increased tolerance to atrial pacing stress, which appears to be due to a combination of effects including reduced myocardial contractility and decreased lipolysis.