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Haemodynamic and metabolic effects of timolol (Blocadren) on ischaemic myocardium
Insights
Timolol, a beta-adrenergic blocker, did not reduce myocardial oxygen consumption or metabolic ischemia during induced angina in patients. This study investigated its effects on coronary hemodynamics and heart metabolism.
Area of Science:
- Cardiology
- Pharmacology
Background:
- Angina pectoris poses significant challenges in cardiovascular medicine.
- Understanding the metabolic effects of beta-adrenergic blockers is crucial for managing ischemic heart conditions.
Purpose of the Study:
- To evaluate the impact of timolol on coronary hemodynamics and myocardial metabolism in patients with angina pectoris.
- To determine if timolol reduces myocardial oxygen consumption and metabolic ischemia during pacing-induced angina.
Main Methods:
- Twenty-six patients with angina pectoris received 2.5 mg of timolol intravenously.
- Cardiac venous flow (CVF) was measured using thermodilution; blood samples were analyzed for metabolic studies.
- Angina was induced by atrial pacing; metabolic ischemia was defined by a significant reduction in myocardial lactate extraction ratio (MLE).
Main Results:
- Beta-adrenergic blockade with timolol significantly reduced myocardial oxygen consumption (MVO2) and CVF at rest.
- During pacing-induced angina, MVO2, CVF, myocardial glucose uptake, and MLE remained unchanged.
- Despite decreased systolic aortic pressure and ejection time, timolol did not alleviate metabolic ischemia.
Conclusions:
- Timolol did not reduce myocardial oxygen consumption during pacing-induced angina.
- The study concludes that timolol is ineffective in reducing metabolic ischemia in this specific clinical context.
- Further research may explore alternative therapeutic strategies for managing pacing-induced angina.
Abstract:
The effects of timolol (2.5 mg i.v.) on coronary haemodynamics and myocardial metabolism were studied in 26 patients with angina pectoris. Cardiac venous flow (CVF) was measured by thermodilution technique. Blood was sampled for metabolic studies. Angina pectoris was induced by atrial pacing and the same heart rate was regained after timolol. Metabolic ischaemia was defined as reduction in myocardial lactate extraction ratio (MLE) by at least 50% and to a ratio below 0.15. The study was completed in 22 patients, 9 of whom fulfilled the metabolic criteria for ischaemia. This subgroup did not differ from the total group in any other respect than in lactate metabolism. Beta-adrenergic blockade reduced myocardial oxygen consumption (MVO2) and CVF significantly at rest, but MVO2, CVF, myocardial glucose uptake and MLE were unchanged during pacing despite a decrease in systolic aortic pressure, ejection time and reduced myocardial free fatty acid uptake. Conclusively, timolol did not reduce MVO2 and metabolic ischaemia during pacing-induced angina.