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Potential deleterious haemodynamic effects of glyceryl trinitrate on myocardial ischaemia in man
Insights
Glyceryl trinitrate infusions effectively reduced myocardial ischemia in patients with coronary heart disease. Both low and high doses showed similar benefits, with adverse effects being minimal and not increasing ischemia.
Area of Science:
- Cardiology
- Pharmacology
Background:
- Glyceryl trinitrate is commonly used for angina.
- Its dose-dependent effects on myocardial ischemia require further investigation.
Purpose of the Study:
- To evaluate the adverse effects of low and high dose glyceryl trinitrate infusions on myocardial ischemia.
Main Methods:
- Studied 10 patients with coronary heart disease undergoing glyceryl trinitrate infusions.
- Measured cardiac venous flow using thermodilution and sampled blood for metabolic studies.
- Provoked angina with atrial pacing to compare pre-infusion and post-infusion states.
Main Results:
- Both low and high doses of glyceryl trinitrate equally reduced myocardial ischemia.
- Systolic aortic pressure decreased significantly with both doses, more so with the high dose.
- Myocardial oxygen uptake decreased due to reduced preload and afterload, particularly with the high dose.
- Transmural perfusion gradient decreased with the high dose, potentially limiting further ischemia reduction.
Conclusions:
- Adverse effects of glyceryl trinitrate infusion are minimal.
- Neither low nor high doses increase myocardial ischemia in patients with coronary heart disease.
Abstract:
The potential adverse effects of glyceryl trinitrate on myocardial ischaemia were studied using low and high dose infusions in 10 patients with coronary heart disease. Cardiac venous flow was measured by the thermodilution technique and blood was sampled for metabolic studies. Angina pectoris was provoked by atrial pacing before drug infusion and the same heart rate was regained with low and high doses of glyceryl trinitrate. Both doses reduced myocardial ischaemia equally. The low dose of glyceryl trinitrate reduced mean systolic aortic pressure from 145(23) to 128(23) mm Hg and the high dose further to 103(9) mm Hg. Myocardial oxygen uptake decreased owing to a combined reduction in preload and afterload with the low dose and was substantially more reduced with the high dose owing to a further afterload reduction. Transmural perfusion gradient did not change with the low dose of glyceryl trinitrate but fell significantly with the high dose. This fall in myocardial perfusion probably accounts for the lack of further reduction in ischaemia with the high dose. Thus the adverse effects of glyceryl trinitrate infusion are small and do not increase myocardial ischaemia.