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[Influence of nitrates on regional myocardial blood flow and left ventricular wall motion]
Insights
Isosorbide dinitrate (ISDN) improves myocardial blood flow and ventricular wall motion in coronary artery disease (CAD) patients by reducing coronary resistance. This nitrate therapy is effective in hypokinetic regions but not akinetic or dyskinetic areas.
Area of Science:
- Cardiology
- Nuclear Medicine
- Pharmacology
Background:
- Coronary artery disease (CAD) affects myocardial blood flow and ventricular function.
- Assessing regional myocardial perfusion is crucial for understanding CAD.
- Pharmacologic interventions aim to improve blood flow and cardiac performance.
Purpose of the Study:
- To evaluate regional myocardial blood flow and ventricular wall motion in CAD patients.
- To assess the effects of isosorbide dinitrate (ISDN) on myocardial perfusion and function.
- To elucidate the mechanism of therapeutic action of nitrates in CAD.
Main Methods:
- Computerized gamma-camera system for regional myocardial blood flow measurement.
- Quantitative analysis of ventricular wall motion.
- Administration of isosorbide dinitrate (ISDN) and assessment of its effects.
Main Results:
- Regional blood flow measurements effectively detected hypoperfused myocardium and intervention effects.
- ISDN increased blood flow in hypoperfused regions by 20% and decreased it in normal regions by 14%.
- Improved ventricular wall motion was observed in 65-75% of hypokinetic areas and 20-25% of akinetic areas after ISDN; no improvement in dyskinetic regions.
Conclusions:
- Nitrate-induced reduction in coronary resistance is the primary mechanism for therapeutic effects.
- ISDN improves myocardial perfusion and ventricular function in specific CAD-related wall motion abnormalities.
- Regional assessment is superior to global measurements for evaluating myocardial perfusion and treatment response in CAD.
Abstract:
Regional myocardial blood flow was measured by means of a computerized gamma-camera system in 30 patients with coronary artery disease (CAD) and in 14 healthy control subjects. Ventricular wall motion was quantitatively analyzed in 65 CAD-patients. Global and semiregional blood flow measurements yielded only limited information. In contrast, measurements of regional blood flow permitted detection of hypoperfused myocardium and the effects of pharmacologic intervention. The administration of 15 mg isosorbide dinitrate (ISDN) resulted in an increase in blood flow in post-stenotic hypoperfused myocardial regions of 20p.c. and a decrease in flow through normal myocardium of 14 p.c. These observations represent the adaption of flow to a newly-established level of metabolic demand. This increase in blood flow coupled with a reduction in afterload leads to improved ventricular wall motion in 65-75 p.c. of areas of hypokinetic myocardium and, to a markedly lesser degree, in only 20-25 p.c. of akinetic regions. Dyskinetic regions show no improvement. As compared with the 13ml/loog/min increase in blood flow seen after intracoronary administration of 0.45 mg ISDN in normal coronary vessels, the compromised dilatory capacity of diseased coronary vessels results in a relatively small increase in flow of 6 ml/100 g/min. The reduction of the extravascular component of coronary resistance, thus, appears to be the mechanism primarily responsible for the therapeutic effect of nitrates.