title: The role of nitrates on regional subendocardial ischaemia--studies with endocardial monophasic action potentials during pacing-induced angina.
abstract: Intracavitary recording of monophasic action potentials (MAP) is a sensitive means of detecting the electrophysiological effects of early or subendocardial ischaemia. The effect of nitroglycerin on the MAP was evaluated during pacing-induced angina in seven patients with localized, reversible ischaemia. Recordings from the ischaemic zone demonstrated a decrease in MAP amplitude and an abnormal rate-corrected shortening of MAP repolarization. The "control" right ventricular MAP showed only the expected rate-dependent decrease in duration throughout the pacing stress test. The ischaemic MAP were unchanged following the intracoronary administration of 100 micrograms nitroglycerin. In contrast, 200-300 micrograms intravenous nitroglycerin produced a normalization of MAP amplitude and duration in spite of continuous pacing at the angina-provoking rate. These changes were preceded by a fall in aortic pressure (from mean 123/84 to 96/62) and subsequent lowering of the rate-pressure product. The major beneficial effects of nitroglycerin on the early electrical changes of pacing-induced ischaemia are thus related to decreased oxygen demand due to cardiac unloading.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000328:Adult; D000787:Angina Pectoris / Q000503:physiopathology*; D001794:Blood Pressure / Q000187:drug effects; D003326:Coronary Circulation / Q000187:drug effects; D003327:Coronary Disease / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D005996:Nitroglycerin / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000187:drug effects
chemical_list: D005996:Nitroglycerin