The role of nitrates on regional subendocardial ischaemia--studies with endocardial monophasic action potentials during pacing-induced angina
Donaldson, R.M.; Taggart, P.; Swanton, H.; Fox, K.; Rickards, A.F.; Noble, D.
Zeitschrift für Kardiologie 72(Suppl 3): 162-167
1983
ISSN/ISBN: 0300-5860 PMID: 6421008 Document Number: 203399
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.