Precordial ST segment mapping. 2. Effects of oxygen inhalation on ischemic injury in patients with acute myocardial infarction

Abstract

Precordial ST segment mapping was serially applied in the Coronary Care Unit for the study of the effect of oxygen inhalation on the ischemic injury in 17 patients with acute anterior transmural myocardial infarction. A 49 lead ECG system was used. The sum of all ST elevations (sigma ST) recorded was taken as an index of magnitude of ischemic injury and the number of recording sites showing ST elevation (NST) was taken as an index of extent of ischemic damage. Stability of the precordial maps was observed over a period of 1 hr while the patients were on ambient air. Oxygen inhalation for a mean of 66 min resulted in a fourfold increase of PaO2 and a mean of 16% reduction of both sigma ST and NST. When the patients were returned to ambient air breathing, a mean of 13% increase of sigma ST and 19% of NST from the levels recorded during oxygen inhalation were observed. Levels of sigma ST and NST on ambient air following discontinuation of oxygen inhalation were not significantly different from the corresponding values from maps recorded before onset of oxygen breathing. Blood pressure and heart rate remained unchanged throughout the study. Clinical status of the patients was unchanged during the study period save for 2 patients who showed changes in intensity of their chest pain.