Noninvasive identification of a high risk subset of patients with acute inferior myocardial infarction

Abstract

Although S-T segment depression of various degrees is known to occur in the precordial electrocardiogram of patients with acute inferior myocardial infarction its prognostic significance is unknown. Left ventricular ejection fraction and regional wall motion were therefore measured noninvaslvely with radionucilde ventriculography and related to the electrocardiographic changes within 48 hours of the onset of acute transmural inferior infarction in 44 patients who had had no previous infarction. The mean ejection fraction of 0.45 ± 0.13 (standard deviation) in Group A (24 patients with greater than 1 mm S-T segment depression in at least two of six precordial leads) was lower (p < 0.001) than that (0.63 ± 0.08) in Group B (20 patients with no or less than 1 mm S-T depression in these leads). A depressed ejection fraction (less than 0.54) was present in 76 percent of patients in Group A and in 10 percent of patients in Group B (p < 0.01). Total wall motion score, a semiquantitative index of regional wall motion abnormality, was lower in Group A (42 ± 6) than in Group B (54 ± 4) (p < 0.001). Severe wall motion abnormalities of remote anteroseptal left ventricular segments were observed in 50 percent of patients in Group A and 15 percent of patients in Group B (p < 0.05). The peak serum MB creatine kinase levels were higher in Group A than in Group B (167 ± 92 versus 84 ± 56, p < 0.001). Left ventricular failure developed in 50 percent of patients in Group A but did not develop in Group B (p < 0.001). Five (19 percent) of 24 patients in Group A died in the hospital (3 from pump failure, 1 from arrhythmia and another from electromechanical dissociation). There were no deaths in Group B. The overall data indicate that patients with inferior wall infarction who have associated precordial S-T segment depression have greater global and regional left ventricular dysfunction presumably due to associated ischemia or infarction in areas remote from the inferior wall and they have relatively high in-hospital mortality and morbidity rates. Early noninvasive detection of this high risk subset may permit the testing of aggresive modes of therapy designed to limit the extent of myocardial ischemic damage with resultant decrease in mortality and morbidity.