Prognostic significance of location and type of myocardial infarction: Independent adverse outcome associated with anterior location

Abstract

To determine the relative prognostic significance of location (anterior or inferior) and type (Q wave or non-Q wave) of infarction, the hospital course and follow-up outcome (mean duration 30.8 months) of 471 patients with a first infarction were analyzed. Analyses were performed grouping the patients according to infarct location (anterior, n = 253; inferior, n = 218), infarct type (Q wave, n = 323; non-Q wave, n = 148), and both location andtype (inferior non-Q wave, n = 85; inferior Q wave, n = 133; anterior non-Q wave, n = 63; and anterior Q wave, n = 190).Patients with anterior infarction had a substantially worse in-hospital and follow-up clinical course compared with those with interior infarction, evidenced by a larger infarct size (21.2 versus 14.9 g Eq/m2creatine kinase, MB fraction [MB CK], p < 0.001), lower admission left ventricular ejection fraction (38.1 versus 55.3%, p < 0.001) and higher incidence of heart failure (40.7 versus 14.7%, p < 0.001), serious ventricular ectopic activity (70.2 versus 58.9%, p < 0.05), in-hospital death (11.9 versus 2.8%, p < 0.001) and total cumulative cardiac mortality (27 versus 11%, p < 0.001). Patients with Q wave infarction similarly experienced a worse in-hospital course compared with patients with non-Q wave infarction, evidenced by a larger infarct size (20.7 versus 12.7 MB CK g Eq/m2, p < 0.001), lower admission left ventricular ejection fraction (43.7 versus 50.6%, p < 0.001), and a hight, incidence of heart failure (31.9 versus 21.6%, p < 0.05) and in-hospital death (9.3 versus 4.1% p < 0.05). However, there was no increased rate of reinfarction or mortality in hospital survivors with non-Q wave infarction compared with those with Q wave infarction, and total cardiac mortality was similar (16 versus 21%, p = NS).To evaluate the role of infarct location and type independent of infarct size, patients were grouped according to quartile of infarct size, and outcome was reanalyzed within each group. Patients with anterior infarction demonstrated a lower left ventricular ejection fraction on admission and after 10 days than did patients with inferior infarction, even after adjustment for infarct size, as well as a higher incidence of congestive heart failure and cumulative cardiac mortality. When patients were evaluated on the basis of both location andtype of infarction, those with anterior infarction exhibited a worse hospital course and cumulative cardiac mortality than did those with inferior infarction, whether the infarction was non-Q wave or Q wave in type. Life-table analysis of cardiac mortality using the Cox proportional hazards regression model demonstrated that location, but not type, of infarction exerted an independent prognostic effect.Thus, patients with anterior infarction experience a more complicated hospital and follow-up course than do patients with inferior infarction despite adjustment for infarct size and regardless of type of infarction (Q wave or non-Q wave). The disparity between outcomes in patients with anterior as opposed to inferior infarction may be due to coexistent right ventricular infarction in patients with inferior infarction, resulting in less left ventricular impairment relative to the total MB CK released, as well as to differences in topographic responses to infarction between the two sites.