Abstract 2899: Patients with Unrecognized Myocardial Infarctions Have Smaller Infarct Size, Lesser Ischemia but Similarly Poor Prognosis as Patients with Recognized Myocardial Infarctions
Background: Unrecognized myocardial infarctions (UMI), as diagnosed by surveillance electrocardiography (ECG), have been shown to carry the same poor prognosis as recognized myocardial infarctions (RMI). The reasons behind the equally poor prognosis are not well understood but since the prognosis after RMI is dependent on infarct size, ischemia and ejection fraction (EF), we hypothesized that the poor prognosis of UMI patients would be explained by the same.
Methods: The study group consisted of 5430 patients who underwent 2 day stress and rest Tc-99m sestamibi studies between 3/1991 and 6/1999. Infarct size and EF were quantitated and the extent of ischemia was measured by sum difference score (SDS) with SDS = 0 for a non-ischemic sestamibi study Survival was determined by a follow-up survey (median of 6 years). UMI were diagnosed if ECG showed Q wave MI in the absence of history of RMI.
Results: Patient subsets included 346 UMI, 628 RMI and 4456 subjects without MI (No MI). Despite smaller infarct size, higher EF and less ischemia (see table⇓), UMI prognosis was as poor as that of RMI (9 year survival 57% vs. 55% with No MI survival at 73%; p<0.001). UMI were associated with increased mortality (p<0.0001) after adjustment for clinical risk factors, infarct size and SDS.
Conclusions: UMI patients have smaller infarct size, lesser ischemia and higher EF than RMI patients. The increased mortality associated with UMI is independent of infarct size, ischemia and ejection fraction, and requires further study.