Does Chronic ST Segment Elevation following Q Wave Myocardial Infarction Exclude Tissue Viability?

Abstract

Purpose: Electrocardiographic (ECG) ST segment elevation lasting 2 or more weeks following Q wave myocardial infarction has been associated with ‘ventricular aneurysm’ and absence of tissue viability. Regional systolic dysfunction may reflect either viable myocardium or scar. Positron emission-tomographic (PET) imaging can distinguish viable from nonviable tissue. We hypothesized that patients with chronic ST segment elevation after Q wave infarction might demonstrate salvageable myocardium in the infarct region. Methods: The ECGs of 1,229 sequential patients undergoing PET scans for viability assessment were reviewed by an electrocardiographer to identify individuals with chronic anteroseptal Q wave infarctions with persistent ST segment elevation exceeding 1 mV. Patients with QRS duration longer than 0.14 ms or rhythm other than sinus were excluded. Viability was considered present if either a reversible stress-induced perfusion defect (ischemia) or a resting perfusion-metabolism mismatch (hibernation) was identified. Results: Anteroseptal ECG Q wave infarction was identified in 132 subjects (74% male, age 61 ± 12 years). Chronic ST segment elevation was present in 84 subjects (64%) and absent in 48. Baseline clinical characteristics and left ventricular systolic function were similar in both groups. 63% of those with and 56% of those without chronic ST elevation had viable myocardium. No relationship was noted between chronic ST segment elevation and the presence or absence of myocardial viability. Conclusions: Chronic ST segment elevation after anteroseptal Q wave myocardial infarction does not exclude myocardial viability in the ‘infarct zone’. Evaluation of residual tissue viability is indicated to assess the benefit of revascularization in patients with Q wave infarction and chronic ST segment elevation.