Electrocardiographic infarct size assessment after thrombolysis: insights from the Acute Myocardial Infarction STudy ADenosine (AMISTAD) trial.

BACKGROUND: Noninvasive methods are needed to evaluate reperfusion success in patients with acute myocardial infarction (MI). The AMISTAD trial was analyzed to compare MI size and myocardial salvage determined by electrocardiogram (ECG) with technetium Tc 99m sestamibi single-photon emission computerized tomography (SPECT) imaging. METHODS: Of 236 patients enrolled in AMISTAD, 166 (70 %) with no ECG confounding factors and no prior MI were included in this analysis. Of these, group 1 (126 patients, 53%) had final infarct size (FIS) available by both ECG and SPECT. Group 2 (56 patients, 24%) had myocardium at risk, FIS, and salvage index (SI) assessed by both SPECT and ECG techniques. Aldrich/Clemmensen scores for myocardium at risk and the Selvester QRS score for final MI size were used. Salvage index was calculated as follows: SI = (myocardium at risk-FIS)/(myocardium at risk). RESULTS: In group 1, FIS was 15% (6, 24) as measured by ECG and 11% (2, 27) as measured by SPECT. In the adenosine group, FIS was 12% (6, 21) and 11% (2, 22). In the placebo group, FIS was 16.5% (7.5, 24) and 11.5% (3.0, 38.5) by ECG and SPECT, respectively. The overall correlation between SPECT and ECG for FIS was 0.58 (P = .0001): 0.60 in the placebo group (P = .0001) and 0.54 (P = .0001) in the adenosine group. In group 2, myocardium at risk was 23% (17, 30) and 26% (10, 50) with ECG and SPECT, respectively (P = .0066). Final infarct size was 17% (6, 21) and 12% (1, 24) (P < .0001). The SI was 29% (-7, 57) and 46% (15, 79) with ECG and SPECT, respectively (P = .0510). CONCLUSIONS: The ECG measurement of infarct size has a moderate relationship with SPECT infarct size measurements in the population with available assessments. This ECG algorithm must further be validated on clinical outcomes.

Role of infarct size in explaining the higher mortality in older patients with acute myocardial infarction

Age is a strong predictor of mortality in acute myocardial infarction (AMI).1–10 Increased mortality in older patients is due in part to a greater prevalence of prior infarction, co-morbid conditions, complications, multivessel coronary artery disease, and less aggressive treatment.1–12 Although left ventricular ejection fraction (LVEF) is also a strong prognostic variable for AMI, few studies have examined the association between age and LVEF.1–3,8 Technetium (Tc)-99m-sestamibi imaging is a newer method of measuring infarct size and predicting outcome.13 A single-center study reported no association between age and infarct size.14 The 2 variables independently predicted mortality after hospitalization. That study was limited by a small number of patients (n 274)with few events (n 11). The Collaborative Organization of RheothRx Evaluation (CORE) study was a multicenter AMI trial that had large subsets of patients who underwent assessment of LVEF and/or infarct size.15,16 The present study examines the associations between age and these radionuclide measurements and assesses their prognostic capabilities.