Electrocardiographic measurement of infarct size after thrombolytic therapy

Objectives. We examined the utility of the 32-point QRS score from the 12-lead electrocardiogram (ECG) for measurement of the ischemic risk region and infarct size in patients receiving thrombolytic therapy. Background. The QRS score offers means of evaluating the therapeutic benefit of thrombolytic therapy by comparing final infarct size with the initial extent of ischemic myocardium. Methods. The study included 38 patients (34 men, 4 women; mean [±SD] age 54 ± 10 years) with first infarction (18 anterior, 20 inferior). The maximal potential QRS score (QRS0) was assigned to all leads with ≥ 100-μV ST elevation on the initial ECG. The QRS scores were calculated at 7 and 30 days after infarction. Left ventricular ejection fraction was measured by radionuclide ventriculography at 1 month. Twenty-eight patients had thallium (T1)-201 and technetium (Tc)-99m pyrophosphate tomographic measurement of the ischemic region and infarct size. Results. The QRS0 was 10.3 ± 3.1 (mean ± SD) for anterior and 10.4 ± 3.5 for inferior infarcts. The QRS scores were similar at 7 and 30 days for both anterior (5.6 ± 3.4 vs. 5.5 ± 3.4) and inferior infarcts (3.7 ± 2.6 vs. 2.9 ± 2.2). The day 7 QRS score and ejection fraction at 1 month were inversely correlated (r = −0.74, p < 0.01). The T1-201 perfusion defect was 34 ± 11% of the left ventricle for anterior and 32 ± 7% for inferior infarcts. Subsequent Tc-99m pyrophosphate infarct size was 15 ± 9% of the left ventricle for anterior and 17 ± 9% for inferior infarcts. The QRS0 was correlated with the extent of the T1-201 perfusion defect (r = 0.79, p < 0.001), and the day 7 QRS score was correlated with Tc-99m pyrophosphate infarct size (r = 0.79, p < 0.005). Conclusions. The 32-point QRS score can provide useful immediate measurements of the ischemic risk region and subsequent infarct size.