A nonischemic electrocardiogram does not always predict a small myocardial infarction: results with acute myocardial perfusion imaging.

ABSTRACT

BACKGROUND: A nonischemic electrocardiogram (ECG) in association with myocardial infarction (MI) indicates a small MI in some but not all cases. Myocardial perfusion imaging using technetium-99m sestamibi offers the ability to better characterize these "electrically silent" infarctions. METHODS: Patients considered low risk for myocardial infarction with a normal or nonischemic ECG (no significant ST elevation, ST depression, ischemic T-wave inversion, or left bundle branch block) underwent early emergency department perfusion imaging, followed by serial myocardial marker sampling. Risk area (defect size) was quantitated by use of a 50% threshold from multiple short-axis slices. RESULTS: A total of 87 patients with nonischemic ECGs had myocardial infarction (mean peak creatine kinase [CK] 710 +/- 720 U/L, range 111-3196 U/L). Peak CKs were lower in the 7 patients with negative perfusion imaging (420 +/- 290 U/L vs 730 +/- 740 U/L, P =.06). Mean risk area was 18% +/- 11% of the left ventricle (range 0%-62%) and was not significantly different among the different infarct-related arteries. Patients with normal ECGs had a similar risk area compared with other patients (16% +/- 12% vs 19 +/- 12%, P =.25). Coronary angiography was performed in 81 patients, with significant stenoses in 74 (91%) (37 one-vessel, 19 two-vessel, 18 three-vessel), with the infarct related artery most commonly the left circumflex (n = 32 [38%]). CONCLUSIONS: The ischemic risk area in patients with a nonischemic ECG was comparable to patients with inferior ST-elevation myocardial infarction found in previous studies. A nonischemic ECG does not predict a small ischemic risk area.