Objective: To determine whether acute myocardial infarction (AMI) patients who have negative ECGs on presentation have significantly lower complication rates than do those AMI patients who have positive ECGs on presentation.
Methods: Retrospective, cohort analysis comparing rates of hospital complications (ventricular fibrillation or tachycardia, shock, atrial arrhythmia or bradyarrhythmia with systolic blood pressure < or = 90 mm Hg, pulmonary edema) or interventions among patients with a final hospital diagnosis of AMI and an initially negative vs positive ECG. A negative ECG was normal or had nonspecific ST-segment and/or T-wave abnormalities (upright, flattened T waves; an isolated inverted T wave; ST depression < 0.1 mV; tall T waves with J-point elevation) or minor nonischemic abnormalities. Sample size was adequate to detect a 30% between-group difference in complication rates [alpha = 0.05, 1 - beta (power) = 0.80].
Results: The 27 negative-ECG AMI patients differed from the 38 control patients in (mean +/- SD) age [57 +/- 12 vs 66 +/- 12 years, p < 0.01] but not in gender or history of AMI. The negative- and positive-ECG groups had similar rates of hospital complications [30% (95% CI: 13-47%) vs 42% (95% CI: 26-58%), p = 0.44] and intensive procedures [19% (95% CI: 4-34%) vs 29% (95% CI: 15-43%), p = 0.50], respectively. The negative-ECG patients with hospital complications had ECG evolution precede the event in 83% (95% CI: 69-97%) of cases; persistently negative-ECG patients had no complications [(95% CI: 0-33%), p = 0.06].
Conclusions: Negative- and positive-ECG AMI patients do not have moderate or large differences in the rates of in-hospital complications. Most negative-ECG patients who suffer complications evolve ECG changes prior to the event and such changes indicate the potential need for a higher level of care.