Initial electrocardiogram as determinant of hospital course in ST elevation myocardial infarction

Background A proportion of patients with ST elevation myocardial infarction (STEMI) have an initial electrocardiogram (ECG) that is nondiagnostic and are definitively diagnosed on a subsequent ECG. Our aim was to assess whether patients with a nondiagnostic initial ECG are different than those with a diagnostic initial ECG. Methods We collected demographic, ECG, medication, angiographic, and in-hospital clinical outcome data in consecutive patients undergoing primary percutaneous coronary intervention for STEMI at our institution from June 2009 to June 2013. Results A total of 334 patients were included, 285 (85%) diagnosed on the initial ECG and 49 (15%) on a subsequent ECG. Patients with a nondiagnostic initial ECG had more comorbidities including prior congestive heart failure (14% vs. 3%, p < .001), coronary artery disease (47% vs. 24%, p = .001), diabetes (37% vs. 16%, p = .001), and hyperlipidemia (55% vs. 40%, p = .048); higher rates of chronic medication use including aspirin (47% vs. 27%, p = .005), beta-blocker (47% vs. 22%, p < .001), and statins (53% vs. 28%, p = .001); longer door-to-balloon times (106 min vs. 45 min, p < .001); lower peak troponin levels (25 ng/ml vs. 50 ng/ml, p = .004), longer diagnostic ECG to balloon times (84 min vs. 75 min, p = .006); and higher rates of a patent infarct-related artery on baseline angiography (41% vs. 24%, p = .018) which remained significant in a multivariable logistic regression model. Conclusions Approximately one in seven STEMI patients had an initial ECG that was nondiagnostic for STEMI. These patients had more comorbidities, higher rates of medication use, and received delayed intervention (even after the diagnosis was definitive).