Abstract 18750: The Prevalence of Secondary Repolarization Abnormalities Confounding the Electrocardiographic Diagnosis of Acute Myocardial Ischemia in Patients Presenting With Chest Pain

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Introduction: Chest pain has a plethora of etiologies and ECG manifestations. The presence of non-specific ST-T changes (NSSTTC) on the ECG alters the ST-segment for reasons unrelated to acute myocardial ischemia, and hence contributes to alarm fatigue, misdiagnosis, or inappropriate treatment. We sought to determine the prevalence and clinical significance of NSSTTC on the presenting ECG in patients evaluated at the emergency department for chest pain.

Methods: This was a prospective, observational, cohort study that enrolled consecutive chest pain patients transported by ambulance to three UPMC-affiliated tertiary care hospitals between 2013 and 2014. Important clinical data were obtained from charts. Patients were grouped according to etiology of chest pain as acute coronary syndrome (ACS), non-ischemic cardiopulmonary etiology, non-cardiac etiology, or undifferentiated chest pain. Presenting 12-lead ECG was interpreted by two independent reviewers blinded from clinical data. ECGs were classified according to the presence or absence of NSSTTC (i.e., bundle branch block, left ventricular hypertrophy with strain pattern, ventricular pacing, ventricular rhythm, or coarse atrial fibrillation). Chi-square was used to compare percentages among different groups.

Results: This study included 750 patients (age 59±17, 58% males, 40% Blacks). Overall, 17% had ACS, 32% had non-ischemic cardiopulmonary etiology, 9% had non-cardiac etiology, and 42% had undifferentiated chest pain. The prevalence of NSSTTC among these groups was 20%, 21%, 12%, and 12% respectively (p<0.001). On average, 16% of all patients had NSSTTC, including 12% of patients admitted for overnight observation, and 22% of those admitted for treatment. The presence of NSSTTC was associated with 1 day longer length of stay (p<0.01).

Conclusions: NSSTTC that confound the diagnosis of acute myocardial ischemia are prevalent in patient evaluated at the emergency department for chest pain, accounting for nearly 1 in 6 emergency department evaluations and 1 in 5 hospital admission. These abnormalities are still prevalent in those with non-cardiac or undifferentiated etiologies, which warrants caution in interpretation.

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