Background: Identifying ST-segment elevation myocardial infarctions (STEMIs) by paramedics can decrease door-to-balloon times. While many paramedics are trained to obtain and interpret electrocardiograms (ECGs), it is unknown how accurately they can identify STEMIs.
Objective: This study evaluated paramedics' accuracy in recognizing STEMI on ECGs when faced with potential STEMI mimics.
Methods: This was a descriptive cohort study using a survey administered to paramedics. The survey contained questions about training, experience, and confidence, along with 10 ECGs: three demonstrating STEMIs (inferior, anterior, and lateral), two with normal results, and five STEMI mimics (left ventricular hypertrophy [LVH], ventricular pacing, left and right bundle branch blocks [LBBB, RBBB], and supraventricular tachycardia [SVT]). We calculated the overall sensitivity and specificity and the proportion correct with 95% confidence intervals (CIs).
Results: We obtained 472 surveys from 30 municipal emergency medical services (EMS) agencies in five counties with 15 medical directors from seven hospitals. The majority (69%) reported ECG training within the preceding year, 31% within six months; and 74% were confident in recognizing STEMIs. The overall sensitivity and specificity for STEMI detection were 75% and 53% (95% CI 73%-77%, 51%-55%), respectively. Ninety-six percent (453/472, 95% CI 94%-98%) correctly identified the inferior myocardial infarction (MI), but only 78% (368/472, 94% CI 74%-82%) identified the anterior MI and 51% (241/472, 46%-56%) the lateral MI. Thirty-seven percent (173/472, 95% CI 32%-41%) of the paramedics correctly recognized LVH, 39% (184/472, 95% CI 35%-44%) LBBB, and 53% (249/472, 95% CI 48%-57%) ventricular pacing as not a STEMI. Thirty-nine percent (185/472, 95% CI 35%-44%) correctly identified all three STEMIs; however, only 3% of the paramedics were correct in all interpretations. The two normal ECGs were recognized as not a STEMI by 97% (459/472, 95% CI 95%-99%) and 100% (472/472, 95% CI 99%-100%). There was no correlation between training, experience, or confidence and accuracy in recognizing STEMIs.
Conclusions: Despite training and a high level of confidence, the paramedics in our study were only able to identify an inferior STEMI and two normal ECGs. Given the paramedics' low sensitivity and specificity, we cannot rely solely on their ECG interpretation to activate the cardiac catheterization laboratory. Future research should involve the evaluation of training programs that include assessment, initial training, testing, feedback, and repeat training.