PR Depression Is Useful in the Differential Diagnosis of Myopericarditis and ST Elevation Myocardial Infarction

BACKGROUND: Deviation of the PR segment is a common but often ignored ECG finding in acute myopericarditis, but seems to be rare in the acute phase of ST elevation myocardial infarction (STEMI). Since rapid bedside differential diagnosis of acute myopericarditis and STEMI is essential, we decided to assess the diagnostic power of PR depressions in patients presenting with ST elevations in the emergency room. METHODS: Thirty-four consecutive patients with acute myopericarditis and 46 STEMI patients presenting with ST elevations fulfilling the criteria for STEMI were included. The first ECG recorded in the emergency room was analyzed with a focus on the PR segment. The diagnoses of myopericarditis and STEMI were ascertained with clinical follow-up together with rise in troponin levels, and in the STEMI patients also with coronary angiography. RESULTS: In myopericarditis, the most common location for PR depression was lead II (55.9%), while this ECG finding least likely appeared in lead aVL (2.9%). PR depression in any lead had a high sensitivity (88.2%), but fairly low specificity (78.3%) for myopericarditis. The combination of PR depressions in both precordial and limb leads had the most favorable predictive power to differentiate myopericarditis from STEMI (positive 96.7% and negative power 90%). CONCLUSIONS: Our present observations show that PR segment analysis is a powerful tool in the differential diagnosis of myopericarditis and STEMI. This simple information should be added to the diagnostic workup of patients presenting with ST elevations.