The Diagnostic Value of C-reactive protein to Troponin Ratio for the Differentiation of Perimyocarditis from Acute Myocardial Infarction

Differentiation between perimyocarditis and acute myocardial infarction (AMI) is frequently difficult despite a disparate pathogenesis. Perimyocarditis is primarily an inflammatory disease associated with high C-reactive protein (CRP) and low troponin concentrations, while AMI is characterized by significantly elevated troponin with relatively lower CRP levels. We surmised that the CRP/troponin ratio could enhance the differentiation between these entities. We evaluated this ratio among patients consecutively included between January 2011 and April 2017 in a large coronary care unit registry. CRP and troponin were sampled on admission with troponin measured again during the first day with both ratios assessed against discharge diagnosis. AMI was diagnosed by acute ischemic symptoms, typical electrocardiographic changes, elevated troponin levels, and occlusive coronary artery disease.

Perimyocarditis was diagnosed by typical or atypical chest pain, elevated CRP, electrocardiographic changes, and either coronary angiography or cardiac CT angiography excluding obstructive coronary disease, or CMR. The ROC of the CRP/troponin ratios was evaluated for diagnosis of perimyocarditis against ST-elevation myocardial infarction (STEMI) with or without Non-STEMI (NSTEMI) patients.

The registry included 1669 patients comprising 1025 STEMI patients, 518 NSTEMI patients, and 126 patients with perimyocarditis. Median CRP/troponin ratios on presentation were 84, 65, and 322 mg×ml/liter×ng in the STEMI, NSTEMI and perimyocarditis groups (p<0.001). CRP/later troponin ratios were 21.2, 22.3, and 207 in the non-reperfused STEMI, NSTEMI and perimyocarditis groups, respectively (p<0.001). The ROC of the CRP/troponin ratio on admission yielded an AUC of 0.69 and 0.7, respectively. The CRP/later troponin ratio for diagnosis of perimyocarditis against STEMI excluding reperfused STEMI patients with or without NSTEMI patients generated an AUC of 0.79 for both (p<0.0001) demonstrating excellent differentiating capability. CRP/late troponin ratio>300 resulted in specificity exceeding 95%. The CRP/troponin ratio seems to enhance the differentiation between perimyocarditis and AMI, which in the appropriate context may preclude further evaluation.