Differentiating type 1 and 2 acute myocardial infarctions using the N-terminal pro B-type natriuretic peptide/cardiac troponin T ratio.

ABSTRACT

PURPOSE: Differentiation of type 1 (T1MI) from type 2 myocardial infarction (T2MI) is important as recommended treatments for each differ. Patients with T2MI may have more/earlier cardiac wall stress resulting in an increased N-terminal pro B-type natriuretic peptide (NT-proBNP)/cTnT generation 5 ratio (cTnT Gen 5). METHODS: Emergency Department (ED) patients presenting with symptoms suspicious for acute coronary syndrome (ACS) were enrolled from 2013 to 2015. Baseline blood samples were collected within 60 min of a triage ECG, with additional draws at 30, 60 and 180 min. NT-proBNP and cTnT Gen 5 levels were measured later in an independent laboratory. Acute myocardial infarction (AMI) was adjudicated using the Third Universal Definition of Myocardial Infarction. RESULTS: 575 patients were enrolled with 44 (7.7%) having AMI [25 T1MI (59.1%) and 18 T2MI (40.9%)]. Patient characteristics showed very few AMI type differences so accurate clinical differentiation was difficult. The median NT-proBNP/cTnT Gen 5 ratios were significantly higher in T2MI when compared to T2MI at baseline and 30, 60 and 180 min later [7.3 v 53.0 (p = 0.003), 5.8 v 49.5 (p = 0.002), 6.3 v 47.5 (p = 0.003) and 4.3 v 33.7 (p = 0.016) respectively]. CONCLUSIONS: The clinical determination of whether an AMI is type 1 or 2 is difficult as the ED patient characteristics of each are similar. The NT-proBNP/cTnT Gen 5 ratio can aid in making this differentiation. Additional multicenter trials are needed to validate our results.