An Hypothesis: Disproportion Between Cardiac Troponin and B-Type Natriuretic Peptide Levels-A High Risk and Poor Prognostic Biomarker in Patients With Fulminant Myocarditis?

In our clinical practice, we recently found some patients with severe fulminant myocarditis (FM) who showed persistently elevated cardiac troponin (cTn) levels and "seemingly normal" B-type natriuretic peptide (BNP) level, and who subsequently progressed to poor outcomes. Indeed, this sounds contrary to conventional wisdom, but it is not an accidental phenomenon. Fulminant myocarditis is a rapidly progressive disease associated with high mortality. Recent studies have shown that patients with FM are significantly more likely to require heart transplantation than those without FM. Prompt diagnosis of FM and the institution of advanced cardiac life support will save more lives. Cardiac troponin and BNP are widely used diagnostic markers. Cardiac troponin is a specific marker of cardiac injury and its level correlates with the severity of cardiac injury. However, plasma BNP has a dual identity; it is not only a marker of cardiac pressure/volume overload, but it is also a cardioprotective factor that provides effective neurohormonal compensation to maintain homeostasis. Similar to fulminant hepatitis (characterised by diffuse inflammation and massive parenchymal cell necrosis) sometimes showing disproportion between transaminase level and bilirubin level, the disproportion between cTn and BNP levels in FM seems to be consistent with its severe histopathological changes, including diffuse infiltration of the myocardium by inflammatory cells, as well as severe cardiomyocyte injury and necrosis. Moreover, in previous studies, a lower BNP level was found to be an adverse prognostic marker in end-stage heart failure. All these findings indicate that in patients with FM with a persistently high cTn level and ominous clinical presentation, a "seemingly normal" BNP level is not a friendly signal. We hypothesise that the combination of a persistently elevated cTn level and low BNP level in patients with FM indicates worse myocardial injury and poor prognosis.