The main findings of this study include three aspects: 1) we firstly described the tendency and extent of hs-cTnI change within 24 h and 48 h after admission in FM; 2) we determined the tendency of hs-cTnI change within 24 h was associated with in-hospital outcome of FM; 3) we further determined that the extent of hs-cTnI change as absolute change and relative change within 24 h and 48 h were significant factors to predict outcome of FM.
Detection of hs-cTnI at admission is recommended in guidelines regarding myocarditis17, 18, for almost all patients showed elevated troponin. Enrico Ammirati reported a cohort study comprised 118 myocarditis patients with left ventricular ejection fraction (LVEF) less than 50% and 325 myocarditis patients with no such complications, above 99% of whom in both groups have increased troponin at admission19. Little research focused on the relationship between the serial change of cardiac troponin and the outcome of myocarditis, the majority of which explored hs-cTnI baseline prognostic value. There were studies demonstrated that the level of cardiac troponin was not associated with the outcome20–22. In contrary, other studies reported that elevated troponin in the early phase for myocarditis was associated with ECMO or worse prognosis23, 24. It is still debated that the prognostic value of cardiac troponin baseline in myocarditis.
Though the increased level of hs-cTnI in FM is well-recognized, it is unknown that the tendency and exact extent of hs-cTnI change in reality. This study described the situation of hs-cTnI change, revealing that it is regular for hs-cTnI change in FM. Most survive patients experienced decline of hs-cTnI change within 24 h while few patients in death group had decreased hs-cTnI, significantly differently compared to survive group. Within 24 h after admission, 40% of survive patients had absolute change of hs-cTnI dropped by 0–10 ng/ml and 58% of survive patients showed relative change of hs-cTnI dropped by 25%-75%. While patients in death group have absolute change of hs-cTnI increased by 0–10 ng/ml, accounting for 50%. The depiction of hs-cTnI change in FM is of importance for us to know more about fulminant myocarditis and give better treatment for patients.
Besides, the declined tendency of hs-cTnI change within 24 h was found to be associated with in-hospital outcome of FM, after the adjustment of the abnormal of creatinine, IVIG treatment and time from onset to hospital. The declined tendency may reveal that treatment for FM in our center was effective, including anti-viral therapy, immunomodulating therapy, circulation support, and respiratory support, resulting in the relief of inflammation reaction which caused myocardium injury and reduction of incidence of ventricular tachycardia or ventricular fibrillation. In contrary, the opposite tendency may inflected that inflammation reaction was still severe after treatment, with high incidence of arrhythmia.
Furthermore, the prognostic value of extent of hs-cTnI change, as absolute change and relative change, within 24 h and 48 h was explored. The results revealed that the concrete absolute and relative change within 24 h and 48 h were associated with in-hospital outcome of FM. Specifically, if FM patients have absolute change of hs-cTnI within 24 h dropped as to 0.618 ng/ml or relative change dropped as to 28.46%, it is more likely for them to survive, which can also be predicted by the absolute change of hs-cTnI within 48 h dropped as to 4.389 ng/ml or relative decline change dropped as to 52.23%. This result is beneficial for doctors to evaluate treatment regimen and patients’ prognostication. If patients experience declined tendency within 24 h with the magnitude reached our proposed cutoff value, the outcome may be good. But the patient's hs-cTnI change within 24 h show increased tendency or the magnitude dropped not reach the cut-off value, it may remind doctor to reassess the treatment for better control of inflammation reaction.
There are still some limitations in the current study. The retrospective nature of this research may have introduced potential bias. Although we collect all FM patients in our singer center for 10 years, the cases are not enough for further subanalysis. The median time for patients from onset to hospital was three days, thus the peak time of hs-cTnI is undetermined for patients experienced declined tendency of hs-cTnI after admission. The prospective research with more regular and frequent detection of hs-cTnI need to be performed for better understanding of hs-cTnI change in FM.