Methods and Results: In this prospective, observational study (“Evaluation of Risk Factors for Therapeutic Outcome in Patients with Tachycardiomyopathy” (EMPATHY study, ClinicalTrials.gov: NCT03418467)) 54 patients with TCM were prospectively analyzed, including histopathological analyses of 38 endomyocardial biopsy samples. As enrichment of mitochondria at the intercalated discs (EMID-sign) has been described in the patients, we observed that EMID-sign intensity was inversely correlated with a recovery in left ventricular function (p<0.05). The EMID-sign was furthermore correlated with endomyocardial fibrosis in these patients. Patients with high intensity EMID sign showed only slight or no increase in left ventricular ejection fraction whereas patients with no or low EMID sign intensity had excellent prognosis regarding LVEF recovery after rhythm control. Furthermore, CRP levels were found to be predictive for LVEF recovery, while other inflammatory markers were not.

Conclusion: In this study we have prospectively analyzed clinical and bioptic parameters as predictive markers for clinical outcome in patients with tachycardiomyopathy. As TCM is still a retrospective diagnosis, we provide evidence to help identify patients with TCM early on in the diagnostic process. Further studies are warranted to investigate mechanism and novel therapeutic strategies in these patients.