Successful transcatheter mitral valve repair for mitral regurgitation complicating fulminant eosinophilic myocarditis: a case report.

Background: Fulminant eosinophilic myocarditis (EM) has a poor prognosis. Acute severe mitral regurgitation (MR) is a life-threatening complication of EM: however, no established treatment thereof exists. Case summary: Herein, we report a case of a 70-year-old woman diagnosed with fulminant EM. She was in cardiogenic shock and treatment was initiated with an implanted intra-aortic balloon pump in addition to steroids and inotropes. Functional MR gradually worsened, and cardiogenic shock did not improve. Our cardiology team discussed the treatment plan and performed transcatheter mitral valve repair (TMVr). Immediately after the procedure, MR was well-controlled, and the patient's hemodynamics improved dramatically. After discharge, there was no recurrence of heart failure. Discussion: We identified two important clinical issues: first, acute functional MR requiring invasive treatment can be associated with fulminant EM; and second, TMVr is useful as an invasive treatment strategy for such MR. Although MR caused by EM improves with pharmacological therapies in many cases, invasive treatment strategies may be required in some case, as seen in this case. Compared with surgeries, TMVr is less invasive and carries a lower risk of postoperative low cardiac output syndrome compared with surgical procedures when MR is well-controlled. If the response to pharmacological therapies is poor, early TMVr should be considered.