TNNI3 and polymorphic ventricular tachycardia: The first case was a 74-year-old woman who suffered from sustained polymorphic ventricular tachycardia, elevated N-terminal pro-B type natriuretic peptide (NT-proBNP) and cardiac troponin I (cTnI) levels, and an impaired ejection fraction (EF) of 40%, despite treated with steroid pulse therapy and intravenous immunoglobulin therapy.