TNNI3 and cardiomyopathy: In another study of 48 patients with persistent AF who underwent electrical cardioversion with biphasic or single-phase defibrillators and had cTnI measured before and after six and 24 hours of cardioversion, no significant increase in cTnI was observed after cardioversion with biphasic defibrillation DCCV of atrial arrhythmias with and without cardiomyopathy and received troponin I before and six hours after cardioversion, and no significant change in cTnI levels was observed [21].