Flecainide in structural heart diseases: A contemporary reappraisal beyond the CAST

Flecainide has been contraindicated in patients with structural heart disease since the 1991 Cardiac Arrhythmia Suppression Trial showed increased mortality in post-myocardial infarction patients. This review argues that the Cardiac Arrhythmia Suppression Trial findings were overgeneralized, resulting in the underutilization of a valuable antiarrhythmic medication. Emerging observational evidence suggests that flecainide may be safe and effective in specific structural heart disease populations, including those with stable coronary artery disease without active ischemia and preserved ventricular function. Its use also shows promise in various cardiomyopathies (CMs) such as arrhythmogenic right ventricular CM and premature ventricular complex-induced CM, supporting a nuanced, patient-specific approach that challenges existing flecainide safety dogma and moves beyond outdated misconceptions. Randomized controlled trials are needed to confirm the recent observational findings and redefine the role of flecainide in contemporary cardiology.