[Anomalies of the T waves induced by flecainide]

Flecainide is a class I antiarrhythmic agent which depresses depolarization and conduction velocities in myocardial and Purkinje's fibres, thereby extending their refractory period. As the drug belongs to the IC group, it may increase--moderately as a rule--the duration of QRS, but it does not alter the action potential duration and therefore does not increase the JT interval. In 3 patients treated with flecainide we observed a peculiar alteration in the shape of T waves, the peak of which was flattened and notched, forming a double hump. This abnormality, most clearly visible on precordial leads, remained isolated with no changes in other electrocardiographic parameters. It appeared independently of any circumstance likely to modify repolarization. It remained stable throughout treatment with flecainide and vanished when the drug was discontinued. It was regularly observed with the recommended therapeutic doses (200-300 mg/day) and was unaccompanied by signs of toxicity. To our knowledge, these T wave abnormalities have not yet been reported. Yet they deserve to be known and correctly interpreted, since they reflect impregnation of the myocardium by the antiarrhythmic agent which should not be withdrawn on this account.