Can treatment with beta blockers trigger episodes of atrial fibrillation in healthy patients

We present 2 patients with no cardiac history who were prescribed beta blockers for extracardiac disease. The first patient was a 47-yearold man who engaged in moderate aerobic sports 2– 3t imes aw eek, a musician by profession, who took 20 mg of propranolol every 12 h daily for treatment of emotional tremors. The second patient was a 55-year-old man recently diagnosed with mild mitral prolapse with no significant regurgitation but with symptoms of short sporadic palpitations attributed to low-density isolated supraventricular extrasystole detected with a Holter monitor, he was prescribed treatment with bisoprolol 5 mg daily for this condition. After a short treatment period (between 1 and 2 months), both patients experienced a first episode of atrial fibrillation and were highly symptomatic, with rapid palpitations, in both cases nocturnal and after a large dinner. In the emergency department, they were diagnosed with paroxysmal atrial fibrillation, which resolved spontaneously in one of the patients and after a 100mg oral dose of flecainide in the other. A complete cardiac study was performed, which ruled out potential cardiac or systemic triggers as causes of the atrial fibrillation. In the clinical follow-up, both patients presented similar recurrences a few weeks later of nocturnal episodes of rapid atrial fibrillation during sleep, which resolved after the oral ingestion of 200-mg flecainide. In both cases, use of flecainide 100 mg every 12 h was initiated after the clinical recurrence. However, rapid andprogressive clinicalworseningoccurred, witha continuousincrease in the number of atrial fibrillation episodes within a few weeks. These episodes were generally triggered in conditions of vagal predominance (postprandial, evenings, alcohol intake), were highly symptomatic and preceded by focal extrasystolic bigeminy (verified in Holter), with a periodicity of up to 6–7 episodes daily. In many cases, these episodes wereself-limitingto20–30min.Atothertimes,theepisodeswerepharmacologically cardioconverted with extra doses of oral flecainide a few hours after its start. Both patients were assessed in the cardiology department, and both cases were diagnosed as vagal focal atrial fibrillation due to the clinical characteristics. Beta-blocker treatment was discontinued and pulmonary vein ablation was scheduled. Three to 4 days after discontinuing the beta-blocker treatment, both patients had full remission of the symptoms; the procedure was therefore postponed.Afterremainingasymptomaticfor6months,thepatients'antiar