Atrial standstill

A 37-year-old male patient was referred to our cardiology division with a longstanding and worsening history of short episodes of dizziness and reduced effort tolerance. He denied any syncope, palpitations or chest pain. His medical history was unremarkable and he took no medication. Family history was negative for cardiac diseases at a young age or premature sudden death. On clinical examination, the patient appeared in good general condition. He was bradycardic at 40 bpm and normotensive; heart and lung auscultation was normal, the jugular veins distended. The resting ECG displayed a junctional rhythm at 35 bpm with complete right bundle-branch block and no atrial electrical activity (fig. 1). A chest X-ray showed cardiomegaly without pulmonary congestion. During a 24-hour Holter ECG, no atrial activity was discernible and a constant bradycardic junctional rhythm was noted, with a mean heart rate of 36 bpm. Moreover, 83 episodes of asystole lasting more than 3 seconds were recorded, of which 11 lasted more than 6 seconds, with the longest episode in the night being of 10.5 seconds duration (fig. 2). There were no serious ventricular arrhythmias and only 62 isolated premature ventricular beats were