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All that is irregular is not AF!


Clinical record

A 64-year-old man with no significant past medical history presented to a district hospital in June 2012 with a 3-week history of palpitations and breathlessness. The electrocardiogram (ECG) showed an irregularly irregular wide complex tachycardia at a rate of 150 beats/min with right bundle branch block-like morphology (Box 1). A transthoracic echocardiogram showed moderate segmental left ventricular dysfunction. Coronary angiography showed no evidence of significant coronary artery disease to account for his left ventricular impairment. A diagnosis of atrial fibrillation (AF) with a rapid ventricular response and tachycardia-mediated cardiomyopathy was made.

Therapy with diuretics and antiarrhythmic medications was commenced. Despite substantial doses of amiodarone (600 mg daily), metoprolol (200 mg daily), verapamil (240 mg daily) and digoxin (250 µg daily) over 2 weeks, his heart rate remained uncontrolled at between 100 and 200 beats/min. A transoesophageal echocardiogram-guided cardioversion was performed, but failed to restore normal rhythm. He was subsequently referred to our tertiary cardiac centre for further management.

The patient was haemodynamically stable on arrival. He had mild renal impairment (creatinine level, 114 µmol/L [reference interval (RI), 60–110 µmol/L];…