A diagnostically challenging case of wide complex tachycardia

A woman in her 60s with non-obstructive coronary artery disease, aortic valve replacement and aortic arch repair, chronic diastolic heart failure and paroxysmal atrial fibrillation (AF) and flutter (AFL), presented with 3 days of sustained palpitations that felt similar to prior episodes of AF/AFL. She was euvolemic, haemodynamically stable, with a regular rhythm. Home medications included apixaban, carvedilol and flecainide. Presenting ECG (figure 1A) was compared with baseline ECG (figure 1B) and ECG from a recent admission for AF with rate-related aberrancy (figure 1C). There was no atrioventricular dissociation or fusion/capture beats. High-sensitivity troponin I was undetectable. Serum creatinine had fluctuated recently between 1.3 and 2.0 mg/dL from a baseline of 1.0 mg/dL (estimated glomerular filtration rate approximately 25–45 from a baseline of >60 mL/min/1.73 m2). Electrolytes …