Clinical introduction An 89-year-old man with a history of heart failure with preserved ejection fraction presented with worsening dyspnoea, reduced exercise capacity and peripheral oedema. His medical history was significant for hypertension, paroxysmal atrial fibrillation (AF), chronic obstructive pulmonary disease and Lyme disease (1983). Admission cardiovascular medications included aspirin 75 mg once a day, perindopril 6 mg once a day, furosemide 40 mg two times a day, flecainide 100 mg two times a day and simvastatin 40 mg one a night. On examination, he was normothermic and clinically in heart failure with raised jugular venous pressure, bibasal pulmonary crepitations and oedema up to abdomen. Cardiac markers were negative. Other laboratory tests demonstrated a normocytic anaemia, C reactive protein 18.7 mg/L (0–7.9), urea 19.4 mmol/L (2.8–7.2) and creatinine 162 µmol/L (72–127), which had trended above a baseline of 110 µmol/L for 4 months. Electrolytes including sodium, potassium, magnesium, corrected calcium and inorganic phosphate were within normal range. His admission ECG is shown in figure 1. Chest X-ray confirmed moderate right pleural effusion and left costophrenic blunting. Transthoracic echocardiogram demonstrated normal LV size and systolic function. The RV was dilated with mildly reduced systolic function. There was biatrial dilatation (right > left) with moderate-to-severe tricuspid regurgitation (due to annular dilatation), aortic sclerosis and a small circumferential pericardial effusion.

Question What is the most likely explanation for the ECG appearance?

1. Atrial fibrillation with extreme right bundle branch block

2. Class Ic antiarrhythmic agent toxicity

3. Long-term sequelae of Lyme carditis

4. Missed hyperkalaemia

5. Tricyclic poisoning.

For the answer see page 650

For the question see page 633