ECG Case of the Month: Wide-QRS Rhythm in a Man with a Clotted Dialysis Fistula.

A 57-year-old man with diabetes mellitus, systemic arterial hypertension, and end-stage kidney disease came to the hospital because his arteriovenous fistula used for hemodialysis had clotted. His blood hemoglobin level was 12.8 g/dL (reference, 13.5-17.5); and serum chemistry levels were creatinine 6.7 mg/dL (0.7-1.3), sodium 132 mEq/L (136-146), potassium 4.0 mEq/L (3.5-5.1), chloride 94 mEq/L (98-106), carbon dioxide 24 mEQ/L (23-29), calcium 9.1 mg/dL (8.4-10.2), and phosphorus 9.1 mg/dL (2.7-4.5). An electrocardiogram was recorded (Figure 1).