Complete Heart Block with Wide Escape

A 74-year-old man with hypertension, type 2 diabetes mellitus, and prior inferior myocardial infarction presents with progressive fatigue, lightheadedness, and one syncopal episode. Vital signs show HR 32 bpm, BP 78/48 mmHg, with cool extremities and delayed capillary refill. Examination reveals cannon A waves in the jugular venous pulse. Twelve-lead ECG demonstrates regular P waves at 85 bpm marching independently through regular wide-complex QRS at 32 bpm with 160 ms duration and left bundle branch block morphology. The rhythm strip marked **B** shows complete atrioventricular dissociation defining third-degree AV block with a wide-complex ventricular escape. Which of the following best describes the anatomical level of block and the immediate management priority in this patient?