A 60-year-old male with heart failure and severely reduced left ventricular function was scheduled for elective implantation of a cardiac resynchronisation therapy defibrillator device. Coronary artery angiography revealed no significant coronary artery disease. He remained symptomatic despite guideline-directed optimal medical therapy. The ambulatory electrocardiogram (ECG) showed sinus rhythm with a slightly prolonged PR interval, ventricular ectopic beats and complete left bundle branch block (LBBB) with QRS duration ~150 ms and mid-QRS notching in > 2 leads, consistent with the Strauss criteria for LBBB (Fig. 1; [1]). The device implantation was successful, and there were no procedural complications. A postoperative ECG was obtained on the cardiology ward shortly after the procedure (Fig. 2).

Fig. 1
figure 1

Preoperative electrocardiogram

Fig. 2
figure 2

Postoperative electrocardiogram

What type of pacing can be seen, and what other distinctive pathology is revealed?

Answer

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