Answer

The electrocardiogram in Fig. 2 shows atrioventricular (AV) sequential pacing at a rate of 60 bpm with QRS duration ~90 ms. The QRS morphology is consistent with conduction system pacing, in particular selective His bundle pacing (HBP) with correction of LBBB.

HBP is a cardiac pacing technique with the potential of preserving or restoring normal His-Purkinje activation in the presence of AV conduction block or BBB. A prerequisite for successful HBP in the setting of LBBB is the presence of a proximal or intra-His conduction block, which can be circumvented by pacing the distal His bundle and thereby recruiting the otherwise ‘healthy’ left-sided conduction system. LBBB can be corrected with HBP in up to 80% of patients depending on the site of the block [1], and the conduction block site correlates reasonably well with surface ECG. The Strauss criteria have a positive predictive value of 71% for identifying patients eligible for corrective HBP [2]. Although, as of yet, there is no clear benefit of HBP over traditional biventricular pacing because this has not been investigated properly, HBP is potentially the ultimate form of cardiac resynchronisation therapy [3].

In our patient, pathological Q waves in the inferior and lateral leads, which were previously not visible (see Fig. 1), were revealed postoperatively in conjunction with a dominant R wave in the right precordial leads (Fig. 2), as a result of normalisation of ventricular electrical activation. These ECG findings could be related to the findings of cardiac magnetic resonance imaging (MRI), which revealed transmural inferolateral myocardial infarction (Fig. 3).

Fig. 1
figure 1

Preoperative electrocardiogram

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Fig. 2
figure 2

Postoperative electrocardiogram

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Fig. 3
figure 3

Cardiovascular MRI with gadolinium contrast showing transmural myocardial infarction of inferolateral wall

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