Excerpt

A 70-year-old gentleman presented to us with recurrent syncope, intermittent left bundle branch block (LBBB) (Fig. 1a) and left ventricular ejection fraction of 35%. He had undergone percutaneous coronary intervention for inferior wall myocardial infarction 5 months ago. Holter monitoring showed intermittent LBBB and high-grade AV block. A3830 Selectsecure^tm lead was deployed using C315-His sheath to capture the left bundle branch (LBB) [1]. Electrocardiography showed narrow QRS duration during the procedure. After 4 rapid rotations, LBB potential was noted (Fig. 2a) but the peak left ventricular activation time (pLVAT) at 2 V/0.5 ms pacing output was 93 ms. One more rotation resulted in negative LBB current of injury (LBB-COI) with disappearance of LBB potential (Fig. 2b) but pLVAT improved to 53 ms at 2 V/0.5 ms. Resurgence of concealed LBB potential was noted after 20 min. A predominant negative deflection followed by sharp high frequency biphasic potential was observed (Fig. 2c–f), which was different from the three types of LBB-COI described by Su et al. [2]. This type IV LBB-COI pattern concealing the LBB potential has to be considered before repositioning the lead due to sudden loss of LBB potential during deployment.

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