A Technique for Cardiac Resynchronization Therapy Using Left Bundle Branch Area and Left Ventricular Pacing
Cardiac resynchronization therapy (CRT) has been a cornerstone in the management of heart failure (HF) patients with left bundle branch block (LBBB) and reduced left ventricular (LV) function. Traditional CRT involves biventricular pacing (BVP), which has been shown to improve clinical outcomes and reduce all-cause mortality. However, recent advancements have introduced left bundle branch area pacing (LBBAP) as a promising alternative, particularly for patients with LBBB. This article delves into a novel technique that combines LBBAP with sequential LV pacing, termed LBB-optimized CRT (LOT–CRT), and explores its clinical efficacy, procedural details, and outcomes.
Background and Rationale
CRT via BVP is well-established in improving symptoms, LV function, and survival in HF patients with LBBB. However, not all patients respond favorably to BVP, and the reasons for non-response are multifactorial, including LV scar burden, suboptimal LV lead placement, and limited electrical or mechanical dyssynchrony. LBBAP has emerged as a viable alternative, offering the potential to correct LBBB by pacing the left bundle branch region beyond the block site. This approach has demonstrated stable pacing thresholds and shorter QRS durations (QRSd) compared to traditional BVP.
The LOT–CRT technique was developed to enhance the efficacy of CRT by combining LBBAP with sequential LV pacing. This method aims to provide better electrical resynchronization and clinical outcomes than conventional BVP or standalone LBBAP. The technique involves implanting a right ventricular (RV) defibrillator electrode as a backup, placing an LV coronary sinus (CS) lead, and performing LBBAP using a SelectSecure pacing lead.
Procedural Details
The LOT–CRT procedure begins with the implantation of an RV defibrillator electrode to ensure backup ventricular pacing in case of transient complete atrioventricular (AV) block during LBBAP lead placement. The LV CS lead is then implanted using standard techniques, targeting sites with maximal LV delay. The LBBAP lead is placed using a SelectSecure pacing lead (model 3830, Medtronic Inc.), with the RV septal location identified using anatomical landmarks and pacing localization within a nine-grid system.
The LBBAP lead is advanced deep into the septum while monitoring unipolar pacing impedance, electrogram characteristics, and paced QRS morphology. The lead orientation is adjusted to ensure proper placement, typically pointing in the 12- to 1-o’clock direction from a right anterior oblique viewing angle of 30° and the 2- to 3-o’clock direction from a left anterior oblique viewing angle of 30°. In patients undergoing CRT-defibrillator (CRTD) treatment, the LBBAP lead is connected to the pace-sensing portion of the RV port, and the LV CS lead is connected to the LV port. For CRT-pacemaker (CRTP) treatment, the LV CS lead is placed first, followed by the LBBAP lead.
Patient Characteristics and Follow-Up
The study included five patients with cardiomyopathy (two non-ischemic and three ischemic), all of whom had at least one HF hospitalization within three months before LBBAP implantation. The mean age was 71.8 ± 5.1 years, and all patients had hypertension. Baseline LV ejection fraction (LVEF) was 32.0% ± 4.2%, and baseline QRSd with LBBB was 158.0 ± 13.0 ms. All patients were prescribed Entresto (sacubitril/valsartan), beta-blockers, and loop diuretics.
LOT–CRT was successfully achieved in all five patients, with an operation duration of 152.0 ± 31.1 minutes and X-ray fluoroscopy duration of 26.2 ± 5.9 minutes. CRTDs were implanted in four patients, and CRTP was implanted in one patient. Both LBBAP and LV capture thresholds remained stable during follow-up, with significant narrowing of the QRSd observed in all patients. Unipolar LBBAP resulted in a right bundle branch block pattern with a paced QRSd of 123.0 ± 5.7 ms, and LOT–CRT further reduced the QRSd to 119.0 ± 7.6 ms.
Clinical Outcomes
The mean follow-up time was 296 ± 201 days, during which the LBBAP capture threshold, R-wave amplitude, and lead impedance remained stable. No patients experienced lead dislodgement, loss of capture, infections, embolism, or stroke. Transthoracic echocardiogram evaluations showed significant improvements in LV end-diastolic dimension (LVEDD) and LVEF at the three-month follow-up. The NYHA classification score improved from 3.2 ± 0.5 to 2.4 ± 0.6, indicating better functional status.
Discussion
LOT–CRT offers several advantages over traditional BVP, particularly in patients with intraventricular block and higher LV scar burden. By combining LBBAP with sequential LV pacing, LOT–CRT provides better electrical resynchronization and clinical outcomes. The technique is particularly beneficial for patients with ischemic cardiomyopathy, where BVP response rates may be suboptimal due to scar burden and distribution.
However, LOT–CRT is not without limitations. The procedure is time-consuming, with longer operation and fluoroscopy durations compared to previous reports. The study also had a small sample size and short follow-up interval, necessitating further clinical trials to validate its long-term efficacy. Despite these limitations, LOT–CRT represents a significant advancement in CRT, offering a promising alternative for HF patients with LBBB and reduced LV function.
Conclusion
LOT–CRT is a clinically feasible technique for cardiac resynchronization therapy in patients with systolic HF and LBBB. The method combines LBBAP with sequential LV pacing, resulting in significant reductions in QRSd and improvements in LV function. While further studies are needed to confirm its long-term benefits, LOT–CRT offers a promising new approach to CRT, particularly for patients with ischemic cardiomyopathy and higher LV scar burden.
doi.org/10.1097/CM9.0000000000001622
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