Influence of Capture Selectivity and Left Intrahisian Block on QRS Characteristics During Left Bundle Branch Pacing

Difference of ventricular synchrony between LBBP, LBFP and LVSP: A speckle tracking echocardiographic study

PURPOSE

Left bundle branch area pacing (LBBAP) has emerged as a physiological and stable form of pacing. We aim to compare the mechanical ventricular synchrony of LBBP, LBFP, and LVSP.

METHODS

Proximal Left bundle branch pacing (LBBP), left bundle fascicular pacing (LBFP) and left ventricular septal pacing (LVSP) were identified in patients with bradycardia who successfully underwent LBBAP. Patients with left ventricular ejection fraction (LVEF) < 50% or QRS duration (QRSd) ≥ 120 ms were excluded. By using electrocardiograms, the left ventricular activation time (LVAT) and QRS duration (QRSd) were measured to examine electrophysiological synchrony. As indications of mechanical synchrony, global longitudinal strain (GLS), global circumferential strain (GCS), global radial strain (GRS), and peak strain dispersion (PSD) were evaluated by using 2-dimensional speckle tracking echocardiography (2D-STE).

RESULTS

In 56 patients, data were collected during LBBP (n = 18), LBFP (n = 16), and LVSP (n = 22). LVSP resulted in a longer LVAT (91.3 ± 14.9 ms) than LBBP (77.1 ± 10.8 ms, P < 0.05) and LBFP (72.1 ± 9.6 ms, P < 0.05), but all three groups had similar QRSd. There were no differences in GLS, GCS, GRS, or PSD between LBBP, LBFP, and LVSP.

CONCLUSIONS

In patients with normal cardiac function and narrow QRS, though LBBAP with LBB capture resulted in better electrophysiological synchrony than without, the mechanical synchrony of the three groups was comparable.

Discrimination between ventricular tachycardia and wide-QRS preexcited tachycardia

BACKGROUND

To develop a new algorithm to differentiate ventricular tachycardia (VT) from preexcited tachycardia (pre-ET) according to left bundle branch block (LBBB) and right bundle branch block (RBBB) patterns.

METHODS

This study included 67 electrocardiograms (ECGs) with VT and 63 ECGs with pre-ET, collected from our hospital and through PubMed. Of those, 64 were allocated to the derivation cohort and the rest to the validation cohort. The diagnoses of the ECGs were confirmed using an electrophysiological study. Parameters and classifiers from prior algorithms along with the propagation speeds in the early portion of the QRS complex (initial deflection index) in leads V1, V6, aVR, II, and III were manually measured. The performance of the new algorithm was compared with that of prior algorithms.

RESULTS

The initial deflection index in lead III was the strongest predictor of pre-ET in LBBB-pattern wide-QRS tachycardia (p = 0.003, AUC 0.805). The initial deflection index in lead V1 was the most powerful predictor of pre-ET in RBBB-pattern wide-QRS tachycardia (p = 0.001, AUC 0.848). Compared to earlier algorithms, those using the initial deflection indexes: lead III in LBBB patterns (cutoff value >0.3) and lead V1 in RBBB patterns (cutoff value ≤0.48), demonstrated superior performance in screening VT, with AUC values of 0.828. The initial deflection indexes proved effective as discriminators between VT and pre-ET in the validation cohort.

CONCLUSIONS

In LBBB-pattern wide-QRS tachycardia, the early propagation speed of pre-ET was faster than that in VT. Conversely, in RBBB-pattern wide-QRS tachycardia, it was slower.

Tailored electrocardiographic-based criteria for different pacing locations within the left bundle branch

BACKGROUND

Electrocardiographic (ECG)-based criteria are used to confirm left bundle branch (LBB) pacing (LBBP), but current cutoff values have never been validated for different pacing locations.

OBJECTIVE

The purpose of this study was to describe diagnostic performance of V6-R wave peak time (RWPT), V6-V1 interpeak interval, and aVL-RWPT for different pacing sites within the LBB and to determine 100% specific values for each criterion at each pacing location.

METHODS

Consecutive patients with confirmed LBBP were selected. Population was divided into subgroups based on the site of pacing: left bundle trunk pacing (LBTP), left septal fascicular pacing (LSFP), left posterior fascicular pacing (LPFP), and left anterior fascicular pacing (LAFP).

RESULTS

A total of 147 patients with unequivocal LBB capture were analyzed. Left fascicular pacing was more frequently achieved (82.8%) than LBTP (17.2%). Diagnostic performance of V6-RWPT, V6-V1 interpeak interval, and aVL-RWPT for discrimination of LBBP was good in all subgroups. V6-RWPT cutoff values with 100% specificity (SP) for LBBP discrimination were 75 ms in LBTP, 68 ms in LPFP, 81 ms in LAFP, and 79.5 ms in LSFP. V6-V1 interpeak interval cutoff values with 100% SP for LBBP discrimination were 35.5 ms in LBTP, 53.5 ms in LPFP, 41 ms in LAFP, and 46 ms in LSFP. In LAFP, aVL-RWPT cutoff value with 100% SP for LBBP discrimination was 68 ms, but was 74 ms in LBTP, 74.5 ms in LSFP, and 73.5 ms in LPFP.

CONCLUSIONS

Tailored ECG-based criteria might be useful to confirm LBBP at different pacing locations within the LBB.

Left bundle branch pacing with and without anodal capture: impact on ventricular activation pattern and acute haemodynamics

AIMS

Left bundle branch pacing (LBBP) can deliver physiological left ventricular activation, but typically at the cost of delayed right ventricular (RV) activation. Right ventricular activation can be advanced through anodal capture, but there is uncertainty regarding the mechanism by which this is achieved, and it is not known whether this produces haemodynamic benefit.

METHODS AND RESULTS

We recruited patients with LBBP leads in whom anodal capture eliminated the terminal R-wave in lead V1. Ventricular activation pattern, timing, and high-precision acute haemodynamic response were studied during LBBP with and without anodal capture. We recruited 21 patients with a mean age of 67 years, of whom 14 were males. We measured electrocardiogram timings and haemodynamics in all patients, and in 16, we also performed non-invasive mapping. Ventricular epicardial propagation maps demonstrated that RV septal myocardial capture, rather than right bundle capture, was the mechanism for earlier RV activation. With anodal capture, QRS duration and total ventricular activation times were shorter (116 ± 12 vs. 129 ± 14 ms, P < 0.01 and 83 ± 18 vs. 90 ± 15 ms, P = 0.01). This required higher outputs (3.6 ± 1.9 vs. 0.6 ± 0.2 V, P < 0.01) but without additional haemodynamic benefit (mean difference -0.2 ± 3.8 mmHg compared with pacing without anodal capture, P = 0.2).

CONCLUSION

Left bundle branch pacing with anodal capture advances RV activation by stimulating the RV septal myocardium. However, this requires higher outputs and does not improve acute haemodynamics. Aiming for anodal capture may therefore not be necessary.

Conduction System Pacing versus Conventional Biventricular Pacing for Cardiac Resynchronization Therapy: Where Are We Heading?

Over the last few years, pacing of the conduction system (CSP) has emerged as the new standard pacing modality for bradycardia indications, allowing a more physiological ventricular activation compared to conventional right ventricular pacing. CSP has also emerged as an alternative modality to conventional biventricular pacing for the delivery of cardiac resynchronization therapy (CRT) in heart failure patients. However, if the initial clinical data seem to support this new physiological-based approach to CRT, the lack of large randomized studies confirming these preliminary results prevents CSP from being used routinely in clinical practice. Furthermore, concerns are still present regarding the long-term performance of pacing leads when employed for CSP, as well as their extractability. In this review article, we provide the state-of-the-art of CSP as an alternative to biventricular pacing for CRT delivery in heart failure patients. In particular, we describe the physiological concepts supporting this approach and we discuss the future perspectives of CSP in this context according to the implant techniques (His bundle pacing and left bundle branch area pacing) and the clinical data published so far.

Diverse QRS morphology reflecting variations in lead placement for left bundle branch area pacing

AIMS

Left bundle branch area pacing (LBBAP) is a potential alternative to His bundle pacing. This study aimed to investigate the impact of different septal locations of pacing leads on the diversity of QRS morphology during non-selective LBBAP.

METHODS AND RESULTS

Non-selective LBBAP and left ventricular septal pacing (LVSP) were achieved in 50 and 21 patients with atrioventricular block, respectively. The electrophysiological properties of LBBAP and their relationship with the lead location were investigated. QRS morphology and axis showed broad variations during LBBAP. Echocardiography demonstrated a widespread distribution of LBBAP leads in the septum. During non-selective LBBAP, the qR-wave in lead V1 indicated that the primary location for pacing lead was the inferior septum (93%). The non-selective LBBAP lead was deployed deeper than the LVSP lead in the inferior septum. The Qr-wave in lead V1 with the inferior axis in aVF suggested pacing lead placement in the anterior septum. The penetration depth of the non-selective LBBAP lead in the anterior septum was significantly shallower than that in the inferior septum (72 ± 11 and 87 ± 8%, respectively). In lead V6, the deep S-wave indicated the time lag between the R-wave peak and the latest ventricular activation in the coronary sinus trunk, with pacemaker leads deployed closer to the left ventricular apex.

CONCLUSION

Different QRS morphologies and axes were linked to the location of the non-selective LBBAP lead in the septum. Various lead deployments are feasible for LBBAP, allowing diversity in the conduction system capture in patients with atrioventricular block.

Stepwise application of ECG and electrogram-based criteria to ensure electrical resynchronization with left bundle branch pacing

AIMS

To define a stepwise application of left bundle branch pacing (LBBP) criteria that will simplify implantation and guarantee electrical resynchronization. Left bundle branch pacing has emerged as an alternative to biventricular pacing. However, a systematic stepwise criterion to ensure electrical resynchronization is lacking.

METHODS AND RESULTS

A cohort of 24 patients from the LEVEL-AT trial (NCT04054895) who received LBBP and had electrocardiographic imaging (ECGI) at 45 days post-implant were included. The usefulness of ECG- and electrogram-based criteria to predict accurate electrical resynchronization with LBBP were analyzed. A two-step approach was developed. The gold standard used to confirm resynchronization was the change in ventricular activation pattern and shortening in left ventricular activation time, assessed by ECGI. Twenty-two (91.6%) patients showed electrical resynchronization on ECGI. All patients fulfilled pre-screwing requisites: lead in septal position in left-oblique projection and W paced morphology in V1. In the first step, presence of either right bundle branch conduction delay pattern (qR or rSR in V1) or left bundle branch capture Plus (QRS ≤120 ms) resulted in 95% sensitivity and 100% specificity to predict LBBP resynchronization, with an accuracy of 95.8%. In the second step, the presence of selective capture (100% specificity, only 41% sensitivity) or a spike-R <80 ms in non-selective capture (100% specificity, sensitivity 46%) ensured 100% accuracy to predict resynchronization with LBBP.

CONCLUSION

Stepwise application of ECG and electrogram criteria may provide an accurate assessment of electrical resynchronization with LBBP (Graphical abstract).

New criterion to determine left bundle branch capture on the basis of individualized His bundle or right ventricular septal pacing

BACKGROUND

Left bundle branch pacing (LBBP) is an emerging physiological pacing modality. How to differentiate LBBP from left ventricular septal pacing (LVSP) remains challenging.

OBJECTIVE

We aimed to develop a new personalized intraoperative criterion to confirm left bundle branch (LBB) capture in patients with or without heart failure (HF).

METHODS

Patients were enrolled if 12-lead surface electrocardiograms of LBBP, LVSP, temporary His bundle pacing (HBP), and right ventricular septal pacing (RVSP) were recorded during the procedure, with the leads placed in the basal midseptal region. Left ventricular activation time (LVAT) was measured during different pacing modalities. ΔLVAT1 was defined as the difference in LVAT between HBP and LBBP/LVSP. ΔLVAT2 was estimated by the difference in LVAT between RVSP and LBBP/LVSP. ΔLVAT1% and ΔLVAT2% were calculated as the percent reduction of ΔLVAT1 and ΔLVAT2, respectively.

RESULTS

A total of 105 consecutive patients were included, of whom 80 (76.2%) had normal cardiac function (65 LBBP and 15 LVSP) and 25 had HF. Patients with LBBP showed significantly shorter LVAT than did those with LVSP. In patients with normal cardiac function, a cutoff value of ΔLVAT1 > 12.5 ms showed 73.9% sensitivity and 93.3% specificity to confirm LBB capture. In patients with HF, a cutoff value of ΔLVAT1% > 9.8% exhibited great accuracy for LBB capture (sensitivity 92.0%; specificity 92.3%). The optimal value of ΔLVAT2% for differentiating LBBP from LVSP was 21.2%.

CONCLUSION

Temporary HBP and RVSP can serve as references to confirm LBB capture in an individualized fashion in patients with or without HF.

The left bundle branch has been captured but shows the left ventricular septal pacing:What is the mechanism?

It was shown that V6 R-wave peak time (V6 RWPT) prolongs with transition form non-selective left bundle branch pacing (ns-LBBP) to left ventricular septal pacing (LVSP) but remains constant or slightly prolongs with transition to selective left bundle branch pacing (sel-LBBP) [1,2]. Here, we report on a patient who was observed with a LBB potential, isoelectric interval, where the V6 RWPT substantially prolonged with transition from ns-LBBP to sel-LBBP at near threshold output.

Left bundle branch area pacing outcomes: the multicentre European MELOS study

Aims

Permanent transseptal left bundle branch area pacing (LBBAP) is a promising new pacing method for both bradyarrhythmia and heart failure indications. However, data regarding safety, feasibility and capture type are limited to relatively small, usually single centre studies. In this large multicentre international collaboration, outcomes of LBBAP were evaluated.

Methods and results

This is a registry-based observational study that included patients in whom LBBAP device implantation was attempted at 14 European centres, for any indication. The study comprised 2533 patients (mean age 73.9 years, female 57.6%, heart failure 27.5%). LBBAP lead implantation success rate for bradyarrhythmia and heart failure indications was 92.4% and 82.2%, respectively. The learning curve was steepest for the initial 110 cases and plateaued after 250 cases. Independent predictors of LBBAP lead implantation failure were heart failure, broad baseline QRS and left ventricular end-diastolic diameter. The predominant LBBAP capture type was left bundle fascicular capture (69.5%), followed by left ventricular septal capture (21.5%) and proximal left bundle branch capture (9%). Capture threshold (0.77 V) and sensing (10.6 mV) were stable during mean follow-up of 6.4 months. The complication rate was 11.7%. Complications specific to the ventricular transseptal route of the pacing lead occurred in 209 patients (8.3%).

Conclusions

LBBAP is feasible as a primary pacing technique for both bradyarrhythmia and heart failure indications. Success rate in heart failure patients and safety need to be improved. For wider use of LBBAP, randomized trials are necessary to assess clinical outcomes.