Biventricular endocardial pacing and left bundle branch area pacing for cardiac resynchronization: Mechanistic insights from electrocardiographic imaging, acute hemodynamic response, and magnetic resonance imaging.

Biventricular endocardial pacing (BiV-endo) has demonstrated superior cardiac resynchronization compared to conventional biventricular epicardial pacing (BiV-epi). Left bundle branch area pacing (LBBAP) may also achieve effective cardiac resynchronization therapy (CRT). The purpose of this study was to compare the acute electrical and hemodynamic effects of BiV-epi, BiV-endo, and LBBAP delivered from the LV endocardium and to assess how myocardial scar affects response. Eleven patients with heart failure and indications for CRT underwent a temporary pacing study with electrocardiographic imaging (ECGi) and hemodynamic assessment. BiV-endo was delivered by stimulation of the left ventricular (LV) lateral wall, and LBBAP was delivered by stimulation of the LV septum, at the site of a Purkinje potential. LV activation time (LVAT-95), LV dyssynchrony index (LVDI), biventricular activation time (BIVAT-90), and biventricular dyssynchrony index (BIVDI) were calculated. Myocardial scar was assessed using magnetic resonance imaging (MRI). The protocol was completed in 10 patients. Compared to BiV-epi (LVAT-95: 79.2 ± 13.1 ms; LVDI: 26.6 ± 3.4 ms) LV resynchronization was superior during BiV-endo (LVAT-95: 48.5 ± 14.9 ms; P = .001; LVDI: 16.6 ± 6.4 ms; P = .002) and LBBAP (LVAT-95: 48.9 ± 12.5 ms; P = .001; LVDI: 15.3 ± 3.4 ms; P = .001). Biventricular resynchronization was similarly superior during BiV-endo and LBBAP vs BiV-epi (BIVAT-90 and BIVDI; P <.05). The rate of acute hemodynamic responders was higher during BiV-endo (90%) and LBBAP (70%) vs BiV-epi (50%). The benefits of LBBAP (but not BiV-endo) on LV resynchronization were attenuated when septal scar was present in a subset of 8 patients who underwent MRI. Our findings suggest superior electrical resynchronization and a higher proportion of acute hemodynamic responders during BiV-endo and LBBAP compared to BiV-epi. Electrical resynchronization was similar between BiV-endo and LBBAP; however, septal scar seemed to attenuate response to LBBAP.

Elliott MK ，Strocchi M ，Sieniewicz BJ ，Sidhu B ，Mehta V ，Wijesuriya N ，Behar JM ，Thorpe A ，Martic D ，Wong T ，Niederer S ，Rinaldi CA ... -  《-》

Effect of scar and His-Purkinje and myocardium conduction on response to conduction system pacing.

Conduction system pacing (CSP), in the form of His bundle pacing (HBP) or left bundle branch pacing (LBBP), is emerging as a valuable cardiac resynchronization therapy (CRT) delivery method. However, patient selection and therapy personalization for CSP delivery remain poorly characterized. We aim to compare pacing-induced electrical synchrony during CRT, HBP, LBBP, HBP with left ventricular (LV) epicardial lead (His-optimized CRT [HOT-CRT]), and LBBP with LV epicardial lead (LBBP-optimized CRT [LOT-CRT]) in patients with different conduction disease presentations using computational modeling. We simulated ventricular activation on 24 four-chamber heart geometries, including His-Purkinje systems with proximal left bundle branch block (LBBB). We simulated septal scar, LV lateral wall scar, and mild and severe myocardium and LV His-Purkinje system conduction disease by decreasing the conduction velocity (CV) down to 70% and 35% of the healthy CV. Electrical synchrony was measured by the shortest interval to activate 90% of the ventricles (90% of biventricular activation time [BIVAT-90]). Severe LV His-Purkinje conduction disease favored CRT (BIVAT-90: HBP 101.5 ± 7.8 ms vs. CRT 93.0 ± 8.9 ms, p < .05), with additional electrical synchrony induced by HOT-CRT (87.6 ± 6.7 ms, p < .05) and LOT-CRT (73.9 ± 7.6 ms, p < .05). Patients with slow myocardium CV benefit more from CSP compared to CRT (BIVAT-90: CRT 134.5 ± 24.1 ms; HBP 97.1 ± 9.9 ms, p < .01; LBBP: 101.5 ± 10.7 ms, p < .01). Septal but not lateral wall scar made CSP ineffective, while CRT was able to resynchronize the ventricles in the presence of septal scar (BIVAT-90: baseline 119.1 ± 10.8 ms vs. CRT 85.1 ± 14.9 ms, p < .01). Severe LV His-Purkinje conduction disease attenuates the benefits of CSP, with additional improvements achieved with HOT-CRT and LOT-CRT. Septal but not lateral wall scars make CSP ineffective.

Strocchi M ，Gillette K ，Neic A ，Elliott MK ，Wijesuriya N ，Mehta V ，Vigmond EJ ，Plank G ，Rinaldi CA ，Niederer SA ... -  《-》

Efficacy on resynchronization and longitudinal contractile function comparing His-bundle pacing with conventional biventricular pacing: a substudy to the His-alternative study.

His-bundle pacing has emerged as a novel method to deliver cardiac resynchronization therapy (CRT). However, there are no data comparing conventional biventricular (BiV)-CRT with His-CRT with regard to effects on mechanical dyssynchrony and longitudinal contractile function. Patients with symptomatic heart failure, left ventricular ejection fraction ≤ 35%, and left bundle branch block (LBBB) by strict ECG criteria were randomized 1:1 to His-CRT or BiV-CRT. Two-dimensional strain echocardiography was performed prior to CRT implantation and at 6 months after implantation. Differences in changes in mechanical dyssynchrony (standard deviation of time-to-peak in 12 midventricular and basal segments) and regional longitudinal strain in the six left ventricular walls were compared between the BiV-CRT and His-CRT groups.In the on-treatment analysis, 31 received BiV-CRT and 19 His-CRT. In both groups, mechanical dyssynchrony was significantly reduced after 6 months [BiV group from 120 ms (±45) to 63 ms (±22), P < 0.001, and His group from 116 ms (±54) to 49 ms (±11), P < 0.001] but no significant differences in changes could be demonstrated between groups [-9.0 ms (-36; 18), P = 0.50]. Global longitudinal strain (GLS) improved in both groups [BiV group from -9.1% (±2.7) to -10.7% (±2.6), P = 0.02, and His group from -8.6% (±2.1) to -11.1% (±2.0), P < 0.001], but no significant differences in changes could be demonstrated from baseline to follow-up [-0.9% (-2.4; -0.6), P = 0.25] between groups. There were no regional differences between groups. In heart failure, patients with LBBB, BiV-CRT, and His-CRT have comparable effects with regard to improvements in mechanical dyssynchrony and longitudinal contractile function.

Højgaard EV ，Philbert BT ，Linde JJ ，Winsløw UC ，Svendsen JH ，Vinther M ，Risum N ... -  《-》

Left bundle branch area pacing reduces epicardial dispersion of repolarization compared with biventricular cardiac resynchronization therapy.

Biventricular endocardial pacing (BiV-endo) and left bundle branch area pacing (LBBAP) are novel methods of delivering cardiac resynchronization therapy. These techniques are associated with improved activation times and acute hemodynamic response compared with conventional biventricular epicardial pacing (BiV-epi); however, the effects on repolarization and arrhythmic risk are unknown. The purpose of this study was to compare the effects of temporary BiV-epi, BiV-endo, and LBBAP on epicardial left ventricular (LV) repolarization using electrocardiographic imaging (ECGi). Eleven patients indicated for cardiac resynchronization therapy underwent a temporary pacing protocol with ECGi. BiV-endo was delivered via endocardial stimulation of the LV lateral wall. LBBAP was delivered by pacing the LV septum. Epicardial LV repolarization time (LVRT-95; time taken for 95% of the LV to repolarize), LV RT dispersion, mean LV activation recovery interval (ARI), LV ARI dispersion, and RT gradients were calculated. The protocol was completed in 10 patients. During LBBAP, there were significant reductions in LVRT-95 (94.9 ± 17.4 ms vs 125.0 ± 29.4 ms; P = .03) and LV RT dispersion (29.4 ± 6.3 ms vs 40.8 ± 11.4 ms; P = .015) compared with BiV-epi. In contrast, there were no significant differences between baseline, BiV-epi, or BiV-endo. There was a nonsignificant reduction in mean RT gradients between LBBAP and baseline rhythm (0.74 ± 0.22 ms/mm vs 1.01 ± 0.31 ms/mm; P = .07). There were no significant differences in mean LV ARI or LV ARI dispersion between groups. Temporary LBBAP reduces epicardial dispersion of repolarization compared with conventional BiV-epi. Further study is required to determine whether these repolarization changes on ECGi translate into a reduced risk of ventricular arrhythmia in clinical practice.

Elliott MK ，Strocchi M ，Sieniewicz BJ ，Mehta V ，Wijesuriya N ，deVere F ，Howell S ，Thorpe A ，Martic D ，Bishop MJ ，Niederer S ，Rinaldi CA ... -  《-》

Evaluation of Right Heart Structure and Function in Pacemaker-dependent Patients by Two-Dimensional Speckle Tracking Echocardiography: A 1-Year Prospective Cohort Study.

Left bundle branch area pacing (LBBAP) has evolved into a practical and secure pacing procedure. However, previous studies of LBBAP focused on left heart function and synchronization and lacked assessment of right heart structure and function and interventricular synchrony. The objective of this study was to examine the impacts of LBBAP, right ventricular (RV) septal pacing (RVSP), and RV apical pacing (RVAP) on right heart structure, function and interventricular synchrony. Between January and July 2021, A total of 90 patients exhibited a normal left ventricular (LV) ejection fraction and received dual chamber pacemaker implantation for bradycardia at Beijing Anzhen Hospital. The patients were assigned to three groups based on the pacing site: LBBAP, RVSP, or RVAP. RV function was evaluated using right ventricular fractional area change (RVFAC), tricuspid annular plane systolic excursion (TAPSE), tissue Doppler-derived tricuspid lateral annular systolic velocity (S'), right ventricular myocardial performance index (RVMPI), global longitudinal strain of the right ventricle (GLSRV), and right ventricular free wall longitudinal strain (RVFWLS). Tricuspid regurgitation (TR) was assessed using vena contracta magnitude (VCM) and the ratio of TR jet area to right atrial area (RAA). Interventricular mechanical synchrony was evaluated using interventricular mechanical delay (IVMD) and left ventricular to right ventricular time-to-peak standard deviation (LV-RV TPSD). Baseline echocardiographic parameters and characteristics were comparable among the three groups. No significant differences were observed in the LBBAP group from baseline to follow-up for QRS duration (p = 0.783), TAPSE (p = 0.122), RVFAC (p = 0.679), RVMPI (p = 0.93), GLSRV (p = 0.511), RVFWLS (p = 0.939), VCM (p = 0.467), and TR jet area/RAA (p = 0.667). In contrast, a significant decline was observed in the RVAP group (all p < 0.05). RVSP resulted in a similar percentage reduction in TAPSE, GLSRV, and RVFWLS (all p > 0.05). However, there were significant differences in RVFAC (p = 0.009), RVMPI (p = 0.037), TRVCM (p = 0.046), and TR jet area/RAA (p = 0.033) in the RVSP group. Moreover, compared to baseline, a 1-year follow-up showed that LBBAP significantly reduced IVMD (from 17.3 ± 26.5 ms to 8.6 ± 7.1 ms, p < 0.05) and LV-RV TPSD [from 16.41 (8.81-42.5) to 12.28 (5.64-23.7), p < 0.05], while RVSP and RVAP worsened IVMD and LV-RV TPSD (all p < 0.05). Compared with RVSP or RVAP, LBBAP can maintain RV function and improve electrical and interventricular synchrony, with limited TR deterioration after a 1-year follow-up. No. ChiCTR2100048503, https://www.chictr.org.cn/showproj.html?proj=129290.

Mei Y ，Han R ，Cheng L ，Li H ，He Y ，Liu W ，Wu Y ... -  《-》