| Background:Left bundle branch area pacing(LBBAP)is a novel physiological pacing technique applicable to patients with bradycardia and also a new option for cardiac resynchronization therapy(CRT).The initial methodology of LBBAP emphasized left bundle trunk pacing(LBTP),resulting in a relatively lower success rate,serious septal injury,and longer operation time.Recently,many physicians proposed the concept of branch pacing,such as left anterior branch pacing(LAFP)and left posterior branch pacing(LPFP),which substantially facilitates the procedure with various pacing QRS morphology.However,whether the outcomes of various pacing modes differ in heart failure(HF)patients is still unclear.This study aimed to compare the electrophysiological characteristics and echocardiographic response rate among those distinct modes of LBBAP.Methods:HF patients undergoing successful LBBAP at our center were retrospectively included.Different modes of pacing were determined based on paced QRS morphology.The fluoroscopic images were collected to compare the lead tip position between the groups.The electrocardiograms(ECG)before and after LBBAP were used to measure the depolarization parameters(QRS duration[QRSd]and the interventricular delay[IVD]),and the repolarization parameters(QTc,TpeakTend[TpTe],and TpTe/QTc).The left ventricular ejection fraction(LVEF)and left ventricular end-diastolic diameter(LVEDD)of patients at baseline and follow-up were also recorded from medical records systems.The comparison of those ECG and echocardiographic parameters among groups were then performed.In addition,the lead parameters(R wave perception,pacing threshold,and impedance)and complications were compared.Results:A total of 64 HF patients were finally included,including 16(25.0%)patients in the LBTP group,22(34.4%)patients in the LAFP group,and 26(40.6%)patients in the LPFP group.The LBBAP lead tips were mainly distributed in zone 4 and zone 5,and the distribution features were significantly related to different pacing modes:LBTP was more likely to be in zone 4 while LAFP or LPFP was prone to locate in zone 5.After LBBAP,the ventricular depolarization parameters(QRSd and IVD)and repolarization parameters(QTc,TpTe,and TpTe/QTc)were significantly decreased,regardless of paced QRS morphology.Besides,the LVEF of the patients was significantly increased(LVEF 47.15 ±10.75 vs 32.81 ± 6.79%,P<0.001),LVEDD was significantly decreased(LVEDD 56.44 ±8.44 vs 65.00 ± 8.94 mm,P<0.001).There was no difference in the response rate and superresponse rate among groups(response rate:LAFP vs.LBTP vs.LPFP:89.5%vs.84.6%vs.75.0%;super-response rate:LAFP.vs.LBTP vs.LPFP:42.1%vs.38.5%vs.30.0%;P>0.05).In addition,the lead parameters remained stable and no significant differences were observed among groups.Conclusion:LPFP was the main pacing mode among HF patients after LBBAP.The paced QRS morphology was significantly related to the position of lead tips.After LBBAP,the ventricular depolarization synchronization and repolarization stability were both significantly improved,regardless of pacing modes.There was no significant difference in the echocardiographic response rate among distinct LBBAP modes.Background:Traditional biventricular pacing(BiVP)is an effective strategy for heart failure(HF)patients to improve cardiac function and reduce mortality,although 5%～10%of patients undergo BiVP failure due to anatomical factors,phrenic nerve stimulation,or unacceptable thresholds,and up to 30%-50%of BiVP patients showed non-responsive.Left bundle branch area pacing(LBBAP)has become a new option for cardiac resynchronization therapy(CRT)patients with remarkable performance in improving ventricular depolarization synchronization and cardiac function.Yet its influence on the dispersion of ventricular repolarization(DVR)remains unclear.The study aimed to assess the immediate effects of LBBAP and its optimization approaches on DVR and further compared those effects with BiVP,thus exploring better CRT delivery concerning repolarization stability in HF patients.Methods:HF patients undergoing successful BiVP or LBBAP implantation were retrospectively and consecutively enrolled for analysis.Electrocardiograms(ECGs)were collected before and around 24 hours after implantation.QRSd and repolarization parameters(QTc,Tpeak-Tend[TpTe],and TpTe/QTc)were measured.The changes of those ECG parameters after LBBAP and various LBBAP optimization approaches(including AV interval optimization,LBBAP-optimized CRT[LOT-CRT],and the addition of right ventricular pacing[RVP])were assessed in the LBBAP group.Besides,the comparison of the above parameters between LBBAP and BiVP was also performed.Results:A total of 109 HF patients were included in the study,with 49 patients in the LBBAP group and 60 in the BiVP group.After LBBAP,the QRSd shortened(128.83±10.93 vs.171.06±17.12ms,P<0.001)and DVR significantly improved:QTc(450.50 ±34.11 vs 477.07 ± 46.27 ms,P<0.001),TpTe(83.13 ± 12.40 vs 105.42± 15.11 ms,P<0.001),and TpTe/QTc(0.20[0.19,0.22]vs.0.23[0.21,0.24],P<0.001)all decreased.Various optimization approaches of LBBAP showed different influences on DVR.Both AV optimization and LOT-CRT further shortened QRSd,but the former showed no effect on DVR while the latter significantly increased DVR(TpTe[95.58±15.86 vs.77.84 ±17.51ms,P=0.003)]and TpTe/QTc[0.23±0.02 vs.0.19±0.02,P=0.001]).The addition of RVP increased DVR(TpTe[91.57 ± 12.45 vs.86.38±12.29ms,P=0.03]and TpTe/QTc[0.21 ± 0.02 vs.0.20± 0.02,P=0.03])without shortening QRSd.The post-operative DVR decreased in the LBBAP group while increased in the BiVP group compared to baseline.A significant difference was shown between LBBAP and BiVP groups in post-operative TpTe(84.39± 14.12 vs.113.20 ± 15.68,P<0.001),QTc(446.85 ± 38.56 vs.480.47 ± 34.69,P<0.001),and TpTe/QTc(0.20 ± 0.02 vs.0.25±0.03,P<0.001)despite their baseline consistency.Conclusions:LBBAP significantly improved DVR while shortening QRSd in HF patients.Various optimization approaches of LBBAP showed different influences on DVR:both AV optimization and LOT-CRT further shortened QRSd,but the former showed no effect on DVR while the latter significantly increased DVR;the addition of RVP increased DVR without shortening QRSd.LBBAP may provide better repolarization stability in comparison with BiVP immediately after the implantation in HF patients.Background:Left bundle branch area pacing(LBBAP)has become a safe and effective strategy for end-stage heart failure(HF)patients indicated for cardiac resynchronization therapy(CRT)and/or ventricular pacing.Yet the response rate for LBBAP was only 70%.The predictive factors for LBBAP response remain to be further elucidated.Repolarization parameters were demonstrated to be associated with cardiac mechanics and systolic function.This study aimed to investigate the effects of LBBAP on repolarization parameters and then evaluate the potential predictive value of those parameters for the echocardiographic response.Methods:HF patients undergoing successful LBBAP were consecutively included in the study.The parameters reflecting dispersion of ventricular repolarization(DVR),including QTc,Tpeak-Tend(TpTe),and TpTe/QTc,were measured before and around 24 hours after LBBAP implantation.The baseline and pacing parameters were compared according to baseline QRS morphology.Baseline and follow-up echocardiographic indices such as left ventricular ejection fraction(LVEF)and left ventricular end-diastolic diameter were recorded.The association between repolarization parameters and LBBAP response was then evaluated among patients with wide QRS using multivariate logistic analysis.Receiver operating characteristic analysis was further performed to get the optimal cutoff value.The predictive value was then assessed in the left bundle branch block(LBBB)group and the non-LBBB group,respectively.Results:A total of 59 HF patients were finally included.Tends of repolarization parameters varied according to different QRS configurations at baseline:DVR decreased among patients with bundle branch block(BBB)or CRT upgrade while slightly increased in patients with narrow QRS.LVEF was significantly improved with a response rate equal to 74.6%(44/59)for the total cohort.Among the 48 patients with QRS≥130ms,baseline characteristics were comparable between responders(n=36)and non-responders(n=12),with only post-implant TpTe significantly longer in non-responders than responders(90.1[82.0,99.3]vs.77.2[73.3,81.0],P<0.01).Multivariate analysis including postimplant TpTe and previously identified predictors demonstrated that post-implant TpTe was the independent predictor of LBBAP response(P<0.05).ROC analysis indicated an area under the curve of 0.77(95%CI,0.60-0.93)with a cutoff value of 81.2ms(P<0.01).Patients with post-implant TpTe<81.2ms had a significantly higher rate of echocardiographic response(93.3 vs 44.4%,P<0.01).Further subgroup analysis indicated that the predictive value of post-implant TpTe for LBBAP response was more significant in non-LBBB patients than in LBBB patients.Besides,no association between postimplant TpTe and LBBAP response was identified among patients with narrow QRS.Conclusions:Trends of repolarization parameters after LBBAP varied according to different QRS configurations at baseline:DVR significantly decreased among patients with BBB or CRT upgrade while slightly increased in patients with narrow QRS.Postimplant TpTe was associated with the echocardiographic response after LBBAP among patients with wide QRS,especially for non-LBBB patients. |
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