Accidental Conduction System Pacing in Patient with Displaced Cardiac Resynchronization Therapy Leads.

A 69-year-old woman with a history of heart failure with reduced ejection fraction presented for device interrogation of her cardiac implantable electronic device (CIED), revealing lead and pulse generator displacement. Surprisingly, she exhibited a narrow QRS on the ECG despite an underlying right bundle branch block, suggesting unintentional conduction system pacing (CSP). Traditional cardiac resynchronization therapy has been widely used for patients with heart failure, but alternatives like CSP are emerging as viable options. Given the global rise in CIED utilization, regular follow-up, device troubleshooting, and embracing remote monitoring are essential to manage and optimize patient outcomes.

Interaction of left ventricular size with the outcome of cardiac resynchronization therapy in Japanese patients.

BACKGROUND: We analyzed the influence of the QRS duration (QRSd) to LV end-diastolic volume (LVEDV) ratio on cardiac resynchronization therapy (CRT) outcomes in heart failure patients classified as III/IV per the New York Heart Association (NYHA) and with small body size. HYPOTHESIS: We proposed the hypothesis that the QRSd/LV size ratio is a better index of the CRT substrate. METHODS: We enrolled 114 patients with advanced heart failure (NYHA class III/IV, and LV ejection fraction >35%) who received a CRT device, including those with left bundle branch block (LBBB) and QRSd ≥120 milliseconds (n = 60), non-LBBB and QRSd ≥150 milliseconds (n = 30) and non-LBBB and QRSd of 120-149 milliseconds (n = 24). RESULTS: Over a mean follow-up period of 65 ± 58 months, the incidence of the primary endpoint, a composite of all-cause death and hospitalization for heart failure, showed no significant intergroup difference (43.3% vs. 50.0% vs. 37.5%, respectively, p = .72). Similarly, among 104 patients with QRSd/LVEDV ≥ 0.67 (n = 54) and QRSd/LVEDV < 0.67 (n = 52), no significant differences were observed in the incidence of the primary endpoint (35.1% vs. 51.9%, p = .49). Nevertheless, patients with QRSd/LVEDV ≥ 0.67 showed better survival than those with QRSd/LVEDV < 0.67 (14.8% vs. 34.6%, p = .0024). CONCLUSION: Advanced HF patients with a higher QRSd/LVEDV ratio showed better survival in this small-body-size population. Thus, the risk is concentrated among those with a larger QRSd, and patients with a relatively smaller left ventricular size appeared to benefit from CRT.

Impact of New-Onset Right Bundle-Branch Block After Transcatheter Aortic Valve Replacement on Permanent Pacemaker Implantation.

BACKGROUND: A delayed and recurrent complete atrioventricular block (CAVB) is a life-threatening complication of transcatheter aortic valve replacement (TAVR). Post-TAVR evaluation may be important in predicting delayed and recurrent CAVB requiring permanent pacemaker implantation (PPI). The impact of new-onset right bundle-branch block (RBBB) after TAVR on PPI remains unknown. METHODS AND RESULTS: In total, 407 patients with aortic stenosis who underwent TAVR were included in this analysis. Intraprocedural CAVB was defined as CAVB that occurred during TAVR. A 12-lead ECG was evaluated at baseline, immediately after TAVR, on postoperative days 1 and 5, and according to the need to identify new-onset bundle-branch block (BBB) and CAVB after TAVR. Forty patients (9.8%) required PPI, 17 patients (4.2%) had persistent intraprocedural CAVB, and 23 (5.7%) had delayed or recurrent CAVB after TAVR. The rates of no new-onset BBB, new-onset left BBB, and new-onset RBBB were 65.1%, 26.8%, and 4.7%, respectively. Compared with patients without new-onset BBB and those with new-onset left BBB, the rate of PPI was higher in patients with new-onset RBBB (3.4% versus 5.6% versus 44.4%, P<0.0001). On post-TAVR evaluation in patients without persistent intraprocedural CAVB, the multivariate logistic regression analysis showed that new-onset RBBB was a statistically significant predictor of PPI compared with no new-onset BBB (odds ratio [OR], 18.0 [95% CI, 5.94-54.4]) in addition to the use of a self-expanding valve (OR, 2.97 [95% CI, 1.09-8.10]). CONCLUSIONS: Patients with new-onset RBBB after TAVR are at high risk for PPI.

A Revised Definition of Left Bundle Branch Block Using Time to Notch in Lead I.

Importance: Current left bundle branch block (LBBB) criteria are based on animal experiments or mathematical models of cardiac tissue conduction and may misclassify patients. Improved criteria would impact referral decisions and device type for cardiac resynchronization therapy. Objective: To develop a simple new criterion for LBBB based on electrophysiological studies of human patients, and then to validate this criterion in an independent population. Design, Setting, and Participants: In this diagnostic study, the derivation cohort was from a single-center, prospective study of patients undergoing electrophysiological study from March 2016 through November 2019. The validation cohort was assembled by retrospectively reviewing medical records for patients from the same center who underwent transcatheter aortic valve replacement (TAVR) from October 2015 through May 2022. Exposures: Patients were classified as having LBBB or intraventricular conduction delay (IVCD) as assessed by intracardiac recording. Main Outcomes and Measures: Sensitivity and specificity of the electrocardiography (ECG) criteria assessed in patients with LBBB or IVCD. Results: A total of 75 patients (median [IQR] age, 63 [53-70.5] years; 21 [28.0%] female) with baseline LBBB on 12-lead ECG underwent intracardiac recording of the left ventricular septum: 48 demonstrated complete conduction block (CCB) and 27 demonstrated intact Purkinje activation (IPA). Analysis of surface ECGs revealed that late notches in the QRS complexes of lateral leads were associated with CCB (40 of 48 patients [83.3%] with CCB vs 13 of 27 patients [48.1%] with IPA had a notch or slur in lead I; P = .003). Receiver operating characteristic curves for all septal and lateral leads were constructed, and lead I displayed the best performance with a time to notch longer than 75 milliseconds. Used in conjunction with the criteria for LBBB from the American College of Cardiology/American Heart Association/Heart Rhythm Society, this criterion had a sensitivity of 71% (95% CI, 56%-83%) and specificity of 74% (95% CI, 54%-89%) in the derivation population, contrasting with a sensitivity of 96% (95% CI, 86%-99%) and specificity of 33% (95% CI, 17%-54%) for the Strauss criteria. In an independent validation cohort of 46 patients (median [IQR] age, 78.5 [70-84] years; 21 [45.7%] female) undergoing TAVR with interval development of new LBBB, the time-to-notch criterion demonstrated a sensitivity of 87% (95% CI, 74%-95%). In the subset of 10 patients with preprocedural IVCD, the criterion correctly distinguished IVCD from LBBB in all cases. Application of the Strauss criteria performed similarly in the validation cohort. Conclusions and Relevance: The findings suggest that time to notch longer than 75 milliseconds in lead I is a simple ECG criterion that, when used in conjunction with standard LBBB criteria, may improve specificity for identifying patients with LBBB from conduction block. This may help inform patient selection for cardiac resynchronization or conduction system pacing.

Response predictors to cardiac resynchronization therapy in chronic heart failure: a 10-year-cardiovascular center experience.

BACKGROUND: Cardiac resynchronization therapy (CRT) has been established as an effective therapy for heart failure with reduced ejection fraction. Randomized clinical trials have shown its impact on mortality and HF hospitalizations, as well as improvement of symptoms and quality of life. OBJECTIVES: Finding clinical, electrocardiographic, and echocardiographic variables that may predict the response to cardiac resynchronization therapy (CRT). METHODS: We performed a single-center, observational, analytic, and retrospective study that included 102 patients with heart failure (HF) diagnosis who underwent CRT according to guideline-directed therapy from January 2010 to April 2020 in a third-level center. CRT response was defined as an improvement of New York Heart Association functional class in at least 1 category associated with a recovery of ≥ 5% in the left ventricular ejection fraction (LVEF). RESULTS: Our study population was 102 patients of which 61 (59.8%) were men. The mean age at HF diagnosis was 54 ± 18.7 years. Ischemic heart disease was the etiology in 37 (36.3%) cases. Fifty-one (50%) patients were classified as responders. Responders had wider QRS, and lower LVEF and right ventricular fractional area change at baseline. After CRT, responders had a greater reduction of QRS duration, and improvement in LVEF, global longitudinal strain, and echocardiographic dyssynchrony parameters. Multivariate regression analysis showed that left bundle branch block (LBBB), left ventricular end-diastolic volume (LVEDV), tricuspid annular plane systolic excursion (TAPSE), and baseline difference of pre-ejection periods were predictors of a positive response to CRT in this population. CONCLUSIONS: LBBB, TAPSE, LVEDV, and pre-ejection time difference are independent variables that can predict adequate response to CRT.

ANTECEDENTES: La terapia de resincronización cardíaca (TRC) se ha establecido como una terapia efectiva para la insuficiencia cardíaca con fracción de eyección reducida. Ensayos clínicos aleatorizados han demostrado su impacto en la mortalidad y hospitalizaciones por insuficiencia cardíaca, así como la mejora de los síntomas y la calidad de vida. OBJETIVOS: Determinar las variables clínicas, electrocardiográficas y ecocardiográficas que puedan predecir la respuesta a la terapia de resincronización cardíaca (TRC). MÉTODO: Estudio unicéntrico, observacional, analítico, retrospectivo, que incluyó 102 pacientes con diagnóstico de IC sometidos a TRC y terapia dirigida por guías, de enero de 2010 a abril de 2020, en un centro de tercer nivel. La respuesta a TRC fue definida como mejoría de la clase funcional de la New York Heart Association en al menos 1 categoría, asociado con una recuperación ≥ 5% en la fracción de expulsión del ventrículo izquierdo (FEVI). RESULTADOS: Incluimos a 102 pacientes, 61 (59.8%) fueron hombres. El promedio de edad al diagnóstico de IC fue 54 ± 18.7 años. La cardiopatía isquémica fue la etiología en 37 (36.3%) pacientes. 51 (50%) pacientes, fueron clasificados como respondedores. Los respondedores presentaron QRS amplio, menor FEVI y menor fracción de acortamiento del ventrículo derecho al inicio del estudio. Después de la TRC, los respondedores tuvieron una mayor reducción en la duración del QRS, mejoría en la FEVI, strain longitudinal global y parámetros de disincronía ecocardiográfica. El análisis de regresión multivariado mostró que el bloqueo de rama izquierdo (BRI), el volumen telediastólico del ventrículo izquierdo (VTDVI) la excursión sistólica del plano anular tricuspídeo (TAPSE) y la diferencia basal del período expulsivo fueron predictores de respuesta positiva a TRC. CONCLUSIONES: BRI, TAPSE, VTDVI y la diferencia basal de períodos preexpulsivos son variables independientes que predicen respuesta adecuada a TRC.

Prediction of pacemaker-induced cardiomyopathy using a convolutional neural network based on clinical findings prior to pacemaker implantation.

Risk factors for pacemaker-induced cardiomyopathy (PICM) have been previously reported, including a high burden of right ventricular pacing, lower left ventricular ejection fraction, a wide QRS duration, and left bundle branch block before pacemaker implantation (PMI). However, predicting the development of PICM remains challenging. This study aimed to use a convolutional neural network (CNN) model, based on clinical findings before PMI, to predict the development of PICM. Out of a total of 561 patients with dual-chamber PMI, 165 (mean age 71.6 years, 89 men [53.9%]) who underwent echocardiography both before and after dual-chamber PMI were enrolled. During a mean follow-up period of 1.7 years, 47 patients developed PICM. A CNN algorithm for prediction of the development of PICM was constructed based on a dataset prior to PMI that included 31 variables such as age, sex, body mass index, left ventricular ejection fraction, left ventricular end-diastolic diameter, left ventricular end-systolic diameter, left atrial diameter, severity of mitral regurgitation, severity of tricuspid regurgitation, ischemic heart disease, diabetes mellitus, hypertension, heart failure, New York Heart Association class, atrial fibrillation, the etiology of bradycardia (sick sinus syndrome or atrioventricular block) , right ventricular (RV) lead tip position (apex, septum, left bundle, His bundle, RV outflow tract), left bundle branch block, QRS duration, white blood cell count, haemoglobin, platelet count, serum total protein, albumin, aspartate transaminase, alanine transaminase, estimated glomerular filtration rate, sodium, potassium, C-reactive protein, and brain natriuretic peptide. The accuracy, sensitivity, specificity, and area under the curve of the CNN model were 75.8%, 55.6%, 83.3% and 0.78 respectively. The CNN model could accurately predict the development of PICM using clinical findings before PMI. This model could be useful for screening patients at risk of developing PICM, ensuring timely upgrades to physiological pacing to avoid missing the optimal intervention window.

Paced QRS morphology mimicking complete left bundle branch block induced by right ventricular pacing is associated with pacing-induced cardiomyopathy.

INTRODUCTION: Right ventricular (RV) pacing sometimes causes left ventricular (LV) systolic dysfunction, also known as pacing-induced cardiomyopathy (PICM). However, the association between specifically paced QRS morphology and PICM development has not been elucidated. This study aimed to investigate the association between paced QRS mimicking a complete left bundle branch block (CLBBB) and PICM development. METHODS: We retrospectively screened 2009 patients who underwent pacemaker implantation from 2010 to 2020 in seven institutions. Patients who received pacemakers for an advanced atrioventricular block or bradycardia with atrial fibrillation, baseline LV ejection fraction (LVEF) ≥ 50%, and echocardiogram recorded at least 6 months postimplantation were included. The paced QRS recorded immediately after implantation was analyzed. A CLBBB-like paced QRS was defined as meeting the CLBBB criteria of the American Heart Association/American College of Cardiology Foundation/Heart Rhythm Society in 2009. PICM was defined as a ≥10% LVEF decrease, resulting in an LVEF of <50%. RESULTS: Among the 270 patients analyzed, PICM was observed in 38. Baseline LVEF was lower in patients with PICM, and CLBBB-like paced QRS was frequently observed in PICM. Multivariate analysis revealed that low baseline LVEF (odds ratio [OR]: 0.93 per 1% increase, 95% confidence interval [CI]: 0.89-0.98, p = 0.006) and CLBBB-like paced QRS (OR: 2.69, 95% CI: 1.25-5.76, p = 0.011) were significantly associated with PICM development. CONCLUSION: CLBBB-like paced QRS may be a novel risk factor for PICM. RV pacing, which causes CLBBB-like QRS morphology, may need to be avoided, and patients with CLBBB-like paced QRS should be followed-up carefully.

Incidence, Risk Factors, and Outcomes Associated With Permanent Pacemaker Implantation Following Tricuspid Valve Surgery.

BACKGROUND: Data regarding permanent pacemaker (PPM) implantation following tricuspid valve surgery (TVS) are limited. We sought to evaluate its incidence, risk factors, and outcomes. METHODS AND RESULTS: Medicare beneficiaries who underwent TVS from 2013 to 2020 were identified. Patients who underwent TVS for endocarditis were excluded. The primary exposure of interest was new PPM after TVS. Outcomes included all-cause mortality and readmission with endocarditis or heart failure on follow-up. Among the 13 294 patients who underwent TVS, 2518 (18.9%) required PPM placement. Risk factors included female sex (relative risk [RR], 1.26 [95% CI, 1.17-1.36], P<0.0001), prior sternotomy (RR, 1.12 [95% CI, 1.02-1.23], P=0.02), preoperative second-degree heart block (RR, 2.20 [95% CI, 1.81-2.69], P<0.0001), right bundle-branch block (RR, 1.21 [95% CI, 1.03-1.41], P=0.019), bifascicular block (RR, 1.43 [95% CI, 1.06-1.93], P=0.02), and prior malignancy (RR, 1.23 [95% CI, 1.01-1.49], P=0.04). Tricuspid valve (TV) replacement was associated with a significantly higher risk of PPM implantation when compared with TV repair (RR, 3.20 [95% CI, 2.16-4.75], P<0.0001). After a median follow-up of 3.1 years, mortality was not different in patients who received PPM compared with patients who did not (hazard ratio [HR], 1.02 [95% CI, 0.93-1.12], P=0.7). PPM placement was not associated with a higher risk of endocarditis but was associated with a higher risk of heart failure readmission (HR, 1.28 [95% CI, 1.14-1.43], P<0.001). CONCLUSIONS: PPM implantation frequently occurs after TVS, notably in female patients and patients undergoing TV replacement. Although mortality is not increased, it is associated with higher rates of heart failure rehospitalization.

Predictors for new-onset conduction block in patients with pure native aortic regurgitation after transcatheter aortic valve replacement with a new-generation self-expanding valve (VitaFlow Liberty™): a retrospective cohort study.

BACKGROUND: New-generation self-expanding valves can improve the success rate of transcatheter aortic valve replacement (TAVR) for severe pure native aortic regurgitation (PNAR). However, predictors of new-onset conduction block post-TAVR using new-generation self-expanding valves in patients with PNAR remain to be established. Therefore, this study aimed to identify predictors of new-onset conduction block post-TAVR using new-generation self-expanding valves (VitaFlow Liberty™) in patients with PNAR. METHODS: In this retrospective cohort study, patients were categorized into pacemaker and non-pacemaker groups based on their need for new postoperative permanent pacemaker implantation (PPI). Based on the postoperative presence of either new-onset complete left bundle branch block (cLBBB) or high-grade atrioventricular block (AVB), patients were further classified into conduction disorder and non-conduction disorder groups. Laboratory, echocardiographic, computed tomography, preoperative and postoperative electrocardiography, and procedural and clinical data were collected immediately after TAVR and during hospitalization and compared between the groups. Multivariate logistic regression analysis was performed incorporating the significant variables from the univariate analyses. RESULTS: This study examined 68 consecutive patients with severe PNAR who underwent TAVR. In 20 patients, a permanent pacemaker was fitted postoperatively. Multivariate logistic regression analysis revealed an association between the need for postoperative PPI and preoperative complete right bundle branch block (cRBBB) or first-degree AVB, as well as a non-tubular left ventricular outflow tract (LVOT). In addition, valve implantation depth and angle of aortic root were independent predictors of new-onset cLBBB or high-grade AVB developing post-TAVR. The predictive value of valve implantation depth and angle of aortic root was further supported by receiver operating characteristic curve analysis results. CONCLUSIONS: In patients with PNAR undergoing TAVR using self-expanding valves, preoperative cRBBB or first-degree AVB and a non-tubular LVOT were indicators of a higher likelihood of PPI requirement. Moreover, deeper valve implantation depth and greater angle of aortic root may be independent risk factors for new-onset cLBBB or high-grade AVB post-TAVR. Valve implantation depth and angle of aortic root values may be used to predict the possibility of new cLBBB or high-grade AVB post-TAVR.

Treatment strategy for heart failure complicated with complete left bundle branch block and atrial tachycardia: a case report.

BACKGROUND: For patients with heart failure combined with complete left bundle branch block, cardiac resynchronization therapy is an important therapeutic method. If these patients also have atrial tachycardia, how to choose a treatment strategy deserves discussion. CASE PRESENTATION: A Chinese woman in her early 70s was admitted due to recurrent episodes of chest distress and asthma for 1 year. Physical and laboratory examinations showed filling of the jugular vein, lung rales, left enlargement of the heart boundary, edema of the lower limbs and elevation of N-terminal pro b-type natriuretic peptide. An electrocardiogram showed atrial tachycardia and a left bundle branch block. An echocardiography revealed enlargement of the left ventricle and left ventricular systolic dysfunction. After obtaining informed consent, the treatment strategy decided upon by the team was to use biventricular cardiac resynchronization therapy treatment and to not intervene for the atrial tachycardia, with left bundle branch area pacing as a backup. Due to twisted and narrow coronary vein branches, traditional biventricular pacing failed, and then, left bundle branch area pacing was attempted successfully. A follow-up echocardiography at 1 year showed improved systolic function. The outcomes for this patient are favorable, but the choice of interventional strategy is worthy of discussion in this case. CONCLUSION: For patients with heart failure combined with left bundle branch block and atrial tachycardia, left bundle branch area pacing can replace traditional biventricular pacing for cardiac resynchronization therapy treatment, and the therapeutic effect is significant. However, multiple factors need to be considered when formulating strategies, including whether there is bundle branch block under sinus rhythm, the success and recurrence rate of atrial tachycardia ablation, the response of cardiac resynchronization therapy, the costs of different strategies, and instrument implantation issues.

How to assess and treat right ventricular electromechanical dyssynchrony in post-repair tetralogy of Fallot: insights from imaging, invasive studies, and computational modelling.

BACKGROUND AND AIMS: Right bundle branch block (RBBB) and resulting right ventricular (RV) electromechanical discoordination are thought to play a role in the disease process of subpulmonary RV dysfunction that frequently occur post-repair tetralogy of Fallot (ToF). We sought to describe this disease entity, the role of pulmonary re-valvulation, and the potential added value of RV cardiac resynchronization therapy (RV-CRT). METHODS: Two patients with repaired ToF, complete RBBB, pulmonary regurgitation, and significantly decreased RV function underwent echocardiography, cardiac magnetic resonance, and an invasive study to evaluate the potential for RV-CRT as part of the management strategy. The data were used to personalize the CircAdapt model of the human heart and circulation. Resulting Digital Twins were analysed to quantify the relative effects of RV pressure and volume overload and to predict the effect of RV-CRT. RESULTS: Echocardiography showed components of a classic RV dyssynchrony pattern which could be reversed by RV-CRT during invasive study and resulted in acute improvement in RV systolic function. The Digital Twins confirmed a contribution of electromechanical RV dyssynchrony to RV dysfunction and suggested improvement of RV contraction efficiency after RV-CRT. The one patient who underwent successful permanent RV-CRT as part of the pulmonary re-valvulation procedure carried improvements that were in line with the predictions based on his Digital Twin. CONCLUSION: An integrative diagnostic approach to RV dysfunction, including the construction of Digital Twins may help to identify candidates for RV-CRT as part of the lifetime management of ToF and similar congenital heart lesions.

Membranous Septum Length Predicts New Conduction Abnormalities in Surgical Aortic Valve Replacement: A Novel Predictor for Permanent Pacemaker Implantation After Surgical Aortic Valve Replacement.

INTRODUCTION: The membranous septum (MS) length measured by cardiac computed tomography (CT) is useful for the prediction of permanent pacemaker implantation (PPMI) and new left bundle branch block (LBBB) after transcatheter aortic valve replacement. However, its predictive value for patients undergoing surgical aortic valve replacement (SAVR) is unknown. METHODS: A total of 2531 consecutive patients were registered in the institutional Society of Thoracic Surgeons database between July 2017 and June 2020. Patients who underwent non-SAVR procedures, had prior pacemaker/implantable cardioverter defibrillator, prior SAVR, no preprocedural CT assessment, or suboptimal CT imaging were excluded. RESULTS: A total of 126 SAVR with preprocedural CT assessment were analyzed. Bicuspid aortic valve morphology was confirmed on CT in 59.5% of patients. There were three new PPMIs and five new LBBBs observed after SAVR at the time of discharge. In-hospital mortality was 0.8%. Low left ventricular (LV) ejection fraction (<50%), LV mass index >120 g/m2, large right coronary artery height, and MS length <1.5 mm predicted new PPMI/LBBB. Multivariate analysis showed LV mass index >120 g/m2 (odds ratio: 9.165; 95% confidence interval: 1.644-51.080; P = 0.011) and MS length <1.5 mm (odds ratio: 14.449; 95% confidence interval: 1.632-127.954; P = 0.016) were independent predictors for new PPMI/LBBB. CONCLUSIONS: Short MS length on preoperative cardiac CT is a powerful and novel predictor for the risk of new PPMI/LBBB after SAVR. Special care should be taken in patients with short MS length to avoid suture-mediated trauma.

Left ventricular lead placement in cardiac resynchronization therapy: Current data and potential explanations for the lack of benefit.

The present article reviews the literature on image-guided cardiac resynchronization therapy (CRT) studies. Improved outcome to CRT has been associated with the placement of a left ventricular (LV) lead in the latest activated segment free from scar. The majority of randomized controlled trials investigating guided LV lead implantation did not show superiority over conventional implantation approaches. Several factors may contribute to this paradoxical observation, including inclusion criteria favoring patients with left bundle branch block who already respond well to conventional anatomical LV lead implantation, differences in activation wavefronts during simultaneous right ventricular and LV pacing, incorrect definition of target regions, and limitations in coronary venous anatomy that prevent access to target regions that are detected by imaging. It is imperative that exclusion of patients lacking access to target regions from these studies would lead to larger benefit of image-guided CRT.

A shorter R wave peak time in left bundle branch pacing may not be a marker of more physiological ventricular activation: A case report.

Left bundle branch pacing (LBBp) is a promising alternative to conventional biventricular pacing cardiac resynchronization therapy. The left anterior fascicle (LAF) is adjacent to the left ventricular outflow tract, while the left posterior fascicle (LPF) dominates a broader area of the left ventricle. Whether LAF or LPF dominates ventricular activation has not been determined. We present the case of a 76-year-old man who underwent LBBp implantation and propose the left ventricular activation domination in LPF pacing, an alternative when LBBp is unavailable.