Effects of left bundle branch block on echocardiographic coronary flow assessment: A systematic review.

This systematic review investigates the diagnostic and prognostic utility of coronary flow reserve (CFR) assessment through echocardiography in patients with left bundle branch block (LBBB), a condition known to complicate the clinical evaluation of coronary artery disease (CAD). The literature search was performed on PubMed, EMBASE, Web of Science, Scopus, and Google Scholar, was guided by PRISMA standards up to March 2024, and yielded six observational studies that met inclusion criteria. These studies involved a diverse population of patients with LBBB, employing echocardiographic protocols to clarify the impact of LBBB on coronary flow dynamics. The findings emphasize the importance of CFR in stratifying cardiovascular risk and guiding clinical decision-making in patients with LBBB. Pooled results reveal that patients with LBBB and significant left anterior descending (LAD) artery stenosis exhibited a marked decrease in stress-peak diastolic velocity (MD = -19.03 [-23.58; -14.48] cm/s; p < .0001) and CFR (MD = -.60 [-.71; -.50]; p < .0001), compared to those without significant LAD lesions, suggesting the efficacy of stress echocardiography CFR assessment in the identification of clinically significant CAD among the LBBB population. This review highlights the clinical relevance of echocardiography CFR assessment as a noninvasive tool for evaluating CAD and stratifying risk in the presence of LBBB and underscores the need for standardized protocols in CFR measurement.

Assessment of three-dimensional (3-D) left ventricular ejection fraction and speckled tracking echocardiographic strain parameters in non-ischemic left bundle branch block (LBBB) patients and their association with cardiovascular events - A prospective observational study.

OBJECTIVE: To investigate the association between three-dimensional (3-D) left ventricular ejection fraction (LVEF) and various speckle tracking echocardiographic (STE) strain parameters in non-ischemic left bundle branch block (LBBB) patients with major adverse cardiovascular events (MACE) during a one-year follow-up phase. METHOD: A total of 50 patients with non-ischemic LBBB were assessed using various parameters of 3-D echocardiography. They were compared with their same-age and sex control group and then followed up with repeat 3-D echocardiography for MACE for one year. RESULTS: Composite outcomes were seen in (n = 11 [22 %], including cardiovascular mortality (n = 2 [4.0 %]) and hospitalization for heart failure (n = 9 [18.0 %]). Mean values of the left ventricle (LV) global longitudinal (GLS), circumferential (GCS), and radial (GRS) strains were -14.4 ± 5.6, -14.3 ± 5.8, and 15.3 ± 5.9 respectively in the study cases. Initial GLS values were significantly impaired among those who had clinical events (-9.2 vs -15.9). Also, significant worsening of GLS (p value < 0.001) was seen in patients with composite outcomes on follow-up. Cut-off values in receiver operating characteristic analyses for composite outcomes were: GLS more than -13.5, GCS more than -12.5, and GRS less than 14.5. Intra-class correlations for both intra-observer and inter-observer variability were found to be good. CONCLUSION: Impaired LV GLS and low 3-D LVEF are significantly associated with the occurrence of MACE in patients with non-ischemic LBBB. This strong association of LV GLS with outcomes can aid in risk stratification, prognostication, and clinical decision-making in non-ischemic LBBB.

A porcine large animal model of radiofrequency ablation-induced left bundle branch block.

Background: Electrocardiographic (ECG) features of left bundle branch (LBB) block (LBBB) can be observed in up to 20%-30% of patients suffering from heart failure with reduced ejection fraction. However, predicting which LBBB patients will benefit from cardiac resynchronization therapy (CRT) or conduction system pacing remains challenging. This study aimed to establish a translational model of LBBB to enhance our understanding of its pathophysiology and improve therapeutic approaches. Methods: Fourteen male pigs underwent radiofrequency catheter ablation of the proximal LBB under fluoroscopy and ECG guidance. Comprehensive clinical assessments (12-lead ECG, bloodsampling, echocardiography, electroanatomical mapping) were conducted before LBBB induction, after 7, and 21 days. Three pigs received CRT pacemakers 7 days after LBB ablation to assess resynchronization feasibility. Results: Following proximal LBB ablation, ECGs displayed characteristic LBBB features, including QRS widening, slurring in left lateral leads, and QRS axis changes. QRS duration increased from 64.2 ± 4.2 ms to 86.6 ± 12.1 ms, and R wave peak time in V6 extended from 21.3 ± 3.6 ms to 45.7 ± 12.6 ms. Echocardiography confirmed cardiac electromechanical dyssynchrony, with septal flash appearance, prolonged septal-to-posterior-wall motion delay, and extended ventricular electromechanical delays. Electroanatomical mapping revealed a left ventricular breakthrough site shift and significantly prolonged left ventricular activation times. RF-induced LBBB persisted for 3 weeks. CRT reduced QRS duration to 75.9 ± 8.6 ms, demonstrating successful resynchronization. Conclusion: This porcine model accurately replicates the electrical and electromechanical characteristics of LBBB observed in patients. It provides a practical, cost-effective, and reproducible platform to investigate molecular and translational aspects of cardiac electromechanical dyssynchrony in a controlled and clinically relevant setting.

Impact of DCM-Causing Genetic Background on Long-Term Response to Cardiac Resynchronization Therapy.

BACKGROUND: Patients with nonischemic dilated cardiomyopathy (DCM), severe left ventricular (LV) dysfunction, and complete left bundle branch block benefit from cardiac resynchronization therapy (CRT). However, a large heterogeneity of response to CRT is described. Several predictors of response to CRT have been identified, but the role of the underlying genetic background is still poorly explored. OBJECTIVES: In the present study, the authors sought to define differences in LV remodeling and outcome prediction after CRT when stratifying patients according to the presence or absence of DCM-causing genetic background. METHODS: From our center, 74 patients with DCM subjected to CRT and available genetic testing were retrospectively enrolled. Carriers of causative monogenic variants in validated DCM-causing genes, and/or with documented family history of DCM, were classified as affected by genetically determined disease (GEN+DCM) (n = 25). Alternatively, by idiopathic dilated cardiomyopathy (idDCM) (n = 49). The primary outcome was long-term LV remodeling and prevalence of super response to CRT (evaluated at 24-48 months after CRT); the secondary outcome was heart failure-related death/heart transplant/LV assist device. RESULTS: GEN+DCM and idDCM patients were homogeneous at baseline with the exception of QRS duration, longer in idDCM. The median follow-up was 55 months. Long-term LV reverse remodeling and the prevalence of super response were significantly higher in the idDCM group (27% in idDCM vs 5% in GEN+DCM; P = 0.025). The heart failure-related death/heart transplant/LV assist device outcome occurred more frequently in patients with GEN+DCM (53% vs 24% in idDCM; P = 0.028). CONCLUSIONS: Genotyping contributes to the risk stratification of patients with DCM undergoing CRT implantation in terms of LV remodeling and outcomes.

Conduction disorders following transcatheter aortic valve replacement using acurate Neo2 transcatheter heart valve: A propensity matched analysis.

BACKGROUND: The ACURATE neo2 transcatheter aortic valve was developed to improve paravalvular leak (PVL) rates while maintaining low rates of conduction disturbances and permanent pacemaker implantation (PPMI) seen with its predecessor. We aimed to compare conduction disturbances rates of transcatheter aortic valve replacement (TAVR) using ACURATE Neo2 with other commonly used valves. METHODS: A retrospective analysis of the Israeli TAVR registry between the years 2014-2023 was performed to compare conduction disturbances and PVL rates, and procedural outcomes, among patients treated with ACURATE neo2, Edwards Sapien 3 (S3), and Evolut PRO valves. Propensity score matching was performed to compare groups with similar characteristics. RESULTS: Following exclusion of patients with non-femoral access, unknown valve type, older-generation valves, and less commonly used valves or (n = 4387), our analysis included 3208 patients undergoing TAVR using ACURATE neo2, Edwards S3, and Evolut PRO valves. Propensity matched groups comprised 169 patients each. Rates of any conduction disturbances [left bundle branch block (LBBB), atrioventricular block, or PPMI] were lower in the ACURATE neo2 group compared to both other valves [15.8 %, S3-37.5 % (p < 0.001), Evolut PRO-27.5 % (p = 0.02)] as were LBBB rates [9.0 %, S3-31.3 % (p < 0.001); Evolut PRO-20.1 % (p = 0.01). Atrioventricular block and PPMI rates were lower without statistical significance, as were rates of above-moderate PVL. CONCLUSIONS: In this analysis, TAVR using ACURATE neo2 was associated with a lower composite rate of conduction disturbances in comparison to the Evolut PRO and Edwards S3 valves, mainly due to lower left bundle branch block rates, with non-significantly lower rates of PPMI and PVL.

Left bundle branch block-induced dilated cardiomyopathy: Definitions, pathophysiology, and therapy.

Left bundle branch block (LBBB) is a frequent finding in patients with heart failure (HF), particularly in those with dilated cardiomyopathy (DCM). LBBB has been commonly described as a consequence of DCM development. However, a total recovery of left ventricular (LV) function after cardiac resynchronization therapy (CRT), observed in patients with LBBB and DCM, has led to increasing acknowledgement of LBBB-induced dilated cardiomyopathy (LBBB-iDCM) as a specific pathological entity. Its recognition has important clinical implications, as LBBB-iDCM patients may benefit from an early CRT strategy rather than medical HF therapy only. At present, there are no definitive diagnostic criteria enabling the universal identification of LBBB-iDCM, and no defined therapeutic approach in this subgroup of patients. This review compiles the main findings about LBBB-iDCM pathophysiology and the current proposed diagnostic criteria and therapeutic approach.

Depth of implantation in relation to membranous septum as a predictor of conduction disturbances after transcatheter aortic valve implantation.

BACKGROUND: Conduction disturbances remain one of the most common complications occurring post TAVI. We aim to determine the predictors of cardiac conduction disturbances after Transcatheter Aortic Valve Implantation (TAVI) and propose a relevant predictive model. We included 70 consecutive patients with severe symptomatic AS who underwent TAVI using the self-expanding valve Evolut R or the balloon expandable Sapien XT valve. All patients were subjected to electrocardiographic evaluation pre- and post-TAVI and at 30 days. Clinical, echocardiographic, CT-derived, and procedural parameters were collected and analyzed. RESULTS: Conduction disturbances affected 28 patients (40%): 16 patients (22.9 %) developed Left Bundle Branch Block (LBBB), 7 patients (10%) experienced transient Complete Heart Block (CHB), and 5 patients (7.1%) experienced permanent CHB requiring Permanent Pacemaker Implantation (PPI). We classified predictors into preprocedural and procedural predictors. Multivariate logistic regression analysis of pre-procedural predictors showed that the presence of basal septal calcification is the most powerful independent predictor (OR: 28.63, 95% CI: 4.59-178.68, p < 0.001). Multivariate logistic regression analysis for pre and post procedural predictors showed that the relationship between depth of implantation at the septum and membranous septum expressed in percentage (sDIMS) with cut-off >70.42% is the most powerful independent procedural predictor (OR: 1.11, 95% CI: 1.03-1.2, p 0.006). CONCLUSION: Conduction disturbances remain a common complication of TAVI. Presence of basal septal calcification is a non-modifiable risk factor that increase patient propensity of development such complication after TAVI. A depth of implantation exceeding 70% of the membranous septal length has been found to strongly predict conduction disturbances post TAVI. sDIMS can be used in planning the depth of implantation to reduce incidence of conduction disturbances post TAVI.

New-Onset Intermittent Deceleration-Dependent Left Bundle Branch Block Following Induction of General Anesthesia in a Healthy Patient: A Case Report.

This case report aims to highlight an atypical presentation of deceleration-dependent aberrancy (DDA) following the induction of general anesthesia in a patient with no known cardiac history. It emphasizes the critical role of intraoperative monitoring and the potential effects of anesthetic agents on the cardiac conduction system. A 46-year-old Hispanic male with no significant past medical or surgical history presented for surgical repair of a comminuted radial fracture. Following anesthesia induction with propofol, midazolam, and fentanyl, he developed a transient left bundle branch block (LBBB) exhibiting deceleration-dependent characteristics. Despite stable hemodynamics, the LBBB pattern appeared at heart rates below 60 beats per minute and resolved with heart rates above 90 beats per minute. This was managed intraoperatively with glycopyrrolate. Postoperative evaluations, including a 12-lead ECG, echocardiogram, and nuclear stress test, indicated normal biventricular function with a small to moderate reversible perfusion defect. The patient did not report cardiac symptoms postoperatively and did not prefer to undergo a coronary angiogram. This report underscores the importance of recognizing rate-dependent LBBB as a potential intraoperative complication, even in patients without pre-existing cardiac conditions. The transient nature of DDA, influenced by anesthetic agents and managed through careful monitoring and pharmacological intervention, highlights the necessity for vigilance in perioperative settings. This case contributes to a growing body of evidence suggesting that anesthetic management may require tailored approaches for patients experiencing or at risk for conduction abnormalities. This case illustrates the complexities of cardiac conduction disturbances such as DDA in the context of general anesthesia, serving as a reminder of the importance of thorough monitoring and the judicious use of rate-modifying drugs. It fosters a deeper understanding of the interaction between anesthesia and cardiac electrophysiology. Further research is needed to explore the mechanisms and management strategies for anesthetic-related cardiac conduction abnormalities.

Unmasking Coronary Artery Disease With Intermittent Left Bundle Branch Block: A Case Report.

Intermittent left bundle branch block (LBBB) is an unusual phenomenon, with very few cases documented in the literature. It is often considered a reflection of underlying conditions known to increase the risk of cardiovascular morbidity and death, including coronary artery disease (CAD), cardiomyopathy, hypertensive heart disease, and aortic valve disease. In rare instances, coronary vasospasm is the sole underlying condition. It is typically diagnosed by ECG and managed according to the underlying cause. We describe a case of intermittent LBBB presenting with chest pain. The ECG showed dynamic changes with transient/intermittent LBBB. An angiogram was performed, revealing significant coronary lesions. The patient was eventually managed conservatively and discharged on dual antiplatelet therapy for a duration of one year with a one-month clinic follow-up where his condition improved. Intermittent LBBB represents a transient disturbance in the intraventricular conduction system, where diseased conduction occurs secondary to an underlying cause, but normal conduction eventually restores. This results in complexes where LBBB appears alongside normally conducted beats in a single ECG tracing. There is limited knowledge about the prognosis of patients with intermittent LBBB; therefore, patients with LBBB should undergo careful evaluation due to the known association with serious cardiac pathologies, particularly cardiac ischemia. It is important to consider the potential adverse effects on ventricular function.

Long-term efficacy of left bundle branch pacing and biventricular pacing in patients with heart failure complicated with left bundle branch block.

Background: Left bundle branch pacing (LBBP) can physiologically correct complete left bundle branch block (CLBBB), and has become the best alternative to biventricular pacing (BiVP). Objective: To compare the efficacy of LBBP and BiVP in patients with heart failure (HF) complicated with CLBBB. Methods: This was a single-center retrospective study. Patients with HF complicated with CLBBB who underwent successful cardiac resynchronization therapy (CRT) in Wuhan Asian Heart Hospital from June 2018 to June 2023 were enrolled and divided into LBBP group and BiVP group according to the pacing method. The primary endpoints were the absolute increase of left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter (LVEDD), and echocardiographic response rate. Secondary endpoints were all-cause mortality, heart failure hospitalization (HFH), NT-proBNP, paced QRS duration, pacing threshold, and procedural duration. Results: A total of 120 patients were enrolled in this study, including 60 patients in LBBP group and 60 patients in BiVP group. The median follow-up time was 37 ± 19 months. Compared with BiVP group, LBBP group had a more significant increase in absolute LVEF (ΔLVEF) (14.8 ± 9.9% vs. 10.7 ± 9.0%, P = 0.02), a more significant reduction in LVEDD (56.9 ± 10.9 mm vs. 61.1 ± 10.8 mm, P = 0.03), and a higher echocardiographic super response rate (65% vs. 45%, P = 0.02). There were no significant differences in all-cause mortality (1.7% vs. 10.0%, P = 0.11) and HFH (6.7% vs. 13.3%, P = 0.22). In terms of paced QRS duration (128.7 ± 14.1 ms vs. 137.5 ± 16.5 ms, P = 0.002), pacing threshold (0.72 ± 0.21 V/0.4 ms vs. 1.39 ± 0.51 V/0.4 ms, P < 0.001), procedural duration (134.1 ± 32.2 min vs. 147.7 ± 39.4 min, P = 0.04), the LBBP group was superior to the BiVP group. Conclusion: In nonischemic cardiomyopathy (NICM) patients with HF combined with CLBBB and LVEF ≤ 35%, LBBP is better than BiVP.

Assessment of myocardial strain patterns in patients with left bundle branch block using cardiac magnetic resonance.

Recently, a classification with four types of septal longitudinal strain patterns was described using echocardiography, suggesting a pathophysiological continuum of left bundle branch block (LBBB)-induced left ventricle (LV) remodeling. The aim of this study was to assess the feasibility of classifying these strain patterns using cardiovascular magnetic resonance (CMR), and to evaluate their association with LV remodeling and myocardial scar. Single center registry included LBBB patients with septal flash (SF) referred to CMR to assess the cause of LV systolic dysfunction. Semi-automated feature-tracking cardiac resonance (FT-CMR) was used to quantify myocardial strain and detect the four strain patterns. A total of 115 patients were studied (age 66 ± 11 years, 57% men, 28% with ischemic heart disease). In longitudinal strain analysis, 23 patients (20%) were classified in stage LBBB-1, 37 (32.1%) in LBBB-2, 25 (21.7%) in LBBB-3, and 30 (26%) in LBBB-4. Patients at higher stages had more prominent septal flash, higher LV volumes, lower LV ejection fraction, and lower absolute strain values (p < 0.05 for all). Late gadolinium enhancement (LGE) was found in 55% of the patients (n = 63). No differences were found between the strain patterns regarding the presence, distribution or location of LGE. Among patients with LBBB, there was a good association between strain patterns assessed by FT-CMR analysis and the degree of LV remodeling and LV dysfunction. This association seems to be independent from the presence and distribution of LGE.

Understanding the Application of Mechanical Dyssynchrony in Patients with Heart Failure Considered for CRT.

Over the past two decades of CRT use, the failure rate has remained around 30-35%, despite several updates in the guidelines based on the understanding from multiple trials. This review article summarizes the role of mechanical dyssynchrony in the selection of heart failure patients for cardiac resynchronization therapy. Understanding the application of mechanical dyssynchrony has also evolved during these past two decades. There is no role of lone mechanical dyssynchrony in the patient selection for CRT. However, mechanical dyssynchrony can complement the electrocardiogram and clinical criteria and improve patient selection by reducing the failure rate. An oversimplified approach to mechanical dyssynchrony assessment, such as just estimating time-to-peak delays between segments, should not be used. Instead, methods that can identify the underlying pathophysiology of HF and are representative of a substrate to CRT should be applied.

Redefining left bundle branch block from high-density electroanatomical mapping.

BACKGROUND: The existing ECG criteria for diagnosing left bundle branch block (LBBB) are insufficient to distinguish between true and false blocks accurately. METHODS: We hypothesized that the notch width of the QRS complex in the lateral leads (I, avL, V5, V6) on the LBBB-like ECG could further confirm the diagnosis of true complete left bundle branch block (t-LBBB). We conducted high-density, three-dimensional electroanatomical mapping in the cardiac chambers of 37 patients scheduled to undergo CRT. These patients' preoperative electrocardiograms met the ACC/AHA/HRS guidelines for the diagnosis of complete LBBB. If the left bundle branch potential could be mapped from the base of the heart to the apex on the left ventricular septum, it was defined as a false complete left bundle branch block (f-LBBB). Otherwise, it was categorized as a t-LBBB. We conducted a comparative analysis between the two groups, considering the clinical characteristics, real-time correspondence between the spread of ventricular electrical excitation and the QRS wave, QRS notch width of the lateral leads (I, avL, V5, V6), and the notch width/left ventricular end-diastolic diameter (Nw/LVd) ratio. We performed the ROC correlation analysis of Nw/LVd and t-LBBB to determine the sensitivity and specificity for diagnostic authenticity. RESULTS: Twenty-five patients were included in the t-LBBB group, while 12 patients were assigned to the f-LBBB group. Within the t-LBBB group, the first peak of the QRS notch correlated with the depolarization of the right ventricle and septum, the trough corresponded to the depolarization of the left ventricle across the left ventricle, and the second peak aligned with the depolarization of the left ventricular free wall. In contrast, within the f-LBBB group, the first peak coincided with the depolarization of the right ventricle and a majority of the left ventricle, the second peak occurred due to the depolarization of the latest, locally-activated myocardium in the left ventricle, and the trough was a result of delayed activation of the left ventricle that did not align with the usual peak timing. The QRS notch width (45.2 ± 12.3 ms vs. 52.5 ± 9.2 ms, P < 0.05) and the Nw/LVd ratio (0.65 ± 0.19 ms/mm vs. 0.81 ± 0.17 ms/mm, P < 0.05) were compared between the two groups. After conducting the ROC correlation analysis, a sensitivity of 56% and a specificity of 91.7% for diagnosing t-LBBB using Nw/LVd were obtained. CONCLUSION: By utilizing the current diagnostic criteria for LBBB, an increased Nw/LVd value can enhance the effectiveness of diagnosing LBBB.

LBBB and heart failure-Relationships among QRS amplitude, duration, height, LV mass, and sex.

BACKGROUND: Height, left ventricular (LV) size, and sex were proposed as additional criteria for patient selection for cardiac resynchronization therapy (CRT) but their connections with the QRS complex in left bundle branch block (LBBB) are little investigated. We evaluated these. METHODS: Among patients with "true" LBBB, QRS duration (QRSd) and amplitude, and LV hypertrophy indices, were correlated with patient's height and LV mass, and compared between sexes. RESULTS: In this study cohort (n = 220; 60 ± 12 years; left ventricular ejection fraction [LVEF] 21 ± 7%; mostly New York Heart Association II-III, QRSd 165 ± 19 ms; 57% female; 70% responders [LVEF increased ≥5%]), LV mass was increased in all patients. QRS amplitude did not correlate with LV mass or height in any individual lead or with Sokolow-Lyon or Cornell-Lyon indices. QRSd did not correlate with height. In contrast, QRSd correlated strongly with LV mass (r = .51). CRT response rate was greater in women versus men (84% vs. 58%, p < .001) despite shorter QRSd [7% shorter (p < .0001)]. QRSd normalized for height resulted in a 2.7% and for LV mass 24% greater index in women. CONCLUSION: True LBBB criteria do not exclude HF patients with increased LV mass. QRS amplitudes do not correlate with height or LV mass. Height does not affect QRSd. However, QRSd correlates with LV size. QRSd normalized for LV mass results in 24% greater value in women in the direction of sex-specific responses. LV mass may be a significant nonelectrical modifier of QRSd for CRT.

Chronic Chagas Cardiomyopathy in the Brazilian Amazon region: clinical characteristics and regional distinctiveness.

Objectives: This study aims to provide a comprehensive analysis of clinical and epidemiological data related to Chronic Chagas Cardiomyopathy (CCC) in the Amazon region of Brazil. Methods: A review of observational, retrospective, and cross-sectional studies related to Chagas Disease in the Amazon region of Brazil was conducted, and a case series addressing CCC in patients treated at the FMT-HVD outpatient clinic, a reference center for Chagas disease in Brazil, was carried out. Results: Clinical characteristics of 55 patients from the Amazon region with CCC were described. The most common electrocardiographic alteration observed was abnormal ventricular repolarization (AVR), present in 40% of cases. The most common echocardiographic finding was left ventricular systolic dysfunction (49%), followed by akinesia or hypokinesia of the inferior and/or inferolateral walls (38.1%) and the presence of an apical aneurysm (32.7%). Conclusions: Overall, this study demonstrates that CCC in the Amazon region presents clinical characteristics and severity that are similar to those observed in other regions. However, certain peculiarities, such as the frequency of right bundle branch block (RBBB) and anterior and septal involvement during the acute phase, require additional investigation to better comprehend the disease in the region. Overall, the study provides crucial clinical insights for the diagnosis and treatment of CCC in the Amazon region.

Useful Electrocardiographic Signs to Support the Prediction of Favorable Response to Cardiac Resynchronization Therapy.

Cardiac resynchronization therapy (CRT) is a cornerstone therapeutic opportunity for selected patients with heart failure. For optimal patient selection, no other method has been proven to be more effective than the 12-lead ECG, and hence ECG characteristics are extensively researched. The evaluation of particular ECG signs before the implantation may improve selection and, consequently, clinical outcomes. The definition of a true left bundle branch block (LBBB) seems to be the best starting point with which to select patients for CRT. Although there are no universally accepted definitions of LBBB, using the classical LBBB criteria, some ECG parameters are associated with CRT response. In patients with non-true LBBB or non-LBBB, further ECG predictors of response and non-response could be analyzed, such as QRS fractionation, signs of residual left bundle branch conduction, S-waves in V6, intrinsicoid deflection, or non-invasive estimates of Q-LV which are described in newer publications. The most important and recent study results of the topic are summarized and discussed in this current review.

Antidromic AVRT with changing His activation. What is the mechanism?

We present a case of antidromic AVRT involving an atriofascicular pathway in a patient with an atretic coronary sinus os. This patient had left ventricular dysfunction with rate-related left bundle branch block aberrancy in sinus rhythm. In the electrophysiology lab, there was VA dissociation for a few beats during antidromic tachycardia. The possible mechanisms that could explain this intracardiac finding are discussed.

Lower incidence of new-onset severe conduction disturbances after transcatheter aortic valve implantation with bicuspid aortic valve in patients with no baseline conduction abnormality: a cross-sectional investigation in a single center in China.

Background: With technological advancements, the incidence of most transcatheter aortic valve implantation (TAVI)-related complications, with the exception of conduction disturbances, has decreased. Bicuspid aortic valve (BAV) is also no longer considered a contraindication to TAVI; however, the effect of BAV on postoperative conduction disturbances after TAVI is unknown. Methods: We collected information on patients who met the indications for TAVI and successfully underwent TAVI at our center between January 2018 and January 2021. Patients with preoperative pacemaker implantation status or conduction disturbances (atrioventricular block, bundle branch block, and intraventricular block) were excluded. Based on imaging data, the patients were categorized into the BAV group and the tricuspid aortic valve (TAV) group. The incidence of new perioperative conduction disturbances was compared between the two groups. Results: A total of 187 patients were included in this study, 64 (34.2%) of whom had BAV. The incidence of third-degree block in the BAV group was 1.6%, which was lower than that (13.0%) in the TAV group (P < 0.05). Multivariate logistic regression results showed that the risk of third-degree conduction disturbances was 15-fold smaller in the BAV group than that in the TAV group [relative risk (RR) = 0.067, 95% CI = 0.008-0.596, P < 0.05]. The risk of other blocks in the BAV group was about half of that in the TAV group (RR = 0.498, 95% CI = 0.240-1.032); however, the difference was not statistically significant (P > 0.05). Conclusion: The present study found that patients with BAV had a lower rate of third-degree conduction disturbances after TAVI than patients with TAV.