Intraventricular Conduction Delay Research Articles

Sleep-Disordered Breathing and Cardiac Arrhythmias

A narrative review was performed, analyzing peer-reviewed articles from databases such as PubMed, EMBASE, Scopus, and Web of Science to examine the mechanistic links between sleep-disordered breathing (SDB), and cardiac arrhythmias, emphasizing intermittent hypoxia, autonomic imbalance, and intrathoracic pressure swings as key pathways. Studies, including the DREAM and CESAAR trials, consistently demonstrate that SDB patients face elevated risks: more than doubling the likelihood of overall arrhythmias (OR 2.24; 95% CI 1.48–3.39), quadrupling the risk of AF (OR 4.02; 95% CI 1.03–15.74), and tripling the risk of non-sustained ventricular tachycardia (NSVT) with higher apnea-hypopnea index (AHI) values. Additionally, SDB doubles the risk of bradyarrhythmia, such as sinus pause, second and third-degree atrioventricular block, and intraventricular conduction delay (OR 2.50; 95% CI 1.58–3.95). According to meta-analytical findings, continuous positive airway pressure (CPAP) therapy is a pivotal intervention, significantly reducing AF recurrence by 42% and lowering VA incidence by 58%. Moreover, CPAP therapy diminishes sinus bradycardia and occurrences of sinus pause and may reduce the necessity for pacemaker implantation. Recognizing SDB as a modifiable risk factor for cardiac arrhythmias highlights the importance of early diagnosis and effective management, primarily through CPAP therapy, to improve cardiovascular outcomes.

Utilizing unsupervised machine learning to uncover novel phenogroups within the broad QRS complex

Abstract Background Conduction disease can manifest as a broad QRS complex on the ECG. Broad QRS is conventionally categorised as left bundle branch block (LBBB) and right bundle branch block (RBBB) or non-specific intraventricular conduction delay (IVCD), based on QRS morphology. These subgroups were coined over a century ago and have been relevant for heart failure with reduced ejection fraction and cardiac resynchronization therapy (CRT). However, there may be more precise phenogroups underlying broad QRS complexes. Purpose Using unsupervised machine learning to define novel broad QRS phenogroups and characterise them using clinical variables and disease outcomes. Methods We extracted 51 relevant features using a Variational Autoencoder from 47,456 median-beat ECGs with broad QRS intervals (QRS ≥ 130ms) from a secondary care cohort. These were input into Discriminative Dimensionality Reduction via Learning a Tree (DDRTree), a clustering method that models the continuum of heterogeneity by projecting the underlying distribution as a tree structure in a low-dimensional space, while assigning distinct branch/cluster labels. Results Six distinct phenogroups were identified within broad QRS morphologies (Figure-1). Two branches were RBBB dominant (Branch 1: more males, high-comorbidity; Branch 6: low-comorbidity/healthy-RBBB). Two branches were LBBB dominant (Branch 4: mixed IVCD with CHB burden; Branch 5: more females, CRT responders). Two branches were IVCD/mixed-phenotype (Branch 2: IVCD-dominant, high risk of future cardiovascular events; Branch 3: average/core branch). Within LBBB, Branch 4 and 5 showed similar trends with improving echocardiography profiles and CRT response when adjusted for covariates, each compared against the core branch. Branch 5 was distinct due its high risk of future HF (HR 1.19 [1.07-1.33] p < 0.01), cardiovascular death (HR 1.35 [1.20-1.50] p < 0.0001), all-cause mortality (HR 1.08 [1.01-1.16] p < 0.05) and CHB (HR 1.35 [1.16-1.56] p < 0.0001) (Figure-2). Conversely within RBBB, Branch 1 and 6 showed stark differences across various traits. Branch 1 captured a high-risk profile associated to higher risk of cardiovascular death (HR 1.37 [1.24-1.52] p < 0.0001), all-cause mortality (HR 1.20 [1.12-1.29] p < 0.0001) and CHB (HR 1.15 [1.01-1.32] p < 0.05) (Figure-2), while Branch 6 retained a low-risk phenotype. The tree dimensions also revealed relevant trends in cardiac anatomy and valvular dysfunction; the top-left region in Figure-1 associated with higher left ventricular ejection fraction and lower left ventricular end-diastolic dimension, lower left ventricular end-systolic dimension and a greater CRT response. Conclusion Through unsupervised methods we have identified conduction disease phenogroups with additive value for disease prognosis and CRT response prediction beyond traditional LBBB and RBBB labels. These novel phenogroups may help guide precision care for patients with a broad QRS complex.Figure-1Figure-2

Preoperative electrocardiogram in prediction of 90-day postoperative mortality: retrospective cohort study

BackgroundThere are conflicting data on the relationship between preoperative electrocardiogram and postoperative mortality. We aimed to assess the predictive value of preoperative ECG on postoperative all-cause mortality in patients undergoing non-cardiac surgery (NCS).MethodsWe retrospectively reviewed records of hospitalized patients who underwent an internal preoperative examination and subsequent NCS in the years 2015–2021. We recorded patient comorbidities, vital functions, results of biochemical tests, ECG. The primary end point was 90-day postoperative all-cause mortality, acquired from the hospital records and the nationwide registry run by the Institute of Health Information and Statistics of the Czech Republic.ResultsWe enrolled a total of 2219 patients of mean age 63 years (48% women). Of these, 152 (6.8%) died during the 90-day postoperative period. There were statistically significant associations between increased 90-day postoperative all-cause mortality and abnormal ECG findings in resting heart rate (≥ 80 bpm, relative risk [RR] = 1.82 and ≥ 100 bpm, RR = 2.57), presence of atrial fibrillation (RR = 4.51), intraventricular conduction delay (QRS > 0.12 s, RR = 2.57), ST segment changes and T wave alterations, left bundle branch hemiblock (RR = 1.64), and right (RR = 2.04) and left bundle branch block (RR = 4.13), but not abnormal PQ and QT intervals, paced rhythm, incomplete right bundle branch block, or other ECG abnormalities. A resting heart rate (≥ 80 bpm, relative risk [RR] = 1.95 and ≥ 100 bpm, RR = 2.20), atrial fibrillation (RR = 2.10), and right bundle branch block (RR = 2.52) were significantly associated with 90-day postoperative all-cause mortality even in subgroup of patients with pre-existing cardiac comorbidities.ConclusionsPatients with abnormal preoperative ECG findings face an elevated risk of all-cause mortality within 90 days after surgery. The highest mortality risk is observed in patients with atrial fibrillation and left bundle branch block. Additionally, an elevated heart rate, right bundle branch block, and atrial fibrillation further increase the risk of death in patients with pre-existing cardiac conditions.

Predictors of success in left bundle branch area pacing with stylet-driven pacing leads: a multicenter investigation.

Although left bundle branch area pacing (LBBAP) is an emerging conduction system pacing modality, it is unclear which parameters predict procedural success and how many implant attempts are acceptable. This study aimed to assess predictors of successful LBBAP, left bundle branch (LBB) capture, and factors associated with the number of LBBAP implant attempts. This retrospective observational multicenter study was conducted in Korea. LBBAP was attempted in 119 patients; 89.3% of patients had bradyarrhythmia (atrioventricular block 82.4%), and 10.7% of patients had heart failure (cardiac resynchronization therapy) indication. Procedural success and electrophysiological and echocardiographic parameters were evaluated. The acute success rate of lead implantation in LBBAP was 95.8% (114 of 119 patients) and that of LBB capture was 82.4% (98 of 119 patients). Fewer implant attempts were associated with LBBAP success (three or fewer vs. over three times, p = 0.014) and LBB capture (three or fewer vs. over three times, p = 0.010). In the multivariate linear regression, the patients with intraventricular conduction delay (IVCD) required a greater number of attempts than those without IVCD [estimates = 2.33 (0.35-4.31), p = 0.02], and the larger the right atrial (RA) size, the more the attempts required for LBBAP lead implantation [estimates = 2.08 (1.20-2.97), p < 0.001]. An increase in the number of implant attempts was associated with LBBAP procedural failure and LBB capture failure. The electrocardiographic parameter IVCD and the echocardiographic parameter RA size may predict the procedural complexity and the number of lead implant attempts for LBBAP.

Reversibility of acritical intraventricular conduction delay under flecainide and lacosamide by sodium bicarbonate

The case of a72-year-old female patient with arrhythmogenic syncope associated with acombination therapy of flecainide and lacosamide is presented. The authors believe in an additive effect of both drugs on myocardial voltage-gated sodium channels with extraordinary QRS widening, exit block with temporary pacing and complete reversibility through infusion of sodium bicarbonate as bail-out therapy.

Association between anti-SSA autoantibodies and conduction disturbances in heart failure

BackgroundConduction disturbances play an important role in the occurrence and development of heart failure (HF). Studies suggest autoantibodies may attack the conduction system. However, whether autoantibodies are associated with conduction disturbances in patients with HF is unclear. ObjectiveThe purpose of this study was to assess whether anti-SSA, anti-Ro/Sjögren syndrome-related antigen A antibodies known for congenital atrioventricular block (AVB), is associated with conduction disturbances in patients with HF. MethodsThis retrospective observational study used data from patients with HF who were admitted to Beijing Anzhen Hospital between January 2018 and June 2022. Patients who were tested for anti-SSA and had undergone electrocardiographic examination during hospitalization were included. Conduction disturbances, including AVB, bundle branch block (BBB), and intraventricular conduction delay, were confirmed by a cardiologist blinded to anti-SSA status. Univariate and multivariable logistic regression analyses were performed to assess the association between anti-SSA and conduction disturbances. ResultsA total of 766 patients were included in this study, of whom 70 (9.1%) were anti-SSA positive. Subjects who were anti-SSA positive showed a higher prevalence of AVB (20% vs 10.6%) and BBB (27.3 % vs 10.9 %), including both left BBB and right BBB (all P <.05). After adjusting for known risk factors, anti-SSA was independently associated with AVB (odds ratio [OR] 2.42; 95% confidence interval [CI] 1.18–5.43; P = .03) and BBB (OR 3.15; 95% CI 1.68–5.89; P <.001). ConclusionAnti-SSA is independently associated with AVB and BBB in patients with HF. Further study of the role of autoantibodies in the development of conduction abnormalities in patients with HF to generate possible targeted treatments is required.

Left bundle branch area pacing optimized cardiac resynchronization therapy (LOT CRT) -comparative results to a CRT implanted patient population

Abstract Background Cardiac resynchronization therapy (CRT) is gold standard treatment option among patients with symptomatic heart failure with reduced left ventricular ejection fraction (LVEF) and intraventricular conduction delay of left bundle branch block (LBBB) morphology. Purpose Left bundle branch area pacing optimized cardiac resynchronization therapy (LOT CRT) is a novel and promising approach for CRT candidate patients even in advanced intraventricular conduction delay, however convincing follow-up data regarding this patient group is still lacking. Methods In our observational registry 35 LOT CRT vs. 35 conventional CRT patients were consecutively implanted according to current guidelines. All the patients had LBBB morphology QRS width of &amp;gt;150 ms. The two compared patient group did not show significant difference in age, gender, baseline non-ischemic etiology, LVEF, NYHA functional class, LBBB QRS width. Results Immediate postoperative results showed significantly increased QRS width reduction (p=.028) and at 6 months of follow-up a significantly greater improvement in LVEF(p=.031), NYHA functional class (p=.04) and Nt-ProBNP levels (p=0.043) were seen in LOT CRT patient group compared to conventional CRT patients. Conclusion Our single center observational study showed significant improvement in prompt postoperative QRS width and clinical follow-up parameters in LOT CRT implanted patients compared to conventional CRT implanted patients.LOTCRTvs.CRTQRSwidthreductionLOTCRTXray

Impact of non-typical LBBB on CRT response

Abstract Introduction Cardiac resynchronization therapy (CRT) benefits have been established in patients with heart failure and reduced left ventricular ejection fraction (HFrEF) who have a broad QRS and remain symptomatic despite optimized medical therapy. Responders typically are female, with LBBB and broader QRS. It remains uncertain to what extent do patients with non-LBBB QRS complex morphology respond to CRT and also if there are differences among various types of intraventricular conduction delays. Purpose To evaluate the impact of non-typical left bundle branch block (LBBB) on reverser remodeling and clinical events. Methods Single center, observational, retrospective study including patients (pts) who implanted CRT in the context of HFrEF, from 2015 to 2020. Evaluation of QRS morphology analysis was conducted. CRT response was defined by a reduction of LVESV≥15% or an increase in LVEF≥10%. Predictors of CRT response were evaluated with Chi-square and Mann- Whitney analysis. Impact on reverse remodeling and clinical outcomes was performed with Kaplan-Meyer analysis. Results A total of 361 pts were included for analysis, of which 184 had non-typical LBBB. Pts had a mean age of 71±9years old, the majority of pts were female (61%), and almost half were ischemic (47.8%). EGC evaluation prior to CRT implantation, revealed an atypical LBBB in 83 (45.1%) pts, typical RBBB in 23 (12.5%) pts, atypical RBBB 94.(9%) pts and nonspecific intraventricular conduction delay in 69 (37.5%) pts. During a mean time of follow-up of 2.9 ±2.4years, 33 pts (18%) had hospitalizations due to HF and 68 (37%) died. In this cohort, 78 pts (42.4%) were deemed as responders, who presented a better clinical outcome when compared to non-responders (p &amp;lt; 0.001, HR 2.629 [95% CI 1.635-4.225]. There was no difference among the four types of intraventricular conduction analyzed in respect to degree of CRT response – figure 1. Regarding clinical events during follow-up, there was once again no significant difference among the different patterns of non-typical LBBB– figure 2. In this subset population we found no independent predictors of CRT response, although non-responders were significantly older than responders (72±8 vs 69±10 years-old (p=0.016). Conclusion Although pts with non-typical LBBB morphology display a lower therapy response to CRT than reported for LBBB pts, the rate of response is not negligible and represents a protective factor for clinical outcomes. Different types of intraventricular conduction delay present no difference regarding long- term prognosis or reverse remodeling.Survival according to CRT response

AI-based heart monitoring: the FIFPRO player pilot study

Abstract Background The implementation of remote global heart screening and monitoring services in professional players is essential as it allows: (1) efficient and rapid identification of cardiac abnormalities ensuring their safety and health; (2) standardizing the quality of medical heart checkups in low-resource regions to promote health equity; (3) prioritizing diversity in data collection to aid in the research and prevention of sudden cardiac death in sports. Purpose To demonstrate the feasibility of a global standardized heart screening program for professional footballers by leveraging an artificial intelligence platform to efficiently identify cardiac patterns from Holter’s records. In this study, we presented the most prevalent cardiac patterns, the patterns that prompted further assessment by the cardiologist, and an example of a typical research question exploring the effect of age on the prevalence of cardiac patterns. Methods The pilot study included 100 players from 9 different countries: Australia, Botswana, Bulgaria, Ghana, Greece, Indonesia, Panama, Spain and the UK. Holter data (Bittium Faros 180) were acquired in real-life monitoring from 24h to 48h including training sessions. Electrocardiograms were analyzed through an AI platform with a deep learning-based methodology to detect over 20 cardiac patterns. Medical team reviewed labels of detected cardiac patterns to validate and further train the AI algorithm. Thereafter cardiologists reviewed the cardiac patterns to determine whether further cardiac assessment was required. Results 145 sessions were recorded, with 100 players having one session and 45 players having two sessions. The mean age was 27.5 years (minimum 15, maximum 41), with 31 female players. The median duration of the Holter session was 25.1 hours. Table 1 presents the most frequently detected cardiac patterns: low density premature atrial complex, mild sinus bradycardia and low density premature ventricular complex in over 50% of the players. 18 players were identified with abnormalities requiring further study. 14 presented altered cardiac patterns (6 with negative T-waves, 5 with intraventricular conduction delay, 2 with QRS low voltage and 1 with P wave enlargement) and 3 presented premature ventricular complexes during exercise or high density. 1 was excluded because of inadequate clinical information. Regarding the effect of age, players with mild sinus bradycardia, premature ventricular complex, pause (2-3 seconds) or 2-degree atrioventricular block were found to be significantly older than players without those patterns (Figure 1). Conclusion This is the first global AI-based platform to obtain standardized heart screening program in professional athletes remotely. This study has been validated using diverse data from groups on 5 continents. This approach is beneficial to promote health equity in screening and monitoring of possible cardiomyopathies and channelopathies in order to prevent sudden cardiac death.Table 1Figure 1

Implant failure predictors of left bundle branch pacing used as cardiac resynchronization therapy: importance of left ventricular diameter and QRS morphology

Abstract Background Left bundle branch pacing (LBBP) is considered an alternative to cardiac resynchronization therapy (CRT). However, LBBP is not suitable for all heart failure patients. Purpose The aim of our study was to identify predictors of unsuccessful LBBP implantation in CRT candidates. Methods A cohort of consecutive patients with indications for CRT were included. Clinical, echocardiography and electrocardiographic variables were prospectively recorded. Results A total of 157 patients were included in the analysis. The LBBP implant was successful in 129/157 (82.2%) patients, and the implant failed in 28/157 patients (17.8%). The causes of failed implantation were as follows: unsatisfactory paced QRS (21/28; 75%); impossibility of screwing the helix (4/28; 14.3%); lead instability (2/28; 7.1%); and high pacing thresholds (1/28; 3.6%). Left ventricular end diastolic diameter (LVEDD), nonspecific intraventricular conduction delay morphology (IVCD), and QRS width were predictors of failed implants according to the univariate analysis. In a multivariable regression analysis, LVEDD [OR 1.44 per 5 mm increase (95% CI 1.13, 1.82) p=0.003] and IVCD [OR 2.96 (95% CI 0.74, 11.84) p=0.09] were independent predictors of unsuccessful LBBP implantation. An LVEDD of 60 mm has 75% sensitivity and 67% specificity to predict LBBP implant failure. Conclusions When LBBP was used as CRT, LVEDD and IVCD predicted unsuccessful implantation. IVCD triples the possibility of failed implantation independently of LVEDD. Caution should be exercised when considering these parameters to plan the best pacing strategy in patients.

Gender matters. Impact of gender on the utilization of defibrillators with cardiac resynchronisation therapy and outcome: results from the German DEVICE registry

Abstract Background Defibrillators with cardiac resynchronisation therapy (CRT-Ds) are widely used in patients with left ventricular (LV) systolic dysfunction and high-grade intraventricular conduction delays. Real world data regarding the impact of gender on CRT-D implantation and outcome are scarce. Purpose To determine the impact of gender on the CRT-D devices implantation and outcome. Methods The German DEVICE registry is a prospective, nationwide database of ICD and CRT devices implantations and revisions. A total of 1536 patients undergoing CRT-D implantations and revisions were included between March 2007 and February 2014 in 44 centres and monitored for a median of 17.2 months. Herein we conducted the gender-based analysis of the CRT-D recipients. Results Only a minority of the patients in this registry was females (329; 21,4%). The demographic data (age and BMI) were similar between genders. The female population was less likely to have a coronary artery disease (35.3% vs. 56.7%; p&amp;lt;0.001), but more likely to have dilated cardiomyopathy (61.1% vs. 49.5%; p&amp;lt;0.001). Significantly less women had a LVEF ≤ 35% (90.6% vs. 94.8%, p=0.005). A total of 84.2% of females and 80.2% of males received a device for the primary prevention of sudden cardiac death (SCD; p=0.10). Women were more likely to have a history of ventricular fibrillation (44.2% vs. 23.0%, p=0.002) and resuscitation (p=0.01), but less likely to have a history of ventricular tachycardia (44.2% vs. 61.9%; p=0.019). Significantly more women than men showed a left bundle branch block at implantation (89.7% vs. 80.9%, p&amp;lt;0.001). A QRS duration of at ≥ 150 ms was noted in 74.8% of women and 71.5% of men (p=0.25), while significantly more women had a QRS of ≥ 120 ms (97.0% vs. 94.2%; p=0.043). The overall incidence of major periprocedural complications and in hospital complications was similar between groups (3.6% vs 2.4%, p=0.25 and 6.0% vs. 5.8%, p=0.88 respectively), however a pneumothorax requiring intervention was more common among women (1.8% vs. 0.5%, p=0.027). The rate of device revision until discharge and the in-hospital mortality did not differ between genders. The Kaplan-Meier estimated 1-year all-cause mortality was 6.3% for women and 8.2% for men (p=0.25, Fig.1), while the estimated incidence of death or defibrillator shocks was 11.0% and 15.1%, respectively (p=0.051). The non-lethal complications and device revisions during follow-up (FU) were similar between genders. Women showed a lower non-device-dependent cardiovascular hospitalisation rate (8.2% vs. 13.1%; p=0.043) and had more fear of receiving a device shock than men (p=0.002). Conclusions In this real-life CRT-D patient cohort only a minority of patients were females. Women had a higher rate of pneumothorax requiring intervention. The 1-year mortality and the complications during FU were similar between genders. Women had a lower rate of non-device-dependent cardiovascular hospitalisation during FU.Fig.1. Kaplan-Meier estimated survival.

A RARE CASE OF INTERVENTRICULAR SEPTUM DUPLICATION

Abstract Case Report A 62–year–old man, history of hypertension. In 2015, there was suspicion of non–compaction cardiomyopathy, and he underwent cardiac MRI at another facility (report not available). The patient reported palpitations and dyspnea with exertion, leading to a follow–up visit. EKG showed sinus rhythm 90/min, nonspecific intraventricular conduction delay and isolated monomorphic ventricular ectopic beats. Echo revealed a mildly dilated left ventricle (end–diastolic volume 88 ml/m), systolic function at the lower limits of normal (EF 53%), and prominent muscular structures near the posterior interventricular septum (SIV), likely related to anomalies of the papillary muscles (prominent and possibly duplicated posterior–medial papillary muscle). There was apical trabecular protrusion, which did not meet the criteria for non–compaction (NC/C ratio in systole approximately 1), with no other significant findings. The cardiac MRI, performed to assess dilated cardiomyopathy, revealed a conspicuous structural abnormality in the septo–papillary region, located medio–apically and paraseptal–endocardial in the left ventricle. This anomaly lacked evident chordae tendineae with the mitral valve leaflets and exhibited synchronous systo–diastolic motion with the left ventricular wall, suggesting septal duplication. The septal thickness was slightly reduced, particularly in the medio–apical region. Additionally, there was hypertrabeculation of the posterior and lateral walls of the left ventricle, exceeding the threshold for non–compaction (NC/C ratio in end–diastole: 2.6 – normal range: &amp;lt;2.3). Left ventricular mass was normal (mass: 173.52 g; mass/body surface area (BSA): 86.58 g/m). Basal septum, medio–apical septum and medio–apical lateral wallshowed hypokinetic contractility. The left ventricle was dilated (end–diastolic diameter: 55.0 mm; end–systolic diameter: 45.3 mm – end–diastolic volume: 230 ml; stroke volume/BSA: 57.6 ml/m² – EF: 51%). Areas of late gadolinium enhancement (LGE) were observed in the anterior medio–basal septum and at the site of the described structural muscular anomaly, both displaying an intramural non–ischemic pattern. Conclusions The described findings suggest a picture of dilated cardiomyopathy and an associated structural septo–papillary anomaly of uncertain diagnostic interpretation (septum duplication with associated non–compacted myocardium? duplicated posterior–medial papillary muscle with associated non–compacted myocardium?).

Pseudo precordial ST-segment depression

We present a case with acute coronary syndrome and very unusual QRS widening in the acute phase. The case highlights that non-specific intraventricular conduction delay should be considered as a high risk ECG pattern predicting poor prognosis.

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

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. 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. 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. Patients were classified as having LBBB or intraventricular conduction delay (IVCD) as assessed by intracardiac recording. Sensitivity and specificity of the electrocardiography (ECG) criteria assessed in patients with LBBB or IVCD. 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. 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.

Prevalence and Clinical Significance of Electrocardiographic Complete Right Bundle Branch Block in Young Individuals.

There is limited information on the clinical significance of complete right bundle branch block (CRBBB) in young individuals. The aim of this study was to determine the prevalence and significance of CRBBB in a large cohort of young individuals aged 14-35 years old. From 2008 to 2018, 104,369 consecutive individuals underwent a cardiovascular assessment with a health questionnaire, electrocardiogram, clinical consultation, and selective echocardiography. Follow-up was obtained via direct telephone consultations. Mean follow-up was 7.3 ± 2.7 years. CRBBB was identified in 154 (0.1%) individuals and was more prevalent in males compared with females (0.20% vs. 0.06%; p<0.05) and in athletes compared with non-athletes (0.25% vs. 0.14%; p<0.05). CRBBB-related cardiac conditions were identified in 7 (5%) individuals (4 with atrial septal defect, 1 with Brugada syndrome, 1 with progressive cardiac conduction disease and 1 with atrial fibrillation). Pathology was more frequently identified in individuals with non-isolated CRBBB compared with individuals with isolated CRBBB (14% vs 1%; p < 0.05) and in individuals with a QRS duration of ≥130 milliseconds (ms) compared with individuals with a QRS of <130ms (10% vs 1%; p<0.05). The prevalence of CRBBB in young individuals was 0.1% and was more prevalent in males and athletes. CRBBB-related conditions were identified in 5% of individuals and were more common in individuals with non-isolated CRBBB and more pronounced intraventricular conduction delay (QRS duration of ≥130ms). Secondary evaluation should be considered for young individuals with CRBBB with symptoms, concerning family history, additional electrocardiographic anomalies or significant QRS prolongation (≥130ms).

Ultra-High-Frequency ECG in Cardiac Pacing and Cardiac Resynchronization Therapy: From Technical Concept to Clinical Application.

Identifying electrical dyssynchrony is crucial for cardiac pacing and cardiac resynchronization therapy (CRT). The ultra-high-frequency electrocardiography (UHF-ECG) technique allows instantaneous dyssynchrony analyses with real-time visualization. This review explores the physiological background of higher frequencies in ventricular conduction and the translational evolution of UHF-ECG in cardiac pacing and CRT. Although high-frequency components were studied half a century ago, their exploration in the dyssynchrony context is rare. UHF-ECG records ECG signals from eight precordial leads over multiple beats in time. After initial conceptual studies, the implementation of an instant visualization of ventricular activation led to clinical implementation with minimal patient burden. UHF-ECG aids patient selection in biventricular CRT and evaluates ventricular activation during various forms of conduction system pacing (CSP). UHF-ECG ventricular electrical dyssynchrony has been associated with clinical outcomes in a large retrospective CRT cohort and has been used to study the electrophysiological differences between CSP methods, including His bundle pacing, left bundle branch (area) pacing, left ventricular septal pacing and conventional biventricular pacing. UHF-ECG can potentially be used to determine a tailored resynchronization approach (CRT through biventricular pacing or CSP) based on the electrical substrate (true LBBB vs. non-specified intraventricular conduction delay with more distal left ventricular conduction disease), for the optimization of CRT and holds promise beyond CRT for the risk stratification of ventricular arrhythmias.

Personalized cardiac resynchronization therapy guided by real-time electrocardiographic imaging for patients with non–left bundle branch block

BackgroundPatients with heart failure and a non–left bundle branch block (non-LBBB) QRS pattern have a limited response to biventricular pacing (BVP). ObjectiveA personalized cardiac resynchronization therapy (CRT) implantation approach guided by real-time electrocardiographic imaging (ECGi) was studied. MethodsTwenty patients with left ventricular ejection fraction (LVEF) ≤ 35%, QRS duration ≥ 120 ms, and non-LBBB [13 (65%) with right bundle branch block and 7 (35%) with intraventricular conduction delay] were recruited. During CRT implantation, right atrial, right ventricular, coronary sinus, His-bundle, and/or left bundle leads were inserted. The total activation time (TAT) with different pacing combinations were measured in real time during implantation by ECGi. The configuration producing the shortest TAT was chosen. Clinical response was defined as ≥1 New York Heart Association class improvement. Echocardiographic response was defined as left ventricular end-systolic volume reduction ≥ 15% and/or LVEF improvement ≥ 10% at 6 months. ResultsAfter ECGi-guided CRT implantation, LVEF improved from 26% ± 6% to 34% ± 11% (P < .01) and New York Heart Association class improved from 3.0 ± 0.5 to 2.0 ± 0.6 (P < .01). Both clinical and echocardiographic response rates were 70%. The ECGi approach resulted in better acute electrical resynchronization over BVP as measured by TAT reduction (40% vs 14%; P < .01). The percentage of TAT reduction was found to be a strong predictor for echocardiographic response (area under the curve for the receiver operating characteristic curve 0.91; 95% confidence interval 0.78–1.00). A strong positive correlation between percentage TAT reduction and percentage LVEF improvement (Pearson R = 0.70; P = .001) was found. ConclusionECGi-guided CRT implantation in patients with non-LBBB generates superior acute electrical resynchronization compared with BVP and is associated with favorable clinical and echocardiographic outcomes.

Reverse Septal Movement: A Step Forward in the Comprehension of the Underlying Causes.

(1) Background: Reverse septal movement (RSM) often occurs after cardiac surgery, consisting of a paradoxical systolic movement of the interventricular septum. In this retrospective study, we aimed to investigate possible determinants of RSM after coronary artery bypass surgery (CABG). (2) Methods: Patients who underwent CABG with on- or off-pump techniques at our center from March 2019 to October 2021 were retrospectively included. Exclusion criteria were: exposure to combined procedures (e.g., valve implantation), prior cardiac surgery, intraventricular conduction delays, and previous pacemaker implantation. Laboratory tests and echocardiographic and cardiopulmonary bypass (CPB) duration data were collected. (3) Results: We enrolled 138 patients, of whom 32 (23.2%) underwent off-pump CABG. Approximately 89.1% of the population was male; the mean age was 70 ± 11 years. There was no difference in RSM incidence in patients undergoing the off-pump and on-pump techniques (71.9% vs. 62.3%; p = 0.319). In patients undergoing on-pump surgery, the incidence of RSM was slightly higher in longer CPB procedures (OR 1.02 (1.00-1.03) p = 0.012), and clamping aortic time was also greater (OR 1.02 (1.00-1.03) p = 0.042). (4) Conclusions: CPB length seems to be correlated with a higher RSM appearance. This better knowledge of RSM reinforces the safety of CABG and its neutral effect on global biventricular function.

Local VA index for the differential diagnosis of supraventricular tachycardia

BackgroundDifferentiating between atypical atrioventricular nodal reentrant tachycardia (AVNRT) and orthodromic reciprocating tachycardia utilizing a septal accessory pathway is a complex challenge. ObjectiveThe purpose of this study was to describe the "local VA index," a straightforward method based on signals from the coronary sinus catheter, to distinguish between these arrhythmias during tachycardia and entrainment. The ventriculoatrial (VA) interval on the coronary sinus catheter is measured during tachycardia and entrainment, at the site of earliest atrial activity. The difference between these 2 situations defines the “local VA index.” We also propose a mechanism to clarify the limitations of historical pacing maneuvers, such as postpacing interval minus tachycardia cycle length (PPI-TCL) and stimulus–atrial interval minus ventriculoatrial interval (SA-VA), by examining nodal decrement and intraventricular conduction delay. MethodsIn a retrospective study of 75 patients referred for supraventricular tachycardia evaluation, 37 were diagnosed with atrioventricular reentrant tachycardia (AVRT) with orthodromic reciprocating tachycardia, and 38 with AVNRT (27 typical, 11 atypical). ResultsIn comparison to AVRT patients, AVNRT patients exhibited longer PPI-TCL (176 ± 47 ms vs 113 ± 42 ms; P <.01) and SA-VA (138 ± 47 ms vs 64 ± 28 ms; P <.01). The AVRT group had mean local VA index of –1 ± 13 ms, whereas the AVNRT group had a significantly longer index of 91 ± 46 ms (P <.01). An optimal threshold for differentiation was a local VA index of 40 ms. Importantly, there was no significant correlation between pacing cycle length and nodal decrement as well as intraventricular delay related to pathway location. This interindividual variability might explain misleading interpretations of PPI-TCL and SA-VA. ConclusionThis novel approach is advantageous because of its simplicity and effectiveness, requiring only 2 diagnostic catheters. A local VA interval difference <40 ms provides a clear distinction for AVRT.

Clinical characteristics, diagnosis and management of nivolumab-induced myocarditis.

Nivolumab can cause fatal myocarditis. We aimed to analyze the clinical characteristics of nivolumab-induced myocarditis and provide evidence for clinical diagnosis, treatment, and prevention. Studies involving nivolumab-induced myocarditis were identified in electronic databases from 2000 to 2023 for retrospective analysis. A total of 66 patients were included, with a median age of 68 years. The median onset time of myocarditis is 11.5 days. The main organs affected in persons presented with myocarditis are heart (100.0%) and skeletal muscle (22.7%). The main clinical manifestations are dyspnea (49.2%), fatigue (47.6%), and myalgias (25.4%). The levels of troponin, troponin T, troponin I, creatine kinase, creatine kinase myocardial band, creatine phosphokinase, C-reactive protein, brain natriuretic peptide, and N-terminal brain natriuretic peptide precursor were significantly increased. Histopathology often shows lymphocyte infiltration, myocardial necrosis, and fibrosis. Myocardial immunological parameters usually present positive. Cardiac imaging often suggests complete heart block, intraventricular conduction delay, arrhythmia, myocardial infarction, edema, left ventricular ejection fractions reduction, ventricular dysfunction, and other symptoms of myocarditis. Forty-two (63.6%) patients achieved remission within a median time of 8 days after discontinuation of nivolumab and treatment with systemic corticosteroids, immunoglobulins, plasmapheresis, and immunosuppressant. Thirty-five patients eventually died attributed to myocarditis (68.6%), cancer (20.0%), respiratory failure (5.7%), and other reasons (5.7%). Nivolumab-induced myocarditis should be comprehensively diagnosed based on clinical symptoms, histopathological manifestations, immunological parameters, and cardiac function imaging examinations. Nivolumab should be discontinued immediately, plasmapheresis and systemic corticosteroids combined with immunoglobulins or immunosuppressants may be an effective treatment.