Bundle Branch Block Morphology Research Articles

Accelerated idioventricular rhythm after left bundle branch pacing lead implantation

Premature ventricular contractions with right bundle branch block morphology induced during left bundle branch (LBB) pacing (LBBP) lead implantation serve as a marker indicating that the lead is close to or has reached the LBB region. However, no reports to date have described accelerated idioventricular rhythm (AIVR) induced by LBBP lead deployment.We herein describe a patient who underwent LBBP for complete atrioventricular block. The patient's intrinsic escape rhythm was overtaken by AIVR induced immediately after LBBP lead deployment.AIVR is another marker indicating that the lead has reached the LBB region.

Impact of left bundle branch area pacing on right cardiac chambers dimensions and function. a medium term single center echocardiographic study

Abstract Introduction Left bundle branch area pacing (LBBAP) has become, in the last years, the preferred method for physiological pacing due to a wider target area, optimal pacing and sensing thresholds, and stable parameters over time. LBBAP ensures rapid and synchronous left ventricular (LV) activation through the left-sided conduction system. On the other hand, there is little data on right ventricular (RV) activation in LBBAP. The purpose of this study was to evaluate the impact of LBBAP on the right heart anatomy and function over a mid-term follow-up period. Material and methods All consecutive patients with successful LBBAP for bradyarrhythmic indications between February 2021 and July 2022 at our institution were eligible for this study. Left bundle branch capture was defined as a paced QRS complex of right bundle branch block morphology, and proof of transition from non-selective to selective capture with differential pacing maneuvers. To avoid confounders, patients with LV ejection fraction below 40% and with severe valvular disease were excluded. In the end, 57 patients were prospectively evaluated. Patient and procedural characteristics were recorded at baseline and follow-up. Also, right atrial (RA) volume, RV basal diameter, tricuspid annulus peak systolic elevation (TAPSE), RV S` wave (RVS`W), and tricuspid regurgitation (TR) were evaluated before the procedure and at the end of the follow-up period. Results The mean age of the patients was 68.9± 10 years, and 70% were males. 29.8% had a baseline right bundle branch block, and 22.8% had a left bundle branch block morphology. The baseline LV ejection fraction was 54.3 ± 9.9 %. The paced QRS duration was similar to the baseline values (128.5 ± 16.3 vs. 134.4 ± 30.4 msec, p=0.119). The pacing and sensing thresholds were 0.7 ± 0.3 V at 0.4 ms pulse duration and 9.7 ± 4.2 mV, respectively. The mean LV activation time (measured as the R wave peak time in V6) was 80.9 ± 12 msec, and the mean RV activation time (measured as the difference between QRS duration and LV activation time) was 51.9 ± 24.2 msec. The patients were followed over a mean period of 591.2 ± 150.3 days. There were no complications over the follow-up period that led to pacing interruption. The follow-up pacing (0.6 ± 0.2 V, p=0.003) and sensing (11.7 ± 6 mV, p= 0.023) thresholds showed significant improvement compared to the procedural values. The right heart echocardiographic evaluation showed non-statistically significant changes between the follow-up and the baseline values for RA volumes (57.9 ± 33.7 vs. 51.5 ± 28.4 ml, p=0.122), RV basal diameter (32.8 ± 5.4 vs. 31.8 ± 6.4 mm, p=0.31), RVS`W (12.8 ± 3.2 vs. 12.85 ± 2.7 cm/sec, p=0.933), and TR (1.8±0.8 vs. 2±1, p=0.07). On the other hand, there was a significant improvement in the TAPSE (22.2±4.3 vs. 20.7±3.6 mm, p=0.021). Conclusions LBBAP was associated with preserved dimensions and function of the right cardiac chambers over a medium-term follow-up period.

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 >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

Electrocardiographic features in the early differential diagnosis of cardiac amyloidosis from cardiac sarcoidosis

Abstract Introduction Amyloidosis and sarcoidosis are both systemic infiltrative diseases which can cause cardiac involvement. Differentiating early-stage cardiac amyloidosis (CA) from cardiac sarcoidosis (CS) is still challenging, although hypertrophy for CA and septal thinning for CS are characteristic echocardiographic findings in each late-stage. The diagnosis is a time-sensitive issue, given the therapies for CA and CS likely to be effective at early disease stages. Purpose We aimed to evaluate the utility of electrocardiography (ECG) for distinguishing CA from CS before or early in the course of cardiomyopathy. Methods This study enrolled 36 consecutive patients (20 male, 75±13 years) diagnosed with transthyretin-CA in 25 (CA group) and isolated CS in 11 patients (CS group) according to accepted criteria at our institute from July 2014 to July 2023. We retrospectively reviewed electrocardiographic characteristics and clinical outcomes of early-stage CA and CS. Results The CS group were younger than the CA group at the time of diagnosis (59±9 vs 83±7 years, P<0.01) and had a shorter period between the date of their first ECG recording at our institute and the date of diagnosis (18±3 vs 62±67 months, P=0.012). Furthermore, the CA group showed specific P-waves with longer duration (142±19 vs 126±8 ms, P=0.003) and more notches and/or fragmentation (91% vs 33%, P=0.003) in the limb leads on the initial ECG than the CS group, although prolonged PR-interval is common in both CA and CS (191±44 vs. 208±43 ms, P=0.359). Unexpectedly, the CA group had a shorter QRS duration (103±25 vs 123±31 ms, P=0.047) and a higher R-wave in V5 (2.0±0.9 vs 1.3±1.1 mV, P=0.039) than the CS group. In addition, the low voltage in all limb leads, pseudoinfarct pattern and bundle branch block morphology characteristic of CA patients did not differ between diagnosis and initial examination. There were also no differences in atrial and ventricular arrhythmias. During the follow-up period, 5 patients (20%) in the CA group, but no patients in the CS group died. Conclusion CA and CS shares several electrocardiographic features. Prolonged P-wave with notches and fragmentation, suggesting atrial conduction disturbance, may be associated with amyloid deposition in CA. This finding might be useful in the early differential diagnosis for CA from CS.

Unfolding the transition ratio: insight into the diagnostic criteria for the diagnosis of the origin of outflow tract ventricular arrhythmias

Abstract Background algorithms for the diagnosis of the site of origin of ventricular outflow tract arrhythmias (OTVA) share the rationale that more posterior structures (LVOT) produce a greater vector approaching the precordial leads than anterior structures (RVOT), i.e. R waves in V1-V3 of greater amplitude and duration, a transition generally earlier than the QRS in sinus rhythm (SR), and vice-versa. Methods in a retrospective cohort of 45 patients (53.3% LVOT, 46.7% RVOT) with OTVA (left bundle branch block morphology, transition in lead V3, absence of conduction aberrancy in SR, who underwent successful catheter ablation were retrospectively analyzed, comparing the diagnostic yield of the main literature criteria. a) The V2 transition ratio, (TR) calculated with the formula [(R\R+S)PVC : (R\R+S)SR] (LVOT if > 0.6) [1]. b) The V1-V2 S-Rd, calculated as [(V1S + V2S) – (V1R + V2R)] (LVOT if < 1.625) [2]. c) The V2S\V3R amplitude ratio (LVOT if < 1.5) [3]. d) The transition zone index (TZI), obtained by subtracting the transition zone of the PVC with that of the SR (LVOT if < 0) [4]. We extended the use of these criteria to the precordial leads V1 to V3; for TR the equation was applied to amplitude as well as duration measurements. Results Comparison of PVC QRS morphology with that of SR. 1. The diagnostic accuracy of the TR showed incremental values moving from lead V1 to V3, both using amplitude and duration measurements; compared to the modest accuracy of the V2 TR (AUC 0.630, 0.727), the V3 TR (LVOT if > 1) showed an accuracy of 85.3% (AUC 0.804, 0.855). 2. Simplifying the complex TR equation, comparing R or S waves of the PVC with those of the SR, we again found incremental values of accuracy moving from lead V1 to V3, with better results for the SVT\SSR compared to the RVT\RRS; the V3 SVT\SRS) (LVOT if < 1) showed an accuracy of 86.6% (AUC 0.917). 3. The TZI showed in our series a lower diagnostic yield compared to that of the literature (AUC 0.748, accuracy 73.3%) Comparison of PVC QRS morphology between two contiguous leads: 4. Compared to the V1-V2 S-Rd (AUC 0.830), the V2-V3 S-Rd (AUC 0.855), calculated as [(V2S + V3S) – (V2R + V3R)] showed greater accuracy (82.2%). 5. Similarly, compared to the V1S\V2R amplitude ratio (AUC 0.774), the V2S\V3R (AUC 0.930) showed the greatest accuracy (88.8%, with a more balanced sensitivity and specificity moving the cut-off for the diagnosis of origin from LVOT to < 2), resulting the criterion with the highest diagnostic yield. Conclusions variables that compare the morphology of the QRS of the PVC of two contiguous leads have greater accuracy than those that compare the morphology of the QRS of the PVC with that of the SR, with greater diagnostic yield when applied from lead V1 to V3; the V2S\V3R ratio represents the best criterion, with high sensitivity, like the V3 transition ratio; the simple ratio (SVT\SSR) can virtually replace the more complex TR, with similar accuracy but high specificity.

Artificial intelligence enabled electrocardiogram for mortality and ventricular arrhythmia prediction

Abstract Background Artificial intelligence-enhanced electrocardiograms (AI-ECG) can be used to predict risk of events but existing models suffer from lack of actionability, explainability and biological plausibility, and therefore are not used clinically. Purpose We sought to address these limitations of previous AI-ECG approaches by developing the AI-ECG risk estimator (AIRE). Methods AIRE was developed in a dataset of 1,163,401 ECGs from 189,539 patients from a secondary care setting in the USA. Uniquely, AIRE uses deep learning with a residual convolutional neural network with a discrete-time survival loss function to create a subject-specific survival curve using a single ECG. AIRE was trained to predict time-to-mortality and fine-tuned for the additional endpoints described below. Results AIRE outputs a subject-specific survival curve that predicts not only mortality but time-to-mortality, using only a single ECG (Figure 1A). AIRE accurately predicts risk of all-cause mortality (C-index 0.775 (0.773-0.776), Figure 2) and can differentiate prognosis in high and low risk subjects even when only cardiologist reported normal ECGs are considered (Figure 2). AIRE also accurately predicted cardiovascular (CV) death 0.832 (0.831-0.834), future ventricular arrhythmia (0.760 (0.756-0.763)), future atherosclerotic cardiovascular disease (0.696 (0.694-0.698)) and future heart failure (0.787 (0.785-0.889))). In particular AIRE was superior to left ventricular ejection fraction (LVEF) in predicting risk of future ventricular arrhythmias in subjects with LVEF <50% (C-index 0.649 (0.638 – 0.660) vs 0.615 (0.603 – 0.626) p < 0.0001 ) and in dilated cardiomyopathy (C-index 0.690 (0.669-0.711) vs 0.608 (0.584 – 0.631), p < 0.0001). We used a variational autoencoder (VAE) to visualise the features most correlated with the mortality predictions. Features of QRS morphology, particularly broader and more left bundle branch block morphologies, inverted and biphasic T waves as well as ST segment changes were associated with high predicted mortality (Figure 1B). We externally validated our findings in four diverse, transnational cohorts from Brazil and the UK including volunteers and primary care subjects (Figure 2), and found AIRE accurately predicted all-cause mortality in all four external cohorts. Through phenome- and genome-wide association studies, we identified candidate biological pathways for the prediction of increased risk, including changes in cardiac structure and function (LV mass, LVEF, LV trabeculation), and genes associated with cardiac structure, QT interval, biological aging and metabolic syndrome (VGLL2, KCNQ1, CCDC91, TBX3). Conclusion AIRE is an explainable, biologically plausible and actionable AI-ECG risk estimation platform that has the potential for use worldwide across a wide range of clinical contexts for short- and long-term risk estimation.Figure 1Figure 2

Impact of left bundle branch block morphology in predicting response to left bundle branch area pacing for cardiac resynchronization therapy

Abstract Background Left bundle branch area pacing (LBBAP) is a novel pacing technique with an emerging role in resynchronization therapy [1-4]. QRS morphology has shown to significantly influence cardiac resynchronization therapy (CRT) response [5-6]. Purpose The aim of this study was to assess whether different left bundle branch block (LBBB) definitions are associated with response to LBBAP resynchronization therapy. Methods 40 consecutive CRT candidates with previously unsuccessful biventricular (BiV) pacing or in which effective CRT could not be achieved with BiV pacing based on anatomical or functional criteria were selected for this study. Both ischemic and non-ischemic heart failure (HF) patients were included. Patients were divided into two groups according to LBBB morphology. Group 1 included 20 patients (45% ischemic HF) with strict LBBB definition according to Strauss criteria [7], while 20 patients in Group 2 (55% ischemic HF) had conventional LBBB morphology. Response to CRT was defined for (1) reduction in QRS duration; (2) increase in left ventricular ejection fraction (LVEF) ≥ 5% and (3) decrease in left ventricular end systolic volume (LVESV) ≥ 15%. Results LBBAP was successfully achieved in all patients (mean age: 72.0 years; male: 29). The mean baseline QRS duration before implantation was 178.6±13.8 in the Group 1 and 170.8±29.4 in the Group 2, without a statistically significant difference. Over a mean follow-up of 5.6 months, LBBAP resulted in QRS narrowing in both groups, with a greater reduction in Group 1 (-40.6 ms) compared to Group 2 (-15.1 ms), (p 0.002). Pre-implantation ventricular systolic function did not show significant differences between the two groups, with a mean of 30.1±3.5% in the Strauss LBBB group and 31.0±6.0% in the conventional LBBB group. After implantation LVEF was 42.1±8.5 % in the true LBBB patients and 33.2±7.5 in the conventional LBBB group. Echocardiographic response was observed in 65% of patients with a statistically significant difference between Group 1 (90% of responders) and Group 2 (40% of responders), (p 0,001). HF etiology did not impact the response to LBBAP CRT. Conclusions Strict LBBB definition is associated to a greater electrocardiographic and echocardiographic response in patients receiving LBBAP CRT compared to conventional LBBB criteria.\

Determinants of Ventricular Arrhythmias in Mitral Valve Prolapse

BackgroundMitral valve prolapse (MVP) may be associated with ventricular arrhythmias (VA) even in the absence of significant valvular regurgitation. Curling, mitral annulus disjunction (MAD) and myocardial fibrosis (late gadolinium enhancement [LGE]) may account for arrhythmogenesis. ObjectivesThis study investigated the determinants of VA in patients with MVP without significant regurgitation. MethodsThis study included 108 patients with MVP (66 female; median age: 48 years) without valve regurgitation. All patients underwent 12-lead electrocardiography, 12-lead 24-hour electrocardiographic Holter monitoring, exercise stress test, and cardiac magnetic resonance. Patients were divided into 2 groups (arrhythmic and no-arrhythmic MVP), according to the presence of VA with a right bundle branch block pattern. ResultsThe 62 patients (57%) with arrhythmic MVP showed: 1) higher MAD (median length: 6.0 vs 3.2 mm; P = 0.017); 2) higher prevalence of curling (79% vs 52%; P = 0.012); and 3) higher prevalence of left ventricular LGE (79% vs 52%; P = 0.012). Mediation analysis showed that curling had both a direct (P = 0.03) and indirect effect mediated by LGE (P = 0.04) on VA, whereas the association between MAD and VA was completely mediated by LGE. Patients with severe VA showed more pronounced morphofunctional alterations, in terms of MAD (7.0 vs 4.6 mm; P = 0.004) and presence and severity of curling (respectively, 91% vs 64%; P = 0.010; and 4 vs 3 mm; P = 0.004), compared to those without severe VA. ConclusionsIn patients with MVP the occurrence of VA with right bundle branch block morphology is the expression of more severe morphologic, mechanical, and tissue alterations. Curling has both a direct and an indirect effect on VA.

Electrocardiographic predictors of left ventricular scar in athletes with right bundle branch block premature ventricular beats.

Right bundle branch block (RBBB) morphology non-sustained ventricular arrhythmias (VAs) have been associated with the presence of non-ischaemic left ventricular scar (NLVS) in athletes. The aim of this cross-sectional study was to identify clinical and electrocardiogram (ECG) predictors of the presence of NLVS in athletes with RBBB VAs. Sixty-four athletes [median age 39 (24-53) years, 79% males] with non-sustained RBBB VAs underwent cardiac magnetic resonance (CMR) with late gadolinium enhancement in order to exclude the presence of a concealed structural heart disease. Thirty-six athletes (56%) showed NLVS at CMR and were assigned to the NLVS positive group, whereas 28 athletes (44%) to the NLVS negative group. Family history of cardiomyopathy and seven different ECG variables were statistically more prevalent in the NLVS positive group. At univariate analysis, seven ECG variables (low QRS voltages in limb leads, negative T waves in inferior leads, negative T waves in limb leads I-aVL, negative T waves in precordial leads V4-V6, presence of left posterior fascicular block, presence of pathologic Q waves, and poor R-wave progression in right precordial leads) proved to be statistically associated with the finding of NLVS; these were grouped together in a score. A score ≥2 was proved to be the optimal cut-off point, identifying NLVS athletes in 92% of cases and showing the best accuracy (86% sensitivity and 100% specificity, respectively). However, a cut-off ≥1 correctly identified all patients with NLVS (absence of false negatives). In athletes with RBBB morphology non-sustained VAs, specific ECG abnormalities at 12-lead ECG can help in detecting subjects with NLVS at CMR.

His bundle pacing in nodal versus infranodal atrioventricular block: a mid-term follow-up study

IntroductionThis study evaluated the feasibility of His bundle pacing (HBP) in consecutive, unselected patients with advanced atrioventricular block (AVB) over a medium-term follow-up period, comparing procedural characteristics between nodal and...

Left ventricular afterload reduction by transcatheter aortic valve implantation acutely alleviates right ventricular pacing-induced left ventricular dysfunction in patients with aortic stenosis

Abstract Introduction In patients with left bundle branch block (LBBB) cardiac function has been found to be particularly sensitive to alterations in left ventricular (LV) afterload. Nevertheless, whether the detrimental hemodynamic effect of right ventricular pacing (RVP)-induced electromechanical dyssynchrony on LV function is also associated with afterload dependency, has not been investigated yet. Purpose Hence, in the current study we sought to examine the acute effect of RVP on LV function in patients with aortic stenosis (AS) before (with elevated afterload) and after (without elevated afterload) transcatheter aortic valve implantation (TAVI). Methods Patients with a previously implanted permanent pacemaker (PM) and significant AS referred for TAVI at our heart and vascular center university were screened for this observational study. Only those patients who had an intrinsic, regular, narrow QRS or right bundle branch block (RBBB) morphology rhythm were included. From 2022 March to 2023 February, nine patients with a DDD PM (with sick sinus syndrome and maintained AV conduction) and four patients with a VVI PM (with atrial fibrillation and complete AV block but stable junctional escape rhythm) were enrolled. Following TAVI, four patients were excluded due to the development of new-onset persistent LBBB. Transthoracic conventional and advanced echocardiography and non-invasive blood pressure monitoring were performed immediately before TAVI and on the second postoperative day. The measurements were carried out during intrinsic QRS rhythm and during frequency-matched RVP as well. Global longitudinal strain was determined by speckle-tracking echocardiography, then using LV pressure curves estimated from systolic blood pressure and mean aortic gradient, global myocardial work index (GMWI) was calculated to assess LV contractility. Results Mean aortic gradient was decreased after TAVI (40.2±3.6 vs. 6.7±1.3mmHg before vs. after TAVI, P<0.001) indicating successful reduction of LV afterload. Compared to the intrinsic QRS rhythm, RVP decreased GMWI before TAVI (GMWI: 1967±206 vs. 1240±174mmHg% intrinsic QRS vs. RVP, P<0.001) and after TAVI (GMWI: 1399±149 vs. 1020±121mmHg% intrinsic QRS vs. RVP, P=0.019) as well. Nevertheless, the extent of RVP-induced LV contractility impairment (expressed as ΔGMWI) was significantly alleviated after pressure unloading therapy (ΔGMWI: -37.1±6.6 vs. -24.5±7.8% before TAVI vs. after TAVI, P=0.024). Conclusion Our preliminary results indicate that RVP-induced LV dysfunction is afterload dependent. Hence, in patients with AS and a high percentage of RVP, TAVI might entail substantial functional improvement.

Arrhythmic form of mitral valve prolapse: presentation, risk stratification and management

Abstract Background Mitral valve prolapse (MVP) is a common finding that has been considered as benign condition for a long time. However, some anatomic forms have been recently recognized to be associated with life-threatening ventricular arrhythmia and sudden cardiac death (SCD), recently known as arrhythmic MVP (AMVP). Objectives This study is aiming to clinically characterize and risk stratify patients with malignant phenotype of MVP of high risk for ventricular arrhythmia which may lead to SCD. We aim to explore characteristics and assess potential markers for MVP induced ventricular arrhythmia that might need monitoring and follow up with medical or invasive treatment as implantable cardioverter-defibrillator, catheter ablation or even surgical repair. Methods A prospective cohort study of 45 (age 35±8, 29 females), consecutive patients with MVP and/or mitral annular disjunction (MAD) and comprehensive clinical arrhythmia on resting electrocardiography (ECG) or 48-hours Holter monitoring , Doppler echocardiography and contrast based cardiac magnetic resonance (CMR) characterization were identified. Patients were followed-up for a period of maximum one year to identify any further management needed. Results Frequent ventricular arrhythmia was evidently seen associated to MVP (69% with at least ventricular ectopy ≥5%), as well as complex ventricular arrhythmia (31% with sustained or non-sustained ventricular tachycardia ) P<0.001. AMVP was strongly associated with premature ventricular contractions (PVCs) having Right bundle branch block (RBBB) morphology on ECG and late gadolinium enhancement (LGE) on CMR (all p<0.05). Furthermore, it was shown to be associated with bileaflet prolapse and higher left ventricular volumes, however not statistically significant. On Follow-up, Out of 36 patients with ventricular arrhythmia, 64% were controlled on medical anti-arrhythmic and some others were referred either for ablation after worsening of symptoms despite of medical treatment (27.8%), implantable cardioverter-defibrillator device for secondary VT prophylaxes (5.6%) or surgery (2.8%) due to progression in mitral regurgitation severity and deterioration of symptoms. Conclusion In this small cohort study, characteristic form of MVP was found to be associated with ventricular arrhythmia more common in the form of frequent PVCs and less common in the complex form. Although majority of patients were controlled on medical treatment, few patients required further invasive management despite of medical treatment . Thus, arrhythmia associated with a special form of MVP could be life threatening and needs close monitoring, long follow-up and proper management approach to prevent SCD. Large prospective studies with comprehensive approach and long term follow up is pivotal. CMR T1 mapping and electro anatomical CARTO mapping could help in better detection and proper defining of arrhythmia substrate in future studies.AMVP illustration

Abstract 17127: Rapid Progression of Conduction System Disease in Suspected Fulminant Nivolumab Myocarditis

Background: Immune checkpoint inhibitors (ICI) have shown efficacy in treating a wide spectrum of malignancies, but have a known risk of cancer therapy related cardiac toxicity. We present a case that demonstrates how conduction system disease can rapidly progress in a patient with suspected nivolumab (PD1) induced fulminant myocarditis. Case: An 82-year-old male with a history of esophageal carcinoma presented with agonal breathing and altered mental status. He had received his second dose of PD1 therapy three days prior. He was intubated and admitted for hypoxic respiratory failure and elevated troponin. His initial EKG demonstrated new marked 1st degree AV block with right bundle branch block (RBBB) morphology. A stat echocardiogram noted an EF of 60-65% with no wall motion abnormalities. Decision-making: On Day 2, Mobitz Type I block was appreciated on telemetry. The patient met criteria for acute myocarditis with his clinical presentation, new conduction system disease, and high sensitivity troponin of 13,000. Given recent PD1 therapy, lack of infectious prodrome, and lack of prior heart disease, suspicion for ICI induced myocarditis was high. High dose steroid therapy was initiated. On Day 3, the patient was noted to have alternating left bundle branch block and RBBB. On Day 4, he progressed to complete heart block, prompting transvenous pacemaker (PM) placement with subsequent permanent PM placement. A repeat echo showed global hypokinesis with an EF of 40-45% and reduced RV function. He also required vasopressor support meeting criteria for fulminant myocarditis. Due to his hemodynamic instability and low clinical suspicion, he did not receive cardiac catheterization. Cardiac MRI and cardiac biopsy were not readily available in this institution. Conclusion: The clinical findings, lack of infectious prodrome, and worsening arrhythmia requiring pacing and vasopressor support, in patient with recent PD1 treatment suggests nivolumab induced fulminant myocarditis. In institutions without advanced testing infrastructure, rapid recognition of progressive conduction system disease may be used as an early marker for diagnosis, treatment initiation, and referral to tertiary care centers for advanced management of fulminant ICI myocarditis.

Abstract 15885: A Masquerading Early Beat Induces Ventricular Fibrillation

Clinical Case: A 51 year old male with a history of hypertension, G6PD deficiency, thrombotic thrombocytopenic purpura, prior stroke, and morbid obesity presented with resuscitated out of hospital VF arrest. Electrolytes and ECG were normal. During his admission, the patient had two VF events that were induced by what appeared to be a short coupled right bundle branch block (RBBB) morphology PVC. He was brought to the electrophysiology lab for PVC ablation and ICD implantation. Baseline rhythm was sinus with what appeared to be both RBBB morphology PVCs and junctional extrasystoles. With both extrasystoles, the His potential preceded the QRS by 50 ms, and atrial activation in the His catheter and coronary sinus catheter was also earlier than the QRS. Activation mapping of the right bundle showed later activation than the His potential. This was all consistent with junctional premature complexes (JPC) with frequent RBBB aberrancy rather than fascicular PVCs. Slow pathway modification was performed to attempt to ablate the JPCs. After multiple ablations along the tricuspid annulus and back to the coronary sinus os that triggered slow junctional beats, the patient’s JPC burden was significantly reduced. An ICD was also implanted. The patient was discharged on flecainide. At 4 month follow up he had not had recurrence. Discussion: Early coupled PVCs are a well-known cause of ventricular fibrillation, but JPCs inducing VF have not been described previously. Placement of a coronary sinus and His catheter helped identify early that this was not simply a fascicular PVC. This case demonstrates the importance of keeping a broad differential diagnosis when starting any EP study. Ablating the slow pathway area can be effective to treat JPCs while preserving native AV conduction as demonstrated in this case.

A wobble tachycardia… supraventricular, ventricular or both?

We present the case of a 77-year-old man with ischemic heart disease and baseline right bundle branch block having a well-tolerated and regular wide complex tachycardia with right bundle branch block morphology. A wide complex tachycardia (WCT) could be of supraventricular or ventricular origin. In this setting, we discuss the differential diagnosis of WCT, the usefulness and limitations of the diagnostic criteria for ventricular tachycardia.

Significance of left posterior extension of early repolarization in patients with J-wave syndrome

J waves in the inferior or lateral leads are characteristic electrocardiographic (ECG) changes in patients with early repolarizationsyndrome (ERS). However, the presence of J waves in the left posterior region has not yet been evaluated. The purpose of this study was to clarify the significance of J waves in the posterior left ventricle using leads V7-V9 and a body surface mapping (BSM) system. Forty patients diagnosed with ERS were included. All patients exhibited J waves in either the contiguous inferior, lateral, or posterior leads. We evaluated the incidence of J waves in the inferolateral and posterior leads using a 15-lead ECG with synthesized V7-V9 and an 87-lead BSM. Additionally, we assessed the arrhythmogenicity of the posterior regions based on the morphology ofthe premature ventricular complexes (PVCs) associated with ventricularfibrillation (VF). J waves were observed in the lateral, inferior, and posterior leads of 26 (65%), 31 (78%), and 39 (97%) patients, respectively. J waves were found only in the posterior leads of 5 patients. BSM was evaluated in 9 patients, all of whom exhibited a positive area on the posterior region. PVCs associated with VF were recorded in 5 patients. Among patients with inferolateral and posterior J waves, all except 1 patient who displayed left bundle branch block morphology showed PVCs originating from the posterior left ventricular region. Posterior J waves are common in ERS patients. This abnormality can be detected using leads V7-V9 and the BSM system and may be associated with arrhythmogenesis.

Selective and non-selective right bundle pacing for the diagnosis of bundle branch reentry ventricular tachycardia.

Bundle branch reentry ventricular tachycardia (BBRVT) can be seen in patients with conduction disease. In this report, we describe the use of conduction system pacing for its diagnosis. BBRVT was induced in two patients with infra-nodal conduction disease. Bundle branch reentry ventricular tachycardia with a left bundle branch block morphology was observed in the first patient (type A), whereas the second patient had a right bundle branch block morphology (type C).The diagnosis of BBRVT was confirmed in both patients by ventriculo-atrial dissociation, and the interdependence of the conduction system and the ventricular tachycardia cycle length variations.Selective and non-selective RB pacing was observed in the two patients during apical right ventricular pacing for entrainment of BBRVT with evidence of manifest entrainment with non-selective RB capture in the first patient, and concealed entrainment by selective RB capture in the second patient. Other criteria for entrainment including a short post-pacing interval at the right bundle pacing site were noted. Right bundle pacing is feasible in patients with BBRVT and may be a helpful manoeuver for the diagnosis of BBRVT.

Optimizing electrophysiology studies to prevent sudden cardiac death after myocardial infarction.

This study assessed associations of minimum final extrastimulus coupling interval utilized within electrophysiology study (EPS) after myocardial infarction (MI) and possible site of origin of induced ventricular tachycardia (VT) with long-term occurrence of spontaneous ventricular tachyarrhythmia and long-term survival. This prospective study recruited consecutive patients with left ventricular ejection fraction (LVEF) ≤ 40% who underwent EPS days 3-5 after MI between 2004 and 2017. Positive EPS was defined as sustained monomorphic VT cycle length ≥200 ms for ≥10 s or shorter duration if haemodynamic compromise occurred. Each of the four extrastimuli was shortened by 10 ms at a time, until it failed to capture the ventricle (ventricular refractoriness) or induced ventricular tachyarrhythmia. Outcomes included spontaneous ventricular tachyarrhythmia occurrence and all-cause mortality. Shorter coupling interval length of final extrastimulus that induced VT was associated with higher risk of spontaneous ventricular tachyarrhythmia (P < 0.001). Significantly higher rates of spontaneous ventricular tachyarrhythmia (65.2% vs. 23.2%; P < 0.001) were observed for final coupling interval at EPS <200 ms vs. >200 ms. Right bundle branch block (RBBB) morphology of induced VT, with possible site of origin from the left ventricle, was associated with all-cause mortality [hazard ratio (HR) 3.2, P = 0.044] and a composite of spontaneous ventricular tachyarrhythmia recurrence or mortality (HR 1.8, P = 0.043). Ventricular tachycardia induced with shorter coupling intervals was associated with higher risk of spontaneous ventricular tachyarrhythymia on follow-up, indicating that the final extrastimulus coupling interval at EPS early after MI should be determined by ventricular refractoriness. Induced VT with possible origin from left ventricle was associated with increased risk of spontaneous ventricular tachyarrhythmia recurrence or death.

Feasibility of Permanent His Bundle Pacing in the Elderly vs the Very Elderly. A Single-Center Mid-Term Follow-Up Study.

Although feasibility studies have included older patients, specific data for His bundle pacing (HBP) in this population is scarce. The aim of this study was to evaluate the feasibility and mid-term performance of HBP in the elderly (70 to 79 years old) versus the very elderly (80 years old and above) patients with conventional indications for pacing. About 105 patients older than 70 years of age with attempted HBP from the 1st of January 2019 to the 31st of December 2021 were reviewed. Clinical and procedural characteristics were recorded at baseline, and after a mid-term follow-up period. The procedural success rate was similar in both age groups (68.49% vs 65.62%). There was no significant difference in pacing or sensing thresholds, impedance, and fluoroscopy times. For both age intervals, patients with a baseline narrow QRS maintained a similar QRS duration after pacing, while in patients with a wide QRS, the paced QRS was significantly shorter. Baseline QRS duration, left bundle branch block morphology, and ejection fraction, were significantly associated with HBP procedural failure. The mean follow-up period was 830.34 days for the elderly and 722.76 days for the very elderly. After the follow-up period, both sensing and pacing thresholds were similar between the groups. Compared to the baseline values, there were no significant changes in both pacing and sensing parameters, irrespective of the age interval. During follow-up, no lead dislodgements were recorded. There were two cases of significant pacing threshold rise in the elderly (4%) and three cases in the very elderly group (14.2%) which were managed conservatively, without lead revision. In elderly and very elderly patients, HBP is a feasible procedure associated with constant pacing and sensing parameters and with low complication rates over mid-term follow-up.

Diagnostic gain of cardiac MR in patients with premature ventricular complexes and structurally normal hearts on echocardiography

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): KG Jebsen Centre for Cardiac Research, University of Oslo, Oslo, Norway Background An important part of the diagnostic evaluation of patients with premature ventricular complexes (PVCs) is to identify underlying cardiac disease. The majority of these patients referred to catheter ablation have PVCs with inferior axis and left bundle branch block morphology (I-LBBB). Although this is the most common morphology in patients with idiopathic PVCs, cardiac magnetic resonance (CMR) is recommended to exclude potential other underlying pathology. However, the diagnostic gain of CMR in patients with I-LBBB PVCs is uncertain. Purpose The purpose of this study was to explore the prevalence of cardiac abnormalities identified by CMR in patients with I-LBBB PVCs evaluated for catheter ablation without signs of underlying cardiac disease from resting ECG, stress test, or echocardiography. Methods We retrospectively collected data from consecutive patients with I-LBBB PVCs evaluated for catheter ablation at our tertiary referral centre from 2011 to 2022. We included patients with normal ECG and stress test, and no evidence of functional or structural heart disease by echocardiography. We categorized CMR examinations as normal or as having signs of functional or structural abnormalities. Results We identified a total of 63 patients with I-LBBB PVCs evaluated for catheter ablation, with no signs of underlying conditions from sinus rhythm ECG, stress test or echocardiography. All were studied by CMR at our institution. The median age was 49 years (IQR 36-61), and 39 were females (62 %). The maximum PVC burden recorded in each patient prior to referral was 20 % (IQR 11-29.5). Left ventricular (LV) ejection fraction by echocardiography was 56±4 %. CMR was normal in 52 patients (83 %), while functional or structural abnormalities were detected in 11 patients (17 %). These abnormalities comprised reduced LV systolic function (2 patients), dilated right ventricle (2 patients), dilated LV (1 patient), ventricular septal defect (2 patients), non-compaction cardiomyopathy (1 patient), mitral annular disjunction (2 patients), tricuspidal annular disjunction (1 patient), and myocardial fibrosis by late contrast enhancement (3 patients). Conclusions In patients with I-LBBB PVCs evaluated for catheter ablation, and with no signs of underlying pathology from standard diagnostic work-up, CMR detected abnormalities in 17 %. These results support the routine use of CMR in the evaluation of patients with I-LBBB PVCs referred for catheter ablation.