Bundle Branch Block Pattern Research Articles

Classification of Premature Ventricular Contractions in Athletes During Routine Preparticipation Exams.

Large-scale data on incidental premature ventricular contraction (PVC) prevalence and morphologies have been lacking, leaving many providers without guidance on further cardiac testing for patients with incidental PVCs on ECG. Athletes offer an intriguing cohort to understand the clinical significance, prevalence, and common morphologies of incidental PVCs because they often undergo ECG screening during preparticipation exams. Digital ECGs were obtained from 10 728 screened athletes aged 14 to 35 years during mass screenings in schools and professional sports teams between 2014 and 2021. A retrospective analysis of ECGs with PVCs was performed using the simultaneous display of frontal (limb) and horizontal (precordial) plane leads. PVCs were coded for morphology and categorized as benign or nonbenign using recommended criteria. Twenty-six athletes (0.24%) were found to have at least 1 PVC. Among these, 50% were female, 65% were White, 8% were Asian, 4% were Hispanic, and 23% were Black. Nineteen of the 26 (73%) ECGs had PVCs with a left bundle branch block pattern compared with 7 (27%) with a right bundle branch block pattern. Twenty-four ECGs (96%) had PVCs with benign patterns, including 18 with right ventricular outflow tract, 5 with left anterior fascicle, and 2 with left posterior fascicle morphology. There is a low prevalence of PVCs on routine ECG screening of young athletes, and most PVCs are of benign morphology in this population. This study highlights the value of using digital ECG recorders with simultaneous lead display to guide decision-making about further cardiac testing and referrals in young athletes with PVCs. Using our results and review of the literature, we propose methods and algorithms of PVC evaluation on screening ECGs to help guide many providers with risk stratification and decision-making about further cardiac testing and electrophysiology referrals in young athletes with PVCs.

Discrimination between ventricular tachycardia and wide-QRS preexcited tachycardia.

To develop a new algorithm to differentiate ventricular tachycardia (VT) from preexcited tachycardia (pre-ET) according to left bundle branch block (LBBB) and right bundle branch block (RBBB) patterns. This study included 67 electrocardiograms (ECGs) with VT and 63 ECGs with pre-ET, collected from our hospital and through PubMed. Of those, 64 were allocated to the derivation cohort and the rest to the validation cohort. The diagnoses of the ECGs were confirmed using an electrophysiological study. Parameters and classifiers from prior algorithms along with the propagation speeds in the early portion of the QRS complex (initial deflection index) in leads V1, V6, aVR, II, and III were manually measured. The performance of the new algorithm was compared with that of prior algorithms. The initial deflection index in lead III was the strongest predictor of pre-ET in LBBB-pattern wide-QRS tachycardia (p = 0.003, AUC 0.805). The initial deflection index in lead V1 was the most powerful predictor of pre-ET in RBBB-pattern wide-QRS tachycardia (p = 0.001, AUC 0.848). Compared to earlier algorithms, those using the initial deflection indexes: lead III in LBBB patterns (cutoff value >0.3) and lead V1 in RBBB patterns (cutoff value ≤0.48), demonstrated superior performance in screening VT, with AUC values of 0.828. The initial deflection indexes proved effective as discriminators between VT and pre-ET in the validation cohort. In LBBB-pattern wide-QRS tachycardia, the early propagation speed of pre-ET was faster than that in VT. Conversely, in RBBB-pattern wide-QRS tachycardia, it was slower.

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.

Real-time three-dimensional transthoracic echocardiography in quantification of left ventricular dyssynchrony

Aim. To compare endocardial and epicardial left ventricular (LV) pacing using real-time electrocardiography (ECG)-synchronized three-dimensional echocardiography (3DE).Methods. Experimental intraoperative study included 88 points obtained from 12 patients with compensated heart failure of II-IV functional class NYHA (LV ejection fraction < 35%) and cardiac resynchronization therapy indications - ECG pattern of complete left bundle branch block (LBBB) and QRS complex duration > 150 ms. During isolated LV pacing as part of cardiac resynchronization therapy implantation procedure endocardial and epicardial stimulation points matched under fluoroscopic control using quadripolar coronary sinus leads and endocardial electrodes for temporary pacing were obtained. The overall number of corresponding pacing sites included 44 endocardial and 44 epicardial stimulation positions. The mean age of patients was 68.5 [63; 73.5] years, 83% males (n=10). Before study enrollment, 12-channel ECG, echocardiography, and a six-minute walk test were performed for all participants along with cardiac magnetic resonance imaging and control coronary angiography if indicated. The prevalence of coronary heart disease was 50% (n=6) while dilated cardiomyopathy was the most common etiology of chronic heart failure in other cases. Intraoperative ECG with estimation of paced QRS complex morphology at each point was registered via LabSystem Pro Electrophysiological Recording System (Bard Electrophysiology, USA). 3DE was performed using TomTec and Philips Qlab 3DQ Advanced software (Philips Medical Systems, USA).Results. Three-dimensional parametric imaging of LV regional segmental excursion and myocardial contractility using 3DE revealed statistically significant difference in semi-quantative parameters such as ExcAvg (p<0.001), ExcMax (p=0.001), ExcMin (p<0.001) and LV ejection fraction based on 3D modelling (p=0.003) while endocardial pacing was more beneficial. During the course of endocardial stimulation, the 3DE dyssynchrony index estimated at the 2nd stimulation site was also significantly lower (p=0.03). Identical dyssynchrony parameters valid for the 16 and 12-segment 3D models (SDI-16, Tmsv-12SD) (at p=0.06) demonstrated only a tendency for significant difference. The duration of QRS complex at the time of endocardial pacing was significantly shorter (<190 [179;215] ms) (p=0.0008). Semi-quantitative and quantitative 3DE parameters showed the benefit of endocardial pacing resulting in cardiac contractility improvement with less dyssynchrony and LV volume reducing during intraoperative period.Conclusion. Endocardial pacing has potential benefit over the epicardial pacing represented by intraoperative dynamics of LV global and local contractility, intraventricular dyssynchrony estimated by 3DE and also ECG criteria. 3DE is helpful in more precise and reproducibile determing of late activation zone for target LV lead placement that is more manoeuvrable in case of endocardial stimulation.

Feasibility of Conduction System Pacing in Patients with Baseline Bundle Branch Block-A Single-Center Mid-Term Follow-Up Study.

The primary prerequisite for a successful conduction system pacing (CSP) procedure is the integrity of the conduction system, which may be impaired if a baseline bundle branch block (BBB) is present. This study aimed to evaluate the feasibility and mid-term performance of permanent CSP in patients with baseline BBB and to compare the results between left bundle branch block (LBBB) and right bundle branch block (RBBB) patterns. A total of 101 patients with typical BBB and an attempt at CSP were retrospectively reviewed. Procedural characteristics, pacing, sensing parameters, and complications at baseline and after a mid-term follow-up were analyzed. The global procedural success for CSP was 93%. His bundle pacing (HBP) had a significantly lower success rate than left bundle branch area pacing (LBBAP) (50.5% vs. 86%). The paced QRS duration was significantly narrower with HBP. The pacing and sensing thresholds were significantly better with LBBAP. Procedural complications occurred only in the LBBAP group (two acute perforations in the LV cavity and one acute chest pain during lead fixation) without long-term sequelae. The HBP and the LBBAP procedural success rates were higher in the RBBB versus the LBBB group (62.5% vs. 44.9% and 100% vs. 81.5%, respectively). Baseline QRS duration, atrial volumes, and right ventricular diameters were significantly associated with HBP procedural failure. The follow-up pacing and sensing thresholds were similar to the baseline values for all pacing methods and BBB morphology. Only one device-related complication leading to pacing interruption was recorded. In patients with bundle branch blocks, CSP is a feasible procedure associated with a high success rate, stable pacing and sensing parameters, and low complication rates over a mid-term follow-up.

Tall R waves in the right precordial leads as a possible expression of left septal fascicular block

Histological, physiological and pathophysiological studies have shown that the left bundle branch mainly divides into three fascicles, and a septal (middle) fascicle is present in over half of human hearts. Electrocardiographic criteria for the diagnosis of the block of this fascicle have been suggested by some authors: tall R waves in lead V2 and sometimes in V1 in the absence of a right bundle branch block pattern or a well evident jump of R waves from V1 to V2, absence of initial septal q waves and/or possible small q waves in the right precordial leads, normal QRS duration and normal QRS axis. At present, this intraventricular block can only be suspected but not diagnosed with certainty even after clinical/instrumental exclusion of pathological situations associated with tall R waves in leads V1 and V2 (right ventricular hypertrophy, lateral infarction, severe septal hypertrophy) because of the marked variability of normal ECG and the potential presence of confounding diseases.

The impact of right bundle branch block and SIQIII-type patterns in determining risk levels in acute pulmonary embolism

The impact of right bundle branch block and SIQIII-type patterns in determining risk levels in acute pulmonary embolism

Differentiating Origins of Outflow Tract Ventricular Arrhythmias: The Correction of Transitional Zone Index Is Not Superior to the Original One

Introduction: Our team once proposed a correction of transitional zone index (CTZI) based on the transitional zone index (TZI) in view of achieving a more precise prediction of outflow tract ventricular arrhythmia (OTVA). The predictive accuracy of these two electrocardiogram (ECG) algorithms has not been validated and compared. The purpose of this study was to compare the predictive accuracy of TZI and CTZI in a much larger population with idiopathic OTVA. Methods: The predictive accuracy of TZI and CTZI was compared in 695 individuals with idiopathic premature ventricular complex or ventricular tachycardia which exhibited a left bundle branch block pattern and inferior axis QRS morphology. Receiver operating characteristic curve analysis, decision curve analysis, and calibration curve were used to compare the predictive accuracy of TZI and CTZI. Results: TZI and CTZI manifested the similar area under the curve. While a TZI of <0 predicted a left ventricular outflow tract (LVOT) origin with a high specificity of 88.2% but a low sensitivity of 67.1%, a CTZI of <0 yielded a high sensitivity of 84.3% but a low specificity of 59.5% in the overall analysis. Similar results were yielded in the sub-analysis of participants with a precordial transition occurring at lead V3. In the sub-analysis of participants with a TZI = 0, CTZI demonstrated a bit higher but not satisfactory predictive accuracy than TZI. Conclusion: Based on the scientific spirit of self-criticism and seeking truth from facts, our team disproves the correction of TZI proposed previously.

High frame rate speckle tracking echocardiography to visualize the mechanical activation sequence of the left ventricle

Abstract Background Cardiac arrhythmias are a known cause of morbidity and mortality, with catheter ablation being an effective treatment. In order to detect the focal source or the re-entrant circuit of the arrhythmia, i.e. the ablation target, current practice includes performing an electrophysiological study. This technique is invasive, with increased patient related risk and variable success rate. Conversely, echocardiography could be used to determine the correct ablation target. High frame rate (HFR) ultrasound has a temporal resolution adequately high to detect the onset of myocardial deformation and could assist the accurate localisation of the arrhythmia source. Purpose To test whether HFR speckle tracking echocardiography (STE) can be used to create cardiac mechanical activation maps. Methods 18 healthy volunteers (HV) (age 30±6y; 69 %males) and 12 heart failure patients treated with cardiac resynchronisation therapy (CRT) (age 69±10y; 75 %males) were included. All participants were scanned with a research HFR ultrasound scanner (∼849fps) and the 3 standard apical views were acquired. Patients were scanned with CRT on and after turning CRT off, in order to allow intrinsic ventricular conduction. Data from one CRT patient were acquired by temporarily altering the pacing pole of the CRT LV lead. All patients had a left bundle branch block (LBBB) pattern of native activation on the surface ECG. For each view, a manually placed contour was tracked during the cardiac cycle by a custom-made 2D HFR STE algorithm; the contours were divided in a standard 16 segment model and segmental strain rate (SR) curves were computed and used to measure the temporal distance between electrical and mechanical activation (i.e. distance between the beginning of QRS and the first positive to negative zero crossing in the SR curve). Finally, an activation map for each subject was created by placing the extracted timings in the middle of the corresponding segment of a bull’s-eye plot and interpolating values between them. Results Tracking was feasible in 94% of the segments; SR curves showed a physiological pattern (Fig. 1A). For the HV, mechanical activation started from mid anteroseptal (72%) or mid inferoseptal (28%) segment at 23±5ms, spreading to basal posterolateral segment at 49±8ms from the start of QRS, in all but one case, where activation ended at basal inferoseptal segment (Fig. 1B). During CRT off, septal wall was activated 31±9ms and lateral wall 74±20ms after the beginning of QRS (p&amp;lt;0.01) (Fig. 1C), whereas during CRT on, septal wall was activated 41±11ms and lateral wall 38±7ms after the beginning of QRS (p=0.3) (Fig. 1D). Changing the pacing pole of the LV lead in one CRT patient also changed the start of mechanical activation in the lateral wall (Fig. 2). Conclusion Our findings comply with left ventricular activation as described in the literature and show that HFR STE could be a useful tool in defining the ablation target for arrhythmia treatment.

Abstract 16631: Isolated Cardiac Sarcoidosis Presenting as Recurrent Transient Ischemic Attacks

Background: Cardiac sarcoidosis (CS) is a rare disease that can present with a variety of clinical scenarios including, heart failure and sudden death. We present a case of isolated CS presenting as recurrent transient ischemic attacks (TIA) in a previously asymptomatic patient. Description of Case. A 54-year-old female with a history of two previous TIAs presented 30 minutes after the onset of left-sided facial droop and incomprehensible speech. CT and MRI brain did not show acute infarction. ECG showed a right bundle branch block pattern. Transthoracic echocardiogram (TTE) showed an abnormal global longitudinal strain of 12.8%, a left ventricular ejection fraction of 40%, segmental wall motion abnormalities involving the apex and basal inferior walls, and swirling of contrast at the apex. She had no previous history of cardiomyopathy. CTA was unrevealing for coronary artery disease but a cardiac MRI showed areas of late gadolinium enhancement and a RV wall aneurysm. PET scan revealed multifocal patchy nodular areas of FDG uptake within the myocardium. A diagnosis of isolated CS was made. At a three-month follow-up, TTE showed a new apical thrombus measuring 0.8cm x 0.6 cm. The patient was started on anticoagulation with the eventual resolution of the thrombus. She had no further ischemic events. Discussion. TIAs and ischemic stroke are extremely rare complications of CS and are largely attributed to cardioembolic phenomena, in the absence of systemic disease. Cardiac structural changes that lead to arrhythmias, hypokinesis, and stasis with clot formation largely explain embolic events in these patients. In addition, evidence suggests that the inflammatory cytokines, such as IFN gamma and IL-12, released by the sarcoid granuloma may also have an independent role in clot formation. The combination of stagnant flow in akinetic areas and a strong inflammatory bed of cytokines led to recurrent TIAs in this patient and the apical thrombus that was later identified.

Abstract 15650: Recovery of Cardiomyopathy Following Accessory Pathway Ablation

Background: Wolf-Parkinson-White (WPW) can cause significant arrhythmia in addition to left ventricular (LV) dessynchrony and cardiomyopathy, which may be reversible by accessory pathway ablation. Case: A 21-year-old female athletics major college student presents with dyspnea, fatigue and occasional palpitations associated with dizziness. Electrocardiogram (EKG) revealed WPW with left bundle branch block pattern suggestive of right-sided bypass tract (panel A). Transthoracic echocardiogram (TTE) revealed LV ejection fraction (LVEF) 35 - 40% and significant interventricular dessynchrony on M-mode (panel B). Decision-making: It was felt that her symptoms and LV dysfunction are due to QRS widening and possibly arrhythmia caused by the bypass tract, and that ablation is warranted. Electrophysiology study 3-D map revealed 2 insertion points of the bypass tract along the tricuspid annulus (panel C). Ablation was performed initially along the inferior tricuspid annulus, leading to QRS complex narrowing with a change in the delta wave axis. Another activation site was mapped separately to the anterolateral tricuspid annulus; ablation at this site eliminated pre-excitation altogether. Post procedure EKG revealed normalization of the PR interval and diffuse T wave abnormalities likely due to cardiac memory (panel D). Follow-up in 6 weeks revealed an LVEF of 60 - 65% and normal wall motion on TTE with improvement of her symptoms; she was cleared to resume sports. Conclusion: WPW can be associated with significant cardiomyopathy and heart failure due both to arrhythmia and marked LV dessynchrony, which may be reversed by radiofrequency ablation.

Misplacement of pacemaker leads: How to avoid and how to approach?

The use of cardiac implantable electronic devices has increased in recent years due to factors such as a growing population, increased life expectancy, and improved access to healthcare services. In parallel with this trend, complications related to pacemakers have also increased. One of the most important and preventable complications among these is lead misplacement. Misplacement of a permanent pacemaker lead in the LV can lead to a variety of complications, including damage to the heart muscle, arrhythmias, blood clotes and cerebrovascular events. It is recommended to use the fluoroscopic 40° LAO view during implantation. That view clearly defines the interatrial and interventricular septum. Right bundle branch block pattern on ECG is an important clue to suspected misplaced lead. In addition to the postero-anterior (PA) projection of x-ray, the latero-lateral (LL) projection provides a clearer view of lead malposition. In the LL view, the tip of an incorrectly positioned LV lead is characteristically directed toward the spine. If diagnosed soon after implantation, percutaneous lead extraction can reduce the risk of future thromboembolic events without the need for lifelong anticoagulation. It should be noted that in cases with a lead in the LV for a long time, lead removal is not the primary recommendation. Patient-based approach should be fundamental.

Triggers of Ventricular Fibrillation in Patients With Inferolateral J-Wave Syndrome

BackgroundThere are few data on ventricular fibrillation (VF) initiation in patients with inferolateral J waves. ObjectivesThis multicenter study investigated the characteristics of triggers initiating spontaneous VF in inferolateral J-wave syndrome. MethodsA total of 31 patients (age 37 ± 14 years, 24 male) with spontaneous VF episodes associated with inferolateral J waves were evaluated to determine the origin and characteristics of triggers. The J-wave pattern was recorded in inferior leads in 11 patients, lateral leads in 3, and inferolateral leads in 17. ResultsThe VF triggers (n = 37) exhibited varying QRS durations (176 ± 21 milliseconds, range 119-219 milliseconds) and coupling intervals (339 ± 46 milliseconds, range 250-508 milliseconds) with a right (70%) or left (30%) bundle branch block (BBB) pattern. Trigger patterns were associated with J-wave location: left BBB triggers with inferior J waves and right BBB triggers with lateral J waves. Electrophysiologic study was performed for 22 VF triggers in 19 patients. They originated from the left or right Purkinje system in 6 and from the ventricular myocardium in 10 and were undetermined in 6. Purkinje vs myocardial triggers showed distinct electrocardiographic characteristics in coupling interval and QRS-complex duration and morphology. Abnormal epicardial substrate associated with fragmented electrograms was identified in 9 patients, with triggers originating from the same region in 7 patients. Catheter ablation resulted in VF suppression in 15 patients (79%). ConclusionsVF initiation in inferolateral J-wave syndrome is associated with significant individual heterogeneity in trigger characteristics. Myocardial triggers have electrocardiographic features distinct from Purkinje triggers, and their origin often colocalizes with an abnormal epicardial substrate.

Prognostic significance of quantitative electrocardiographic parameters in patients with non-high-risk pulmonary embolism

BackgroundElectrocardiogram (ECG) abnormalities indicating right ventricular strain have been reported to have prognostic value in severe cases of acute pulmonary embolism (PE). We aimed to analyze the prognostic significance of other quantitative ECG parameters in non-high-risk acute PE. MethodsConsecutive patients with non-high-risk acute PE were prospectively enrolled. The following baseline ECG parameters were collected: rhythm, heart rate, QRS axis, right bundle branch block (RBBB) pattern, S1Q3T3 pattern, T-wave inversion, ST-segment elevation, Qr in lead V1, PR Interval, QRS complex duration, QT interval, P-wave amplitude and duration, R- and S-wave amplitudes. The primary endpoint was early discharge within three days. Associations between ECG parameters and early discharge were analyzed. ResultsOverall, 383 patients were enrolled (median age: 67 years, 57% female): 277 (72.3%) with low-risk and 106 (27.7%) with intermediate-risk. The two groups of patients differed in several ECG signs of right ventricular strain and many other quantitative parameters like R- and S-wave amplitudes. In the multivariate logistic regression analysis, the S-wave depth in lead V5 (S-V5) was the only independent prognostic factor for early discharge (odds ratio = 0.137, 95% confidence interval = 0.031-0.613, p = 0.009). The optimum cutoff value of S-V5 for predicting early discharge derived from the receiver operative characteristic curve was 0.15 mv (c-statistic = 0.66, p =0.003). ConclusionsSeveral ECG signs of right ventricular strain and many other quantitative parameters were associated with disease severity in non-high-risk acute PE. An S-V5 lesser than 0.15 mv was predictive for early discharge in these patients.

ECG characteristics of “true” left bundle branch block: Insights from transcatheter aortic valve–related LBBB and His-Purkinje conduction system pacing–correctable LBBB

Left bundle branch block (LBBB) pattern on the electrocardiogram includes patients with both complete conduction block in the His-Purkinje system as well as nonspecific left ventricular conduction delay without discrete block. The purpose of this study was to characterize electrocardiographic morphological features of LBBB patterns in patients with (1) LBBB after transcatheter aortic valve replacement (TAVR) and (2) LBBB correctable by conduction system pacing (CSP). Consecutive patients with post-TAVR (n = 123) or CSP-correctable LBBB (n = 58) from 2 centers were included in this retrospective evaluation. QRS durations as well as detailed morphological features, including notching and slurring, of QRS complexes in leads I, aVL, V1, V2, V5, and V6 and in all 3 inferior leads were recorded. The mean age of the entire cohort was 78.3 ± 10.1 years, with 48% of the cohort being male(87/181). In the CSP-correctable group (n = 58), 14 (24.1%) underwent His-bundle pacing and 44 (75.9%) left bundle branch area pacing. A total of 17 of 181 (9.4%) of the combined cohort failed to completely meet the Strauss criteria. QRS morphology in lead V1/V2 was always either rS or QS, and there were no q/Q waves noted in lead V5/V6. Although dominant R waves were seen in leads I and aVL of 176 of 181 (97.2%), q/Q waves were present in only 21 of 181 (11.6%). Importantly, notched or slurred QRS complexes were identified in at least 1 lead of 4 leads I, aVL, V5, and V6 in 181 of 181 (100%). Strauss criteria and QRS notching are highly prevalent in LBBB after TAVR and in LBBB correctable by CSP.

Abstract P3131: SIRTUIN5 Modulates Na + /Ca 2+ Handling Through Oxidative Stress Dependent Mechanism In Mouse Heart

Mutations in cardiac sodium channel Na V 1.5 (encoded by SCN5A) can cause inherited or acquired arrhythmias, including ~20% of cases of Brugada Syndrome (BrS) and inherited conduction disease. The peak Na V 1.5 current (I Na, Peak ) and the late current (I Na, Late ) govern the fast upstroke and plateau of the cardiac action potential, respectively. Ca 2+ ions impact excitation-contraction coupling, and imbalance in Na + /Ca 2+ homeostasis can cause electrical disturbance. BrS is characterized by a right bundle branch block pattern on EKG, arrhythmias, and sudden cardiac death. Recently, potential mutations in SIRT5, including P114T-SIRT5, were identified in small families with BrS. SIRT5 is a member of the Sirtuin family, acts as NAD + -dependent deACYLase.We explored the potential role of SIRT5 in BrS using heterologous expression systems and homozygous P114T-SIRT5 knock-in (P114T-KI) mice. SIRT5 co-immunoprecipitates with Na V 1.5 in HEK293 cells. Live-cell staining using DCFDA or mitoSOX showed that P114T-KI hearts had increased basal reactive oxygen species (ROS) and were more sensitive to oxidative stress induced by H 2 O 2 than wild-type littermates. P114T mice displayed Ca 2+ -mishandling as measured by Ca 2+ imaging in perfused hearts, increased I Na, Late , prolonged QTc, and arrhythmias. Notably, treatment with mitochondrial ROS scavenger mitotempo mitigated the aberrant Ca 2+ handling and arrhythmia in P114T mice.Together, these suggest that P114T-SIRT5 causes Na + /Ca 2+ mishandling-induced arrhythmias in ROS-dependent manner, highlighting potential mechanisms underlying BrS. They pave the way for using SIRT5 or its activators as novel anti-arrhythmic therapies.

Utility of the Inferior Axis and Left Bundle Branch Block Pattern for Categorization of Patients With Premature Ventricular Complexes Before Catheter Ablation

Utility of the Inferior Axis and Left Bundle Branch Block Pattern for Categorization of Patients With Premature Ventricular Complexes Before Catheter Ablation

High frame rate speckle tracking echocardiography for the mapping of cardiac mechanical activation sequence

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): KU Leuven. Background Cardiac arrhythmias are a leading cause of worldwide morbidity and mortality, with catheter ablation being an effective treatment. Current clinical practice includes performing an electrophysiological study in order to detect the focal source or the re-entrant circuit of the arrhythmia, i.e. the ablation target. This technique is invasive, with increased patient related risk and variable success rate. Conversely, echocardiography could be used to determine the correct ablation target. Indeed, high frame rate (HFR) ultrasound provides an adequately high temporal resolution, has proven helpful in detecting the onset of myocardial deformation and could be used for accurate localization of the arrhythmia sources. Purpose To test whether HFR speckle tracking echocardiography (STE) can be employed to construct cardiac mechanical activation maps. Methods 16 healthy volunteers (age: 30±6y; 69% males) and 11 heart failure patients treated with cardiac resynchronisation therapy (CRT) (age: 69±10y; 73% males) were included. All participants were scanned with a research high frame rate ultrasound scanner (frame rate: 848±101fps) and apical 4-, 2- and 3-chamber views were acquired. Patients were scanned with CRT on and after turning the device off, in order to allow native ventricular conduction. All patients had a left bundle branch block (LBBB) pattern of intrinsic activation on the surface ECG. For each apical view, a manually placed contour was tracked during the cardiac cycle by a custom-made 2D HFR STE algorithm; the contours were divided in a standard 16 segment model and segmental strain rate (SR) curves were computed and used to measure the temporal distance between electrical and mechanical activation (i.e. distance between the beginning of QRS and the first zero crossing in the SR curve representing the onset of segmental shortening). Finally, an activation map for each subject was created by placing the extracted timings in the middle of the corresponding segment of a bull’s-eye plot and interpolating values between them. Results Tracking was feasible in 96% of the segments; extracted curves showed a physiological pattern (Fig. 1A). For the healthy participants, mechanical activation started from the mid-anteroseptal (69%) or mid-inferoseptal (31%) segment at 22±5ms, spreading to the basal posterolateral segment at 50±8ms from the start of QRS, in all but two cases, where activation ended in the basal inferoseptal and basal inferior segment respectively (Fig. 1B). During CRT off, the septal wall was activated 31±9ms and the lateral wall 73±20ms after the beginning of QRS (p&amp;lt;0.01) (Fig. 1C), whereas during CRT on, the septal wall was activated 40±11ms and the lateral wall 37±7ms after the beginning of QRS (p = 0.3) (Fig. 1D). Conclusion Our findings comply with left ventricular activation as described in the literature and show that HFR STE could be a useful tool in defining the ablation target for arrhythmia treatment.

The impact of right bundle branch block and SIQIII-type patterns in determining risk levels in acute pulmonary embolism.

Background: Electrocardiography (ECG) findings in acute pulmonary embolism (PE) are known to be related to various right ventricular (RV) alterations. These abnormalities are not included in risk stratification algorithms despite emerging evidence of their association with patient outcomes. We aimed to analyze the impact of right bundle branch block (RBBB) and/or SIQIII patterns as indicators for determining the level of risk in patients with PE. Methods: We performed a retrospective cohort study including all patients with confirmed acute PE hospitalized from January 2008 to December 2019 in two tertiary care cardiology departments. The first ECG taken at admission was selected and the analysis focused on the presence of a complete or an incomplete RBBB and SIQIII-type patterns. Results: A total of 255 patients were divided into two groups: Group I (47.8%, n=122) included patients with PE without RBBB nor SIQIII patterns, and Group II (52.2%, n=133) included patients with RBBB and/or SIQIII patterns. Patients in group II presented significantly more frequently with acute right heart symptoms (45.1% vs. 18%, p<0.001) and cardiogenic shock at admission (31.6 vs. 4.1%, p<0.001). Echocardiographic parameters indicating right heart injury also occurred more significantly in group II patients (p<0.001). By univariate analysis, patients in group II were found to be significantly associated with in-hospital mortality (22.6 vs. 6.1%, p=0.002) and major cardiovascular events (MACEs) during hospitalization (43.3 vs. 13.7%, p<0.001). Multivariate logistic regression analysis identified five independent factors predictive of MACEs: SIQIII and/or RBBB, renal failure, positive troponin levels, RV dysfunction and right heart failure symptoms during initial presentation. Kaplan-Meier survival analysis identified the inclusion in Group II and the presence of SIQIII pattern as predictors of overall mortality (p<0.001). Conclusions: Our study suggests an important and independent prognostic value of RBBB and SIQIII patterns and their usefulness in determining the outcome of PE patients.

Left bundle branch area pacing versus biventricular pacing for cardiac resynchronisation therapy

Abstract Funding Acknowledgements Type of funding sources: None. Background Conventional right ventricular pacing induces dyssynchrony and 20% of patients may need upgrade for resynchronisation therapy (CRT). Currently, left bundle branch area pacing (LBBAP) is growing as an alternative for conventional pacing, preserving left ventricular function. Purpose We aimed to describe procedural characteristics of a group of consecutive patients submitted to LBBAP, and to compare the final QRS duration to a group of consecutive idiopathic LBB patients submitted to conventional CRT. Methods Single-centre cohort including consecutive patients submitted to LBBAP or CRT since November 2021. Feasibility, procedure and fluoroscopy times, final QRS duration during pacing immediately after implantation, and periprocedural complications were assessed. Successful implantation of LBBA pacing was defined as a left ventricular activation time (LVAT) &amp;lt; 90ms plus right bundle branch block pattern in V1. Results A total of 91 patients (mean age 75±11 years, 70.3% male, and 43 [47.3%] with LBBAP) were included. Total procedure (63min [50-76] vs. 91min [71-131], p&amp;lt;0.001) and fluoroscopy times (4.1min [2.4-6.4] vs. 13.4min [8.3-23.1], p&amp;lt;0.001) were significantly lower in the LBBAP vs. CRT group, respectively. In the LBBA pacing group, median LVAT was 86ms (IQR 81-94) and no cases of electrode dislocation or perforation at discharge were reported. Final QRS duration was 112ms (IQR 105-125) vs 127ms (IQR 115-143) in the LBBAP vs CRT groups respectively (p&amp;lt;0.001). Conclusion When compared to a group of idiopathic LBB block patients submitted to CRT, LBBAP was faster, required less fluoroscopy time and was associated with final narrower QRS. Further studies are necessary to understand its role in patients with LV dysfunction and indication for resynchronisation therapy.