Broad QRS Research Articles

Severe Hyperkalemia in a Child with Vomiting and Diarrhea

Case Presentation: A 13-month-old child with past medical history of congenital adrenal insufficiency presented to the emergency department with vomiting and diarrhea. Initially the child was noticed to have bradycardia with normal blood pressure. An electrocardiogram (ECG) showed tall T waves, broad QRS complex, and widened PR interval suggestive of severe hyperkalemia. The initial blood gas showed potassium of 10.7 millimoles per liter. The patient was started on calcium gluconate with immediate resolution of ECG changes. Further management with insulin, dextrose, and sodium olystyrene sulfonate led to normal potassium levels. Discussion: Hyperkalemia is a life-threatening condition in children, especially in those with congenital adrenal insufficiency. The ECG showed different changes as the levels of serum potassium levels increased ranging from tall T waves, wide QRS complex, increased PR interval to arrythmias. Immediate treatment with calcium gluconate in such cases has significant cardioprotective effect. It is important to recognize the ECG changes manifested by changes in serum potassium levels. Our patient had classic ECG changes manifested in severe hyperkalemia.

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

Atypical Presentation of Pre-excited Atrial Fibrillation in an Elderly Patient: A Case Report

Pre-excited atrial fibrillation (AF) is a significant clinical condition associated with Wolff-Parkinson-White (WPW) syndrome, characterized by an accessory pathway that enables rapid conduction of atrial fibrillatory waves to the ventricles, leading to dangerously elevated ventricular rates. While WPW syndrome is typically diagnosed in younger individuals, its occurrence in elderly patients is rare and often underreported. This case report discusses a 79-year-old male with well-controlled hypertension who was admitted for poorly tolerated irregular tachycardia with broad QRS complexes, indicative of pre-excited atrial fibrillation (AF). Urgent synchronized electrical cardioversion successfully restored sinus rhythm. Although catheter ablation was proposed as a definitive treatment, the patient chose to postpone the procedure, with close monitoring implemented afterward. This case underscores the challenges of diagnosing WPW syndrome in elderly patients, the potential dangers of pre-excited AF, and the importance of individualized management strategies tailored to patient preferences and comorbidities.

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 < 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

Multicenter hemodynamic assessment of the LOT-CRT strategy: when is one lead enough for resynchronization?

Abstract Background Left bundle branch area pacing (LBBAP) has been postulated as an alternative to traditional cardiac resynchronization therapy via biventricular pacing (BiV) in heart failure patients with wide QRS. Limited data is available regarding the acute hemodynamic response of LBBAP and the combination of LBBAP and coronary venous (LVcv) pacing (LOT-CRT). Purpose We sought to compare the acute hemodynamic and ECG effects of traditional CRT (BiV or LV-only) versus LBBAP and LOT-CRT in CRT candidates with advanced conduction disease. Methods In this multi-centre study (5 EU and 7 US centres), 48 subjects (mean age 65.8 years, 67% males, LV ejection fraction 29.4%) with either nonspecific interventricular conduction delay (NIVCD, n = 29) or left bundle branch block (LBBB; n =19; based upon strict criteria AHA/ACC/HRS plus Strauss) underwent an acute hemodynamic study to determine the % change in +LV dP/dtmax from baseline atrial pacing versus BiV, LBBAP, or LOT-CRT. Each therapy pacing configuration was applied 4 times at 5 different atrioventricular (AV) delays. QRS shortening was assessed using standard 12-lead ECG. Results Successful LBBAP lead implantation was achieved in 27 patients (56%) using current EHRA criteria. Twenty-one patients (44%) were categorized as deep septal pacing (DSP), due to suboptimal lead penetration or advanced left conduction system disease with broad paced QRS complexes and absent V1-r-wave. The increase in AV-optimized dP/dtmax for the different pacing configurations is displayed in the Figure, left panel. LOT-CRT dP/dtmax % improvement was 25.8%, significantly higher than LBBAP configurations (p<0.01), either unipolar-LBBAP (19.3%), or bipolar-LBBAP (16.4%), but not different from BiV (26.4%). QRS shortening was greater in LOT-CRT (29.5ms) vs. unipolar-LBBAP (11.9ms), bipolar-LBBAP (11.7ms), or BiV (18.5ms), all p<0.01. Sub-group analysis indicated the hemodynamic benefit of adding LVcv pacing when LBBAP strategy was pursued (Figure, right panel) depended on obtaining LBBAP rather than DSP (p < 0.01) and baseline QRS duration (p = 0.03). The largest benefit was observed among subjects with a baseline QRS wider than the observed cohort mean (171ms) and DSP only, where LOT-CRT provided 14.5% (5.0-24.1%) greater dP/dtmax improvement and 20.8ms (12.8-28.8ms) greater QRS duration shortening than unipolar DSP. Conclusions In a CRT cohort with advanced conduction disease, LOT-CRT provided greater acute hemodynamic benefit than LBBAP strategy (i.e. including also DSP cases). Patients with wider QRS or suboptimal outcome of LBBAP strategy (DSP) are more likely to benefit from addition of a LVcv lead to implement LOT-CRT.Figure 1

Left bundle branch area pacing in the setting of cardiac amyloidosis: a case series

Abstract Background Cardiac amyloidosis (CA) is a highly prevalent cause of congestive heart failure. It often requires cardiac pacing due atrioventricular conduction (AV) system disorders, often with cardiac resynchronization (CRT) to prevent development/deterioration of left ventricular (LV) dysfunction. Left bundle branch area pacing (LBBAP) is an emerging alternative to CRT, offering a strict physiological LV activation and very limited use of iodinated contrast. The feasibility of LBBAP in CA is considered limited due to the presence of septal pseudohypertrophy which theoretically limits left-sided conduction system engagement. Purpose To evaluate the feasibility and effectiveness of LBBAP in cardiac amyloidosis. Methods Consecutive patients with CA (both light-chain -AL- or wild-type transtiretin -wtATTr) with a pacing indication for AV conduction disorders were enrolled. Patients underwent baseline echocardiographic examination. LBBAP was achieved by means of stylet-driven leads advanced transeptally (right ventricle (RV) to LV) via dedicated delivery systems, with continuous monitoring of 12-lead electrocardiographic morphology and impedance until a typical QRS morphology in V1 was obtained (usually rSr’ or Sr’). Standard measures for left bundle (LB) capture were used (stimulus to peak R in V6 – S-RV6, V6-V1 interpeak interval, presence of transition in these measures during threshold testing, presence of fascicular signal during spontaneous QRS). Results Between January 2022 and June 2023, among 63 patients undergoing LBBAP, 7 patients (11%) had CA, 2 AL (28%) and 5 (72%) wtATTR. Patients were prevalently old (78±7 y) males (6, 85%); LV mean septal thickness was 17±2 mm (min 16, max 20 mm) and mean LV ejection fraction (LVEF) was 45±6%. Indications were PR prolongation in 3, bradycardic atrial fibrillation and LB branch block (LBBB) in 2, primary LBBB in 1 and chronic RV pacing in 1. Baseline QRS duration was 145±47 ms (QRS<120 ms: 97±15 ms, QRS>120 ms: 182±13 ms). LBBAP success was 100%. Fascicular electrograms were observed in ¾ of patients without LBBB; S-RV6 interval was 74 ±11 ms (³70 ms in 3), RV6-RV1 interpeak interval was 47±9 ms (³ 30 ms in 6 patients). DQRS in baseline broad QRS was -52 ms and +32 ms in narrow. No complications were observed. Over a short follow up of 6 months, an increase in average LVEF was observed (LVEF at 6 months: 51±3%, p<0.05). Conclusions In patients with CA, LBBAP is easily achievable with stylet-driven systems with frequent selective engagement of conduction system. QRS narrowing in baseline broad QRS is significant while QRS broadening in baseline narrow QRS is limited. Early results regarding follow-up of surrogate endpoint such as LVEF are promising.

Temporal evolution of His bundle pacing thresholds: a sub-study of the PACE-CONDUCT trial

Abstract Background His bundle pacing (HBP) has become a valuable alternative for cardiac resynchronization therapy, offering physiological pacing. This substudy of the PACE-CONDUCT trial aimed to explore the influence selective and non-selective HBP on threshold height. We assessed these parameters in patients with both normal conduction and bundle branch block conduction. Methods Our study included 61 consecutive patients with a median age of 73 years, who underwent a successful HBP implantation for indications such as sick sinus syndrome, AV Block 2 type 2, binodal disease, and ablate and pace therapy prior to AV-node ablation. Among these patients, 18 exhibited QRS durations exceeding 150 ms, indicating a complete and broad bundle branch block which made them candidates for cardiac resynchronization therapy (CRT). All patients received HBP implantation with the assistance of a 3D electroanatomical system. This system allowed for low-fluoroscopic, atraumatic evaluation of the His bundle (HB) area, presenting the His voltage as a color-coded map for precise electrode placement. Results The feasibility of bundle branch correction is generally accepted in selective HBP distal to the site of block, albeit associated with higher threshold values and potentially lower battery duration. Our analysis encompassed 61 patients who underwent HBP implantation, with 23 patients (37,7%) exhibiting selective HBP and 38 (62,3%) non-selective HBP. Remarkably, 10 out of the 23 patients with selective HBP demonstrated a complete bundle branch block correction after HBP implantation even with a basal QRS durations exceeding 150 ms. We evaluated HBP thresholds at implantation, one day post-implantation, and one month post-implantation, correlating these data with selective and non-selective HBP. Threshold values were converted to volts per millisecond (volts × milliseconds) for analysis. Statistical analysis conducted with IBM SPSS 29.0 revealed a significant difference at the day of implantation, indicating higher threshold capture in selective HBP compared to non-selective HBP (one-sided p-value: < 0.01, two sided p value 0.01). However, this difference could not be sustained at the one-day and one-month threshold follow-ups, suggesting normalization of the selective HBP threshold. Conclusion In our study, the initially higher threshold in selective HBP normalized within 24 hours compared to non-selective HBP. Additionally, our study demonstrated the feasibility of selective His pacing in patients with complete bundle branch block and broad QRS durations. These findings provide insights into HBP optimization and encourage further investigations with larger patient cohorts to validate our observations and enhance patient care in the realm of cardiac pacing.Threshold trend

Comparative Analysis of Response to Cardiac Resynchronisation Therapy Upgrades in Patients with Implantable Cardioverter-Defibrillators and Pacemakers.

Introduction: The efficacy of de novo cardiac resynchronisation therapy (CRT) in patients with heart failure (HF), left ventricular systolic dysfunction (LVSD), and a broad QRS morphology is well established. However, the optimal stage for upgrading patients with existing pacemakers (PPMs) or implantable cardioverter-defibrillators (ICDs) and HF with high-burden right ventricular (RV) pacing remains uncertain. Thus, this multicentre retrospective analysis compared patients with pre-existing PPMs or ICDs who underwent CRT upgrades to investigate the appropriate stage for CRT implantation in these patients and to assess the validity of treating both PPM and ICD recipients under the same recommendation level in the current guidelines. Materials and Methods: A total of 151 participants underwent analysis in this study, comprising 93 upgrades to cardiac resynchronisation therapy with pacemaker (CRT-P) and 58 upgrades to cardiac resynchronisation therapy with defibrillator (CRT-D) across three centres in the UK. The aim of the study was to investigate the safety and efficacy of upgrading to CRT from an existing conventional pacemaker or an ICD in the context of high-burden RV pacing. The analysis was conducted separately for each group, assessing changes in echocardiographic parameters, functional New York Heart Association (NYHA) class, and procedure-related complications. Results: The PPM group had a higher percentage RVP burden compared to the ICD group. Post-upgrade, NYHA functional class and EF and LV volumes improved in both groups; however, the response to an upgrade from a pacemaker was greater compared to an upgrade from an ICD. Post-procedural complication risks were similar across the two subgroups but significantly higher compared to de novo implantation. Conclusions: Within the CRT-P subgroup, participants exhibited better responses than their CRT-D counterparts, evident both in echocardiographic improvements and clinical outcomes. Furthermore, patients with non-ischemic cardiomyopathy (NICM) were better responders than those with ischaemic cardiomyopathy. These findings suggest that international guidelines should consider approaching each subgroup separately in the future.

History of cardiac resynchronization therapy : 30years of electrotherapeutic management for heart failure

The first permanent biventricular pacing system was implanted more than 30years ago. In this article, the historical development of cardiac resynchronization therapy (CRT), starting with the pathophysiological concept, followed by the initial "proof of concept" studies and finally the large prospective-randomized studies that led to the implementation of CRT in heart failure guidelines, is outlined. Since the establishment of CRT, both an expansion of indications, e.g., for patients with mild heart failure and atrial fibrillation, but also the return to patients with broad QRS complex and left bundle branch block who benefit most of CRT has evolved. New techniques such as conduction system pacing will have major influence on pacemaker therapy in heart failure, both as an alternative or adjunct to CRT.

Long-term outcome after upgrade to cardiac resynchronization therapy: A propensity score-matched analysis.

Cardiac resynchronization therapy (CRT) is a cornerstone in the management of chronic heart failure in patients with a broad or paced QRS. However, data on long-term outcome after upgrade to CRT are scarce. This international, multicentre retrospective registry included 2275 patients who underwent a de novo or upgrade CRT implantation with a mean follow-up of 3.6 ± 2.7 years. The primary composite endpoint included all-cause mortality, heart transplantation, or ventricular assist device implantation. The secondary endpoint was first heart failure admission. Multivariable Cox regression and propensity score matching (PSM) analyses were performed. Patients who underwent CRT upgrade (n = 605, 26.6%) were less likely female (19.7% vs. 28.8%, p < 0.001), more often had ischeemic cardiomyopathy (49.8% vs. 40.2%, p < 0.001), and had worse renal function (median estimated glomerular filtration rate 50.3 ml/min/1.73 m2 [35.8-69.5] vs. 59.9 ml/min/1.73 m2 [43.0-76.5], p < 0.001). The incidence rate of the composite endpoint was 10.8%/year after CRT upgrade versus 7.1%/year for de novo implantations (p < 0.001). PSM for the primary endpoint resulted in 488 pairs. After propensity score matching, upgrade to CRT was associated with a higher chance to reach the composite endpoint (multivariable hazard ratio [HR] 1.35, 95% confidence interval [CI] 1.08-1.70), for both upgrade from pacemaker (multivariable HR 1.33, 95% CI 1.03-1.70) and implantable cardioverter-defibrillator (ICD) (multivariable HR 1.40, 95% CI 1.01-1.95). PSM for the secondary endpoint resulted in 277 pairs. After PSM, upgrade to CRT was associated with a higher chance for heart failure admission (HR 1.74, 95% CI 1.26-2.41). In this retrospective analysis, the outcome of patients who underwent upgrades to CRT differed significantly from patients who underwent de novo CRT implantation, particularly for upgrades from ICD. Importantly, this difference in outcome does not imply a causal relation between therapy and outcome but rather a difference between two different patient populations.

Myocardial Fibrosis and Left Bundle Branch Block Complicating an Athlete's Heart Syndrome Treated Homeopathically: A Case Report

Abstract Background During 2013, a 59-year-old male patient, a medical practitioner and lifelong sportsperson, complained of being constantly conscious of his heart action, and left sternal heave, as well as retrosternal heaviness at rest. On October 23, 2013, an electrocardiogram (ECG) showed some signs of an athlete's heart syndrome. An ECG on 11 January, 2019, shockingly showed a complete left bundle branch block (LBBB), a broad complex QRS sinus rhythm ECG, without ever experiencing angina pectoris after doing four sets of 20 push-ups. Methods A complication of an athlete's heart may be myocardial fibrosis (MF). MF is the primary pathology to treat, as well as its comorbidities synergistically, when they obstruct progress. Thus, Calcarea fluorata (Calc-f) was prescribed for endocardial fibrosis, Iberis amara (Iber) for endomyocardial fibrosis, Cactus grandiflorus (Cact) for pulmonary arterial hypertension and right ventricular strain, and Crataegus laevigata (Crat) for subendocardial ischaemia. Results After 17 months on Calc-f, the LBBB was unchanged. Iber was again prescribed on February 13, 2022. On February 23, 2022, after 10 days on Iber, a narrow complex QRS sinus rhythm (SR) ECG was recorded with a QRS of 90 milliseconds. This was the first SR ECG after having had a permanent complete LBBB for at least 3 years. Conclusions This case report documents via ECGs the biological effectiveness of Calc-f and Iber for MF. SR returned after the employment of, respectively, Iber and Cact. After employing Crat, the abnormal inverted T waves in most leads became positive. Since October 16, 2022 and beyond, there is a stable SR, but any intense exertion causes an LBBB.

Prognostic value of nutritional status in post-implant CRT outcomes in patients with chronic heart failure

Abstract Funding Acknowledgements Type of funding sources: None. Introduction There’s a close relationship between chronic heart failure (CHF) and malnutrition, and their main pathophysiological modifications are well known. Cardiac resynchronization therapy (CRT) has proven to be a promising therapy in symptomatic heart failure (HF) patients with broad QRS complexes and impaired systolic function with optimized medical therapy. However, there is still a considerable amount of non-responder patients. The role of nutritional status in CRT therapy response has yet still not been well assessed. Purpose Assess the prognostic value of nutritional status in post-op outcomes in patients with Chronic Heart Failure and (CRT) Methods Single-center retrospective study of patients submitted to CRT implantation between January 2007 and march 2021. Inclusion criteria were patients meeting criteria for CRT implantation, QRS duration ≥ 120ms, FEVE ≤ 35%, NYHA class II–IV and no adverse events during the follow up. Primary outcomes measured were all-cause mortality, cardiovascular mortality, and hospitalizations due to HF in a 1-year follow-up. To evaluate patient's nutritional status the CONUT score was used with patients being categorized in 2 groups: Low CONUT (Score 0-4: normal/low malnutrition) and Hight CONUT (Score 5-12: moderate/severe malnutrition). Results 198 patients (83%) exhibited Low CONUT status, and 41 patients (17%) exhibited High CONUT status. Patients with Hight CONUT were older (72.9 yrs vs 65.9 yrs, p&amp;lt;0.001), and exhibited higher percentage of chronic obstructive pulmonary disease (43.9% vs 27.3%, p=0.004), atrial fibrillation (72.9%, vs 25.3%, p&amp;lt;0.001), hypertension (78.1% vs 60.6%, p=0.038), chronic kidney disease (39.1% vs 21.2%, p=0.016) and NYHA IV (19.5% vs 5.1%, p&amp;lt;0.001). Cardiovascular mortality was 3.7% in the low CONUT group vs 29.3% in the Hight CONUT group (p&amp;lt;0.001; HR, 0.12; 95% CI, 0.05-0.29) and total HF hospitalizations were 16 and43, respectively (p=0.013; HR, 0.482, 95% CI, 0.27 to 0.86). The nutritional status prior to CRT assessed by the CONUT score showed to be an independent predictor of cardiovascular mortality (p=0.007; HR, 0.16 95% CI, 0.04-0,60). Conclusion Malnutrition was a common condition in our CRT patients showing that deficient nutrition status remains highly underdiagnosed. Patients with worse nutritional status before CRT device implantation presented higher morbidity and were more prone to worst outcomes such as cardiovascular mortality and mortality by all causes as well as higher incidence of hospitalizations secondary to HF decompensation. Assessment of nutritional status using screening tools may provide additional prognostic information in patients with HF and help early identification of those who may benefit from further assessment and nutritional intervention.

Wide complex rhythm in a well neonate: Where are the P waves?

A neonate was seen for an evolving broad QRS complex rhythm initially captured at birth as intermittent escape beats on electrocardiogram. Continuous monitoring recorded features mimicking pre-excitation, but closer analysis revealed a regular broad QRS complex rhythm with isorhythmic atrioventricular dissociation, favouring a ventricular source. Treatment with flecainide and propranolol achieved successful control of the incessant arrhythmia with improvement in cardiac function on echocardiogram.

PO-03-021 HIS BUNDLE PACING SUCCESS AND ELECTRICAL PARAMETERS STABILITY REGARDLESS OF THREE-DIMENSIONAL TRANSTHORACIC ECHOCARDIOGRAPHY LEAD LOCALIZATION

His bundle pacing (HBP) is the most physiological form of ventricular pacing. Few prospective studies have analyzed lead localization using imaging techniques and its relationship with electrical parameters and capture patterns. To examine the correlation between electrical parameters and lead localization using three-dimensional transthoracic echocardiography (3D-TTE). This single-center, prospective, nonrandomized clinical research study (January 2018-June 2020) included patients with an indication of permanent pacing, in whom 3D-TTE was performed to define lead localization as supravalvular or subvalvular. A total of 92 patients were included: 56.5% of leads were supravalvular and 43.5% were subvalvular (Figure 1), which resembles previous anatomic descriptions of autopsied hearts of His bundle localization within the triangle of Koch (ToK). Most of our patients (98.9%) did not need a right ventricular backup lead in addition to the His lead. Only in one patient, with alternating BBB after transaortic valve implantation, we implanted a backup lead. R-wave sensing was higher when the His lead was localized subvalvular instead of supravalvular. His lead localization was not associated with HBP threshold or impedance differences, nor with the two different HBP patterns of capture (Table 1). HBP was attempted in 56 patients with baseline broad QRS, and we successfully corrected the baseline conduction disturbance in 45 patients (80.4%); lead localization was not associated with the ability of HBP to correct baseline BBB. The median HBP threshold at implantation was 1.25 V [0.75–2] @0.4ms, with no differences depending on lead localization. The thresholds remained stable during the follow-up visits at 1 and 6 months, regardless of His lead localization. R-wave sensing showed a significant change at follow-up, with higher - but no clinically relevant - R-wave sensing compared to that at baseline, which was mainly observed in the subvalvular His leads (4mV at baseline and 4.3mV at 6-months, p<0.001). However, lead impedances in both positions were decreased at follow-up (median difference -110 Ω). Clinically relevant p-wave oversensing was not observed. Lead localization in relation to the tricuspid valve did not influence the electrical performance of HBPs. Wide anatomical variations of the His bundle within the ToK explain our findings, reinforcing the idea that the technique for HBP should be fundamentally guided by electrophysiological and not anatomical parameters.

Frequency of Left Ventricular Mechanical Dyssynchrony in Chronic Heart Failure

Objective: To determine the frequency of left ventricular mechanical dyssynchrony in chronic heart failure patients. Material and Methods: After approval from the Hospital ethical committee, the study was conducted in the department of cardiology Hayatabad medical complex Peshawar from 1st September 2021 to 28th February 2022. In this descriptive cross-sectional study, 155 patients in total were examined while 27% of heart failure patients had mechanical dyssynchrony, a 95% confidence interval, and a 7% margin of error were maintained according to WHO sample size computations. Results: This study's participants had an average age of 60, with a standard deviation of ±1.26 years. 62% of the patients were male, compared to 38% of females. 35% of patients had a Broad QRS complex, whereas 65% of patients had a Narrow QRS complex. Mechanical dyssynchrony was identified in 32% of chronic heart failure patients. Conclusion: Patients in chronic heart failure with QRS &gt; 150ms and having mechanical dyssynchrony are benefited with Cardiac Ressynchronisation Therapy (CRT) implantation which reduces morbidity and mortality, while those with a narrow QRS (&lt;150ms) are generally non – responders. Keywords: Mechanical dyssynchrony, chronic heart failure, left ventricular ejection fraction

A giant heart tumour diagnosed accidentally in a 6-year-old boy with wide QRS complex tachycardia

The paper presents a case report of a 6-year-old boy with broad QRS tachycardia, who was accidentally diagnosed with a cardiac tumour. The tachycardia occurred twice, 10 months apart, and was quickly interrupted in a night medical care unit by performing a carotid sinus massage. Electrocardiography was performed, but its low quality did not allow for a detailed analysis, except for the heart rate, which was 180 bpm. Cardiological diagnosis was performed in a reference centre. No laboratory abnormalities were found. Holter ECG recorded only 374 single ventricular beats, while a routine echo revealed a very large 4.2 × 3.1 cm tumour in the interventricular septum, which did not impede intracardiac blood flow. The presence of the tumour was confirmed by magnetic resonance imaging of the heart, in which a fibroma was suspected. A beta-blocker (metoprolol) was included in the treatment and further cardiac monitoring was recommended. The boy was discharged home with a recommended follow-up in 2 months. He did not report for the appointment, while his parents requested for full imaging documentation.

Confounding factors leading to misdiagnosing ventricular tachycardia as supraventricular in the emergency room

Studies conducted during the last 50 years have proposed electrocardiographic criteria and algorithms to determine if a wide QRS tachycardia is ventricular or supraventricular in origin. Sustained ventricular tachycardia is an uncommon reason for consultation in the emergency room. The latter and the complexity of available electrocardiographic diagnostic criteria and algorithms result in frequent misdiagnoses. Good hemodynamic tolerance of tachycardia in the supine position does not exclude its ventricular origin. Although rare, ventricular tachycardia in patients with and without structural heart disease may show a QRS duration <120 ms. Interruption of tachycardia by coughing, carotid sinus massage, Valsalva maneuver, or following the infusion of adenosine or verapamil should not discard the ventricular origin of the arrhythmia. In patients with regular, uniform, sustained broad QRS tachycardia, the presence of structural heart disease or A-V dissociation strongly suggest its ventricular origin. Occasionally, ventricular tachycardia can present with AV dissociation without this being evident on the 12-lead ECG. Cardiac auscultation, examination of the jugular venous pulse, and arterial pulse palpation provide additional clues for identifying A-V dissociation during tachycardia. This paper does not review the electrocardiographic criteria for categorizing tachycardia as ventricular but rather why emergency physicians misdiagnose these patients.

Can echocardiography facilitate decision-making to CRT?

Abstract Introduction Cardiac resynchronization therapy (CRT) remains underused despite its well-established therapeutic effect and clear guidelines. Among various reasons are the lack of referral, the fear of complications and the high therapy cost. The assessment of mechanical dyssynchrony (MD) on echocardiography has been suggested to aid patient selection. In the past, however, several studies have used old markers of MD producing disappointing results and the use of echocardiography for patient selection became discredited. Promising new markers have been developed since and could aid clinical decision-making for CRT. These should, however, first be thoroughly tested and compared to the old markers. Purpose (I) To confirm the relevance of the new markers of MD for survival free of cardiac death and (II) to compare old and new markers of MD for predicting cardiac death within 5 years post-CRT in patients eligible for CRT according the 2021 ESC guidelines. Methods 222 CRT-patients were analysed retrospectively in a multicentre setting. MD was assessed using three old markers: septal-to-posterior wall-motion-delay (SPWMD), left-ventricular-filling-time/cardiac-cycle ratio (LVFT/RR), and intraventricular mechanical delay (IVMD); and three new markers: systolic stretch index (SSI), myocardial work index (MWI), and visual presence of septal flash or apical rocking (SFoAR). For each marker, patients were categorized using previously published cut-offs as “MD present” (Yes) or “MD not present” (No). Log rank tests were performed on Kaplan-Meier curves for survival free of cardiac death. Cox proportional hazards regressions were used to compute the hazard-ratio (HR) for cardiac death within 5 years after implantation. Results Cardiac death occurred in 37 patients (17%). Patients with MD before CRT according to IVMD (p=0.003), SSI (p&amp;lt;0.001), MWI (p&amp;lt;0.001) or SFoAR (p&amp;lt;0.001) had a significantly better survival. The hazard ratios were 0.34 (95% CI, 0.19–0.75) for IVMD, 0.30 (95% CI, 0.15–0.57) for SSI, 0.26 (95% CI, 0.12–0.54) for MWI and, 0.28 (95% CI, 0.14–0.53) for SFoAR. The other markers for MD were not significant for survival. Conclusion The new markers for dyssynchrony are better than the old. Patients with mechanical dyssynchrony on echocardiography before CRT according to SSI, MWI or SFoAR are 3 to 4 times less likely to die within 5 years after CRT implantation. The presence of one of these markers in patients with a broad QRS (≥130ms) and reduced LVEF (≤35%) should prompt clinicians to refer for or to proceed to CRT. Funding Acknowledgement Type of funding sources: None.

Non-specific intraventricular conduction delay or atypical LBBB - How to predict acute coronary occlusion?

We describe two patient cases with acute coronary syndrome (ACS) and broad QRS in the acute phase electrocardiogram (ECG). The patients' ECG findings resembled left bundle branch block (LBBB), but with atypical features. Broad QRS not fulfilling the criteria for LBBB or right bundle branch block (RBBB) is diagnosed as non-specific intraventricular conduction delay (NSIVCD). The case report deals with the challenges of predicting acute coronary occlusion in patients with NSIVCD in their acute phase ECG. In one of the cases, the ECG changed from typical LBBB to NSIVCD or atypical LBBB with the development of systolic dysfunction and clinical heart failure.

A Peculiar Wide Complex Tachycardia During Flecainide Treatment.

A Peculiar Wide Complex Tachycardia During Flecainide Treatment.