PhyberSIM: a tool for the generation of ground truth to evaluate brain fiber clustering algorithms.

Diffusion Magnetic Resonance Imaging tractography is a non-invasive technique that produces a collection of streamlines representing the main white matter bundle trajectories. Methods, such as fiber clustering algorithms, are important in computational neuroscience and have been the basis of several white matter analysis methods and studies. Nevertheless, these clustering methods face the challenge of the absence of ground truth of white matter fibers, making their evaluation difficult. As an alternative solution, we present an innovative brain fiber bundle simulator that uses spline curves for fiber representation. The methodology uses a tubular model for the bundle simulation based on a bundle centroid and five radii along the bundle. The algorithm was tested by simulating 28 Deep White Matter atlas bundles, leading to low inter-bundle distances and high intersection percentages between the original and simulated bundles. To prove the utility of the simulator, we created three whole-brain datasets containing different numbers of fiber bundles to assess the quality performance of QuickBundles and Fast Fiber Clustering algorithms using five clustering metrics. Our results indicate that QuickBundles tends to split less and Fast Fiber Clustering tends to merge less, which is consistent with their expected behavior. The performance of both algorithms decreases when the number of bundles is increased due to higher bundle crossings. Additionally, the two algorithms exhibit robust behavior with input data permutation. To our knowledge, this is the first whole-brain fiber bundle simulator capable of assessing fiber clustering algorithms with realistic data.

Infarto agudo de miocardio en el paciente con marcapasos / Acute Myocardial Infarction in the Patient with Pacemaker

Resumen El diagnóstico electrocardiográfico de infarto agudo de miocardio (IAM) en el paciente con marcapasos siempre ha sido un problema en la práctica clínica, provocando retrasos en el manejo y peores desenlaces clínicos. Aunque el bloqueo completo de rama izquierda (BCRI) y la estimulación del ventrículo derecho pueden producir anomalías en el electrocardiograma (ECG), cambios morfológicos específicos a menudo permiten el diagnóstico de IAM o un infarto antiguo. Reporte de caso: Paciente de 76 años con antecedente de implante de marcapasos definitivo por bloqueo auriculoventricular de 3° grado, que ingresó por dolor precordial. A su ingreso hemodinámicamente estable, pero con ECG que muestra ritmo de marcapasos con BCRI cumpliendo Sgarbossa 2 puntos (elevación discordante del segmento ST > 5 mm en derivaciones V1 a V3) y relación ST/S < -0.25 en derivaciones V3-V4. Laboratorios con elevación de troponinas, integrándose diagnóstico de IAM y pasando a angiografía coronaria urgente. Se documentó lesión en arteria coronaria descendente anterior y se implantó stent liberador de fármaco angiográficamente exitoso. Se egresó estable, asintomático y con manejo farmacológico para prevención secundaria. Conclusión: La identificación por ECG de un IAM en pacientes portadores de marcapasos es fundamental para iniciar terapia de reperfusión. Las recomendaciones de las guías cambian constantemente, pero un algoritmo que utiliza la inestabilidad hemodinámica y los criterios de Sgarbossa modificados (CSM) para decidir el manejo de estos pacientes pudiera ser una herramienta con una alta sensibilidad y permitirá a los médicos tener la mejor toma de decisiones sin esperar resultados de laboratorio. Los CSM, que son más sensibles que los criterios originales, continúan siendo útiles en el diagnóstico de IAM. Los médicos deben elegir cuidadosamente el límite de CSM apropiado (relación ST/T -0.20 y -0.25) de acuerdo con cada caso.

Abstract The electrocardiographic diagnosis of acute myocardial infarction (AMI) in patients with pacemakers has always been a problem in clinical practice, causing delays in management and worse clinical outcomes. Although complete left bundle branch block (LBBB) and right ventricular pacing can produce electrocardiogram (ECG) abnormalities, specific morphological changes often allow the diagnosis of AMI or an old infarction. Case report: A 76-year-old patient with history of permanent pacemaker implantation due to a 3rd-degree atrioventricular block was admitted for chest pain. Upon admission, he was hemodynamically stable but with ECG showing pacemaker rhythm with LBBB fulfilling 2 points of Sgarbossa criteria (discordant elevation of the ST segment > 5 mm in leads V1 to V3) and ST/S ratio < -0.25 in leads V3-V4. Laboratories showed elevated troponins, integrating diagnosis of AMI, and moving on to urgent coronary angiography. A lesion on the anterior descending coronary artery was documented, and a drug-eluting stent was successfully implanted. The patient was discharged stable, asymptomatic, and with pharmacological management for secondary prevention. Conclusion: ECG identification of an AMI in patients with pacemakers is essential to initiate reperfusion therapy. Guideline recommendations are constantly changing, but an algorithm that uses hemodynamic instability and the modified Sgarbossa criteria (MSC) to decide these patients' management could be a high-sensitivity tool and allow physicians to make the best decisions without waiting for laboratory results. MSC, which are more sensitive than the original criteria, continue to be helpful in the diagnosis of AMI. Clinicians should carefully choose the appropriate MSC cut-off (ST/T Ratio -0.20 and -0.25) on a case-by-case basis.

Short fiber bundle filtering and test-retest reproducibility of the Superficial White Matter.

In recent years, there has been a growing interest in studying the Superficial White Matter (SWM). The SWM consists of short association fibers connecting near giry of the cortex, with a complex organization due to their close relationship with the cortical folding patterns. Therefore, their segmentation from dMRI tractography datasets requires dedicated methodologies to identify the main fiber bundle shape and deal with spurious fibers. This paper presents an enhanced short fiber bundle segmentation based on a SWM bundle atlas and the filtering of noisy fibers. The method was tuned and evaluated over HCP test-retest probabilistic tractography datasets (44 subjects). We propose four fiber bundle filters to remove spurious fibers. Furthermore, we include the identification of the main fiber fascicle to obtain well-defined fiber bundles. First, we identified four main bundle shapes in the SWM atlas, and performed a filter tuning in a subset of 28 subjects. The filter based on the Convex Hull provided the highest similarity between corresponding test-retest fiber bundles. Subsequently, we applied the best filter in the 16 remaining subjects for all atlas bundles, showing that filtered fiber bundles significantly improve test-retest reproducibility indices when removing between ten and twenty percent of the fibers. Additionally, we applied the bundle segmentation with and without filtering to the ABIDE-II database. The fiber bundle filtering allowed us to obtain a higher number of bundles with significant differences in fractional anisotropy, mean diffusivity, and radial diffusivity of Autism Spectrum Disorder patients relative to controls.

Infraorbital canal variants and its clinical and surgical implications. A systematic review.

BACKGROUND: Recent literature highlights anomalous cranial nerves in the sinonasal region, notably in the sphenoid and maxillary sinuses, linked to anatomical factors. However, data on the suspended infraorbital canal (IOC) variant is scarce in cross-sectional imaging. Anatomical variations in the sphenoid sinuses, including optic, maxillary, and vidian nerves, raise interest among specialists involved in advanced sinonasal procedures. The infraorbital nerve's (ION) course along the orbital floor and its abnormal positioning within the orbital and maxillary sinus region pose risks of iatrogenic complications. A comprehensive radiological assessment is crucial before sinonasal surgeries. Cone-beam computed tomography (CBCT) is preferred for its spatial resolution and reduced radiation exposure. OBJECTIVE: The aim of this study was to describe the prevalence of anatomical variants of the infraorbital canal (IOC) and report its association with clinical condition or surgical implication. METHODS: We searched Medline, Scopus, Web of Science, Google Scholar, CINAHL, and LILACS databases from their inception up to June 2023. Two authors independently performed the search, study selection, data extraction, and assessed the methodological quality with assurance tool for anatomical studies (AQUA). Finally, the pooled prevalence was estimated using a random effects model. RESULTS: Preliminary results show that three types are prevalent, type 1: the IOC does not bulge into the maxillary sinus (MS); therefore, the infraorbital foramen through the anterior wall of MS could be used for identification of the ION. Type 2: the IOC divided the orbital floor into medial and lateral aspects. Type 3: the IOC hangs in the MS and the entire orbital floor lying above the IOC. From which the clinical implications where mainly surgical, in type 1 the infraorbital foramen through the anterior wall of MS could be used for identification of the ION, while in type 2, since the lateral orbital floor could not be directly accessed an inferiorly transposition of ION is helpful to expose the lateral orbital wall directly with a 0 scope; or using angled endoscopes and instruments, however, the authors opinion is that direct exposure potentially facilitates the visualization and management in complex situations such as residual or recurrent mass, foreign body, and fracture located at the lateral aspect of the canal. Lastly, in type 3, the ION it's easily exposed with a 0° scope. CONCLUSIONS: This systematic review identified four IOC variants: Type 1, within or below the MS roof; Type 2, partially protruding into the sinus; Type 3, fully protruding into the sinus or suspended from the roof; and Type 4, in the orbital floor. Clinical recommendations aim to prevent nerve injuries and enhance preoperative assessments. However, the lack of consistent statistical methods limits robust associations between IOC variants and clinical outcomes. Data heterogeneity and the absence of standardized reporting impede meta-analysis. Future research should prioritize detailed reporting, objective measurements, and statistical approaches for a comprehensive understanding of IOC variants and their clinical implications. Open Science Framework (OSF): https://doi.org/10.17605/OSF.IO/UGYFZ .

Improved all-cause mortality with left bundle branch area pacing compared to biventricular pacing in cardiac resynchronization therapy: a meta-analysis.

BACKGROUND: Left bundle branch area pacing (LBBAP) has emerged as a physiological alternative pacing strategy to biventricular pacing (BIVP) in cardiac resynchronization therapy (CRT). We aimed to assess the impact of LBBAP vs. BIVP on all-cause mortality and heart failure (HF)-related hospitalization in patients undergoing CRT. METHODS: Studies comparing LBBAP and BIVP for CRT in patients with HF with reduced left ventricular ejection fraction (LVEF) were included. The coprimary outcomes were all-cause mortality and HF-related hospitalization. Secondary outcomes included procedural and fluoroscopy time, change in QRS duration, and change in LVEF. RESULTS: Thirteen studies (12 observational and 1 RCT, n = 3239; LBBAP = 1338 and BIVP = 1901) with a mean follow-up duration of 25.8 months were included. Compared to BIVP, LBBAP was associated with a significant absolute risk reduction of 3.2% in all-cause mortality (9.3% vs 12.5%, RR 0.7, 95% CI 0.57-0.86, p < 0.001) and an 8.2% reduction in HF-related hospitalization (11.3% vs 19.5%, RR 0.6, 95% CI 0.5-0.71, p < 0.00001). LBBAP also resulted in reductions in procedural time (mean weighted difference- 23.2 min, 95% CI - 42.9 to - 3.6, p = 0.02) and fluoroscopy time (- 8.6 min, 95% CI - 12.5 to - 4.7, p < 0.001) as well as a significant reduction in QRS duration (mean weighted difference:- 25.3 ms, 95% CI - 30.9 to - 19.8, p < 0.00001) and a greater improvement in LVEF of 5.1% (95% CI 4.4-5.8, p < 0.001) compared to BIVP in the studies that reported these outcomes. CONCLUSION: In this meta-analysis, LBBAP was associated with a significant reduction in all-cause mortality as well as HF-related hospitalization when compared to BIVP. Additional data from large RCTs is warranted to corroborate these promising findings.

Long-Term Impact of Left Bundle Branch Block on Cardiopulmonary Exercise Test Variables and Left Ventricular Systolic Function: A Two-Stage Observational Study.

INTRODUCTION: Left bundle branch block (LBBB) disrupts the electrical activation of the left ventricle, potentially impairing its systolic function, leading to LBBB-induced cardiomyopathy. This study examined cardiopulmonary exercise test (CPET) variables in patients with and without LBBB and assessed the longitudinal development of left ventricular ejection fraction (LVEF). METHOD: An observational, comparative clinical study was executed in two stages at a private hospital in Brazil. The sample consisted of 27 individuals: 11 with LBBB and 16 without LBBB, all with preserved LVEF (>50%) and without confirmed ischemia. CPET variables were assessed, and after 4 years, participants had a transthoracic echocardiogram for LVEF re-evaluation. Groups were compared using the t test or the χ2 test. Multivariate analysis of covariance determined effect magnitude. RESULTS: Patients with LBBB demonstrated significant differences in CPET variables, particularly in predicted peak V˙O2, predicted peak PO2, V˙E/V˙CO2 slope, and T ½ V˙O2. They also exhibited a more significant decline in LVEF over a 4-year span compared to the patients without LBBB. Although initial preservation of LVEF, changes in contractile patterns due to LBBB interfered with its systolic function, suggesting early ventricular dysfunction indicated by a reduction in LVEF and an increase in the V˙E/V˙CO2 slope. Despite differences in cardiopulmonary function and changes in LVEF over time between patients with and without LBBB, the effect size was considered mild to moderate. CONCLUSIONS: LBBB patients with initially preserved LVEF displayed reduced exercise tolerance and a decrease in LVEF over time, emphasizing the need for vigilant monitoring and early intervention in these patients.

Phybers: a package for brain tractography analysis.

We present a Python library (Phybers) for analyzing brain tractography data. Tractography datasets contain streamlines (also called fibers) composed of 3D points representing the main white matter pathways. Several algorithms have been proposed to analyze this data, including clustering, segmentation, and visualization methods. The manipulation of tractography data is not straightforward due to the geometrical complexity of the streamlines, the file format, and the size of the datasets, which may contain millions of fibers. Hence, we collected and structured state-of-the-art methods for the analysis of tractography and packed them into a Python library, to integrate and share tools for tractography analysis. Due to the high computational requirements, the most demanding modules were implemented in C/C++. Available functions include brain Bundle Segmentation (FiberSeg), Hierarchical Fiber Clustering (HClust), Fast Fiber Clustering (FFClust), normalization to a reference coordinate system, fiber sampling, calculation of intersection between sets of brain fibers, tools for cluster filtering, calculation of measures from clusters, and fiber visualization. The library tools were structured into four principal modules: Segmentation, Clustering, Utils, and Visualization (Fibervis). Phybers is freely available on a GitHub repository under the GNU public license for non-commercial use and open-source development, which provides sample data and extensive documentation. In addition, the library can be easily installed on both Windows and Ubuntu operating systems through the pip library.

Morphology of the male reproductive system and spermatozoa of Mahanarva fimbriolata (Stål, 1854) (Hemiptera: Cercopidae) with evidence of a spermatostyle in the sperm conjugation.

Changes in harvesting methods in the early 1990s led to Mahanarva fimbriolata becoming the most prevalent pest in sugarcane plantations. Encouraged by the scarcity of research on the reproductive system and spermatology of Auchenorrhyncha, we provide a detailed description of the male reproductive system and spermatozoa of this cercopid. This will not only aid in taxonomic purposes but also help in understanding the reproductive biology of the species. The male reproductive system, spermatozoa, and sperm bundles of M. fimbriolata were investigated using light microscopy. Our results reveal a reproductive system consisting of a pair of testes, each with 36 follicles, two vasa deferentia, two well-developed seminal vesicles, a single pair of accessory glands, and an ejaculatory duct. Here, we also describe and explore the particularities of the formation of secondary sperm bundles, where cells interestingly bind only to the apical region of the spermatostyle. We also propose some possible benefits of this unusual organization for the reproductive success of the species.

Drought-adapted leaves are produced even when more water is available in dry tropical forest.

Species in dry environments may adjust their anatomical and physiological behaviors by adopting safer or more efficient strategies. Thus, species distributed across a water availability gradient may possess different phenotypes depending on the specific environmental conditions to which they are subjected. Leaf and vascular tissues are plastic and may vary strongly in response to environmental changes affecting an individual's survival and species distribution. To identify whether and how legumes leaves vary across a water availability gradient in a seasonally dry tropical forest, we quantified leaf construction costs and performed an anatomical study on the leaves of seven legume species. We evaluated seven species, which were divided into three categories of rainfall preference: wet species, which are more abundant in wetter areas; indifferent species, which are more abundant and occur indistinctly under both rainfall conditions; and dry species, which are more abundant in dryer areas. We observed two different patterns based on rainfall preference categories. Contrary to our expectations, wet and indifferent species changed traits in the sense of security when occupying lower rainfall areas, whereas dry species changed some traits when more water was available, such as increasing cuticle and spongy parenchyma thickness, or producing smaller and more numerous stomata. Trischidium molle, the most plastic and wet species, exhibited a similar strategy to the dry species. Our results corroborate the risks to vegetation under future climate change scenarios as stressed species and populations may not endure even more severe conditions.

Coronary artery complications after left bundle branch area pacing: An increasingly reported issue in the era of physiologic pacing.

Coronary artery lesions related to pacemaker implantation are rare complications. With the increasing adoption of the technique of permanent transseptal pacing of the left bundle branch area pacing (LBBAP), an increase in the incidence of these complications may be expected. We report two cases of coronary lesions after permanent transeptal pacing of the LBBAP: the first with a small coronary artery fistula, and the second with an extrinsic coronary compression. Both complications occurred with stylet-driven pacing leads with extendable helix. In the first case, since the shunt volume was small and no major complications were reported, the patient was treated conservatively with good outcome. The second case required lead repositioning due to acute decompensated heart failure.

Left Bundle Branch Pacing vs Left Ventricular Septal Pacing vs Biventricular Pacing for Cardiac Resynchronization Therapy.

BACKGROUND: Left bundle branch pacing (LBBP) and left ventricular septal pacing (LVSP) are considered to be acceptable as LBBAP strategies. Differences in clinical outcomes between LBBP and LVSP are yet to be determined. OBJECTIVES: The purpose of this study was to compare the outcomes of LBBP vs LVSP vs BIVP for CRT. METHODS: In this prospective multicenter observational study, LBBP was compared with LVSP and BIVP in patients undergoing CRT. The primary composite outcome was freedom from heart failure (HF)-related hospitalization and all-cause mortality. Secondary outcomes included individual components of the primary outcome, postprocedural NYHA functional class, and electrocardiographic and echocardiographic parameters. RESULTS: A total of 415 patients were included (LBBP: n = 141; LVSP: n = 31; BIVP: n = 243), with a median follow-up of 399 days (Q1-Q3: 249.5-554.8 days). Freedom from the primary composite outcomes was 76.6% in the LBBP group and 48.4% in the LVSP group (HR: 1.37; 95% CI: 1.143-1.649; P = 0.001), driven by a 31.4% absolute increase in freedom from HF-related hospitalizations (83% vs 51.6%; HR: 3.55; 95% CI: 1.856-6.791; P < 0.001) without differences in all-cause mortality. LBBP was also associated with a higher freedom from the primary composite outcome compared with BIVP (HR: 1.43; 95% CI: 1.175-1.730; P < 0.001), with no difference between LVSP and BIVP. CONCLUSIONS: In patients undergoing CRT, LBBP was associated with improved outcomes compared with LVSP and BIVP, while outcomes between BIVP and LVSP are similar.

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

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

Tetralogy of Fallot with an Anomalous Course of the Brachiocephalic Vein.

CLINICAL DATA: Infant, 11-month-old, male, diagnosis of Tetralogy of Fallot with retrotracheoesophageal course of the brachiocephalic vein. Usual findings of Tetralogy of Fallot on physical examination. Technical description: Chest radiography showed slightly reduced pulmonary vascular markings and no cardiomegaly. Normal preoperative electrocardiogram with postoperative right bundle branch block. Usual findings of Tetralogy of Fallot on echocardiogram. Postoperative computed tomography angiography confirmed left brachiocephalic vein with anomalous retrotracheoesophageal course, configuring a U-shaped garland vein, in addition to postoperative findings of total correction of Tetralogy of Fallot. OPERATION: Complete surgical repair was performed with pulmonary valve commissurotomy and placement of bovine pericardial patch to solve right ventricular outflow tract obstruction, pulmonary trunk enlargement, and ventricular septal defect closure. COMMENTS: Systemic venous drainage may show variations in patients with Tetralogy of Fallot. These abnormalities are usually of little clinical relevance, as they are asymptomatic. We presented a rare case of retrotracheoesophageal course of an anomalous left brachiocephalic vein with intraoperative diagnosis, confirmed by imaging during postoperative follow-up, without compromising clinical management or surgical approach.

Quality improvement collaborative to optimize heart failure care in patients from a network of clinics in Argentina during the COVID-19 pandemic.

Heart failure (HF) is a major clinical and public health problem associated with significant mortality, morbidity, and health-care costs. Despite the existence of evidence-based guidelines for the optimal treatment of HF, the quality of care remains suboptimal. Our aim was to increase the use a care bundle in 50% of enrolled subjects during their hospitalization and discharge and to reduce their readmission for HF causes by 10%. We conducted an uncontrolled before-after study in eight hospitals in Argentina to evaluate the effect of a quality improvement intervention on the use of an HF care bundle in patients with HF New York Heart Association (NYHA) Class II-III. The HF bundle of care included medication, continuum of care, lifestyle habits, and predischarge examinations. Training and follow-up of multidisciplinary teams in each center were performed through learning sessions and plan-do-study-act improvement cycles. Data collectors reviewed bundle compliance in the health records of recruited patients after their hospital discharge and verified readmissions through phone calls to patients within 30-40 days after discharge. We recruited 200 patients (83 before and 127 during the intervention phase), and bundle compliance increased from 9.6% to 28.3% [odds ratio 3.71, 95% confidence interval (8.46; 1.63); P = .002]. Despite a slow improvement during the first months, bundle compliance gained momentum near the end of the intervention surpassing 80%. We observed a non-significant decreased readmission rate within 30 days of discharge due to HF in the postintervention period [8.4% vs. 5.5%, odds ratio 0.63, 95% CI (1.88; 0.21); P = .410]. Qualitative analysis showed that members of the intervention teams acknowledged the improvement of work organization and standardization of care, teamwork, shared mental model, and health record completeness as well as the utility of training fellows. Despite the challenges related to the pandemic, better care of patients with HF NYHA Class II-III was possible through simple interventions and collaborative work. Graphical abstract.

Case report: Challenges and implications of conduction system pacing in pediatrics: Case series.

Cardiac electrical stimulation in children usually is needed in the setting of complete congenital atrioventricular block, atrioventricular block after heart surgery, and bradycardia associated with some specific channelopathies. In cases of atrioventricular block, the high percentage of ventricular stimulation raises concern on the deleterious effects of chronic stimulation of the right ventricle. In recent years, physiologic stimulation has developed as a valid approach for adult patients and a great interest has risen in offering conduction system pacing also to the pediatric population. We present three pediatric cases of stimulation of the conduction system (His bundle or left bundle branch), in order to show the intrinsic particularities and challenges implied in these new techniques.

Meta-analysis of clinical outcomes in cardiac resynchronisation therapy: his bundle pacing vs biventricular pacing.

INTRODUCTION AND OBJECTIVE: Cardiac resynchronization may treat severe heart failure (HF) with pharmacological optimization, left branch block, and an ejection fraction<35%. However, 30-40% of patients fail therapy. HBP could replace biventricular pacing (BiV). We compared the effectiveness of HBP versus BiV in HF patients. METHODS: We searched PubMed, Embase, and Cochrane for studies on QRS, left ventricular ejection fraction (LVEF), New York Heart Association (NYHA) functional class, left ventricular end-systolic volume (LVESV), and 6-minute walk test. RESULTS: Six publications included 774 patients (mean [± standard deviation] age: 66.9 [14.0] years; 484 (62.5%) were males; 408 [52.71%] underwent HBP; the mean follow-up was 6-12 months. The HBP group had a higher QRS reduction in the meta-analysis (median: -17.54 [-20.46, -14.62]; I2 = 89%). LVEF showed a median of 8.48 (7.55, 9.41) and I2 of 98%, with a higher mean in HBP. The LVESV median was -18.89 (-30.03, -7.75) and I2 was 0%, and the HBP group had a lower mean. HBP had a lower NYHA functional class (median= -0.20 [-0.28, -0.12]). CONCLUSION: After implantation, HBP demonstrated bigger QRS shortening, increased LVEF, lower LVES volume, and lower NYHA class than BiV pacing.

Lack of evidence for longitudinal dissociation of the atrioventricular conduction axis.

Longitudinal dissociation of the aggregated specialized cardiomyocytes within the non-branching portion of atrioventricular conduction axis has proved a controversial topic for both morphologists and electrophysiologists. We have now used morphological methods, including three-dimensional assessment, to revisit, in human, canine, and bovine hearts, the presence or absence of interconnections between the aggregated cardiomyocytes making up the non-branching bundle. We analyzed three datasets from human and canine hearts, and two from bovine hearts, using longitudinal and orthogonal serial histological sections. In addition, we assessed three hearts using translucent India ink injected specimens, permitting assessment of the three-dimensional arrangement of the cardiomyocytes. Using the longitudinal sections, we found numerous oblique interconnections between the groups of specialized cardiomyocytes. When assessing orthogonal sections, we noted marked variation in the grouping of the cardiomyocytes. We interpreted this finding as evidence of bifurcation and convergence of the groups seen in the longitudinal sections. The three-dimensional assessment of the bovine material confirmed the presence of the numerous interconnections. The presence of multiple connections between the cardiomyocytes in the non-branching bundle rules out the potential for longitudinal dissociation.