Evolution and environment of Caribbean coastal ecosystems.

Isolation of the Caribbean Sea from the tropical Eastern Pacific by uplift of the Isthmus of Panama in the late Pliocene was associated with major, taxonomically variable, shifts in Caribbean biotic composition, and extinction, but inferred causes of these biological changes have remained elusive. We addressed this through falsifiable hypotheses about how independently determined historical changes in oceanographic conditions may have been responsible. The most striking environmental change was a sharp decline in upwelling intensity as measured from decreases in intra-annual fluctuations in temperature and consequently in planktonic productivity. We then hypothesized three general categories of biological response based upon observed differences in natural history between the oceans today. These include changes in feeding ecology, life histories, and habitats. As expected, suspension feeders and predators became rarer as upwelling declined. However, predicted increases in benthic productivity by reef corals, and benthic algae were drawn out over more than 1 Myr as seagrass and coral reef habitats proliferated; a shift that was itself driven by declining upwelling. Similar time lags occurred for predicted shifts in reproductive life history characteristics of bivalves, gastropods, and bryozoans. Examination of the spatial variability of biotic change helps to understand the time lags. Many older species characteristic of times before environmental conditions had changed tended to hang on in progressively smaller proportions of locations until they became extinct as expected from metapopulation theory and the concept of extinction debt. Faunal turnover may not occur until a million or more years after the environmental changes ultimately responsible.

Three-dimensional cardiac magnetic resonance allows the identification of slow-conducting anatomical isthmuses in tetralogy of Fallot.

BACKGROUND AND AIMS: Patients with repaired tetralogy of Fallot remain at risk of life-threatening ventricular tachycardia related to slow-conducting anatomical isthmuses (SCAIs). Preventive ablation of SCAI identified by invasive electroanatomical mapping is increasingly performed. This study aimed to non-invasively identify SCAI using 3D late gadolinium enhancement cardiac magnetic resonance (3D-LGE-CMR). METHODS: Consecutive tetralogy of Fallot patients who underwent right ventricular electroanatomical mapping (RV-EAM) and 3D-LGE-CMR were included. High signal intensity threshold for abnormal myocardium was determined based on direct comparison of bipolar voltages and signal intensity by co-registration of RV-EAM with 3D-LGE-CMR. The diagnostic performance of 3D-LGE-CMR to non-invasively identify SCAI was determined, validated in a second cohort, and compared with the discriminative ability of proposed risk scores. RESULTS: The derivation cohort consisted of 48 (34 ± 16 years) and the validation cohort of 53 patients (36 ± 18 years). In the derivation cohort, 78 of 107 anatomical isthmuses (AIs) identified by EAM were normal-conducting AI, 22 were SCAI, and 7 blocked AI. High signal intensity threshold was 42% of the maximal signal intensity. The sensitivity and specificity of 3D-LGE-CMR for identifying SCAI or blocked AI were 100% and 90%, respectively. In the validation cohort, 85 of 124 AIs were normal-conducting AI, 36 were SCAI, and 3 blocked AI. The sensitivity and specificity of 3D-LGE-CMR were 95% and 91%, respectively. All risk scores showed an at best modest performance to identify SCAI (area under the curve ≤ .68). CONCLUSIONS: 3D late gadolinium enhancement cardiac magnetic resonance can identify SCAI with excellent accuracy and may refine non-invasive risk stratification and patient selection for invasive EAM in tetralogy of Fallot.

The effect of an initial catheter ablation with an adjunctive ethanol infusion into the vein of Marshall on persistent atrial fibrillation.

INTRODUCTION: Some previous studies have reported that a first-step ethanol infusion into the vein of Marshall (EIVOM) with touch-up radiofrequency (RF) ablation can facilitate mitral isthmus (MI) block and improves the ablation outcomes in persistent atrial fibrillation (PeAF) patients. However, the effect of an initial RF ablation with an adjunctive EIVOM has not been fully investigated. METHODS: This study enrolled 233 PeAF patients undergoing pulmonary vein isolation and linear ablation including an MI, roof line, and cavotricuspid isthmus ablation. An EIVOM was performed when endocardial ablation with or without coronary sinus ablation failed to create MI block. RESULTS: Bidirectional MI block was achieved in 224 patients (96.1%). Among them, MI block was obtained by only RF ablation in 174/224 patients (77.7%) (RF group) and an adjunctive EIVOM was needed in 50/224 (22.3%) (EIVOM group). During the follow-up, 113 (64.9%) RF group patients were free from AF/atrial tachycardia compared to 41 (82.0%) EIVOM group patients (log-rank p = .045). In a multivariate Cox regression analysis, an adjunctive EIVOM was associated with a lower recurrence rate (hazard ratio = 0.39, 95% confidence interval = 0.17-0.78, p = .006). CONCLUSION: An initial RF ablation with an adjunctive EIVOM strategy improved MI ablation's acute success rate and was associated with better clinical outcomes.

Automated prediction of isthmus areas in scar-related atrial tachycardias using artificial intelligence.

INTRODUCTION: Ablation of scar-related reentrant atrial tachycardia (SRRAT) involves identification and ablation of a critical isthmus. A graph convolutional network (GCN) is a machine learning structure that is well-suited to analyze the irregularly-structured data obtained in mapping procedures and may be used to identify potential isthmuses. METHODS: Electroanatomic maps from 29 SRRATs were collected, and custom electrogram features assessing key tissue and wavefront properties were calculated for each point. Isthmuses were labeled off-line. Training data was used to determine the optimal GCN parameters and train the final model. Putative isthmus points were predicted in the training and test populations and grouped into proposed isthmus areas based on density and distance thresholds. The primary outcome was the distance between the centroids of the true and closest proposed isthmus areas. RESULTS: A total of 193 821 points were collected. Thirty isthmuses were detected in 29 tachycardias among 25 patients (median age 65.0, 5 women). The median (IQR) distance between true and the closest proposed isthmus area centroids was 8.2 (3.5, 14.4) mm in the training and 7.3 (2.8, 16.1) mm in the test group. The mean overlap in areas, measured by the Dice coefficient, was 11.5 ± 3.2% in the training group and 13.9 ± 4.6% in the test group. CONCLUSION: A GCN can be trained to identify isthmus areas in SRRATs and may help identify critical ablation targets.

Comparison of anterior mitral line and mitral isthmus line for ablation of mitral annular flutter.

BACKGROUND: Mitral annular flutter (MAF) is the most common left atrial macro-reentrant arrhythmia following catheter ablation of atrial fibrillation (AF). The best ablation approach for this arrhythmia remains unclear. METHODS: This single-center, retrospective study sought to compare the acute and long-term outcomes of patients with MAF treated with an anterior mitral line (AML) versus a mitral isthmus line (MIL). Acute ablation success, complication rates, and long-term arrhythmia recurrence were compared between the two groups. RESULTS: Between 2015 and 2021, a total of 81 patients underwent ablation of MAF (58 with an AML and 23 with a MIL). Acute procedural success defined as bidirectional block was achieved in 88% of the AML and 91% of the MIL patients respectively (p = 1.0). One year freedom from atrial arrhythmias was 49.5% versus 77.5% and at 4 years was 24% versus 59.6% for AML versus MIL, respectively (hazard ratio [HR]: 0.38, confidence interval [CI]: 0.17-0.82, p = .009). Fewer patients in the MIL group had recurrent atrial flutter when compared to the AML group (HR: 0.32, CI: 0.12-0.83, p = .009). The incidence of recurrent AF, on the other side, was not different between both groups (21.7% vs. 18.9%; p = .76). There were no serious adverse events in either group. CONCLUSION: In this retrospective study of patients with MAF, a MIL compared to AML was associated with a long-term reduction in recurrent atrial arrhythmias driven by a reduction in macroreentrant atrial flutters.

Cavotricuspid Isthmus-Dependent Atrial Flutter. Beyond Simple Linear Ablation.

The demonstration of a peritricuspid circular movement with a zone of slow conduction in the cavotricuspid isthmus, together with the high efficacy of linear ablation and widely accepted acute endpoints, has established typical flutter as a disease with a well-defined physiopathology and treatment. However, certain aspects regarding its deeper physiopathology, ablation targets, and methods for verifying the results remain to be clarified. While current research efforts have primarily been focused on the advancement of effective ablation techniques, it is crucial to continue exploring the intricate electrophysiological, ultrastructural, and pharmacological pathways that underlie the development of atrial flutter. This ongoing investigation is essential for the development of targeted preventive strategies that can act upon the specific mechanisms responsible for the initiation and maintenance of this arrhythmia. In this work, we will discuss less ascertained aspects alongside the most widely recognized general data, as well as the most recent or less commonly used contributions regarding the electrophysiological evaluation and ablation of typical atrial flutter. Regarding electrophysiological characteristics, one of the most intriguing findings is the presence of low voltage zones in some of these patients together with the presence of a functional, unidirectional line of block between the two vena cava. It is theorized that episodes of paroxysmal atrial fibrillation can trigger this line of block, which may then allow the onset of stable atrial flutter. Without this, the patient will either remain in atrial fibrillation or return to sinus rhythm. Another of the most important pending tasks is identifying patients at risk of developing post-ablation atrial fibrillation. Discriminating between individuals who will experience a complete arrhythmia cure and those who will develop atrial fibrillation after flutter ablation, remains essential given the important prognostic and therapeutic implications. From the initial X-ray guided linear cavotricuspid ablation, several alternatives have arisen in the last decade: electrophysiological criteria-directed point applications based on entrainment mapping, applications directed by maximum voltage criteria or by wavefront speed and maximum voltage criteria (omnipolar mapping). Electro-anatomical navigation systems offer substantial support in all three strategies. Finally, the electrophysiological techniques to confirm the success of the procedure are reviewed.

Timing of critical isthmus from end of P wave and usefulness of activation mapping with window of interest from end to end of P wave in reentrant atrial tachycardia.

In activation mapping of reentrant atrial tachycardia (AT), there was no reference for window of interest (WOI). We examined the timing of a successful termination site from end of the P wave and attempted to determine whether the critical isthmus can be identified using activation mapping when WOI was set as end to end of the P wave. Forty patients with 54 reentrant AT who underwent 3D electroanatomic mapping and radiofrequency catheter ablation were evaluated retrospectively. The critical isthmus was defined as a successful termination site. We evaluate critical isthmus timing from end of the P wave and percentage of critical isthmus timing from end of the P wave to tachycardia cycle length. In 54 reentrant AT, Macro-reentry was identified in 46 (85.2%) and micro-reentry was identified in eight (14.8%). The timing of the critical isthmus site from end of the P wave was - 4.0 ± 31.1 ms (Macro-reentry vs. Micro-reentry; - 8.9 ± 29.4 ms vs. 24.0 ± 26.7 ms; P = 0.005). The percentage of critical isthmus timing from end of the P wave/tachycardia cycle length was - 1.4 ± 10.5% (Macro-reentry vs. Micro-reentry; - 3.1 ± 9.8% vs. 8.3 ± 9.3%, P = 0.004) The critical isthmus of reentrant AT is located within 10% backward and forward from end of the P wave to tachycardia cycle length. Setting the WOI from end to end of the P wave is useful for identification of the critical isthmus through activation mapping.

Evaluation of risk factors for long-term atrial fibrillation development in patients undergoing typical atrial flutter ablation: a multicenter pilot study.

BACKGROUND: Atrial flutter (AFL) and atrial fibrillation (AF) are the most commonly detected supraventricular arrhythmias and share similar pathophysiological mechanisms. After the successful ablation of AFL, AF frequently occurs in the long-term follow-up. As emphasized in some studies, certain mechanisms seem to predispose to the development of AF in AFL patients, and approximately 20% of these patients have accompanying AFL. PURPOSE: We aimed to analyze independent risk factors that predict the development of AF in patients who underwent typical AFL ablation. METHODS: This was a multicenter, cross-sectional, and retrospective study. A total of 442 patients who underwent typical AFL ablation at three different centers between January 1, 2018 and January 1, 2022 were included retrospectively. After the ablation procedure the patients were divided into those who developed AF and those who did not. The patients were followed up for an average of 12 (4-20) months. In the post-procedural period, atrial arrhythmias were investigated with 24­h Holter and ECG at 1 month, 6 months, and 12 months and then at 6­month intervals thereafter. RESULTS: Overall, AF developed in 206 (46.6%) patients in the long-term follow-up. Age, hypertension (HT), obstructive sleep apnea syndrome (OSAS), previous cerebrovascular accident (CVA), left atrium anteroposterior diameter, severe mitral regurgitation, hemoglobin, blood glucose, and HbA1c values were found to be significant in univariable analysis. According to multivariable analysis, HT (p = 0.014; HR: 1.483 [1.084-2.030]), OSAS (p = 0.008; HR: 1.520 [1.117-2.068]) and previous CVA (p = 0.038; HR: 1.749 [1.031-2.968]) were independently associated with the development of AF in AFL patients who underwent ablation procedure. CONCLUSION: In the present study, we found that HT, OSAS, and previous CVA were independently correlated with the development of AF in the long-term follow-up of patients who underwent typical AFL ablation. We consider that AFL patients with such risk factors should be followed up closely following cavotricuspid isthmus ablation for the development of AF.

The C2 isthmus screw provided sufficient biomechanical stability in the setting of atlantoaxial dislocation-a finite element study.

BACKGROUND: The emerging of the C2 isthmus screw fixation technique is gaining popularity in the setting of atlantoaxial dislocation or other conditions requiring fixation of C2. However, the biomechanical stability of this fixation is poorly understood. PURPOSE: To compare and elucidate the biomechanical stability of C2 pedicle screw (C2PS), C2 isthmus screw (C2IS) and C2 short isthmus screw (C2SIS) fixation techniques in atlantoaxial dislocation (AAD). METHOD: A three-dimensional finite element model (FEM) from occiput to C3 was established and validated from a healthy male volunteer. Three FEMs, C1 pedicle screw (PS)-C2PS, C1PS-C2IS, C1PS-C2SIS were also constructed. The range of motion (ROM) and the maximum von Mises stress under flexion, extension, lateral bending and axial rotation loading were analyzed and compared. The pullout strength of the three fixations for C2 was also evaluated. RESULT: C1PS-C2IS model showed the greatest decrease in ROM with flexion, extension, lateral bending and axial rotation. C1PS-C2PS model showed the least ROM reduction under all loading conditions than both C2IS and C2SIS. The C1PS-C2PS model had the largest von Mises stress on the screw under all directions followed by C1PS-C2SIS, and lastly the C1PS-C2IS. Under axial rotation and lateral bending loading, the three models showed the maximum and minimum von Mises stress on the screw respectively. The stress of the three models was mainly located in the connection of the screw and rod. Overall, the maximum screw pullout strength for C2PS, C2IS and C2SIS were 729.41N, 816.62N, 640.54N respectively. CONCLUSION: In patients with atlantoaxial dislocations, the C2IS fixation provided comparable stability, with no significant stress concentration. Furthermore, the C2IS had sufficient pullout strength when compared with C2PS and C2SIS. C2 isthmus screw fixation may be a biomechanically favourable option in cases with AAD. However, future clinical trials are necessary for the evaluation of the clinical outcomes of this technique.

Electrophysiological Cardiovascular Magnetic Resonance (EP-CMR)-Guided Interventional Procedures: Challenges and Opportunities.

PURPOSE OF REVIEW: Cardiovascular magnetic resonance (CMR) imaging excels in providing detailed three-dimensional anatomical information together with excellent soft tissue contrast and has already become a valuable tool for diagnostic evaluation, electrophysiological procedure (EP) planning, and therapeutical stratification of atrial or ventricular rhythm disorders. CMR-based identification of ablation targets may significantly impact existing concepts of interventional electrophysiology. In order to exploit the inherent advantages of CMR imaging to the fullest, CMR-guided ablation procedures (EP-CMR) are justly considered the ultimate goal. RECENT FINDINGS: Electrophysiological cardiovascular magnetic resonance (EP-CMR) interventional procedures have more recently been introduced to the CMR armamentarium: in a single-center series of 30 patients, an EP-CMR guided ablation success of 93% has been reported, which is comparable to conventional ablation outcomes for typical atrial flutter and procedure and ablation time were also reported to be comparable. However, moving on from already established workflows for the ablation of typical atrial flutter in the interventional CMR environment to treatment of more complex ventricular arrhythmias calls for technical advances regarding development of catheters, sheaths and CMR-compatible defibrillator equipment. CMR imaging has already become an important diagnostic tool in the standard clinical assessment of cardiac arrhythmias. Previous studies have demonstrated the feasibility and safety of performing electrophysiological interventional procedures within the CMR environment and fully CMR-guided ablation of typical atrial flutter can be implemented as a routine procedure in experienced centers. Building upon established workflows, the market release of new, CMR-compatible interventional devices may finally enable targeting ventricular arrhythmias.

Pars interarticularis screws for posterior cervical fusion - investigating a new trajectory using a CT-based multiplanar reconstruction: Part I.

BACKGROUND: Lateral mass screw fixation is the standard for posterior cervical fusion between C3 and C6. Traditional trajectories stabilize but carry risks, including nerve root and vertebral artery injuries. Minimally invasive spine surgery (MISS) is gaining popularity, but trajectories present anatomical challenges. RESEARCH QUESTION: This study proposes a novel pars interarticularis screw trajectory to address these issues and enhance in-line instrumentation with cervical pedicle screws. MATERIALS AND METHODS: A retrospective analysis of reformatted cervical CT scans included 10 patients. Measurements of the pars interarticularis morphology were performed on 80 segments (C3-C6). Two pars interarticularis screw trajectories were evaluated: Trajectory A (upper outer quadrant entry, horizontal trajectory) and Trajectory B (lower outer quadrant entry, cranially pointed trajectory). These were compared to standard lateral mass and cervical pedicle screw trajectories, assessing screw lengths, angles, and potential risks to the spinal canal and transverse foramen. RESULTS: Trajectory B showed significantly longer pars lengths (15.69 ± 0.65 mm) compared to Trajectory A (12.51 ± 0.24 mm; p < 0.01). Lateral mass screw lengths were comparable to pars interarticularis screw lengths using Trajectory B. Both trajectories provided safe angular ranges, minimizing the risk to delicate structures. DISCUSSION: and Conclusion. Pars interarticularis screws offer a viable alternative to lateral mass screws for posterior cervical fusion, especially in MISS contexts. Trajectory B, in particular, presents a feasible and safe alternative, reducing the risk of vertebral artery and spinal cord injury. Preoperative assessment and intraoperative technologies are essential for successful implementation. Biomechanical validation is needed before clinical application.

Thoracic aortic pseudoaneurysm: Inside its pathophysiology.

OBJECTIVES: Our aim was to investigate pathophysiology of pseudoaneurysm of the thoracic aorta, an acute or chronic pathology, respectively, secondary to blunt thoracic trauma and aortitis, or complicating a deep penetrating aortic ulcer, intraparietal hematoma, aortic aneurysm, and even aortic graft, often with atherosclerosis as a common background. METHODS: Given the relative rarity of this disease, an "inductive" retrospective method made it possible to retrieve clinical, radiological, and histopathological elements, which were mutually compared and validated through a "deductive" process of reinterpretation. RESULTS: We have identified three main structural constituents of this disease: a cavity, a single blood entry port, communicating with the aortic lumen, and a pseudocapsule. It is often caused by a chronic degenerative pathology of the intima and medial layers of the aorta, typically involving elastic fibers and smooth muscle cells, with possible intermediate stages of deep aortic ulcer or intraparietal hematoma. Otherwise, the acute onset may be secondary to acute aortitis or aortic injury. CONCLUSIONS: Today, thanks to the current angiographic tools represented by 3-D high resolution multidetector CT and MRI angiography, the diagnosis of thoracic aortic pseudoaneurysm is easier, as well as its surgical indications.

Aberrant Subclavian Artery in Interrupted Aortic Arch with Severe Aortic Outlet Obstruction: Cerebral Blood Flow as a Possible Determinant of Embryonic Cardiovascular Development?

Aberrant subclavian artery (ASCA) is frequently observed in interrupted aortic arch (IAA) with aortic/subaortic obstruction. Developmental significance of ASCA in IAA in utero remains elusive. Newborns with prenatally diagnosed isolated IAA under continuous prostaglandin E1 infusion were studied. Cross-sectional areas of aortic valve opening (AVOCSA) and patent ductus arteriosus (PDACSA) were represented by echocardiographic measurement of (diameter)2 indexed by body surface area (m2). Types of IAA and presence of ASCA were examined in relation to sizes of AVOCSA and PDACSA. Twenty-four newborns with IAA (six type A and 18 type B) were reviewed. Male dominance was seen in type B (male 72%). Twenty-three patients had left aortic arch. No type A patients had ASCA, but 50% of type B had ASCA; AVOCSA was significantly smaller in type B than in type A (p = 0.003). In type B, PDACSA was significantly larger in those with ASCA than without (p = 0.003), but AVOCSA exhibited no significant size difference between these two subgroups. Chromosome 22q11 deletion was only seen in type B (56%) and showed no significant correlation with the presence of ASCA. In type B IAA, the presence of ASCA was associated with larger PDACSA, suggesting an adaptive enlargement of the ductus arteriosus and ASCA in response to reduced antegrade flow across small AVOCSA, which may be augmenting cerebral blood flow. Preservation of cerebral blood flow may be another important determinant affecting embryonic cardiovascular development.

Fetal aortic isthmus Doppler assessment to predict the adverse perinatal outcomes associated with fetal growth restriction: systematic review and meta-analysis.

PURPOSE: Fetal growth restriction (FGR) management and delivery planning is based on a multimodal approach. This meta-analysis aimed to evaluate the prognostic accuracies of the aortic isthmus Doppler to predict adverse perinatal outcomes in singleton pregnancies with FGR. METHODS: PubMed, EMBASE, the Cochrane Library, ClinicalTrials.gov and Google scholar were searched from inception to May 2021, for studies on the prognostic accuracy of anterograde aortic isthmus flow compared with retrograde aortic isthmus flow in singleton pregnancy with FGR. The meta-analysis was registered on PROSPERO and was assessed according to PRISMA and Newcastle-Ottawa Scale. DerSimonian and Laird's random-effect model was used for relative risks, Freeman-Tukey Double Arcsine for pooled estimates and exact method to stabilize variances and CIs. Heterogeneity was quantified using I2 statistics. RESULTS: A total of 2933 articles were identified through the electronic search, of which 6 studies (involving 240 women) were included. The quality evaluation of studies revealed an overall acceptable score for study group selection and comparability and substantial heterogeneity. The risk of perinatal death was significantly greater in fetuses with retrograde Aortic Isthmus blood flow, with a RR of 5.17 (p value 0.00001). Similarly, the stillbirth rate was found to have a RR of 5.39 (p value 0.00001). Respiratory distress syndrome had a RR of 2.64 (p value = 0.03) in the group of fetuses with retrograde Aortic Isthmus blood flow. CONCLUSION: Aortic Isthmus Doppler study may add information for FGR management. However, additional clinical trial are required to assess its applicability in clinical practice.

Biomechanical impact of different isthmus positions in mandibular first molar root canals: a finite element analysis.

OBJECTIVE: This study used image-based finite element analysis (FEA) to assess the biomechanical changes in mandibular first molars resulting from alterations in the position of the root canal isthmus. METHODS: A healthy mandibular first molar, characterized by two intact root canals and a cavity-free surface, was selected as the subject. A three-dimensional model for the molar was established using scanned images of the patient's mandibular teeth. Subsequently, four distinct finite element models were created, each representing varied root canal morphologies: non-isthmus (Group A), isthmus located at the upper 1/3 of the root (Group B), middle 1/3 of the root (Group C), and lower 1/3 of the root (Group D). A static load of 200 N was applied along the tooth's longitudinal axis on the occlusal surface to simulate regular chewing forces. The biomechanical assessment was conducted regarding the mechanical stress profile within the root dentin. The equivalent stress (Von Mises stress) was used to assess the biomechanical features of mandibular teeth under mechanical loading. RESULTS: In Group A (without an isthmus), the maximum stress was 22.2 MPa, while experimental groups with an isthmus exhibited higher stresses, reaching up to 29.4 MPa. All maximum stresses were concentrated near the apical foramen. The presence of the isthmus modified the stress distribution in the dentin wall of the tooth canal. Notably, dentin stresses at specific locations demonstrated differences: at 8 mm from the root tip, Group B: 13.6 MPa vs. Group A: 11.4 MPa; at 3 mm from the root tip, Group C: 14.2 MPa vs. Group A: 4.5 MPa; at 1 mm from the root tip, Group D: 25.1 MPa vs. Group A: 10.3 MPa. The maximum stress in the root canal dentin within the isthmus region was located either at the top or bottom of the isthmus. CONCLUSION: A root canal isthmus modifies the stress profile within the dentin. The maximum stress occurs near the apical foramen and significantly increases when the isthmus is located closer to the apical foramina.

Managing peri-mitral flutter.

The exponential rise in the incidence of peri-mitral flutter has paralleled the increasing use of more extensive atrial substrate ablation for atrial fibrillation (AF). Given the relative paucity of randomized evidence to support its role in AF management, mitral isthmus ablation should largely be reserved for patients with peri-mitral flutter. Catheter ablation for peri-mitral flutter is challenging due to complex anatomic relationships. The aim of this report is to review the anatomic considerations and approaches to catheter ablation for peri-mitral flutter.

Unraveling the complex phylogeographic history of freshwater fishes in Lower Central America: A study of the electric fish Brachyhypopomus occidentalis.

Lower Central America (LCA) has a complex biogeographic history shaped by the rise of the Isthmus of Panama and the global climatic oscillations of the Pleistocene. These events have been crucial in structuring biodiversity in LCA, but their consequences for the distribution and partitions of genetic diversity across the region remain to be elucidated. We combined complete mitochondrial genomes and nuclear ultraconserved elements (UCEs) to study the phylogeographic history and population genetic structure of the electric fish Brachyhypopomus occidentalis in LCA. Our results are consistent with the known phylogeographic history of B. occidentalis in LCA, but we update this history in several important ways that help illuminate the phylogeographic history of freshwater fishes in the region. We provide: i) support for three waves of colonization, two of which occurred prior to the final closure of the Panama Isthmus; ii) a more precise understanding of each colonization event, with evidence for a larger footprint of the first event, as well as genetic exchange across the continental divide in subsequent events; and iii) evidence for high levels of previously unrecognized population genetic structure across LCA. This updated model of colonization and diversification of B. occidentalis consists of three waves of dispersal and colonization, which triggered the evolution of geographic breaks in both nuclear and mitochondrial genomes across LCA. These processes are tightly linked to the dynamic uplift of the Isthmus, recent volcanic activity in the region, and the sea-level oscillations of the Pleistocene. These results improve previous phylogeographic inferences regarding the distribution and diversification of freshwater fishes in LCA, and generate testable hypotheses to guide future research exploring the factors shaping biodiversity in the region.

Phylogeography and taxonomy of Coleonyx elegans Gray 1845 (Squamata: Eublepharidae) in Mesoamerica: The Isthmus of Tehuantepec as an environmental barrier.

Population divergence leading to speciation is often explained by physical barriers causing allopatric distributions of historically connected populations. Environmental barriers have increasingly been shown to cause population divergence through local adaptation to distinct ecological characteristics. In this study, we evaluate population structuring and phylogeographic history within the Yucatán banded gecko Coleonyx elegans Gray 1845 to assess the role of both physical and environmental barriers in shaping the spatio-genetic distribution of a Mesoamerican tropical forest taxon. We generated RADseq and multi-locus Sanger datasets that included sampling across the entire species' range. Results find support for two distinct evolutionary lineages that diverged during the late Pliocene and show recent population expansions. Furthermore, these genetic lineages largely align with subspecies boundaries defined by morphology. Several mountain ranges identified as phylogeographic barriers in other taxa act as physical barriers to gene flow between the two clades. Despite the absence of a physical barrier between lineages across the lowland Isthmus of Tehuantepec, no introgression was observed. Here, a steep environmental cline associated with seasonality of precipitation corresponds exactly with the distributional limits of the lineages, whose closest samples are only 30 km apart. The combination of molecular and environmental evidence, and in conjunction with previous morphological evidence, allows us to reassess the current taxonomy in an integrative framework. Based on our findings, we elevate the previously recognized subspecies from the Pacific versant, the Colima banded gecko C. nemoralis Klauber 1945, to full species status and comment on conservation implications.

Endovascular Recanalization of Aortic Isthmus Atresia with an "Electrified Wire Technique".

PURPOSE: For aortic coarctation in adults endovascular repair is the treatment of choice with an acceptable safety profile. Aortic isthmus atresia is a related condition with a complete occlusion of the aorta not allowing catheterization across the isthmus. This technical note describes a recanalization of an aortic isthmus atresia using radiofrequency with an "electrified wire technique." TECHNIQUE: A guidewire was selectively denuded of PTFE (polytetrafluoroethylene) at the distal end and was placed through a catheter distal to the aortic isthmus atresia. The denuded end of the wire was clamped to an electrosurgery pencil. By pushing the wire toward a tulip-snare, which was placed as a target proximal of the occlusion via left trans-brachial access, and shortly activating of the electrosurgery pencil the electrified wire recanalized the occlusion and was snared and used to guide implantation of a balloon-expandable covered stent. CONCLUSION: The electrified wire puncture technique can be used to recanalize adult aortic isthmus atresia after failed conventional attempts. CLINICAL IMPACT: The electrified wire technique offers an off-the shelf option to modify standard guidewires for the use with radiofrequency to cross a complete aortic isthmus occlusion after failed conventional attempts. This new technique may be applied also in other situations like dissection flap fenestration, transcaval access and similar.

Revisiting the characteristics and ablation strategy of biatrial tachycardias: a case series and systematic review.

AIMS: To describe the role of left atrial (LA) epicardial conduction and targets of ablation in biatrial tachycardias (BiATs). METHODS AND RESULTS: Consecutive patients with BiAT diagnosed by high-density mapping and appropriate entrainment were enrolled. A systematic review of case reports or series was then performed. Biatrial tachycardia was identified in 20 patients aged 63.5 ± 11.1 years. Among them, eight had LA epicardial conduction, including four via the ligament of Marshall, two via myocardial fibres between the great cardiac vein (GCV) and LA, one via septopulmonary bundle, and one via myocardial fibres between the posterior wall and coronary sinus. Ablation was targeted at the anatomical isthmus in 14, including 5 undergoing vein of Marshall ethanol infusion and 2 undergoing ablation in the GCV. Another six underwent ablation at interatrial connections, including one with septopulmonary bundle at the fossa ovalis and five at the atrial insertions of Bachmann's bundle. After a mean follow-up of 8.7 ± 3.8 months, five patients had recurrence of atrial fibrillation/flutter. Systematic review enrolled 87 patients in previous and the present reports, showing a higher risk of impairment in atrial physiology in those targeting interatrial connections (30.4 vs. 5.0%, P < 0.001) but no significant difference in short- and long-term effectiveness. CONCLUSION: Left atrial epicardial conduction is common in BiATs and affects the ablation strategy. Atrial physiology is a major concern in selecting the target of intervention.