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Objective: The development of adjacent segment disease or the progression of spondylosis following the surgical treatment of spinal stenosis and spondylolisthesis is well documented and can lead to subsequent functional decline after a successful index surgery. The early detection of negative inflection points during patients' functional recovery can improve timely intervention. In this study, we developed machine learning (ML) models to predict the occurrence of post-operative decline in patient mobility. Methods: Patients receiving spine surgery for degenerative spinal stenosis or spondylolisthesis were retroactively consented and enrolled. Activity data (steps-per-day) previously recorded across a 4-year peri-operative were collected alongside relevant clinical and demographic variables. Logistic regression (LR), random forest (RF), and extreme gradient boosting (XGBoost) ML models were constructed and trained on 80% of the dataset and validated using the remaining 20%. The study's primary endpoint was the models' ability to predict post-operative decline in patient mobility. Results: A total of 75 patients were included. Following training, RF and XGBoost models achieved accuracy values of 86.7% (sensitivity 80%, specificity 90%) and 80% (sensitivity 60%, specificity 90%), respectively, in predicting post-operative functional decline. The LR model was the least effective with an accuracy of 73.3% (sensitivity 50%, specificity 88.8%). Receiver operating characteristic curves showed an area under the curve of 0.80 for RF, 0.70 for XGBoost, and 0.69 for LR. Conclusions: ML models trained on activity data collected from smartphones successfully forecast functional decline in post-operative activity following spine surgery. These results lay the groundwork for the future integration of ML into the surgeon's toolbox for prognostication and surgical planning.

Ischemic stroke and cerebral amyloid angiopathy (CAA) pose significant challenges in an aging population, particularly in post-stroke recovery. Using the 5xFAD mouse model, we explore the relationship between CAA, ischemic stroke, and tissue recovery. We hypothesize that amyloid-beta accumulation worsens stroke outcomes by inducing blood-brain barrier (BBB) dysfunction, leading to impaired neurogenesis. Our findings show that CAA exacerbates stroke outcomes, with mice exhibiting constricted BBB microvessels, reduced cerebral blood flow, and impaired tissue recovery. Transcriptional analysis shows that endothelial cells and neural progenitor cells (NPCs) in the hippocampus exhibit differential gene expression in response to CAA and stroke, specifically targeting the phosphatidylinositol 3-kinase (PI3K) pathway. In vitro experiments with human NPCs validate these findings, showing that disruption of the CXCL12-PIK3C2A-CREB3L2 axis impairs neurogenesis. Notably, PI3K pathway activation restores neurogenesis, highlighting a potential therapeutic approach. These results suggest that CAA combined with stroke induces microvascular dysfunction and aberrant neurogenesis through this specific pathway., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: Epidural arteriovenous fistulas (eAVFs) are rare vascular malformations often mistaken for their intradural counterparts due to similar angiographic features. Differentiation between epidural and intradural vascular lesions is crucial as it impacts surgical planning and prognosis. Despite advancements in diagnostic imaging, these entities can be misinterpreted and challenge management., Observations: The authors report the case of a 68-year-old male suspected to have a type I dural arteriovenous fistula based on magnetic resonance angiography and angiographic evaluation. He presented with progressive myelopathy and multiple neurological symptoms exacerbated by recent trauma. A superselective angiogram of the right T10 segmental artery suggested an intradural arteriovenous fistula; however, intraoperatively, the lesion was epidural. The arterialized venous structures were obliterated, and the patient reported significant postoperative symptomatic improvement., Lessons: This case highlights the critical importance of comprehensive imaging and cautious interpretation in the diagnosis of spinal vascular malformations. It also underscores the need for a multidisciplinary approach to ensure accurate diagnosis and effective treatment. Surgeons must be prepared for intraoperative findings that diverge from preoperative imaging to adapt surgical strategies accordingly. Furthermore, this case contributes to the evolving understanding of eAVFs, suggesting that revised imaging protocols may be required to better distinguish epidural from intradural vascular abnormalities. https://thejns.org/doi/10.3171/CASE24331.

The intensive nutrient requirements needed to sustain T cell activation and proliferation, combined with competition for nutrients within the tumor microenvironment, raise the prospect that glucose availability may limit CAR-T cell function. Here, we seek to test the hypothesis that stable overexpression (OE) of the glucose transporter GLUT1 in primary human CAR-T cells would improve their function and antitumor potency. We observe that GLUT1OE in CAR-T cells increases glucose consumption, glycolysis, glycolytic reserve, and oxidative phosphorylation, and these effects are associated with decreased T cell exhaustion and increased Th 17 differentiation. GLUT1OE also induces broad metabolic reprogramming associated with increased glutathione-mediated resistance to reactive oxygen species, and increased inosine accumulation. When challenged with tumors, GLUT1OE CAR-T cells secrete more proinflammatory cytokines and show enhanced cytotoxicity in vitro, and demonstrate superior tumor control and persistence in mouse models. Our collective findings support a paradigm wherein glucose availability is rate limiting for effector CAR-T cell function and demonstrate that enhancing glucose availability via GLUT1OE could augment antitumor immune function., (© 2024. The Author(s).)

Background: Prompt diagnosis and treatment of vertebral artery dissection (VAD) is critical for preventing stroke. The use of emboli detection studies (EDS) using Doppler ultrasonography is an emerging method that has been proposed to predict stroke risk and guide subsequent treatment. Limited data exists on the predictive value of this emerging modality in the posterior circulation. This study aims to assess the predictive value of emboli detection studies (EDS) in forecasting inpatient stroke in VAD patients and identify associated risk factors. Patients were recruited between January 2009 and January 2018., Methods: We performed a retrospective analysis of 104 consecutive patients with VAD who underwent EDS at our institution. Patients underwent transcranial ultrasonography for detection of microemboli and were followed clinically and radiographically thereafter for evidence of stroke., Results: A total of 104 patients with spontaneous (58 %), traumatic (39 %) or iatrogenic (4 %) VAD were included in our analysis. Stroke occurred more frequently in patients with spontaneous VAD compared to traumatic VAD (p < 0.001). Microemboli were detected in 17 patients (16 %), including 18.3 % of spontaneous VAD, 12.5 % of traumatic VAD, and 25 % of iatrogenic VAD. 61 patients (59 %) suffered a posterior circulation stroke, however there was no significant association between detection of microemboli and stroke events (60 % of patients without microemboli vs. 53 % of patients with ≥ 1 HITS during EDS; p = 0.6). Similarly, no microemboli were detected in any of the patients who went on to develop a delayed stroke., Conclusions: In our single-institution retrospective analysis of patients with VAD, the detection of microemboli on EDS was not associated with stroke nor was it predictive of delayed stroke. Additionally, patients with spontaneous VAD may be at higher risk for stroke compared to traumatic VAD., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

We present a rare case of an intraparenchymal chordoma in the brain stem of a 69-year-old male with a history of multiple chordoma recurrences. Chordomas are uncommon tumors that originate from notochordal remnants, with intraparenchymal presentations in the brain stem being particularly rare. A 69-year-old male with a history of clival chordoma three years after primary endoscopic resection and adjuvant proton-beam radiotherapy and a recurrence one year postoperatively for which he underwent a second surgery, presented with severe headaches, weakness, diaphoresis, and difficulty ambulating. Head CT in the ER revealed a 2.7 x 3.5 cm hyperdense lesion in the pons, indicating acute hemorrhage. Magnetic resonance imaging (MRI) suggested a hemorrhagic radiation-induced cavernoma. A right retrosigmoid craniotomy was performed, and the lesion was resected without major complications. Final pathology reported an intraparenchymal hemorrhagic chordoma. To our knowledge, this is the first case of intra-axial chordoma, particularly in the brain stem. It highlights the importance of considering intraparenchymal chordoma on the differential when evaluating for recurrence versus other treatment-induced pathologies and changes. This may prompt the neurosurgeon to reconsider treatment options and weigh the risks of watchful waiting versus biopsy or even aggressive surgical management., Competing Interests: Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Bashti et al.)

Background: Adjacent segment disease (ASD) is a known sequela of thoracolumbar instrumented fusions. Various surgical options are available to address ASD in patients with intractable symptoms who have failed conservative measures. However, the optimal treatment strategy for symptomatic ASD has not been established. We examined several clinical outcomes utilizing different surgical interventions for symptomatic ASD., Methods: A retrospective review was performed for a consecutive series of patients undergoing revision surgery for thoracolumbar ASD between October 2011 and February 2022. Patients were treated with endoscopic decompression ( N = 17), microdiscectomy ( N = 9), lateral lumbar interbody fusion (LLIF; N = 26), or open laminectomy and fusion (LF; N = 55). The primary outcomes compared between groups were re-operation rates and numeric pain scores for leg and back at 2 weeks, 10 weeks, 6 months, and 12 months postoperation. Secondary outcomes included time to re-operation, estimated blood loss, and length of stay., Results: Of the 257 patients who underwent revision surgery for symptomatic ASD, 107 patients met inclusion criteria with a minimum of 1-year follow-up. The mean age of all patients was 67.90 ± 10.51 years. There was no statistically significant difference between groups in age, gender, preoperative American Society of Anesthesiologists scoring, number of previously fused levels, or preoperative numeric leg and back pain scores. The re-operation rates were significantly lower in LF (12.7%) and LLIF cohorts (19.2%) compared with microdiscectomy (33%) and endoscopic decompression (52.9%; P = 0.005). Only LF and LLIF cohorts experienced significantly decreased pain scores at all 4 follow-up visits (2 weeks, 10 weeks, 6 months, and 12 months; P < 0.001 and P < 0.05, respectively) relative to preoperative scores., Conclusion: Symptomatic ASD often requires treatment with revision surgery. Fusion surgeries (either stand-alone lateral interbody or posterolateral with instrumentation) were most effective and durable with respect to alleviating pain and avoiding additional revisions within the first 12 months following revision surgery., Clinical Relevance: This study emphasizes the importance of risk-stratifying patients to identify the least invasive approach that treats their symptoms and reduces the risk of future surgeries., Competing Interests: Declaration of Conflicting Interests : Michael Y. Wang discloses that he receives royalty payments from DePuy-Synthes Spine, is a consultant for DePuy-Synthes Spine, Inc., Stryker, Spineology, Surgalign, Pacira, Nuvasive, and has stock in Innovative Surgical Devices, Kinesiometrics, and Medical Device Partners. Michael M.H. Yang reports that he is a consultant for Stryker and DePuy Synthes. Malek Bashti, Manav Daftari, Damian Brusko, Aria M. Jamshidi, Eric B. Singh, V. Boddu, Vignessh Kumar, and Michael Yang have nothing to disclose., (This manuscript is generously published free of charge by ISASS, the International Society for the Advancement of Spine Surgery. Copyright © 2024 ISASS. To see more or order reprints or permissions, see http://ijssurgery.com.)

Background: Brain metastases from esophageal cancer (BMEC) are rare and aggressive, with limited literature on optimal treatment modalities and a standard of care yet to be established. The objective of this study was to systematically review existing literature and perform a retrospective analysis of our institution's patients to evaluate the influence of different treatment modalities on patient outcomes., Methods: A systematic review of the literature following Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines and a retrospective review of our institutional experience with BMEC were both conducted. Data based on mean survival,histology, metastasis location, and treatment modality were abstracted., Results: A total of 48 studies representing 136 patients with BMEC were identified, in addition to the 11 patients treated at our institution. There were a total of 100 males (12 unreported), with a median age of 62.2 at diagnosis in our systematic review, along with 8 males with a median age of 62 in our institutional review. Collectively, survival rates observed based on histology were not similar (squamous cell carcinoma: 9.2 months, adenocarcinoma: 13.4 months), however, based on treatment modalities (surgery: 11.6 months, radiation: 10.4 months, chemotherapy: 12.3 months), and metastasis location (supratentorial: 10.5 months, infratentorial: 9.9 months), the survival times were comparable., Conclusions: Our review suggests that causes of death were often independent of brain metastases highlighting the need for further studies on early detection and prevention of primary esophageal cancer, as well as improved treatment modalities for BMECs., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Colloid cysts are intracranial lesions originating from abnormalities in the primitive neuroepithelium folding of the third ventricle. Various surgical approaches have been explored for the management of colloid cysts, each carrying its own set of advantages and limitations. Tubular retractors developed recently alleviate retraction pressure through radial distribution, potentially offering benefits for colloid cyst resection. This study aims to introduce and assess a modified microsurgical method utilizing the tubular retractor for addressing colloid cysts., Methods: The study included a retrospective assessment of patients who had colloid cysts and who were treated between 2015 and 2023 by one experienced surgeon. The demographic, clinical, radiological, histological, and surgical data regarding these patients were evaluated. The patients were assessed using the colloid cyst risk score, indicating a risk for obstructive hydrocephalus., Results: The minimally invasive microsurgical approach was successfully applied to all 22 identified patients. No postoperative surgical complications were reported. Gross total resection was achieved in 21 (95.5%) patients. The early complication rate was 22.7% ( n = 5). There were no postoperative seizures, permanent neurological deficits, or venous injuries. The average hospital stay was 3 days. There was no evidence of recurrence at an average follow-up length of 25.9 months., Conclusion: The transtubular approach is an effective, safe method for treating colloid cysts. It achieves complete cyst removal with minimal complications, offering the benefits of less invasiveness, improved visualization, and reduced tissue disruption, strengthening its role in colloid cyst surgery., Competing Interests: There are no conflicts of interest., (Copyright: © 2024 Surgical Neurology International.)

Minimally invasive surgical approaches to the spine that leverage indirect decompression are gaining increasing popularity. While there is excellent literature on the value of indirect decompression, there are limitations to this procedure. Specifically, in patients with severe stenosis and neurogenic claudication, there is a concern among many surgeons regarding the adequacy of indirect decompression alone. In these cases, the lateral approach is often abandoned in favor of an open posterior or posterior minimally invasive approach. Unfortunately, some of the distinct benefits of the direct lateral approach are then lost. Here, we present the case of a 58-year-old male who underwent an L4-L5 lateral interbody fusion with an endoscopic ipsi-contra decompression to achieve both direct and indirect treatment of severe neuroforaminal and central stenosis. From this strategy, this patient had complete pre-operative symptom resolution and was able to return to work immediately after surgery without significant restriction. Combining the benefits of direct and indirect using an ultra-minimally invasive decompressive approach offers a potential solution., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2024, Shah et al.)

A major limitation of chimeric antigen receptor (CAR) T cell therapies is the poor persistence of these cells in vivo 1 . The expression of memory-associated genes in CAR T cells is linked to their long-term persistence in patients and clinical efficacy 2-6 , suggesting that memory programs may underpin durable CAR T cell function. Here we show that the transcription factor FOXO1 is responsible for promoting memory and restraining exhaustion in human CAR T cells. Pharmacological inhibition or gene editing of endogenous FOXO1 diminished the expression of memory-associated genes, promoted an exhaustion-like phenotype and impaired the antitumour activity of CAR T cells. Overexpression of FOXO1 induced a gene-expression program consistent with T cell memory and increased chromatin accessibility at FOXO1-binding motifs. CAR T cells that overexpressed FOXO1 retained their function, memory potential and metabolic fitness in settings of chronic stimulation, and exhibited enhanced persistence and tumour control in vivo. By contrast, overexpression of TCF1 (encoded by TCF7) did not enforce canonical memory programs or enhance the potency of CAR T cells. Notably, FOXO1 activity correlated with positive clinical outcomes of patients treated with CAR T cells or tumour-infiltrating lymphocytes, underscoring the clinical relevance of FOXO1 in cancer immunotherapy. Our results show that overexpressing FOXO1 can increase the antitumour activity of human CAR T cells, and highlight memory reprogramming as a broadly applicable approach for optimizing therapeutic T cell states., (© 2024. The Author(s).)

Adenosine (Ado) mediates immune suppression in the tumor microenvironment and exhausted CD8 + CAR-T cells express CD39 and CD73, which mediate proximal steps in Ado generation. Here, we sought to enhance CAR-T cell potency by knocking out CD39, CD73, or adenosine receptor 2a (A2aR) but observed only modest effects. In contrast, overexpression of Ado deaminase (ADA-OE), which metabolizes Ado to inosine (INO), induced stemness and enhanced CAR-T functionality. Similarly, CAR-T cell exposure to INO augmented function and induced features of stemness. INO induced profound metabolic reprogramming, diminishing glycolysis, increasing mitochondrial and glycolytic capacity, glutaminolysis and polyamine synthesis, and reprogrammed the epigenome toward greater stemness. Clinical scale manufacturing using INO generated enhanced potency CAR-T cell products meeting criteria for clinical dosing. These results identify INO as a potent modulator of CAR-T cell metabolism and epigenetic stemness programming and deliver an enhanced potency platform for cell manufacturing., Competing Interests: Declaration of interests D.D.K, S.A.F., and C.L.M. are co-inventors on a pending patent application for inosine media supplementation during cell manufacturing. D.D.K and C.L.M. are inventors on a patent application for the use of T cells overexpressing ADA1/2 for cancer immunotherapy. C.L.M. holds equity in and receives research funding from Lyell Immunopharma, holds equity in and consults for Link Cell Therapies and C.L.M., and L.L. hold equity and consult for CARGO Therapeutics. L.L. and E.S. hold equity in Lyell Immunopharma. E.S consults for Lepton Pharmaceuticals and Galaria. S.A.F. serves on the Scientific Advisory Boards for Alaunos Therapeutics and Fresh Wind Biotech and has equity interest in both; S.A.F. receives research funding from CARGO and Tune Therapeutics. S.P. is a current employee of and holds equity in CARGO. C.L.M. consults for Immatics, Mammoth, and Ensoma. A.T.S. is a cofounder of Immunai and Cartography Biosciences. A.T.S. receives research funding from Allogene Therapeutics and Merck Research Laboratories., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background and Objectives: Smartphone activity data recorded through high-fidelity accelerometry can provide accurate postoperative assessments of patient mobility. The "big data" available through smartphones allows for advanced analyses, yielding insight into patient well-being. This study compared rate of change in functional activity data between lumbar fusion (LF) and lumbar decompression (LD) patients to determine preoperative and postoperative course differences., Methods: Twenty-three LF and 18 LD patients were retrospectively included. Activity data (steps per day) recorded in Apple Health, encompassing over 70 000 perioperative data points, was classified into 6 temporal epochs representing distinct functional states, including acute preoperative decline, immediate postoperative recovery, and postoperative decline. The daily rate of change of each patient's step counts was calculated for each perioperative epoch., Results: Patients undergoing LF demonstrated steeper preoperative declines than LD patients based on the first derivative of step count data (P = .045). In the surgical recovery phase, LF patients had slower recoveries (P = .041), and LF patients experienced steeper postoperative secondary declines than LD patients did (P = .010). The rate of change of steps per day demonstrated varying perioperative trajectories that were not explained by differences in age, comorbidities, or levels operated., Conclusion: Patients undergoing LF and LD have distinct perioperative activity profiles characterized by the rate of change in the patient daily steps. Daily steps and their rate of change is thus a valuable metric in phenotyping patients and understanding their postsurgical outcomes. Prospective studies are needed to expand upon these data and establish causal links between preoperative patient mobility, patient characteristics, and postoperative functional outcomes., (Copyright © Congress of Neurological Surgeons 2024. All rights reserved.)

Introduction: Metastatic spine tumors affect over 30% of patients who have been diagnosed with cancer. While techniques in surgical intervention have undoubtedly evolved, there are some pitfalls when spinal instrumentation is required for stabilization following tumor resection. However, the use of carbon fiber-reinforced polyetheretherketone (CFR-PEEK) implants has become increasingly popular due to improved radiolucency and positive osteobiologic properties. Here, we present a systematic review describing the use of CFR-PEEK-coated instrumentation in the oncologic population while identifying advantages and potential shortcomings of these devices., Methods: In accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, a systematic review was conducted in March 2022 to identify articles detailing the use of CFR-PEEK implants for spinal instrumentation in patients with primary and secondary spine tumors. The search was performed using the PubMed, Scopus, and Embase databases., Results: An initial search returned a total of 85 articles among the three databases used. After the exclusion of duplicates and screening of abstracts, 21 full-text articles were examined for eligibility. Eleven articles were excluded due to not fitting our inclusion and exclusion criteria. Ten articles were subsequently eligible for full-text review., Conclusions: CFR-PEEK possesses a similar safety and efficacy profile to titanium implants but has distinct advantages. It limits artifact, increases early detection of local tumor recurrence, increases radiotherapy dose accuracy, and is associated with low complication rates (9.96%)-making it a promising alternative for the demands unique to the treatment/outcome of spinal oncologic patients., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Background: Minimally invasive surgery bases many of its benefits on decreasing tissue disruption. Endoscopic spine surgery has continued to push the boundaries to accomplish successful clinical outcomes through the evolution of the endoscope and working channel. As the indications for endoscopic spine surgery increase, a more profound discussion of cannula size selection for endoscopic spine surgery is required. The intimate relationship between the working channel, the endoscope and how these choices affect workflow and visualization are paramount to maximize outcomes., Methods: The authors review the nuances of the endoscopic approaches to the various regions of the spine as it relates to the selection of the working channel. The advantages and limitations of various endoscopic working channels were analyzed as to how they address anatomic regional considerations as well as ultimate goals of surgery., Results: In addition to anatomic regional differences and the goals of the surgery other key elements in endoscopic working channel selection included the amount of tissue disruption, regional risk to the neural elements, impact on visualization, optical physics, and the implications for surgical maneuverability/dexterity., Conclusion: Understanding the role and use of the endoscope-working channel combination with its effects on visualization is essential for any surgeon aspiring to perform safe and efficient full endoscopic spine surgery., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier Ltd.)

T cell exhaustion limits immune responses against cancer and is a major cause of resistance to chimeric antigen receptor (CAR)-T cell therapeutics. Using murine xenograft models and an in vitro model wherein tonic CAR signaling induces hallmark features of exhaustion, we tested the effect of transient cessation of receptor signaling, or rest, on the development and maintenance of exhaustion. Induction of rest through enforced down-regulation of the CAR protein using a drug-regulatable system or treatment with the multikinase inhibitor dasatinib resulted in the acquisition of a memory-like phenotype, global transcriptional and epigenetic reprogramming, and restored antitumor functionality in exhausted CAR-T cells. This work demonstrates that rest can enhance CAR-T cell efficacy by preventing or reversing exhaustion, and it challenges the notion that exhaustion is an epigenetically fixed state., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Introduction: Radiofrequency catheter ablation is a common treatment for atrial fibrillation (AF), during which thermal esophageal injury may rarely occur and lead to an atrio-esophageal fistula. Therefore, we studied the utility of the Circa S-Cath™ multi-sensor luminal esophageal temperature (LET) probe to prevent esophageal thermal injury., Methods and Results: Thirty-six patients, enrolled prospectively, underwent circumferential or segmental pulmonary vein isolation for treatment of AF. A maximum ablation electrode temperature of 42ºC was programmed for automatic power delivery cutoff. In addition, energy delivery was manually discontinued when the maximum LET on any sensor of the probe rose abruptly (i.e. ˃0.2ºC) or exceeded 39º C. Esophagoscopy was performed immediately after ablation in 18 patients (with the temperature probe still in place) and at approximately 24 hours after ablation in 18 patients. Esophageal lesions were classified as likely traumatic or thermally related. Of the 36 patients enrolled in the study, 21 had persistent and 15 had paroxysmal AF, average LVEF 57±16% and CHA2DS2VASc score 1.6±1.2 (range 0-4). Average maximum LET was 37.8±1.4ºC, power delivery 31.1±8 watts and ablation electrode temperature 36.4±4.1ºC. Average maximum contact force was 44.5±20.5 grams where measured. Only 1 patient (<3%) had an esophageal lesion that could potentially represent thermal injury and 4 patients (11.1%) had minor traumatic mechanical injury., Conclusions: LET guided titration of power and duration of energy application, using an insulated multi-sensor esophageal temperature probe, is associated with a low risk of esophageal thermal injury during AF ablation. In only rare cases, LET monitoring resulted in the need to manipulate the esophagus to avoid unacceptable temperature rises, that could not be achieved by adjustment of power and duration of energy application.