Accuracy of Static Computer- Assisted Implant Placement in Posterior Edentulous Areas with Different Levels of Tooth- Support by Novice Clinicians

Correct implant placement is necessary for satisfactory implant restoration. Therefore, the use of surgical guide is recommended. This study evaluated the accuracy of implant placement in posterior edentulous areas with different levels of tooth-support by novice clinicians according to fully-guided (FG), pilot-guided (PG), and freehand (FH) placement protocols. A mandibular model with missing first molars was designed. On one side, the model had a bound edentulous area (BEA), and on the other side, a free end edentulous area (FEA). Fourteen clinicians new to implant dentistry participated in the study, and each clinician inserted an implant in the BEA and FEA sites for every placement protocol. Angle, vertical and maximum horizontal platform and apex deviations were measured. The FG placement was more accurate than the PG and FH placements. This was significant for BEA angle deviation, BEA and FEA maximum horizontal platform deviations, and BEA maximum horizontal apex deviation. The PG placement was significantly more accurate than the FH placement for BEA and FEA maximum horizontal platform deviations. FG shows significantly greater angle, maximum horizontal platform and maximum horizontal apex deviations at FEA than BEA. This can be attributed to reduced guide support and the possibility of guide displacement during surgery.

Comparison of the tumor immune microenvironment and checkpoint blockade biomarkers between stage III and IV non-small cell lung cancer

BACKGROUND

Adjuvant immune checkpoint blockade (ICB) following chemoradiotherapy and adding ICB to chemotherapy have been key advances for stages III-IV non-small cell lung cancer (NSCLC) treatment. However, known biomarkers like PD-L1 are not consistently indicative of ICB response. Other markers within the tumor immune microenvironment (TIME) may better reflect ICB response and/or resistance mechanisms, but an understanding of how TIMEs differ between stage III and IV NSCLC has not been explored.

METHODS

Real-world data from unresectable, stage III-IV, non-squamous, pretreatment NSCLCs (stage III n = 106, stage IV n = 285) were retrospectively analyzed. PD-L1 immunohistochemistry (IHC) was compared to CD274 gene expression. Then, differential gene expression levels, pathway enrichment, and immune infiltrate between stages were calculated from whole-transcriptome RNA-seq. Analyses were stratified by EGFR status.

RESULTS

PD-L1 IHC and CD274 expression in tumor cells were highly correlated (n = 295, P < 2.2e-16, ⍴ = 0.74). CTLA4 expression was significantly increased in stage III tumors (P = 1.32e-04), while no differences were observed for other ICB-related genes. Metabolic pathway activity was significantly enriched in stage IV tumors (P = 0.004), whereas several immune-related KEGG pathways were enriched in stage III. Stage IV tumors had significantly increased macrophage infiltration (P = 0.0214), and stage III tumors had a significantly higher proportion of CD4 + T cells (P = 0.017). CD4 + T cells were also relatively more abundant in EGFR-mutant tumors vs. wild-type (P = 0.0081).

CONCLUSION

Directly comparing the TIMEs of stage III and IV NSCLC, these results carry implications for further studies of ICB response in non-resectable stage III NSCLC and guide further research of prognostic biomarkers and therapeutic targets.

Accurate respiratory rate determination using a novel insertable cardiac monitor algorithm: implications for diagnostic and monitoring potentials beyond heart rhythm disorders

Background

Respiratory rate (RR) is a critical vital sign that is highly relevant in patients with cardiopulmonary disorders. The implantable cardiac monitor (ICM) provides useful data pertaining to heart rhythm, but little is known up to this point regarding its potential diagnostic value in the direct measurement of respiratory parameters. The addition of respiration information could improve understanding of overall health status of heart rhythm patients with ICM.

Objective

The primary objective of this study was to evaluate the accuracy of the RR detected by an existing implanted ICM as compared to gold-standard polysomnography (PSG) measurement of respiration.

Methods

This prospective single center study enrolled 25 patients (17 male, 62.7±12.2 yesrs) with an implanted ICM and suspected sleep-disordered breathing. The ICM was custom configured with research software to collect respiration data (Fig. 1). Simultaneous, time-synchronized PSG and ICM data were evaluated in two-minute epochs episodically during the night. The offline novel prototype RR algorithm was evaluated on episodes collected by the ICM and compared against expert manual adjudicated RR from PSG by two separate investigators. The interobserver agreement was assessed using intraclass correlation coefficient (ICC). The performance of the novel algorithm was assessed using Bland-Altman analysis with 95% limits of agreement (LOA).

Results

A total of 495 epochs were graded by two independent observers, with good ICC of 0.83 (95% C.I. 0.79–0.86). Epochs free of severe sleep disordered breathing/apnea (n=363) were included in this analysis with 106 of these containing periods of hypopnea. The development and validation datasets were comprised of 235 and 128 epochs, respectively. In the development data, the mean RR was 14.99±3 breaths per minute, and the mean RR was 13.44±2 breaths per minute in the test data. Using Bland-Altman analysis, the bias for the novel prototype algorithm was only −0.13 and +0.32 breaths per minute with 95% LOA of −2.24 to +1.98 and −2.56 to +3.19 breaths per minute (Fig. 2), in the in the development and test dataset respectively.

Conclusion

The novel prototype algorithm applied to the ICM data provided accurate determination of respiratory rate as compared to gold-standard PSG data. The capability to determine respiratory rate accurately from an existing ICM platform demonstrates the potential to extend the diagnostic power of ICMs beyond heart rhythm abnormalities to address a broad range of comorbidities including breathing disorders and heart failure.

Funding Acknowledgement

Type of funding sources: None.

Clinical, Genomic, and Transcriptomic Data Profiling of Biliary Tract Cancer Reveals Subtype-Specific Immune Signatures

PURPOSE

Biliary tract cancers (BTCs) are aggressive cancers that carry a poor prognosis. An enhanced understanding of the immune landscape of anatomically and molecularly defined subsets of BTC may improve patient selection for immunotherapy and inform immune-based combination treatment strategies.

METHODS

We analyzed deidentified clinical, genomic, and transcriptomic data from the Tempus database to determine the mutational frequency and mutational clustering across the three major BTC subtypes (intrahepatic cholangiocarcinoma [IHC], extrahepatic cholangiocarcinoma, and gallbladder cancer). We subsequently determined the relationship between specific molecular alterations and anatomical subsets and features of the BTC immune microenvironment.

RESULTS

We analyzed 454 samples of BTC, of which the most commonly detected alterations were TP53 (42.5%), CDKN2A (23.4%), ARID1A (19.6%), BAP1 (15.5%), KRAS (15%), CDKN2B (14.2%), PBRM1 (11.7%), IDH1 (11.7%), TERT (8.4%), KMT2C (10.4%) and LRP1B (8.4%), and FGFR2 fusions (8.7%). Potentially actionable molecular alterations were identified in 30.5% of BTCs including 39.1% of IHC. Integrative cluster analysis revealed four distinct molecular clusters, with cluster 4 predominately associated with FGFR2 rearrangements and BAP1 mutations in IHC. Immune-related biomarkers indicative of an inflamed tumor-immune microenvironment were elevated in gallbladder cancers and in cluster 1, which was enriched for TP53, KRAS, and ATM mutations. Multiple common driver genes, including TP53, FGFR2, IDH1, TERT, BRAF, and BAP1, were individually associated with unique BTC immune microenvironments.

CONCLUSION

BTC subtypes exhibit diverse DNA alterations, RNA inflammatory signatures, and immune biomarkers. The association between specific BTC anatomical subsets, molecular alterations, and immunophenotypes highlights new opportunities for therapeutic development.

Next generation sequencing (NGS) to identify relapsed gastrointestinal (GI) solid tumor patients with human leukocyte antigen (HLA) loss of heterozygosity (LOH) for future logic-gated CAR T therapy to reduce on target off tumor toxicity

190

Background: Metastatic colorectal (CRC), pancreatic (PANC), and gastroesophageal (GE) cancers are the leading causes of GI cancer–related mortality (5-yr survival rate, 14%, 3% and ̃5-6%, respectively). T-cell immunotherapy targeting GI-associated tumor antigens has been attempted, but efficacy has been constrained by on-target off-tumor toxicity, limiting the therapeutic window. The Tmod (TM) platform is an AND-NOT logic-gated CAR T modular system, versions of which have a CEA- or MSLN-targeting CAR activator and a separate HLA-A*02-targeting blocker receptor to protect normal cells. Tmod CAR T exploits HLA LOH, common in GI malignancies (10-33% in primary solid tumors [TCGA]) and can kill tumor cells without harming healthy cells in vitro and in vivo. However, the prevalence of HLA LOH across GI tumors is unknown in the real-world setting. We utilized the Tempus xT oncology NGS database of patients with multiple GI tumors. From a standard-of-care NGS assay, GI cancer patients can be readily identified for HLA LOH and future treatment with Tmod CAR T therapy. Methods: The occurrence of HLA LOH in GI tumors of 1439 patients was assessed using paired germline and somatic DNA sequencing using a research assay [6]. CRC, PANC and GE patients with ≥ stage 3 were then extracted, and rates of HLA LOH were identified (ie, whether loss occurred across high-frequency HLA-A alleles). In addition, mutations in KRAS and BRAF, as well as MSI status were stratified to determine any association with HLA-A LOH. Results: HLA-A LOH was detected in 830 (17.3%) of all solid tumor records, and a similar proportion when all GI cancer records were analyzed (17.0%). For GI subtypes, these values ranged from 13.5% to 23.1% (Table). No high-frequency HLA-A allele (A*01, A*02, A*03, A*11) was more likely to be lost. Clinical biomarkers ( KRAS, BRAF and MSI status) were not associated with HLA-LOH. Conclusions: The frequency of HLA LOH among advanced solid tumor cancers in this dataset is 17.3%, with a range of 13.5-23% between CRC, PANC and GE. The HLA LOH frequency observed in these GI tumors is consistent with that in primary tumors from TCGA, which also used germline-matched and tumor samples. Clinical biomarkers were not associated with HLA LOH. Tempus NGS was able to identify HLA LOH, which can be used for Tmod CAR T therapy to an enhanced therapeutic window. Identification of these patients in BASECAMP-1 (NCT04981119) will enable novel Tmod CAR T therapy. [Table: see text]

73 Characterization of tumor-infiltrating T-cell repertoire in human cancers

Background

TCR and BCR repertoire profiling is a promising technique that can provide a clinically useful window into the complex interactions between tumor cells and infiltrating lymphocytes. Despite recent advances in repertoire sequencing methods, the characterization of tumor-infiltrating T-cell repertoires has been limited to small sample sizes due to technical and material constraints. In this study, we constructed a large multidimensional database of repertoire data covering a diverse landscape of HLA genotypes and tumor neoantigens from routine clinical sequencing. We present a descriptive summary of repertoire profiles derived from tens of thousands of tumor samples from over fifty different cancer cohorts and characterize the associations between T-cell repertoires and various clinical and molecular features.

Methods

To enrich immune receptor transcripts detected by the Tempus RNA-sequencing workflow, hybrid capture probes tiling TCR and BCR genes were used. Repertoire profiling reads were aligned, assembled, and annotated against IMGT reference sequences. Repertoires are profiled as a component of Tempus|xT RNA sequencing and are summarized here for >25 thousand tumor samples from over 50 different cancer cohorts.

Results

We demonstrate that the use of TCR/BCR hybrid capture probes is an effective method for enriching immune receptor transcripts in RNA-sequencing data without interfering with downstream transcriptomic analysis. These repertoires were profiled as part of a larger, multimodal DNA/RNA-sequencing pipeline that quantifies a variety of tumor clinical and molecular features. We explored the correlation between high-level repertoire metrics like richness (the number of unique receptor clonotypes in a given repertoire) and clonality/evenness (Shannon entropy) against both gene expression-based metrics (i.e. immune cell infiltration estimates, etc.) and mutational patterns (mutational burden and neoantigen load). Finally, we observed that the repertoire clonality of B-cell and T-cell driven cancers frequently exhibits clear monoclonal dominance for the tumor cells’ lymphoid receptors.

Conclusions

TCR/BCR repertoire profiling can be incorporated into high-volume clinical RNA sequencing to generate a diverse multimodal dataset for studying the tumor-immune microenvironment. By creating a large-scale database of TCR/BCR repertoire profiles from a variety of tissue, HLA genotypes, and mutational contexts, we can better resolve the molecular and clinical correlates of cancer with host adaptive immunity.

Abstract 773: Evaluating clinical features and prognostic factors associated with response to immune checkpoint blockade in mNSCLC patients

In the past decade, immune checkpoint blockade (ICB) has become standard of care for patients with metastatic non-small cell lung cancer (mNSCLC). Biomarkers of response to ICB, such as PD-L1 status, help identify suitable candidates for ICB. However, differences in the underlying clinical features of patients and the association of such features with ICB outcomes has not received significant attention. We sought to evaluate clinical features in mNSCLC patients and determine their prognostic value in predicting response to ICB. We retrospectively analyzed 1,903 patients with mNSCLC using real-world clinical data from the Tempus platform and generated a training and held-out test set with 1,351 and 552 patients, respectively. Clinically relevant features such as age, sex, comorbidity information, smoking status, and self-reported race/ethnicity were selected as clinical features and potential prognostic factors. We used a survival-SVM algorithm to model progression risk based on time to progression (TTP) from the start of first-line, FDA-approved treatment. The predicted risk output of the survival-model was used as a prognostic score for new or held-out patients. We evaluated the prognostic score on an independent clinical-only cohort from ASCO CancerLinQ (n = 3,217). We also examined the utility of the prognostic score by combining it with established biomarkers, such as PD-L1 status , using held-out clinicogenomic data from ICB-treated patients (n = 513). To evaluate model robustness, we examined performance on our held-out test set. We found the combined use of all clinical features produced a more accurate prognostic score for predicting TTP (hazard ratio [HR] = 5.78, P = 1.20e-5) compared to individual clinical features (max individual HR from feature inputs = 1.22, P = 2.55e-3). Next, to evaluate the accuracy of the prognostic score more broadly in mNSCLC irrespective of treatment type, we analyzed an independent cohort of mNSCLC patients from ASCO CancerLinQ. We defined the top 15th percentile as high-risk for progression. We observed a significant stratification between high-risk and other patients (log-rank statistic = 101.68, P = 6.53e-24). Finally, we evaluated the model in the context of predicting ICB outcomes in mNSCLC. We found ICB-treated patients stratified based on prognostic score (15th percentile separation; log-rank statistic = 4.73, P = 0.029). However, when combined with PD-L1 status, we found better stratification of patients (15th percentile separation and PD-L1 positive; log-rank statistic = 14.653, P =1.29e-4) relative to PD-L1 status alone (PD-L1 positive; log-rank statistic = 9.671, P = 1.87e-3). These results suggest that clinical and prognostic factors may augment established biomarkers and improve prediction of response to immune checkpoint blockade in mNSCLC patients.

Citation Format: Prerna Jain, Michelle Stein, Yinjie Gao, Denise Lau, Aly A. Khan. Evaluating clinical features and prognostic factors associated with response to immune checkpoint blockade in mNSCLC patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 773.

Abstract 1487: Cytotoxic CD4+ T cells contribute to anti-tumor immune responses in NSCLC

Immune checkpoint blockade (ICB) is widely used to treat non-small cell lung cancer (NSCLC) patients and works by inhibiting the PD-1/PDL1 axis to reinvigorate exhausted T cells. In the prevailing model, the primary mechanism for direct tumor cell killing occurs through cytotoxic CD8+ T cells. Here, we use single-cell multi-omic profiling (a combination of single-cell RNA sequencing, TCR sequencing, and surface protein profiling) in 10 NSCLC patients to identify a population of CD4+ T cells that are tumor-infiltrating, clonally expanded, and express a cytotoxic gene program. Concordantly, we found in the same patients a subpopulation of tumor cells with elevated HLA class II expression, suggesting a mechanism for tumor-mediated antigen presentation to CD4+ T cells. Finally, we show that a cytotoxic CD4 gene signature is associated with improved progression-free survival in a cohort of 180 NSCLC patients treated with ICB regimens, including those with loss of heterozygosity at the HLA class I locus. Overall, these results suggest a model where cytotoxic CD4+ T cells can perform direct tumor cell killing in a class II restricted manner and that their presence is associated with favorable ICB outcomes in NSCLC.

Citation Format: Denise Lau, Sonal Khare, Derek Reiman, Tim Rand, Ameen A. Salahudeen, Aly Khan. Cytotoxic CD4+ T cells contribute to anti-tumor immune responses in NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1487.

Abstract 1616: Characterizing differences in checkpoint inhibitor biomarkers in a real-world cohort of stage III and IV non-small cell lung cancer patients

Immune checkpoint blockade (ICB) therapies have emerged as an essential treatment modality in lung cancer. While ICB therapies are approved in several indications for stage IV and metastatic non-small cell lung cancers (NSCLC), approvals for early but invasive tumors have been limited. To investigate the molecular landscape potentially underlying this difference, we assessed levels of known ICB biomarkers and transcriptome-wide pathway activity between stage III and IV NSCLC primary tumors across a real-world cohort. Following exome-capture bulk RNA sequencing of tumors with non-squamous NSCLC histology, data underwent quality control and normalization. We employed a linear regression approach adjusted for age, sex, and tumor purity to identify hundreds of differentially expressed (DE) genes by stage (false discovery rate=5%). Correlations were evaluated by Pearson's coefficient, and differences in means were assessed by Mann-Whitney U test and Student's t-test, as appropriate. From KEGG gene set enrichment analysis of the DE genes, we found metabolic pathways were significantly enriched in stage IV tumors. In contrast, several immune-related pathways were relatively depleted in stage IV tumors, including pathways associated with NF-κB signaling, IL-17 signaling, TNF signaling, Th1 and Th2 differentiation, and Th17 differentiation. Consistent with this depletion of immune signaling pathways in stage IV tumors, several important ICB biomarkers including CTLA4 and PDCD1 (PD-1) had increased expression in stage III tumors relative to stage IV. Notably, CD274 (PD-L1) expression did not differ by stage, nor did tumor cell PD-L1 protein levels, as measured by IHC. In addition, PD-L1 gene expression and protein levels were concordant across both stages (P&lt;2.2e-16). Based on these results, we next examined differences in overall level of immune infiltration using estimated immune proportions derived from gene expression data. While overall immune proportion did not differ significantly between stage III and IV tumors, stage III tumors had a significantly higher estimated proportion of CD4+ T cells relative to stage IV, and stage IV tumors had a significantly higher proportion of macrophages relative to stage III. These results demonstrate enrichment of immune activation gene expression pathways and paradoxically, increased expression of immune checkpoint biomarkers in stage III tumors relative to stage IV tumors, suggesting that evolution of metastasis in NSCLC tumors is accompanied by consequential changes in the tumor-immune microenvironment. This comprehensive assessment of the expression of immune checkpoint genes, and the transcriptome more broadly, may help to inform the development of anti-cancer immune modulating agents or use of existing ICB in early-stage NSCLC.

Citation Format: Yinjie Gao, Michelle M. Stein, Prerna Jain, Denise Lau, Kimberly L. Blackwell, Aly A. Khan. Characterizing differences in checkpoint inhibitor biomarkers in a real-world cohort of stage III and IV non-small cell lung cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1616.

Incidence of new-onset atrial fibrillation after cavotricuspid isthmus ablation for isolated typical atrial flutter: a systematic review and meta-analysis

Funding Acknowledgements

Type of funding sources: None.

Background

There is a lack of consensus guidelines regarding the continuation of anticoagulant therapy following cavotricuspid isthmus (CTI) ablation for typical atrial flutter.  This is despite a significant number of patients developing new-onset atrial fibrillation (AF) following the procedure.  Furthermore, a summary of Kaplan-Meier estimates for drug-free, arrhythmia-free survival has never been reported.

Purpose

 To estimate the incidence of drug-free, new-onset AF stratified by rhythm monitoring strategy in patients undergoing  CTI ablation for isolated typical atrial flutter.

Methods

PubMed, Embase and MEDLINE databases were searched to identify relevant studies. Only studies where anti-arrhythmic drugs were discontinued post-ablation and that accounted for patient censoring by reporting results in the form of time to event data were included.  Data was extracted from published Kaplan-Meier curves using a digitizing software and confidence intervals for the survivor function were estimated based on the number at risk at the time point of interest. Results were pooled in a random effects model using the DerSimonian-Laird estimator.

Results

 Thirteen relevant studies incorporating 1712 patients (79 % male, mean age 63.2 +/-11.2 years,  LVEF 55.2 +/-10.8%) were identified. The estimated  freedom from  new-onset atrial fibrillation was 89.7% (95% CI: 80.3-90.1%) at 1 year and 86.2% (95% CI: 78.4-94.0%) at 2 years in patients undergoing predominantly symptom –based monitoring, 74.6% (95%CI: 67.0-82.3%) at 1 year and 69.5% (95%CI: 63.5-75.6%) at 2 years  in patients undergoing regular clinic follow-up with periodic Holter monitoring and 51.4% (95% CI: 41.8-61.0%) at 1 year and 22.7% (95% CI: 8.7% - 36.6%) at 2 years in patients with implantable loop recorders.

Conclusion

 With the advent of implantable loop recorders, it is apparent that most patients with isolated atrial flutter manifest new-onset AF following CTI ablation and the merits of discontinuing anticoagulation must be carefully considered in this population.  Symptom-based monitoring likely severely underestimates the incidence of new-onset AF and may lead to adverse outcomes, particularly in patients with a high risk of stroke.

Real-world experience with the insertion of a new implantable cardiac monitor

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Biotronik SE & Co.KG

OnBehalf

BIO|CONCEPT.BIOMONITOR III study group, BIO|MASTER.BIOMONITOR III study group, BIO|STREAM-ICM study group

Background

Implantable Cardiac Monitors (ICM) provide continuous long-term heart rhythm monitoring. The new ICM BIOMONITOR III / IIIm (BM III) is provided with a single-step insertion tool.

Purpose

To report on the insertion procedure of the BM III in a large real-world patient population.

Methods

The BM III combines a low cross-section (4.5 x 8.5 mm) with an extended ICM length (77 mm, including flexible antenna). It is inserted into subcutaneous tissue with an ‘injection’ tool that forms the pocket and delivers the device in a single step. We report results of the insertion procedure from a pooled data set from the BIO|CONCEPT BM III (completed) and the BIO|MASTER BM III and BIO|STREAM-ICM (ongoing) studies.

Results

From 54 investigational sites in 11 countries, 455 insertions were reported (including 39 BM IIIm). The patients were 63 ± 16 years old, had a BMI of 27.6 ± 5.4, and 43% were women. The indications were syncope or pre-syncope (57%), cryptogenic stroke (23%), management of AF (11%) or other (9%). Insertions took 1.7 ± 1.8 minutes until removal of the insertion tool, 4.7 ± 3.4 minutes until wound closure, and 7.1 ± 5.6 minutes including wound cleaning. The wound was sutured (79%) or closed with staples (10%) or adhesive strips (10%). General anaesthesia was used in 8% of the patients and antibiotic prophylaxis in 50% (44% systemic and 6% local). Insertions took place in the catheter laboratory (62%), operating theatre (22%) or in a consultation room (16%) without specific precautional equipment.

The insertion site was parallel to the heart"s long axis (56%), parasternal (39%), in the 2nd/3rd intercostal space (3.5%), axillary (0.9%) or at the clavicula (0.7%). The device was repositioned in one case (0.2%). 13 adverse events were reported in connection to the insertion procedure. 5 cases of device pocket bleeding or hematoma occurred. In 5 further cases, the device migrated, posing the risk of extrusion, or actually extruded. Three of these cases used only adhesive strips or no wound closure at all. In two cases, an incorrect usage of the incision tool and substantial subcutaneous fatty tissue may have contributed. One device was damaged by a 200 J defibrillation shock with a shock electrode placed over the device. One patient suffered from dyspnoea, possibly due to psychogenic hyperventilation. One patient had a vasovagal syncope due to pain after an insertion with insufficient local anaesthesia. No infections were reported until the day of analysis, which was more than 30 days after insertion in 92% of all cases.

Conclusion

The new BM III was inserted in typically less than 5 minutes until wound closure. A relevant number of insertions took place in a consultation room. Prophylactic antibiotics may be unnecessary, because no pocket infections were reported, although no antibiotic prophylaxis was used in one half of all cases (N = 229). In summary, the insertion with the new tool is fast and has a low risk of complications.

Multimodal profiling of biliary tract cancers to detect potentially actionable biomarkers and differences in immune signatures between subtypes

4023

Background: Biliary tract cancers (BTC) are increasingly subtyped by molecular alterations, but little is known about the relationship between gain-of-function mutations and the RNA transcript expression of immune-related pathways. Methods: A sample of retrospective, clinicogenomic and transcriptomic data from de-identified records of patients with BTC in the Tempus database was selected. We then investigated the relationship between the mutational landscape and immune-related RNA signatures of different anatomic and genomic BTC subtypes. Results: The cohort included 455 samples of intrahepatic bile duct (IH) (n=267), gallbladder (GB) (n=153), and extrahepatic bile duct (EH) (n=35) cancer subtypes. Across all subtypes, we detected alterations in TP53 (43.8%), ARID1A (19.8%), KMT2C (18.2%), BAP1 (14.6%), KRAS (12.7%), TERT (12.0%), IDH1 (11.4%), KMT2D (11.0%), LRP1B (11.0%), and PBRM1 (10.7%), along with FGFR2 fusions (2.6%). Potentially actionable biomarkers ( FGFR2 and NTRK1-3 fusions, IDH1 and BRAFV600E mutations, tumor mutational burden [TMB]>10, HER2 expression, and/or microsatellite instability) were identified in 21.1% of all BTC and 28.6% of IH samples. Mutually exclusive alterations observed between subtypes were TP53 & BAP1, KRAS & BAP1, TP53 & IDH1, KRAS & IDH1, and SMAD4 & BAP1 ( P < 0.001 for all). GB was more inflamed based on RNA signatures and classical immune biomarkers, including PD-L1 and TMB. RNA signature analyses revealed a higher expression of immune-related pathways in GB than IH ( P = 0.001) with no differences in comparison with EH. PD-L1 expression and continuous TMB were elevated in GB versus the other anatomical subtypes. Significant associations were noted between particular genetic mutations and immune profiling features (table). Conclusions: BTC subtypes are diverse in DNA alterations, RNA inflammatory signatures, and immune markers. Notably, potentially actionable biomarkers were identified in a sizable portion of the cohort and varied significantly between subtypes. These results provide guidance for targeted therapy development and support the use of multimodal immune profiling for BTC. For example, GB-specific clinical trials may be considered due to the relative increase in immune-related biomarkers observed in GB and the historically limited success of BTC trials.[Table: see text]

Greater cardiorespiratory fitness reduces incidence of atrial fibrillation: a meta-analysis

Funding Acknowledgements

Type of funding sources: None.

Introduction

 Atrial Fibrillation (AF) is the most common sustained cardiac arrhythmia affecting 1-2% of the global population, with the prevalence of AF increasing dramatically over the past two decades. Although low levels of cardiorespiratory fitness (CRF) and physical activity are predictive of cardiovascular disease onset and mortality, only recently has this emerged as a potential risk factor for AF.

Purpose

The aim of this meta-analysis was therefore to quantify the relationship between CRF, measured by a symptom limited exercise stress test, and incident AF. We hypothesised that there would be an inverse relationship between CRF and the incidence of AF.

Methods

The systematic literature review was conducted using PUBMED, MEDLINE and EMBASE databases, with seven studies meeting the inclusion criteria. A random-effects meta-analysis was then used to compare the multivariate risk estimates of the lowest CRF group from each cohort with the group of the highest CRF.

Results

Data from 206,925 individuals (55.8% males) was used for analysis with a mean age of 55 ± 2.5 years and a mean follow-up period of 10.3 ± 5 years. The total number of AF events across the studies was 19,913. The overall pooled risk of AF in the high-CRF group versus the low-CRF group showed a significant lower risk of incident AF in those with high-CRF (OR: 0.52, 95% CI, 0.44-0.605, p &lt; 0.001). There was evidence of statistical heterogeneity between the studies (I2 = 81%, p &lt; 0.001). AF incidence rates demonstrated an overall decline in rates across the CRF quartiles from low to high. The mean incidence rate for low-CRF was 21 ± 13.4 compared to 6.9 ± 0.7 per 1000 person-years for the high CRF group (p = 0.03).

Conclusion

There is an inverse association between a lower CRF and an increased risk of AF, with a higher level of CRF protective against AF. This study highlights that low-CRF may be an additional risk factor for AF along with already other established lifestyle-based risk factors such as obesity and hypertension. Exercise interventions should be promoted as a primary prevention strategy in those at risk of developing AF with known risk factors. Future studies are warranted to identify the mechanism(s) through which improved CRF confers a reduction in AF incidence.

Abstract Figure. AF risk between high and low-CRF

P1428The outcome of atrial fibrillation ablation in patients undergoing radiofrequency ablation, guided by novel indices incorporating force, time and power

Background

Ablation index (AI) and Lesion Size Index (LSI) are novel parameters that incorporates contact force, time, and power in a weighted formula. Recent studies have shown that such indices predict lesion size and durability of pulmonary vein isolation (PVI). However, the outcomes of ablation guided by indices of force-time-power, such as PV reconnections and atrial fibrillation recurrence, have not been well characterised.

Objectives

To determine the association between indices of force-time-power and acute PV reconnections, procedure and fluoroscopy time and AF recurrence in patients undergoing radiofrequency PVI.

Methods

PUBMED and EMBASE were searched using the terms "catheter ablation" AND "Ablation index" OR "Contact force" OR "Force time integral" OR "lesion size" from inception through 22 May 2019. Studies reporting the procedure time, ablation time, fluoroscopy time, and incidence of AI acute and late reconnection and AF recurrence were included.

Result

 Six studies were included in this study with 530 patients, which n = 416 were paroxysmal AF and 114 non-paroxysmal AF. All procedural characteristics (procedure, radiofrequency, and fluoroscopy times) were similar between AI guided and non-AI guided ablation (p &gt; 0.05). Two studies comparing mean PV reconnections in AI guided vs. AI Blinded. Two studies compared minimum AI in reconnected vs. non-reconnected PV segments. Acute PV segment reconnection was associated with a lower minimum AI vs. non-reconnection. In 3 studies reporting AI guided vs. AI blinded ablations, AI was associated with an increased freedom from AF after average follow-up of 12 months.

Conclusions

Radiofrequency ablation guided by AI/LSI was associated with lower acute PV reconnection rates and improved AF freedom after PVI. There was no difference in fluoroscopy, ablation or procedure time with the use of these novel parameters.

Abstract Figure.

Abstract B57: Integrating RNA expression and visual features for immune infiltrate prediction

Patient responses to cancer immunotherapy are shaped by their unique genomic landscape and tumor microenvironment. Clinical advances in immunotherapy are changing the treatment landscape by enhancing a patient’s immune response to eliminate cancer cells. While this provides potentially beneficial treatment options for many patients, only a minority of these patients respond to immunotherapy. In this work, we examined RNA-seq data and digital pathology images from individual patient tumors to more accurately characterize the tumor-immune microenvironment. Several studies implicate an inflamed microenvironment and increased percentage of tumor-infiltrating immune cells with better response to specific immunotherapies in certain cancer types. We developed NEXT (Neural-based models for integrating gene EXpression and visual Texture features) to more accurately model immune infiltration in solid tumors. To demonstrate the utility of the NEXT framework, we predicted immune infiltrates across four different cancer types and evaluated our predictions against expert pathology review. Our analyses demonstrate that integration of imaging features improves prediction of the immune infiltrate. Of note, this effect was preferentially observed for natural killer, macrophage, and CD8 T cells. In sum, our work effectively integrates both RNA-seq and imaging data in a clinical setting and provides a more reliable and accurate prediction of the immune composition in individual patient tumors.

Citation Format: Derek Reiman, Lingdao Sha, Irvin Ho, Timothy Tan, Denise Lau, Aly A Khan. Integrating RNA expression and visual features for immune infiltrate prediction [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B57.

Abstract PR12: Genomic landscape of immunotherapy resistance in lung cancer

Immune checkpoint inhibitors (ICI) have emerged as an important modality in lung cancer treatment. However, studies have shown that only a fraction of patients will experience any clinical benefit when treated with ICI, and a better understanding of the mechanisms of resistance is still needed. In this study, we sought to characterize the prevalence of known mechanisms of primary and adaptive resistance in the context of the greater immunogenomic landscape in a real-world cohort of 100 non-small cell lung cancer patients treated with ICI. Targeted panel DNA sequencing and whole-transcriptome RNA sequencing were performed on a primary tumor biopsy for each patient, the clinical notes were abstracted and structured, and the digital image of the H&E was processed through a tumor-infiltrating lymphocyte (TIL) analysis pipeline. We evaluated each tumor for evidence of HLA loss of heterozygosity (LOH), mutations in the antigen presentation or interferon gamma signaling pathways, expression of alternative checkpoint molecules, and immune infiltrate exclusion. We found that over 25% of patients in the cohort showed signs of at least one of these mechanisms of ICI resistance. We evaluated the real-world progression-free survival (rwPFS) for these patients and found that the majority experienced a progression event within 6 months of treatment start. This study suggests that primary resistance to ICI affects a significant population of lung cancer patients.

This abstract is also being presented as Poster B22.

Citation Format: Denise Lau, Michelle Stein, Jason Perera, Madhavi Kannan, Aly Khan. Genomic landscape of immunotherapy resistance in lung cancer [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr PR12.

Direct 24-Hour Presumptive Enumeration of Escherichia coli 0157:H7 in Foods Using Hydrophobic Grid Membrane Filter Followed by Serological Confirmation: Collaborative Study

Fifteen laboratories took part in a collaborative study to validate a method for enumerating Escherichia coli 0157:H7. The method is based on use of a hydrophobic grid membrane filter and consists of 24 h presumptive enumeration on SD-39 Agar and serological confirmation to yield a confirmed E. coli 0157:H7 count. Six food products were analyzed: pasteurized apple cider, pasteurized 2% milk, cottage cheese, cooked ground pork, raw ground beef, and frozen whole egg. The test method produced significantly higher confirmed count results than did the reference method for milk, pork, and beef. Test method results were numerically higher than but statistically equivalent to reference method results for cheese, cider, and egg. The test method produced lower repeatability and reproducibility values than did the reference method for most food/inoculation level combinations and values very similar to those of the reference method for the remaining combinations. Overall, 94% of presumptive positive isolates from the test method were confirmed serologically as E. coli 0157:H7, and 98% of these were also biochemically typical of E. coli 0157:H7 (completed test). Corresponding rates for the reference method were 69 and 98%, respectively. On the basis of the results of this collaborative study and the precollaborative study that preceded it, it is recommended that this method be adopted official first action for enumeration of E. coli 0157:H7 in meats, poultry, dairy foods, infant formula, liquid eggs, mayonnaise, and apple cider

Taxonomic Status and Population Oscillations of Aphidius colemani Species Group (Hymenoptera: Braconidae) in Southern Brazil

Aphidius colemani (Viereck) was reported in Brazil before the Biological Control Program of Wheat Aphids (BCPWA) when Mediterranean genotypes were introduced from France and Israel. This species was re-described as a complex called A. colemani group composed of three species. Consequently, uncertainty remains about which parasitoid of the group is occurring in southern Brazil. This study has two main objectives: (i) re-examine the species status of A. colemani group collected during the introduction of parasitoids and from a 10-year (2009-2018) monitoring program in wheat fields in northern Rio Grande do Sul (RS), Brazil; (ii) describe the variation in the population density of parasitoids and its association with meteorological factors during this period. We examined 116 specimens from the Embrapa Wheat entomological collection, and those collected in Moericke traps in Coxilha, RS. All the parasitoids of the A. colemani group from the BCPWA period were identified as Aphidius platensis (Brèthes). In traps, 6541 cereal aphid parasitoids were collected, of which 61.9% (n = 4047) were from A. colemani group and all those were identified as A. platensis. Temperature was the factor that effected population density with the highest number of parasitoids recorded in the winter months. Sex ratio changed between years varying from 0.50 to 0.97. The parasitoid A. platensis was the only species in the A. colemani group sampled during 10 years of monitoring.

Evaluation of VIDAS Listeria monocytogenes II (LMO2) Immunoassay Method for the Detection of Listeria monocytogenes in Foods: Collaborative Study

A multilaboratory study was conducted to compare the VIDAS®Listeria monocytogenes II (LMO2) immunoassay and the standard cultural methods for the detection of Listeria monocytogenes in foods. Five food types—vanilla ice cream, brie cheese, cooked roast beef, frozen green beans, and frozen tilapia fish—at 3 levels were analyzed by each method. A total of 26 laboratories representing government and industry participated. In this study, 1404 test portions were analyzed of which 1152 were used in the statistical analysis. There were 448 positive by the VIDAS LMO2 assay and 457 positive by the standard culture methods. A χ2 analysis of each of the 5 food types, at the 3 inoculation levels tested, was performed. The resulting χ2 value, 0.36, indicates that overall, there are no statistical differences between the VIDAS LMO2 assay and the standard methods at the 5% level of significance.

Evaluation of the VIDAS® Listeria (LIS) Immunoassay for the Detection of Listeria in Foods Using Demi-Fraser and Fraser Enrichment Broths, as Modification of AOAC Official Method 999.06 (AOAC Official Method 2004.06)

A multilaboratory study was conducted to compare the VIDAS® LIS immunoassay with the standard cultural methods for the detection of Listeria in foods using an enrichment modification of AOAC Official Method 999.06. The modified enrichment protocol was implemented to harmonize the VIDAS LIS assay with the VIDAS LMO2 assay. Five food types—brie cheese, vanilla ice cream, frozen green beans, frozen raw tilapia fish, and cooked roast beef—at 3 inoculation levels, were analyzed by each method. A total of 15 laboratories representing government and industry participated. In this study, 1206 test portions were tested, of which 1170 were used in the statistical analysis. There were 433 positive by the VIDAS LIS assay and 396 positive by the standard culture methods. A Chi-square analysis of each of the 5 food types, at the 3 inoculation levels tested, was performed. The resulting average Chi square analysis, 0.42, indicated that, overall, there are no statistical differences between the VIDAS LIS assay and the standard methods at the 5% level of significance.

Enumeration of Total Coliforms and E. coli in Foods by the SimPlate® Coliform and E. coli Color Indicator Method and Conventional Culture Methods: Collaborative Study

The relative effectiveness of the SimPlate® Coliform and E. coli Color Indicator (CEc-CI) method was compared to the AOAC 3-tube Most Probable Number (MPN) methods for enumerating and confirming coliforms and Escherichia coli in foods (966.23 and 966.24). In this study, test portions were prepared and analyzed according to the conditions stated in both the AOAC methods and SimPlate directions for use. Six food types were artificially contaminated with coliform bacteria and E. coli: frozen burritos, frozen broccoli, fluid pasteurized milk, whole almond nut meats, cheese, and powdered cake mix. Method comparisons were conducted. Overall, the SimPlate method demonstrated &lt;0.3 log difference for total coliform and E. coli counts compared to the AOAC reference methods for the majority of food types and levels analyzed. In all cases, the repeatability and reproducibility of the SimPlate CEc-CI method were not different from those of the reference methods and in certain cases, were statistically better than those of the AOAC 3-tube MPN methods. These results indicate that the SimPlate CEc-CI method and the reference culture methods are comparable for enumeration of both total coliforms and E. coli in foods.

Detection of Botulinal Neurotoxins A, B, E, and F by Amplified Enzyme-Linked Immunosorbent Assay: Collaborative Study

An amplified enzyme-linked immunosorbent assay (amp-ELISA) was compared with the AOAC Official Method 977.26 for detection of Clostridium botulinum and its toxins in foods. Eleven laboratories participated and the results of 10 laboratories were used in the study. Two anaerobic culture media, tryptone peptone glucose yeast extract (TPGY) and cooked meat medium (CMM) were used to generate toxic samples with types A, B, E, and F botulinal strains. Nonbotulinal clostridia were also tested. The toxicity of each botulinal culture was determined by the AOAC method, and the cultures were then diluted, if necessary, to high (about 10 000 minimal lethal dose [MLD]/mL) and low (about 100 MLD/mL) test samples. The overall sensitivity of detection in TPGY and CMM cultures with the amp-ELISA was 94.7% at about 100 MLD/mL and 99.6% for samples with ≥10 000 MLD/mL toxicity. The amp-ELISA detection sensitivity for low toxin samples was 92.3% in TPGY and 99.4% in CMM. The false-positive rate ranged from 1.5% for type A to 28.6% for type F in TPGY, and from 2.4% for type A to 11.4% for type F in CMM. Most of the cross-reactivity was due to detection of other botulinal types, especially in high toxin samples. The amp-ELISA could be used to screen suspect cultures for botulinal toxins. Positive amp-ELISA samples would be confirmed by the AOAC reference method.

Determination of Atropine (Hyoscyamine) Sulfate in Commercial Products by Liquid Chromatography with UV Absorbance and Fluorescence Detection: Multilaboratory Study

A liquid chromatographic (LC) method with 2 detection systems for determining atropine (hyoscyamine) sulfate in commercial products was tested in a multilaboratory study. Depending on the type of product, sample solutions are prepared in methanol or methanol–water (1 + 1). The standard solution contains about 1.0 mg atropine sul-fate/100 mL and is prepared in the same solvent used in sample preparation. LC separations are performed on a 7.5 cm Novapak silica column. The mobile phase is prepared by mixing 970 mL methanol with 30 mL of a 1% aqueous solution of 1-pentanesulfonic acid, sodium salt. Detection is by 2 systems, UV absorbance detection at 220 nm and fluorescence detection with excitation at 255 nm and emission at 285 nm. The injection volume is 100 or 200 μL. The following materials were used for the study: 2 separate samples of tablets labeled to contain 0.4 mg atropine sulfate, 2 separate samples of extended-release tablets labeled to contain 0.375 mg hyoscyamine sulfate, one sample of atropine sulfate injection labeled to contain 2 mg/mL, and one sample of 1% (v/v) atropine sul-fate ophthalmic. Eight participants analyzed 2 separate portions of the 6 samples by both detection systems. A ninth participant analyzed the samples in duplicate but only by UV absorbance detection because of the unavailability of a fluorescence detector. The relative standard deviation (RSD) between laboratories ranged from 1.4 to 3.3% for samples of tablets and injections but higher for ophthalmic solutions (5.1–5.2%). A linearity study was conducted in the originating laboratory before the multilaboratory study with 5 solutions ranging in concentration from 0.80 to 1.20 mg atropine sul-fate in 100 mL. Average recoveries were 100.0% by UV absorbance detection and 99.9% by fluorescence detection; the RSDs were 1.1 and 1.2%, respectively.

P3794MOODS: a novel risk score to identify patients with atrial fibrillation and sleep apnoea

Background

Sleep-disordered breathing (SDB) is an important risk factor for developing atrial fibrillation (AF), and treatment of concomitant SDB can improve AF rhythm outcomes. Diagnosis of SDB requires sleep studies which can pose a significant time and resource burden. We sought to develop a prediction score based on clinical characteristics that can help identify AF patients who require further assessment for SDB.

Methods

Prospectively-collected data for 442 consecutive patients treated for AF from 2009 to 2017 were analysed. All patients were considered candidates for rhythm-control and therefore referred for sleep studies. The diagnosis of SDB was confirmed using in-lab polysomnography and classified using the apnoea-hypopnoea-index (AHI), with cut-offs of ≥15/hr and ≥30/hr indicating moderate-to-severe and severe SDB respectively. Patients treated up to 2015 formed the derivation cohort (n=311) and the remainder (n=113) formed the validation cohort. Multivariate logistic regression analysis was used to identify clinical variables predictive of moderate-to-severe SDB. A risk score model was developed based on regression coefficients and tested using receiver-operating-characteristics analyses on the validation cohort.

Results

Overall, mean age was 60±11 years, mean body mass index (BMI) was 30±5 kg/m2 and 69% were men. The prevalence of moderate-to-severe SDB was 33.7%. There were no significant differences in baseline characteristics between the derivation and validation cohorts. Male gender (score=1), overweight (BMI: 25–29 kg/m2, score=2), obesity (BMI≥30 kg/m2, score=3), diabetes (score=1), and stroke (score=2) were significantly independently predictive of moderate-to-severe SDB and formulated the score. The score performed well to predict moderate-to-severe SDB with a C-statistic of 0.73 (95% CI: 0.67–0.79, P<0.001) in the derivation cohort, and 0.67 (95% CI: 0.57–0.77, P<0.001) in the validation cohort. As a rule-out test, a score of ≤3 had a negative predictive value of 77% for moderate-to-severe SDB (91% for severe SDB). A score of ≥4 had an intermediate positive likelihood ratio (PLR) of 2 for moderate-to-severe SDB (2.2 for severe SDB), while a score of ≥5 had a high PLR of 6.5 and 6.8 for moderate-to-severe SDB and severe SDB respectively.

Sensitivity and specificity table

Conclusion

A novel risk score comprising clinical characteristics can identify patients with AF likely to benefit from further assessment for SDB. Application of this model may aid optimise resource utilisation and facilitate timely patient care.

Association between HbA1c and the development of cystic fibrosis-related diabetes

AIMS

To examine HbA_1c as a predictor of risk for future development of cystic fibrosis-related diabetes and to assess the association with the development of retinopathy in people with cystic fibrosis-related diabetes.

METHODS

A 7-year retrospective longitudinal study was conducted in 50 adults with cystic fibrosis, comparing oral glucose tolerance test results with HbA_1c values in predicting the development of cystic fibrosis-related diabetes. Retinal screening data were also compared with HbA_1c measurements to assess microvascular outcome.

RESULTS

An HbA_1c value ≥37 mmol/mol (5.5%; hazard ratio 3.49, CI 1.5-8.1) was significantly associated with the development of dysglycaemia, as defined by the oral glucose tolerance test over a 7-year period. Severity of diabetic retinopathy was associated with a higher HbA_1c and longer duration of cystic fibrosis-related diabetes.

CONCLUSION

There is a link between HbA_1c level and the future development of dysglycaemia in cystic fibrosis based on oral glucose tolerance test, as well as microvascular outcomes. Although current guidance does not advocate the use of HbA_1c as a diagnostic tool in cystic fibrosis-related diabetes, it may be of clinical use in determining individuals at risk of future development of cystic fibrosis-related diabetes.

P2843Impact of bipolar vector orientation and inter-electrode spacing on electrograms during human atrial fibrillation

Background

In patients with atrial fibrillation (AF), local atrial bipolar electrograms (EGM) are clinically used to determine peak-to-peak voltage (Vpp), dominant frequency (DF) and Shannon Entropy (ShEn) for electroanatomical substrate characterization and substrate-based ablation. The effect of bipolar vector orientation and inter-electrode spacing on these EGM-derived measures during AF is unclear.

Methods

To quantify the impact of bipolar vector orientation and inter-electrode spacing, bipolar EGM (10,496 and 20,968 atrial sites, respectively) were reconstructed from unipolar EGM recorded with an array of 18 electrodes in 14 patients with persistent AF. We compared Vpp, DF and ShEn between any two adjacent bipolar vectors with a difference of 45 degree. Vpp, DF and ShEn values were ranked into different classes from highest to lowest value. To quantify the effect of inter-electrode spacing, bipolar EGM were constructed from electrodes spaced 4mm, 8mm, and 12mm apart, respectively.

Results

First, bipolar vector orientation significantly impacts Vpp (maximal difference: 1.341±2.169 mV vs. 0.595±0.652 mV; p<0.01) and the percentage of atrial low voltage areas (Vpp<0.05mV) (maximal difference: 62.31% vs. 32.54%). Bipolar vector orientation also influences DF (maximal difference: 8.547±2.971 Hz vs. 6.360±1.077 Hz; p<0.01) and ShEn (maximal difference: 4.898±0.488 vs. 4.120±0.650; p<0.01) measurements. Second, inter-electrode spacing affects Vppincreasing from 0.854±1.299 mV to 1.013±1.302 mV for 4mm, and 12mm, respectively (p<0.01). The percentage of atrial low voltage areas differed between 53.77% and 42.03% for 4mm and 12mm, respectively. Furthermore, inter-electrode spacing alters DF (maximal difference: 7.316±2.239 Hz vs. 7.234±2.124 Hz; p<0.01) and ShEn (maximal difference: 4.364±0.714 vs. 4.514±0.624; p<0.01) measurements.

Conclusions

Bipolar vector orientation and inter-electrode spacing both significantly affect bipolar EGM-derived measures that may result in significant uncertainty around the electroanatomical substrate characterization in AF patients, which should be considered in the development of future mapping catheter tools and algorithms.

Antimicrobial peptides derived from the cartilage.-specific C-type Lectin Domain Family 3 Member A (CLEC3A) - potential in the prevention and treatment of septic arthritis

OBJECTIVE

To investigate the antimicrobial activity of peptides derived from C-type Lectin Domain Family 3 Member A (CLEC3A), shed light on the mechanism of antimicrobial activity and assess their potential application in prevention and treatment of septic arthritis.

DESIGN

We performed immunoblot to detect CLEC3A peptides in human cartilage extracts. To investigate their antimicrobial activity, we designed peptides and recombinantly expressed CLEC3A domains and used them to perform viable count assays using E.coli, P.aeruginosa and S.aureus. We investigated the mechanism of their antimicrobial activity by fluorescence and scanning electron microscopy, performed ELISA-style immunoassays and transmission electron microscopy to test for lipopolysaccharide binding and surface plasmon resonance to test for lipoteichoic acid (LTA) binding. We coated CLEC3A peptides on titanium, a commonly used prosthetic material, and performed fluorescence microscopy to quantify bacterial adhesion. Moreover, we assessed the peptides' cytotoxicity against primary human chondrocytes using MTT cell viability assays.

RESULTS

CLEC3A fragments were detected in human cartilage extracts. Moreover, bacterial supernatants lead to fragmentation of recombinant and cartilage-derived CLEC3A. CLEC3A-derived peptides killed E.coli, P.aeruginosa and S.aureus, permeabilized bacterial membranes and bound lipopolysaccharide and LTA. Coating CLEC3A antimicrobial peptides (AMPs) on titanium lead to significantly reduced bacterial adhesion to the material. In addition, microbicidal concentrations of CLEC3A peptides in vitro displayed no direct cytotoxicity against primary human chondrocytes.

CONCLUSIONS

We identify cartilage-specific AMPs originating from CLEC3A, resolve the mechanism of their antimicrobial activity and point to a novel approach in the prevention and treatment of septic arthritis using potent, non-toxic, AMPs.

P661Nocturnal hypoxemic burden in ambulatory patients with atrial fibrillation: a disease-orientated assessment of sleep-disordered breathing severity

Background

Studies investigating the relationship between sleep-disordered breathing (SDB) and atrial fibrillation (AF) have largely assessed SDB-severity by the apnea–hypopnea index (AHI). However, the AHI does not incorporate nocturnal hypoxemic burden, which may increase the risk of non-paroxysmal AF (nPAF) as the clinical manifestation of more progressed AF substrates. This investigation sought to systematically characterize and compare the composition of AHI and hypoxemic burden with the aim to defining a disease-orientated metric for SDB-severity best associated with prevalent nPAF.

Methods

Polysomnography including overnight oximetry data were obtained in 435 consecutive ambulatory AF patients to determine the composition of AHI (apneas vs. hypopneas), the number of acute episodic desaturations per hour (oxygen desaturation index, ODI) and the composition of total time spent below 90% oxygen saturation (T90Total) attributed to acute desaturations (T90Desaturation). Logistic regression analysis was used to characterize the association with prevalent nPAF.

Results

One hundred sixty-nine AF patients (38%) had nPAF and one third (n=149, 34%) had moderate-to-severe SDB (AHI>15). 82% of the median total AHI (9.4 [3.6–20.1]) could be attributed to hypopneas. Only 29% of events were associated with episodic desaturations, which contributed to 96% (T90Desaturation) of the variation in T90Total. The high variability in durations and nadirs of distinct desaturation events can expose patients to long T90Total, even if the AHI is low. Not AHI, but T90Total and ODI were associated with nPAF independent of gender and age. However, diabetes, hypertension and body mass index contributed more significantly to the overall risk of nPAF.

Conclusions

In AF patients, hypopneas constitute a majority of respiratory events during sleep. Patients with low AHI can still be exposed to high nocturnal hypoxemic burden, which is mainly a cumulative consequence of episodic desaturations. T90Total and ODI, but not AHI, were associated with nPAF independent of gender and age, but concomitant modifiable risk factors made a more significant contribution to the overall risk of nPAF versus PAF.