External Validation of 8 Normal Tissue Complication Probability Models for Radiation-Associated Primary Hypothyroidism Using Long-Term Thyroid Function Outcomes

PURPOSE/OBJECTIVE(S)

Primary hypothyroidism is a common late complication following neck irradiation. The reported incidences were as high as 20-50% among head and neck cancer survivors. Several normal tissue complication probability models for radiation-associated primary hypothyroidism have been proposed, but none has been externally validated using long-term thyroid function outcome.

MATERIALS/METHODS

We undertook a systematic review of the literature and identified 8 distinct normal tissue complication probability (NTCP) models for radiation-associated primary hypothyroidism (6 logistic regression models and 2 nomograms). We retrospectively contoured and reviewed the thyroid gland dosimetry of all consecutive head and neck cancer patients who underwent definitive radiotherapy between January 2013 and December 2015 in two tertiary oncology centers. Patients with abnormal pre-radiotherapy thyroid function were excluded. Thyroid function was monitored at least yearly after radiotherapy. Primary hypothyroidism was defined as serum thyroid-stimulating hormone levels above the upper limit of normal. Euthyroid controls were defined as patients who had normal thyroid function at least 5 years beyond the completion of radiotherapy. Diagnostic properties (sensitivity, specificity and accuracy) of the 8 NTCP models were determined. Discrimination and calibration of the models were assessed using c-statistics, discrimination slopes, calibration curves and Brier score.

RESULTS

With a median follow-up of 7.0 years, we identified 216 cases of post-radiation primary hypothyroidism and 120 euthyroid controls within the study period. All four logistic regression models (Boomsma 2012, Rønjom 2013, Shen 2021 and Huang 2021) which were based on mean thyroid dose and thyroid volume demonstrated satisfactory diagnostic performances. The accuracy, c-statistic, discrimination slope and Brier score of these four models were > 0.70 (0.711 - 0.732), > 0.75 (0.763 - 0.765), > 0.20 (0.203 - 0.295) and < 0.20 (0.187 - 0.198), respectively. Calibrations of prediction were excellent at ranges of high predicted probabilities. At ranges of low predicted probabilities, these models underestimated the risk of primary hypothyroidism by 10-20%. Other models or nomograms which utilized alternative radiation dose-volume parameters (e.g., V30, V35 or V50), or without factoring in the variation in thyroid volume, had significantly worse performance in terms of both discrimination and calibration.

CONCLUSION

This large external validation study showed that NTCP models that included thyroid volume and mean thyroid dose had satisfactory performances in predicting long-term thyroid function outcomes following neck irradiation. Refinement is required to optimize calibration in patients deemed at low risk of post-radiation primary hypothyroidism.

Evaluation of prognostic risk models for postoperative pulmonary complications in adult patients undergoing major abdominal surgery: a systematic review and international external validation cohort study

BACKGROUND

Stratifying risk of postoperative pulmonary complications after major abdominal surgery allows clinicians to modify risk through targeted interventions and enhanced monitoring. In this study, we aimed to identify and validate prognostic models against a new consensus definition of postoperative pulmonary complications.

METHODS

We did a systematic review and international external validation cohort study. The systematic review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched MEDLINE and Embase on March 1, 2020, for articles published in English that reported on risk prediction models for postoperative pulmonary complications following abdominal surgery. External validation of existing models was done within a prospective international cohort study of adult patients (≥18 years) undergoing major abdominal surgery. Data were collected between Jan 1, 2019, and April 30, 2019, in the UK, Ireland, and Australia. Discriminative ability and prognostic accuracy summary statistics were compared between models for the 30-day postoperative pulmonary complication rate as defined by the Standardised Endpoints in Perioperative Medicine Core Outcome Measures in Perioperative and Anaesthetic Care (StEP-COMPAC). Model performance was compared using the area under the receiver operating characteristic curve (AUROCC).

FINDINGS

In total, we identified 2903 records from our literature search; of which, 2514 (86·6%) unique records were screened, 121 (4·8%) of 2514 full texts were assessed for eligibility, and 29 unique prognostic models were identified. Nine (31·0%) of 29 models had score development reported only, 19 (65·5%) had undergone internal validation, and only four (13·8%) had been externally validated. Data to validate six eligible models were collected in the international external validation cohort study. Data from 11 591 patients were available, with an overall postoperative pulmonary complication rate of 7·8% (n=903). None of the six models showed good discrimination (defined as AUROCC ≥0·70) for identifying postoperative pulmonary complications, with the Assess Respiratory Risk in Surgical Patients in Catalonia score showing the best discrimination (AUROCC 0·700 [95% CI 0·683-0·717]).

INTERPRETATION

In the pre-COVID-19 pandemic data, variability in the risk of pulmonary complications (StEP-COMPAC definition) following major abdominal surgery was poorly described by existing prognostication tools. To improve surgical safety during the COVID-19 pandemic recovery and beyond, novel risk stratification tools are required.

FUNDING

British Journal of Surgery Society.

A226 SEX-BASED DISPARITY COMPLICATIONS FOLLOWING LIVER TRANSPLANTATION

Background

Sex-based disparity exists in liver transplantation (LT) with women being disadvantaged at every stage of the process starting from assessment to post transplantation (Bryce et al., 2009). The reasons for this are multifactorial and include biological disparities, psychosocial, and allocation inequalities (Burra et al., 2013).

Aims

The purpose of this study was to identify differences in immediate or long-term complications post-LT by sex.

Methods

We analyzed 702 patients who underwent LT at the University of Alberta from 2002 to 2015. Patients aged < 18 years or requiring a repeat or multivisceral transplant were excluded. Renal dysfunction was defined according to the KDIGO criteria. Cardiovascular disease (CVD) was defined as hospitalization for or death from coronary artery disease, cardiac arrest or cerebrovascular disease.

Results

Male patients comprised 69% of the population. Time on the waitlist was similar for men (9.3 ± 11.7 months) and women (9.9 ± 12.3 months; p=0.57). Both sexes were comparable in age (males: 53 ± 10 years; females: 52 ± 11 years; p=0.19), MELD (males: 18 ± 9; females: 19 ± 10; p=0.16) and BMI (males: 27.7 ± 5.7 kg/m²; females: 27.3 ± 6.6 kg/m²; p=0.58). Women had lower creatinine pre-LT (males: 1.1 ± 0.60 mg/dL; females 0.96 ± 0.51 mg/dL; p<0.01). There were no differences in donor age, sex or BMI. Women had significantly longer hospital length of stay (males: 18 days [IQR: 11, 32]; females: 25 days [IQR: 14, 43]; p <0.001). There was no difference in risk of acute kidney injury (OR 1.4 [95% CI: 0.98, 2.1]; p=0.06), infection (OR 1.1 [95% CI: 0.8, 1.5]; p=0.52) or rejection episodes (OR 1.1 [95% CI: 0.8, 1.5]; p=0.74) following LT. Women had a higher risk of CKD post-LT (OR 2.3 [95% CI: 1.6, 3.2]; p<0.0001). There was no difference in de-novo diabetes (males: 22%; females: 16%; p=0.10), hypertension (males: 45%; females: 48%; p=0.41), dyslipidemia (males: 37%; females: 39%; p=0.67) and CVD (males: 20%; females: 19%; p=0.84) post-LT. Graft (males: 11.4 ± 0.4 years; females: 11.8 ± 0.5 years; p=0.32) and patient survival (males: 11.8 ± 0.4 years; females: 12.4 ± 0.5 years; p=0.18) were similar over a median follow up of 6.3 years [IQR: 3.5, 9.9].

Conclusions

Women spend a longer time in hospital and are at an increased risk of CKD following LT. Despite these differences, overall graft and patient survival are comparable. Our data suggest the disparity between sexes likely exists pre-LT and females that undergo LT have similar outcomes to their male counterparts.

Funding Agencies

None

A224 COVID-19 INFECTION IN LIVER TRANSPLANT RECIPIENTS: CLINICAL FEATURES, HOSPITALIZATION, AND MORTALITY FROM A CANADIAN MULTICENTRE COHORT

Background

The COVID-19 pandemic has brought significant challenges to clinicians caring for liver transplant (LT) recipients. Researchers have sought to better understand the risk and clinical outcomes of LT recipients infected with COVID-19 globally, however, there is a paucity of data from within Canada.

Aims

Our multi-center study aims to examine the characteristics and clinical outcomes of LT patients with COVID-19 in Canada.

Methods

We identified a retrospective cohort of adult LT recipients with RT-PCR confirmed COVID-19 from 7 Canadian tertiary care centers between March 2020 and June 2021. Demographic and clinical data were compiled by clinicians within those centers. We identified liver enzyme profile at the time of COVID-19 infection, immunosuppression type and post-infection adjustments, rate of hospitalization, ICU admission, mechanical ventilation, and death.

Results

A total of 49 patients with a history of LT and COVID-19 infection were identified. Twenty nine patients (59%) were male, the median time from LT was 66 months (1, 128) and the median age at COVID-19 infection was 59 years (52, 65). At COVID-19 diagnosis, the median ALT was 37 U/L (21, 41), AST U/L was 34 (20, 37), ALP U/L was 156 (88, 156), Total Bilirubin was 11 umol/L (7, 14), and INR was 1.1 (1.0, 1.1). The majority of patients (92%) were on tacrolimus monotherapy or a combination of tacrolimus and mycophenolate mofetil (MMF); median tacrolimus level at COVID-19 diagnosis was 5.3 ug/L (4.0, 8.1). Immunosuppression was modified in 8 (16%) patients post-infection; either the tacrolimus dose was reduced or MMF was held. One patient developed acute cellular rejection which recovered after re-initiation of the prior regimen. Eighteen patients (37%) required hospitalization, 6 (12%) were treated with dexamethasone, and 3 (6%) required ICU admission and mechanical ventilation. Four patients (8%) died due to complications of COVID-19. On univariate analysis, neither age, sex, co-morbidities nor duration post-transplant were associated with risk of hospitalization.

Conclusions

In our national retrospective study, approximately 40% of patients required hospitalization with a mortality rate of &lt; 10%. Previous studies have shown proximity to LT as an independent factor for mortality with COVID-19; the median time from LT for our patients was 5 years, which may explain the lower mortality rate. Of note, the median tacrolimus levels were much lower in comparison to the target of 8–10 ug/L used in the first year post-transplant. As the landscape of COVID-19 changes with vaccination, evolving treatments, and increasing rates of variant transmission, additional studies are required to continue identifying trends in clinical outcomes.

Funding Agencies

None

Minimally Invasive Surgical Approach for Esophageal Adenocarcinoma in a Patient with Previous Belsey Mark IV Fundoplication: A Case Report

Background: Historically, the management for recurrent or persistent Gastro-esophageal reflux disease included selective vagotomy and fundoplication. Despite these surgical interventions, the risk of Barrett’s esophagus (BE) and subsequent malignant transformation remains, requiring cancer resection surgery. We present a case of a patient with a gastro-esophageal junction (GEJ) adenocarcinoma, who underwent a pediatric thoracotomy and Belsey Mark IV fundoplication, and was successfully treated by Laparoscopic Ivor-Lewis Esophagectomy (LILE). Case Presentation: This 64-year-old gentleman with BE and GEJ adenocarcinoma was previously deemed unsuitable for curative surgery due to clinical staging indicating a tumor length of 10cm and suspected invasion of the left pleura. Further staging by Endoscopic ultrasound indicated no evidence of pleural invasion with the distal esophageal thickening in keeping with his previous Belsey Mark IV fundoplication. He underwent neo-adjuvant chemotherapy and a subsequent LILE with complete laparoscopic reversion of the gastric fundoplication without injury to the gastroepiploic artery or fundus. There was sufficient preservation of conduit length to enable a tension free hand-sewn anastomosis with an uneventful post-operative recovery. Final histopathology confirmed ypT1 ypN0 moderately differentiated adenocarcinoma with R0 resection margins. The patient has completed 24 months of cancer recurrence free surveillance. Conclusion: We describe the successful management of a patient by LILE on a background of previous hiatal fundoplication surgery, previously refused curative surgery. We highlight the importance of EUS as a staging modality for such cases showing invasive disease to increase the final clinical staging accuracy. We suggest a minimally invasive approach may be utilized for successful re-do hiatal dissection as an alternative to a conventional open surgery.

Bilateral idiopathic corneal opacity: A report of Ascher ring and a review of the literature

Purpose

To present a case of a rare entity of Ascher ring, a bilateral corneal stromal opacification.

Observation

A 70-year-old male with no ocular history who presented for cataract evaluation was found to have idiopathic bilateral circular stromal corneal rings.

Conclusions

After completion of extensive history, examination, imaging analyses, and laboratory studies for workup of corneal opacities, we arrived at a diagnosis of Ascher corneal ring, an extremely rare entity.

Importance

A rare entity should be considered after excluding other etiologies.

Explanation-visualised deep learning model for accessory pathway localisation using 12-lead electrocardiography

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): British Heart Foundation Imperial Centre of Research Excellence

Background/Introduction

ECG algorithms for identifying accessory pathway (AP) locations are inaccurate and difficult to use. Human expert interpretation is poorly reproducible. Artificial intelligence (AI) techniques such as machine learning can improve accuracy in classification tasks by eschewing theory-driven predictions. More reproducible and accurate AP localisation could shorten procedure time and personalise ablation consent.

Purpose

We developed a neural network to perform AP localisation using 12-lead ECGs. Its decision-making process was analysed to enable explainability of the neural network.

Methods

A convolutional neural network was trained on raw, digital, intra-procedural 12-lead ECGs of patients with manifest APs who underwent successful ablation. ECGs were labelled with AP locations as left-sided, septal or right-sided using procedure reports, fluoroscopy and electro-anatomical maps. Accuracy of the neural network was assessed via 4-fold cross-validation and was compared to the Arruda algorithm. Five cardiologists were also assessed for their accuracy in determining locations in sub-groups of cases. The neural network was retrospectively analysed to identify areas of ECGs most influential to its predictions using importance mapping.

Results 

In 156 cases, accuracy of the neural network (92.9%) was significantly higher than the Arruda algorithm (76.9%; p &lt; 0.0001) and all five cardiologists (37.5% to 65.9%; p = 0.0001 to 0.0290). Importance mapping demonstrated that the QRS complexes of leads aVL and V1 were perceived as most influential, indicating interrogation of the lateral and anterior-posterior axes respectively.

The figure shows (A) architecture of the neural network, (B) accuracy of the neural network, Arruda algorithm and five cardiologists, (*, p = 0.05 – 0.01; **, p = 0.01 – 0.001; ***, p = 0.001 - 0.0001; ****, p &lt; 0.0001; as compared to the neural network) and (C) example importance maps for 12-lead ECGs of left-sided, septal and right-sided APs (in order from left to right), with darker regions corresponding to greater relative importance. 

Conclusion 

AI ECG interpretation allows accurate, reproducible prediction of AP locations, superior to conventional algorithms and human interpretation. Although AI decision-making is thought of as a ‘black box’, explanation visualisation techniques such as importance mapping allow humans to understand aspects of how a neural network make decisions. A prospectively validated neural network could be integrated into clinical practice to improve pre-procedural AP localisation. Abstract Figure. Summary of results

Non-selective and selective His bundle pacing both preserve left ventricular activation time and pattern

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): British Heart Foundation

Background: His bundle pacing can be achieved in two ways

selective His bundle pacing, where the His bundle is captured alone, and non-selective His bundle pacing, where local myocardium is also captured resulting a pre-excited ECG appearance. We assessed the impact of this ventricular pre-excitation on left and right ventricular dys-synchrony.

Methods

We recruited patients who displayed both selective and non-selective His bundle pacing. We performed non-invasive epicardial electrical mapping to determine left and right ventricular activation times and patterns.

Results

In the primary analysis (n = 20, all patients), non-selective His bundle pacing did not prolong LVAT compared to select His bundle pacing by a pre-specified non-inferiority margin of 10ms (LVAT prolongation: -5.5ms, 95% confidence interval (CI): -0.6 to -10.4, non-inferiority p &lt; 0.0001). Non-selective His bundle pacing did not prolong right ventricular activation time (4.3ms, 95%CI: -4.0 to 12.8, p = 0.296) but did prolong QRS duration (22.1ms, 95%CI: 11.8 to 32.4, p = 0.0003).

In patients with narrow intrinsic QRS (n = 6), non-selective His bundle pacing preserved left ventricular activation time (-2.9ms, 95%CI: -9.7 to 4.0, p = 0.331) but prolonged QRS duration (31.4ms, 95%CI: 22.0 to 40.7, p = 0.0003) and mean right ventricular activation time (16.8ms, 95%CI: -5.3 to 38.9, p = 0.108) compared to selective His bundle pacing.

Activation pattern of the left ventricular surface was unchanged between selective and non-selective His bundle pacing. Non-selective His bundle pacing produced early basal right ventricular activation, which was not observed with selective His bundle pacing.

Conclusions

Compared to selective His bundle pacing, local myocardial capture during non-selective His bundle pacing produces right ventricular pre-excitation resulting in prolongation of QRS duration. However, non-selective His bundle pacing preserves the left ventricular activation time and pattern of selective His bundle pacing. When choosing between selective and non-selective His bundle pacing, left ventricular dyssynchrony is not an important factor. Abstract Figure: Selective vs Non-Selective HBP

Pulmonary artery catheterization in cardiogenic shock: a systematic review and meta-analysis

Background

Cardiogenic shock carries high morbidity and mortality. Pulmonary artery catheterization (PAC) allows invasive hemodynamic assessment and tailored therapy; however, evidence supporting this practice is sparse.

Methods

We performed a systematic review and meta-analysis of observational studies and randomized controlled trials comparing PAC versus no PAC in cardiogenic shock. We searched MEDLINE, EMBASE, Cochrane CENTRAL, and grey literature. We screened references, abstracted data and evaluated risk of bias in duplicate. We pooled data using a random-effects model and evaluated the quality of evidence using GRADE. Outcomes of interest were mortality and length of stay (LOS).

Results

We identified 13 observational studies (1,982,047 patients) and no randomized controlled trials; 12 studies were at high risk of bias. When pooling adjusted results, PAC was associated with reduced mortality at hospital discharge (RR 0.64; 95% CI 0.50–0.82) and at longest available follow-up (RR 0.65; 95% CI 0.49–0.87). Unadjusted LOS was 5.0 days longer (95% CI 4.93–5.07) with PAC. Quality of evidence was very low for all outcomes.

Conclusion

Based on very low quality evidence, PAC use in patients with cardiogenic shock may be associated with lower mortality. The observed increase in hospital LOS may represent survivor bias or relate to more aggressive management with PAC. Overall, these results support consideration of PAC for hemodynamic assessment and tailored therapy in cardiogenic shock.

Funding Acknowledgement

Type of funding source: None

The Spirodela polyrhiza genome reveals insights into its neotenous reduction fast growth and aquatic lifestyle

The subfamily of the Lemnoideae belongs to a different order than other monocotyledonous species that have been sequenced and comprises aquatic plants that grow rapidly on the water surface. Here we select Spirodela polyrhiza for whole-genome sequencing. We show that Spirodela has a genome with no signs of recent retrotranspositions but signatures of two ancient whole-genome duplications, possibly 95 million years ago (mya), older than those in Arabidopsis and rice. Its genome has only 19,623 predicted protein-coding genes, which is 28% less than the dicotyledonous Arabidopsis thaliana and 50% less than monocotyledonous rice. We propose that at least in part, the neotenous reduction of these aquatic plants is based on readjusted copy numbers of promoters and repressors of the juvenile-to-adult transition. The Spirodela genome, along with its unique biology and physiology, will stimulate new insights into environmental adaptation, ecology, evolution and plant development, and will be instrumental for future bioenergy applications.

Spirodela, or duckweed, is a basal monocotyledonous plant with both pharmaceutical and commercial value. Here, the authors sequence the genome of Spirodela polyrhiza, suggesting its genome has evolved by neotenous reduction and clonal propagation, and provide a platform for future comparative genomic studies in angiosperms.

Improved upper limits on the stochastic gravitational-wave background from 2009-2010 LIGO and Virgo data

Gravitational waves from a variety of sources are predicted to superpose to create a stochastic background. This background is expected to contain unique information from throughout the history of the Universe that is unavailable through standard electromagnetic observations, making its study of fundamental importance to understanding the evolution of the Universe. We carry out a search for the stochastic background with the latest data from the LIGO and Virgo detectors. Consistent with predictions from most stochastic gravitational-wave background models, the data display no evidence of a stochastic gravitational-wave signal. Assuming a gravitational-wave spectrum of Ω_{GW}(f)=Ω_{α}(f/f_{ref})^{α}, we place 95% confidence level upper limits on the energy density of the background in each of four frequency bands spanning 41.5-1726 Hz. In the frequency band of 41.5-169.25 Hz for a spectral index of α=0, we constrain the energy density of the stochastic background to be Ω_{GW}(f)<5.6×10^{-6}. For the 600-1000 Hz band, Ω_{GW}(f)<0.14(f/900  Hz)^{3}, a factor of 2.5 lower than the best previously reported upper limits. We find Ω_{GW}(f)<1.8×10^{-4} using a spectral index of zero for 170-600 Hz and Ω_{GW}(f)<1.0(f/1300  Hz)^{3} for 1000-1726 Hz, bands in which no previous direct limits have been placed. The limits in these four bands are the lowest direct measurements to date on the stochastic background. We discuss the implications of these results in light of the recent claim by the BICEP2 experiment of the possible evidence for inflationary gravitational waves.

Urinary tract infection and vesicoureteral reflux in children with mild antenatal hydronephrosis

OBJECTIVE

The postnatal management of mild antenatal hydronephrosis (ANH) remains controversial. The purpose of this study was to evaluate the incidence of UTI and VUR in children with mild ANH in order to determine the necessity of antibiotic prophylaxis (ABP) and VCUG.

METHOD

The data of 1511 patients with various grades of ANH who were referred to Department of Urology, Boston Children's Hospital between January 1998 and January 2010 were reviewed and 760 patients who had mild ANH were identified. The inclusion criteria were: 1) A confirmed report of ANH or actual prenatal ultrasound (US) images. 2) Postnatal evaluation and management conducted at the hospital. 3) Persistent mild hydronephrosis on the first US done between two weeks and three months of age. 4) No other US findings such as ureteral dilatation, duplication anomalies or bladder abnormalities. 5) At least one three-month follow up. Univariate statistical analysis was performed using a Student's t test.

RESULTS

Of the 760 patients who were identified, 608 (80%) were males, and 225 (30%) had bilateral mild hydronephrosis. Of these, 475 patients (63%) underwent an initial screening VCUG. VUR was identified in 13 patients (1.7%) with grades varying from 1 to 5. At follow up, hydronephrosis resolved in 67% of the renal units and worsened in 3.3%. Among the 692 patients with available follow-up data, 23 (3.3%) had a documented UTI. Twelve of these children had an initial screening VCUG that was negative for VUR. Of these 12 patients, seven underwent a subsequent RNC with none having VUR; five of the 12 patients did not undergo a repeat evaluation for VUR (four had a UTI after the screening VCUG and one had an afebrile UTI). Eleven of the 23 children with mild ANH did not have an initial screening VCUG, and all underwent a subsequent VCUG/RNC. Only two children were then found to have VUR Grade 4-5.

CONCLUSION

The incidence of UTI and VUR in children with mild ANH is low. Consequently, routine VCUG screening for VUR and the use of long-term ABP is not necessary for all patients with asymptomatic mild AHN. Evaluation for VUR in children with mild ANH should be reserved for those who subsequently present with a UTI.

Constraints on cosmic strings from the LIGO-Virgo gravitational-wave detectors

Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs from cosmic microwave background measurements and pulsar timing data. In particular, if the size of loops is given by the gravitational backreaction scale, we place upper limits on the string tension Gμ below 10(-8) in some regions of the cosmic string parameter space.