Broberg, Craig S.

Abstract This study explores parallels between systemic hypoxia adaptation in high-altitude populations and tumorigenesis. We identified EPAS1, a gene critical for hypoxia adaptation in populations such as Tibetans and Sherpas, as playing a similar adaptive role in tumors arising under hypoxic conditions. Tumors from patients with chronic hypoxia displayed impaired DNA repair and frequent emergence of EPAS1 variants, with frequencies reaching up to 90%, echoing the positive selection seen in high-altitude dwellers. Mechanistically, EPAS1 gain-of-function mutations promote COX4I2 expression, reducing cellular oxygen consumption and supporting tumor proliferation in hypoxia. Analysis of clinical data from patients with hypoxia revealed tissue-specific and time-sensitive tumorigenic effects, particularly impacting oxygen-sensitive cells in the postnatal period. Our findings suggest that EPAS1-driven adaptation mechanisms in high-altitude populations provide a model for understanding tumor evolution under hypoxic stress, highlighting how genetic adaptations to diverse stressors in natural populations may yield insights into tumorigenesis and cancer progression. Significance: This study reveals a broad convergence in genetic adaptation to hypoxia between natural populations and tumors, suggesting that insights from natural populations could enhance our understanding of cancer biology and identify novel therapeutic targets. See related commentary by Lee, p. 875

Introduction: Patients with congenital heart disease (CHD) frequently require implantable cardiac devices. Device infection or malfunction may necessitate lead extraction. Extraction may be challenging due to long lead dwell times, anatomic abnormalities, and prior cardiac surgery. Little is known about extraction outcomes in the CHD population. Methods and Results: This retrospective study included 41 CHD patients and 82 age and gender matched controls that underwent lead extractions at two centers between 2001-2014. Only patients with leads older than 12 months were included. There were 79 leads in CHD patients and 150 in controls. Patients with CHD had a mean age of 39±17 years at extraction and on average their leads had been implanted for 81±84 months, this was not significantly different from the control group. Eighty eight percent of CHD patients had 1 or more cardiac surgeries as compared to only 22% of controls (p<0.001). The number of abandoned leads was also significantly different with 16 abandoned leads in the CHD group and 3 in controls (p<0.001). There was no statistically significant difference in extraction techniques between the groups. Complete extraction was achieved in 94% of patients in both groups. There were no CHD group complications. Control group complications included 3 SVC lacerations requiring sternotomy (one was fatal), and 1 ventricular perforations with tamponade requiring sternotomy. None of these patients had a history of cardiac surgery. The average age of leads in patients with a complication was 15.3 years which was older than the mean lead age seen in the CHD and control populations which was 6.75 and 4.6 years respectively. Conclusions: Lead extraction can be safely performed in patients with CHD. Despite anatomic abnormalities and previous cardiac surgery, the outcome of lead extraction in patients with CHD is comparable to controls. Prior cardiac surgery may lower the risk for extraction complications.

Objectives Women with Turner syndrome (TS) are frequently counselled against pregnancy due to lack of data and unclear aortic dissection risk. However, with advances in fertility therapy, more women with TS are contemplating pregnancy. This study compared rates of adverse cardiovascular (CV) outcomes among: (1) pregnant and non-pregnant women with TS and (2) pregnant women with TS with/without structural heart disease. Methods Retrospective analysis of pregnant and age-matched non-pregnant controls with TS (2005–2017) across 10 CV centres was done. Data were collected at initial evaluation in pregnancy and outcomes were assessed to 6 months postpartum. Adverse CV events were defined as CV death, aortic dissection/rupture and/or aortic intervention. Non-pregnant age-matched controls were followed over the same time period. Results Sixty-eight pregnancies were included (60 women, mean age 33 years, 48% primigravid, 49% fertility therapy, 80% structurally normal heart, 25% XO karyotype). Based on American Society of Reproductive Medicine criteria, 10 pregnancies occurred in women stratified to high-risk category. There were no CV events in the pregnant women or in the non-pregnant women with TS. Obstetric events complicated 12 (18%) pregnancies with 9 (13%) attributed to hypertensive disorder of pregnancy. Fetal events included small for gestational age neonates (18%), preterm delivery (15%) and fetal death (3%). Conclusions This study helps to refine the approach to pregnancy in women with TS. Among women with TS without structural heart disease, pregnancy does not impose an increased risk of CV outcomes. Among women with TS with structural heart disease, the risk of pregnancy is not as prohibitive as previously described but does require ongoing evaluation.

Background In Fontan patients with atrial arrhythmias (AA), non-vitamin K antagonist oral anticoagulants(NOACs) have a class III recommendation according to the Pediatric & Congenital Electrophysiology Society (PACES)/Heart Rhythm Society (HRS) guideline in 2014, due to lack of data on outcomes as opposed to evidence of harm. To address this gap in data, we investigated the safety and efficacy of NOACs in adults with a Fontan circulation in a worldwide study. Methods This is an international multicentre prospective cohort study, using data from the NOTE ( n on-vitamin K antagonist o ral anticoagulants for t hrombo e mbolic prevention in patients with congenital heart disease) registry. The study population comprised consecutive adults with a Fontan circulation using NOACs. Follow-up took place at 6 months and yearly thereafter. The primary endpoints were thromboembolism and major bleeding. Secondary endpoint was minor bleeding. Results From April 2014 onward, 74 patients (mean age 32±10 years (range 18–68), 54% male) with a Fontan circulation using NOACs were included. During a median follow-up of 1.2 (IQR 0.8–2.0) years, three thromboembolic events (2.9 per 100 patient-years (95% CI 0.7 to 7.6)) and three major bleedings (2.9 per 100 patient-years (95% CI 0.7 to 7.6)) occurred in five atriopulmonary Fontan and one total cavopulmonary connection Fontan patients with AA. Fifteen patients experienced minor bleeding episodes (15.8 per 100 patient-years (95% CI 9.1 to 25.2)). In patients (n=37) using vitamin K antagonists (VKAs) prior to the initiation of NOAC, annual incidence of historical thromboembolic events and major bleeding were 2.4% (95% CI 0.4% to 7.4%) (n = 2) and 1.2% (95% CI 0.7% to 5.1%) (n = 1), respectively. Conclusions In this review of the largest Fontan cohort using NOACs with prospective follow-up, NOACs appear to be well tolerated and their efficacy and safety during short-term follow-up seem comparable to VKAs. Longer term data are required to confirm these promising short-term results.