Cardiac muscle-restricted partial loss of Nos1ap expression has limited but significant impact on electrocardiographic features

Genome-wide association studies have identified sequence polymorphisms in a functional enhancer of the NOS1AP gene as the most common genetic regulator of QT interval and human cardiac NOS1AP gene expression in the general population. Functional studies based on in vitro overexpression in murine cardiomyocytes and ex vivo knockdown in zebrafish embryonic hearts, by us and others, have also demonstrated that NOS1AP expression levels can alter cellular electrophysiology. Here, to explore the role of NOS1AP in cardiac electrophysiology at an organismal level, we generated and characterized constitutive and heart muscle-restricted Nos1ap knockout mice to assess whether NOS1AP disruption alters the QT interval in vivo. Constitutive loss of Nos1ap led to genetic background-dependent variable lethality at or right before birth. Heart muscle-restricted Nos1ap knockout, generated using cardiac-specific alpha-myosin heavy chain promoter-driven tamoxifen-inducible Cre, resulted in tissue-level Nos1ap expression reduced by half. This partial loss of expression had no detectable effect on the QT interval or other electrocardiographic and echocardiographic parameters, except for a small but significant reduction in the QRS interval. Given that challenges associated with defining the end of the T wave on murine electrocardiogram can limit identification of subtle effects on the QT interval and that common noncoding NOS1AP variants are also associated with the QRS interval, our findings support the role of NOS1AP in regulation of the cardiac electrical cycle.

Ret deficiency decreases neural crest progenitor proliferation and restricts fate potential during enteric nervous system development

The receptor tyrosine kinase RET plays a critical role in the fate specification of enteric neural crest-derived cells (ENCDCs) during enteric nervous system (ENS) development. RET loss of function (LoF) is associated with Hirschsprung disease (HSCR), which is marked by aganglionosis of the gastrointestinal (GI) tract. Although the major phenotypic consequences and the underlying transcriptional changes from Ret LoF in the developing ENS have been described, cell type- and state-specific effects are unknown. We performed single-cell RNA sequencing on an enriched population of ENCDCs from the developing GI tract of Ret null heterozygous and homozygous mice at embryonic day (E)12.5 and E14.5. We demonstrate four significant findings: 1) Ret-expressing ENCDCs are a heterogeneous population comprising ENS progenitors as well as glial- and neuronal-committed cells; 2) neurons committed to a predominantly inhibitory motor neuron developmental trajectory are not produced under Ret LoF, leaving behind a mostly excitatory motor neuron developmental program; 3) expression patterns of HSCR-associated and Ret gene regulatory network genes are impacted by Ret LoF; and 4) Ret deficiency leads to precocious differentiation and reduction in the number of proliferating ENS precursors. Our results support a model in which Ret contributes to multiple distinct cellular phenotypes during development of the ENS, including the specification of inhibitory neuron subtypes, cell cycle dynamics of ENS progenitors, and the developmental timing of neuronal and glial commitment.

Impact of co-morbidities on survival after heart transplant in females of childbearing age: analysis of the International Society for Heart and Lung Transplantation (ISHLT) Registry

Background

Data on life expectancy specific to female heart transplant (HT) recipients of reproductive age are lacking, but are needed to inform shared decision making at the time of pre-conception counseling. We analyzed the ISHLT registry for post-transplant survival and studied the impact of co-morbidities in women of childbearing age.

Methods

Female HT recipients reported to the ISHLT registry who were aged 15–45 yrs at time of HT were included in this retrospective analysis. Primary outcome was post-transplant survival. Secondary outcomes included the impact of co-morbidities on conditional survival at 5, 10 and 15 years.

Results

Of 121,501 HT recipients (Jan 1992–June 2018), 30,179 (24.8%) were women. 9,229 (7.6%) were 15–45 yrs at time of HT. Overall median post-transplant survival was 15.2 yrs. Diabetes mellitus (DM) and/or severe chronic kidney disease (CKD) at HT adversely impacted long-term survival (Figure 1). Co-morbidities including cardiac allograft vasculopathy (CAV), DM and CKD negatively impacted 5yr and 10yr conditional survival, individually as well as a combination (Figure 2). 15yr conditional survival confirmed the negative impact of DM and CKD, while CAV did not reach statistical significance.

Conclusion

Female HT recipients of childbearing age have favorable survival post-HT. Conditional survival at 5 and 10 yrs is negatively impacted by CAV, DM and CKD. The quantification of survival outcomes after heart transplant in women of childbearing age may improve counseling as part of pre-conception informed decision making.

Funding Acknowledgement

Type of funding sources: None.

Impact of primary diagnosis on survival after heart transplant in female recipients of childbearing age: an analysis of the International Society for Heart and Lung Transplantation (ISHLT) Registry

Background

Women undergoing heart transplantation (HT) for peripartum cardiomyopathy (PPCM) have been reported to have inferior post-transplant survival. Specific data on the impact of pre-transplant diagnosis on survival in female HT recipients of childbearing age are lacking, but important for pre-conception counseling of women considering a pregnancy.

Methods

Retrospective data analysis was conducted using the ISHLT Registry. The primary aim was to study the impact of pre-transplant diagnosis and alloimmunisation on post-transplant survival in women aged 15–45 yrs at time of HT. Secondary outcomes included the impact of primary diagnosis on conditional survival at 5, 10 and 15-yrs post HT.

Results

Of 121,501 HT recipients (Jan 1992–June 2018), 30,179 (24.8%) were women. 9,229 (7.6%) were 15–45 yrs at time of HT. Peripartum cardiomyopathy (PPCM) and congenital heart diseases (CHD) was the primary diagnosis in 8.9% and 9.3%, respectively. Overall median post-transplant survival was 15.2 yrs. Female with PPCM were associated with higher alloimmunisation (Figure 1). PPCM was associated with lower survival (median survival in PPCM vs CHD vs other: 9.1 years vs 15.2 years vs 15.5 years respectively, p<0.05). This was not entirely explained by higher alloimmunisation in this group (Figure 2A). Five-year conditional survival of recipients of childbearing age was significantly affected by primary diagnosis of PPCM, and by pediatric status at HT, defined as age <18-yrs (PPCM vs other diagnosis p<0.05; pediatric vs non-pediatric p 0.003), whilst 10- and 15-year conditional survival was not. The difference in 5-year conditional outcome between PPCM and other diagnosis, was not significant however when female recipients were grouped according to their level of alloimmunisation (Figure 2B).

Conclusion

PPCM as the primary indication for HT is associated with a worse post HT survival. Our data suggest that this is not entirely explained by alloimmunisation. The impact of previous PPCM appears to be greatest in the first 5 yrs post HT. Further research is needed to fully elucidate the mechanisms associated with worse survival in this group and help inform pre-conception counseling in those HT recipients considering a subsequent pregnancy.

Funding Acknowledgement

Type of funding sources: None.

Patterns of anticoagulant prescribing and renal function changes in patients with atrial fibrillation

Background

The prevalence of atrial fibrillation (AF) is nearly three times higher in patients with chronic kidney disease (CKD) than the general population. These patients have an increased risk of stroke and systemic thromboembolism (SSE) as well as bleeding. The role for direct oral anticoagulants (DOACs) in those with advanced CKD and AF remains controversial. Studies show that patients on DOACs for AF with advanced CKD have similar risk of SSE and bleeding compared to those on warfarin, but these failed to account for changes in renal function over time.

Purpose

We sought to evaluate the pattern of oral anticoagulant prescribing, class switching, discontinuation and renal function trajectory in patients with AF in the last decade, coinciding with the development of DOACs.

Methods

Using linked administrative databases, we assessed patients 66 years of age and older with a new diagnosis of non-valvular AF between April 1, 2012 and March 31, 2020 who were started on oral anticoagulation within 90 days of diagnosis. Participants required a baseline serum creatinine (Cr) measurement in the year preceding AF diagnosis. Cr values were used to calculate the estimated glomerular filtration rate (eGFR) using the CKD Epidemiology Collaboration equation. Kidney function was tracked at baseline and longitudinally among patients prescribed DOACs versus warfarin using the Laboratories Information System. Anticoagulant class switching was tracked and discontinuation was defined if a new prescription for anticoagulation was not filled after 90 days of their last prescription ending.

Results

A total of 57,574 participants were included in the study; 48,662 were started on DOACs and 8,912 were started on warfarin. In April 2012, 83.8% of patients were prescribed warfarin; however, the proportion of first prescriptions significantly evolved over time to DOACs (Figure 1). Of those started on DOACs, 13,383 (27.5%) discontinued therapy, 34,918 (71.8%) remained on therapy and 361 (0.7%) switched to warfarin. The rate of discontinuation among those started on warfarin was higher with 4,144 (46.5%) stopping, 3,172 (35.6%) continuing therapy and 1,596 (17.9%) switching to DOACs. Most patients (75.6%) who switched to DOACs from warfarin remained on DOACs until the occurrence of dialysis, renal transplantation, death, or the last follow-up date (March 31, 2020). At baseline, the mean eGFR in the warfarin group was 56.2 compared with 66.3 mL/min/1.73 m2 in the DOAC group (p<0.01). Over the course of study, more than half of the subjects in both groups had a 20% or more decline in eGFR (Figure 2).

Conclusion

Given the degree of renal function decline and frequency of anticoagulant class switching in our cohort, existing observational studies comparing DOACs to warfarin in patients with AF and CKD may be limited. In order to better compare DOACs to warfarin in this population, time-varying covariates like renal function should be included in modelling.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): CIHR Foundation Grant

Multiple, independent, common variants at RET, SEMA3 and NRG1 gut enhancers specify Hirschsprung disease risk in European ancestry subjects

PURPOSE

Hirschsprung disease (HSCR) is a developmental disorder of the enteric nervous system (ENS) characterized by congenital aganglionosis arising from coding variants in ENS genes causing partial or total loss-of-function. Low-penetrance, common, noncoding variants at RET, SEMA3 and NRG1 loci are also associated with HSCR, with small-to-moderate loss of gene expression mediated through sequence variants in cis-regulatory elements (CRE) as another causal mechanism. Since these latter variants are common, many individuals carry multiple risk variants. However, the extent and combinatorial effects of all putative CRE variants within and across these loci on HSCR is unknown.

METHODS

Using 583 HSCR subjects, one of the largest samples of European ancestry studied, and genotyping 56 tag variants, we evaluated association of all common variants overlapping putative gut CREs and fine-mapped causal variants at RET, SEMA3 and NRG1.

RESULTS

We demonstrate that 28 and 8 tag variants, several of which are genetically independent, overlap putative-enhancers at the RET and SEMA3 loci, respectively, as well as two fine-mapped tag variants at the NRG1 locus, are significantly associated with HSCR. Importantly, disease risk increases with increasing numbers of risk alleles from multiple variants within and across these loci, varying >25-fold across individuals.

CONCLUSION

This increasing allele number-dependent risk, we hypothesize, arises from HSCR-relevant ENS cells sensing the reduced gene expression at multiple ENS genes since their developmental effects are integrated through gene regulatory networks.

The Role of DNA Methylation in Transcriptional Regulation of Pro-Nociceptive Genes in Rat Trigeminal Ganglia

Epigenetic modulation by DNA methylation is associated with aberrant gene expression in sensory neurons, which consequently leads to pathological pain responses. In this study, we sought to investigate whether peripheral inflammation alters global DNA methylation in trigeminal ganglia (TG) and results in abnormal expression of pro-nociceptive genes. Our results show that peripheral inflammation remotely reduced the level of global DNA methylation in rat TG with a concurrent reduction in DNMT1 and DNMT3a expression. Using unbiased steps, we selected the following pro-nociceptive candidate genes that are potentially regulated by DNA methylation: TRPV1, TRPA1, P2X3, and PIEZO2. Inhibition of DNMT with 5-Aza-dC in dissociated TG cells produced dose-dependent upregulation of TRPV1, TRPA1, and P2X3. Systemic treatment of animals with 5-Aza-dC significantly increased the expression of TRPV1, TRPA1, and PIEZO2 in TG. Furthermore, the overexpression of DNMT3a, as delivered by a lentiviral vector, significantly downregulated TRPV1 and PIEZO2 expression and also reliably decreased TRPA1 and P2X3 transcripts. MeDIP revealed that this overexpression also significantly enhanced methylation of CGIs associated with TRPV1 and TRPA1. In addition, bisulfite sequencing data indicated that the CGI associated with TRPA1 was methylated in a pattern catalyzed by DNMT3a. Taken together, our results show that all 4 pro-nociceptive genes are subject to epigenetic modulation via DNA methylation, likely via DNMT3a under inflammatory conditions. These findings provide the first evidence for the functional importance of DNA methylation as an epigenetic factor in the transcription of pro-nociceptive genes in TG that are implicated in pathological orofacial pain responses.

P6312Pregnancy outcomes in women with cardiothoracic transplants: a systematic review and meta-analysis

Background

Increasing numbers of women with heart-lung transplants (HLT) are now planning and continuing with pregnancies. The risks of pregnancies in these women have not been systematically assessed.

Methods

A search strategy was designed for MEDLINE, EMBASE, and Cochrane Central from inception to January 2018 to identify studies reporting outcomes in three or more pregnancies following HLT. Pooled incidence of maternal outcomes and fetal and neonatal outcomes were calculated using random-effects meta-analysis and reported per 100 pregnancies with 95% confidence intervals (CI). Risk-of-bias was determined using the Joanna Briggs Checklist for Case Series. Subgroup analysis was conducted based on transplanted organ.

Results

A total of 3658 records were identified, 172 full texts reviewed, and 12 studies included. The included studies reported on 385 pregnancies in 272 transplant recipients. Maternal complications included mortality during pregnancy [0.5% (0, 1.1%)], mortality during the specified follow-up period [15.4% (10,4, 20.3%)], graft rejection during pregnancy [7.4% (4.2, 10.5%)], preeclampsia [12.3% (7.2%, 17.5%)], gestational diabetes [6.4% (2.6, 10.1%)], and caesarean deliveries [41.4% (33.4, 48.7%)]. As many as 78.4% (69.8, 86.9%) pregnancies resulted in live births. Of the remainder, 13.6% (6.3, 20.9%) resulted in miscarriages (fetal loss under 20 weeks of gestation), 2% (0.3, 3.7%) resulted in stillbirths (fetal loss after 20 weeks of gestation), and 6.8% (4.3, 9.3%) in pregnancy terminations for various reasons. Of those born live, 3.4% (1.3, 5.6%) succumbed in the neonatal period. Over half the pregnancies [51.2% (31, 71.3%)] resulted in preterm deliveries (<37 weeks of gestation). There were subgroup-specific variations in the prevalence of complications. For example, lung transplant recipients were less likely than heart transplant recipients to have pregnancies complicated by preeclampsia [8.3% (3.0, 13.6%) vs. 17.8% (10.8, 24.8%)] suffer maternal mortality during the follow up period [41.4% (23.4, 59.3%) vs. 10.8% (5.9, 15.8%)]. Studies had a moderate risk-of-bias.

Conclusions

Although large proportions of pregnancies in women with HLT result in live births and few maternal deaths occur during pregnancy, these women are at increased risk for preeclampsia, preterm birth, perinatal mortality and maternal mortality following childbirth. Subgroup-specific variations should be taken into account while counselling HLT recipients contemplating pregnancies.

Acknowledgement/Funding

None

P2262Intensity and cost of health care at the end of life among patients with heart failure

Background

Health care utilization increase towards the end of life. There is little known about the intensity of care, including use of in-hospital services, critical care units, and invasive procedures at the end of life in heart failure (HF).

Aims

To determine the type and intensity of health care services offered at the end of life to patients with HF, and to establish the determinants of and costs associated with death in the hospital versus at home.

Methods

We conducted a retrospective cohort study of adults (≥18 years) who died between April 1, 2004 and March 31, 2017 in Ontario, Canada. We included decedents with a diagnosis of HF in the 2 years preceding their death and a hospitalization for HF in their last year of life. We obtained demographic, clinical, healthcare utilization, and healthcare cost data from population-based administrative databases, using unique encrypted identifiers to link records. We calculated direct costs from the perspective of the Ministry of Health in our publicly-funded healthcare system. We used descriptive statistics and a 2-level multivariable logistic regression model) with patients (1st level) nested in regions (2nd level) to assess for predictors of death in the hospital versus at home.

Results

We identified 396,024 adults with HF who died between April 1, 2004 and March 31, 2017. Mean (standard deviation [SD]) age at death was 81.8 (10.7) years, and 48.5% were men. During the last 6 months of life, patients commonly experienced hospitalizations (78.1%), care from >10 different physicians (62.2%); intensive care unit (ICU) admissions (26.4%); mechanical ventilation (18.1%); hemodialysis (6.2%); and cardiac catheterization (3.7%). In the last 6 months of life, patients spent a mean (SD) of 17.4 (23.0) days in the hospital; 2.5 (8.3) days in an ICU; and 1.6 (7.9) days on a ventilator. While the proportion of deaths at home increased from 32.6% in 2004–2005 to 38% in 2016–2017, a majority of patients (53.4%) died in hospital during the study period. Factors independently associated with in-hospital death included age (OR 0.53 [95% CI 0.51–0.55] for age >85 years vs <60 years), sex (OR 0.88 [95% CI 0.87–0.89] for female vs male), and socioeconomic status (OR 0.87 [95% CI 0.85–0.89] for highest vs lowest income quintile). Palliative care services in the last 6 months of life was associated with higher odds of in-hospital death (OR 1.73 [95% CI 1.70–1.76]). Death in hospital was associated with higher mean [SD] healthcare costs in the terminal 6 months of life than death out of hospital ($52,349 [55,649] vs $35,943 [31,907]).

Conclusion

In this large cohort study in Ontario, Canada, patients with HF commonly received in-hospital, intensive, and invasive care in the last 6 months of life, and a majority of patients died in hospital. Death in hospital was associated with higher costs of care in the terminal 6 months than death outside hospital.

Acknowledgement/Funding

Heart and Stroke Foundation of Ontario, Canadian Institutes of Health Research

P3519Sex-based disparities in end of life care among patients with heart failure

Background

There are sex-based disparities in care and outcomes among patients with heart failure (HF), but the association between sex and health care services received at the end-of-life health is unknown.

Purpose

To assess for sex-based differences in location of death and the type and intensity of health care services received at the end of life among patients with HF.

Methods

We conducted a retrospective cohort study of adults (≥18 years) who died between April 1, 2004 and March 31, 2017 in Ontario, Canada. We included decedents who had a diagnosis of HF and a hospitalization for HF in the year preceding their death. We obtained demographic, clinical, health care utilization, and healthcare system cost data from population-based administrative databases, using unique encrypted identifiers to link records. We used descriptive statistics and a 2-level multivariable logistic regression model with patients (1st level) nested in regions (2nd level) to assess whether sex was independently associated with death in hospital.

Results

We identified 396,024 adults (51.5% women) who died of HF between April 1, 2004 and March 31, 2017. Mean (SD) age at death was 81.8 (10.7) years and a majority of deaths (53.4%) occurred in the hospital. During the last 6 months of life, a significantly lower proportion of women than men experienced emergency department visits (81.7% vs 86.5%; p<0.001); hospitalizations (75.6% vs 80.8%; p<0.001); intensive care unit (ICU) admissions (22.8% vs 30.1%; p<0.001); mechanical ventilation (15.5% vs 20.8%; p<0.001); cardiac catheterization (2.8% vs 4.6%; p<0.001); coronary revascularization (1.5% vs 2.6%; p<0.001); hemodialysis (4.8% vs 7.7%; p<0.001); or care from 10 or more different physicians (57.6% vs 67.1%; p<0.001). In the last 6 months of life, women spent fewer days than men in the hospital (mean 16.4 vs 18.3; mean difference [MD] 1.9 [95% confidence interval 1.7–2.0]; p<0.001), in an ICU (mean 2.1 vs 3.0; MD 0.9 [95% CI 0.8–0.9]; p<0.001), and on a ventilator (mean 1.4 vs 1.9; MD 0.5 [95% CI 0.5–0.5]; p<0.001). These differences persisted and remained significant in the last month of life. There was no difference in the proportion of women vs men receiving palliative care services (45.1% vs 45.0%; p=0.53) in the last 6 months of life. After adjusting for age, socioeconomic status, comorbidities, place of residence, and year of death, women had lower odds of dying in a hospital than men (adjusted odds ratio 0.88 [95% CI 0.87–0.89]).

Conclusion

In this large cohort study in Ontario, Canada, women with HF received disproportionately lower in-hospital and invasive care services than men in their last 6 months of life and were more likely than men to die at home.

Acknowledgement/Funding

Canadian Institutes of Health Research

Critical care usage after major gastrointestinal and liver surgery: a prospective, multicentre observational study

BACKGROUND

Patient selection for critical care admission must balance patient safety with optimal resource allocation. This study aimed to determine the relationship between critical care admission, and postoperative mortality after abdominal surgery.

METHODS

This prespecified secondary analysis of a multicentre, prospective, observational study included consecutive patients enrolled in the DISCOVER study from UK and Republic of Ireland undergoing major gastrointestinal and liver surgery between October and December 2014. The primary outcome was 30-day mortality. Multivariate logistic regression was used to explore associations between critical care admission (planned and unplanned) and mortality, and inter-centre variation in critical care admission after emergency laparotomy.

RESULTS

Of 4529 patients included, 37.8% (n=1713) underwent planned critical care admissions from theatre. Some 3.1% (n=86/2816) admitted to ward-level care subsequently underwent unplanned critical care admission. Overall 30-day mortality was 2.9% (n=133/4519), and the risk-adjusted association between 30-day mortality and critical care admission was higher in unplanned [odds ratio (OR): 8.65, 95% confidence interval (CI): 3.51-19.97) than planned admissions (OR: 2.32, 95% CI: 1.43-3.85). Some 26.7% of patients (n=1210/4529) underwent emergency laparotomies. After adjustment, 49.3% (95% CI: 46.8-51.9%, P<0.001) were predicted to have planned critical care admissions, with 7% (n=10/145) of centres outside the 95% CI.

CONCLUSIONS

After risk adjustment, no 30-day survival benefit was identified for either planned or unplanned postoperative admissions to critical care within this cohort. This likely represents appropriate admission of the highest-risk patients. Planned admissions in selected, intermediate-risk patients may present a strategy to mitigate the risk of unplanned admission. Substantial inter-centre variation exists in planned critical care admissions after emergency laparotomies.

Undermining government tax policies: Common legal strategies employed by the tobacco industry in response to tobacco tax increases

Effective tobacco tax increases reduce tobacco consumption, threatening the profitability of the tobacco industry. In response, the tobacco industry employs strategies to negate or minimize the full effects of tobacco tax increases. By interacting with various government agencies and non-governmental organizations we identified seven such strategies: stockpiling, changing product attributes or production processes, lowering prices, over-shifting prices, under-shifting prices, timing of price increases, and engaging in price discrimination and/or offering promotions. Each strategy is described in terms of the motivation for their employment, the consequences for tobacco use and tax revenue, and measures to counter them. Country case studies illustrate the successful execution of the strategies and possible government responses. Many of the tobacco industry's responses to tobacco tax increases are predictable, since they are being employed systematically across countries. Governments can and should adopt appropriate measures to eliminate or reduce tobacco industry manipulation. This requires systematic data collection in order to monitor tobacco industry behavior.