Sex-based comparisons of clinical characteristics and outcomes of patients with embolic stroke of undetermined source with implantable loop recorders

Funding Acknowledgements

Type of funding sources: None.

Introduction

Embolic strokes of undetermined source (ESUS) constitute a significant proportion of all ischemic strokes, but sex-based comparisons of clinical characteristics and outcomes of ESUS patients have not been well explored. As such, we aimed to examine how sex influences outcomes of ESUS patients.

Methods

Retrospective cohort study performed on consecutive ESUS patients with an implanted ILR between December 2013 to September 2021. We obtained information on the patients’ characteristics, treatments, and outcomes from the electronic medical records. Cox regression was used to investigate whether sex was independently associated with outcomes.

Results

There were 176 patients included in this study. The mean duration of follow-up was 1254 ± 724 days. Mean age was 60.8 ± 12.0 and 47 (26.7%) of patients were female. On univariable Cox regression analysis for subsequent atrial fibrillation (AF) on implantable loop recorder (ILR), patients with subsequent AF on ILR were more likely to be female (HR 2.19, 95% CI 1.04–4.63, p = 0.040), older (HR 1.07, 95% CI 1.03–1.12, p = 0.001), have a lower glomerular filtration rate (eGFR) (HR 0.98, 95% CI 0.97– 0.99, p = 0.004), and have previous percutaneous coronary intervention (PCI) (HR 2.60, 95% CI 1.05–6.46, p = 0.039). On multivariable Cox regression, after adjustment for age, eGFR and previous PCI status, female sex remained independently associated with the development of subsequent AF on ILR. Female sex was not associated with other outcomes including mortality, subsequent acute myocardial infarction, stroke/transient ischemic attack and heart failure.

Conclusions

In this cohort of ESUS patients with ILR implantation, female sex was independently associated with a higher risk of development of AF on ILR. However, female sex was not a predictor of mortality, subsequent acute myocardial infarction, stroke/transient ischemic attack and heart failure.

Abnormal left atrial strain is associated with eventual diagnosis of atrial fibrillation in patients with embolic stroke of undetermined source

Funding Acknowledgements

Type of funding sources: None.

Background

Patients with embolic stroke of undetermined source (ESUS) have no immediate attributable cause despite initial evaluation. Occult paroxysmal atrial fibrillation (pAF) diagnosed on prolonged electrocardiographic monitoring may be subsequently found in 20% of patients initially classified as ESUS [1]. Anatomic and functional alterations of left atrium (LA) are known to predict pAF in the general population [2]. Recent studies have suggested that LA dysfunction is linked to the risk of development of pAF in stroke patients and may precede LA enlargement [1]. LA strain analysis may be helpful to predict the development of pAF as it can detect subclinical functional impairment [2]. The aim of this study was to analyse whether LA strain can be a marker for the development of new-onset AF in patients with ESUS and sinus rhythm.

Methods

Our single-centre observational cohort study examined 157 patients hospitalised for ESUS in our tertiary hospital between October 2014 and October 2017 who underwent AF monitoring with an implantable loop recorder (ILR). These patients were followed up for occurrence of new-onset pAF and recurrence of ischaemic stroke. All patients underwent transthoracic echocardiography (TTE) during index hospitalisation as part of the workup for ESUS. Echocardiographic images were obtained and analysed post-hoc for two-dimensional (2D) speckle tracing deformation parameters. These LA strain parameters were analysed against the primary outcome of AF detection and secondary outcome of recurrent ischaemic stroke.

Results

A total of 157 ESUS patients, with a mean age of 61.0 (±11.6) years, were followed up for a median duration of 3.5 (interquartile range 3.29) years. ILR monitoring detected AF in 27 patients (17.2%). 27 patients developed recurrent ischaemic strokes. Of the 27 patients with newly diagnosed AF on ILR, 24 (88.9%) were commenced on oral anticoagulation; the remaining 3 patients were not on anticoagulation due to high bleeding risk and frailty.

Patients who had newly diagnosed AF had more impaired left atrial reservoir strain (LASr; 23.5% ± 10.3%, P = 0.042) and left atrial conduit strain (LAScd; -10.5% ± 5.3%, P = 0.003) compared with patients who remained in sinus rhythm. Multivariable logistic regression analysis adjusting for age, sex, hypertension, hyperlipidaemia, diabetes mellitus and left ventricular ejection fraction (LVEF) showed that LAScd was associated with occult AF (adjusted odds ratio [aOR] = 1.110, 95% CI, 1.019-1.209, P = 0.017) and the composite outcome of AF and recurrent ischaemic stroke (OR = 1.069, 95% CI, 1.014-1.138, P = 0.038). Abnormal LAScd was significantly associated with occult AF even when stratified by normal LA volume index (LAVI) (OR = 2.672, 95% CI, 1.035-8.548, P = 0.048) and high LAVI (OR = 1.713, 95% CI, 1.023-2.869, P = 0.041).

Conclusion

Impaired left atrial strain was associated with occult AF detection in patients with ESUS undergoing ILR monitoring.

Interplay between post-myocardial infarction ejection fraction and atrial fibrillation: implications for ischemic stroke

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Singapore Ministry of Health’s National Medical Research Council

Background

There are little data on the interplay between post-acute myocardial infarction (MI), left ventricular systolic dysfunction and atrial fibrillation (AF) and the impact on subsequent acute ischemic stroke (AIS), particularly among patients with moderately reduced ejection fraction (EF).

Purpose

We aimed to study the association between low EF, AF and the risk and severity of AIS.

Methods

This study linked national, population-based data from the Singapore Myocardial Infarction Registry with the Singapore Stroke Registry from 2007 to 2018. The EF and AF status were recorded during the index MI hospitalization. Patients were grouped based on an EF of ≥50% or <50%. An additional grouping of patients with AMI in 2008 to 2018 and EF of ≥50% (normal EF), 40-49% (mildly reduced EF) or <40% (reduced EF) was done. The primary outcome of interest was the risk of developing an AIS after an AMI. The secondary outcome of interest was the National Institute of Health Stroke Scale (NIHSS) across the different strata of EF among AMI patients with subsequent AIS.

Results

There were 64512 patients available for analysis. The median age was 65.7 and 69.5% were male. The median duration from MI to AIS was 16.9 (IQR 1.6-46.1) months. Low EF <40% was independently associated with subsequent AIS (adjusted HR 1.18, 95% CI 1.10-1.27), as was EF 40-49% (adjusted HR 1.16, 95% CI 1.06-1.27). Among patients with AF, EF<50% was not a statistically significant predictor of AIS (adjusted HR 1.08, 95% CI 0.96-1.23). In patients without AF, the mildly reduced EF group had an increased aHR of AIS of 1.18 (95% CI 1.06-1.31), but not those with AF (aHR 1.03, 95% CI 0.87-1.23). The cubic spline curves of continuous EF against relative hazard for stroke stratified by presence of AF is shown in Figure 1. Patients with low EF without AF had highest median NIHSS score during subsequent AIS (EF <40% NIHSS 6-9; EF 40-49% NIHSS 4; EF ≥50% NIHSS 4).

Conclusions

Reduced and moderately reduced EF post-MI was independently associated with subsequent AIS and was associated with increased AIS severity in patients without AF but not in those with AF. Further research is needed to mitigate the risk of late AIS among post-MI patients with reduced EF along with AF.

Rapid, scalable assessment of SARS-CoV-2 cellular immunity by whole-blood PCR

Fast, high-throughput methods for measuring the level and duration of protective immune responses to SARS-CoV-2 are needed to anticipate the risk of breakthrough infections. Here we report the development of two quantitative PCR assays for SARS-CoV-2-specific T cell activation. The assays are rapid, internally normalized and probe-based: qTACT requires RNA extraction and dqTACT avoids sample preparation steps. Both assays rely on the quantification of CXCL10 messenger RNA, a chemokine whose expression is strongly correlated with activation of antigen-specific T cells. On restimulation of whole-blood cells with SARS-CoV-2 viral antigens, viral-specific T cells secrete IFN-γ, which stimulates monocytes to produce CXCL10. CXCL10 mRNA can thus serve as a proxy to quantify cellular immunity. Our assays may allow large-scale monitoring of the magnitude and duration of functional T cell immunity to SARS-CoV-2, thus helping to prioritize revaccination strategies in vulnerable populations.

Association of body mass index with long-term outcomes after elective and semi-urgent percutaneous coronary intervention

Background

While obesity is associated with cardiovascular mortality and morbidity, patients with higher body mass index (BMI) may have better outcomes post-percutaneous coronary intervention (PCI). This “obesity paradox” is controversial and needs clarification.

Purpose

We aimed to investigate the relationship between BMI and outcomes post-PCI in an Asian cohort.

Methods

A retrospective cohort study was performed on consecutive patients who underwent semi-urgent PCI for non-ST elevation myocardial infraction or unstable angina, and elective PCI for stable angina from January 2014 to December 2015 in a tertiary centre. Patients were underweight (BMI <18.5), normal weight (BMI 18.5–22.9), overweight (BMI 23–24.9), pre-obese (BMI 25–29.9) or obese (BMI ≥30), according to the WHO Asian classification. The primary endpoint was all-cause mortality. The secondary outcomes were subsequent events of stroke or transient ischemic attack, myocardial infarction (MI) and congestive cardiac failure (CCF).

Results

1,610 patients were followed up for 3.71 (±0.97) years, 19.7% were female and mean age was 62.1 years (Table 1). BMI showed a U-shaped relationship with the incidence of death (p<0.001), MI (p=0.005), and CCF (p<0.001) (Figure 1A), which was also shown on Kaplan Meier analysis (Figures 1B-E). With reference to normal weight patients on multivariable Cox analysis, overweight (adjusted HR 0.64, 95% CI 0.42–0.97) and pre-obese (adjusted HR 0.55, 95% CI 0.38–0.80) patients had lower mortality. Underweight patients had higher risk (adjusted HR 2.12, 95% CI 1.01–4.46), while pre-obese patients had lower risk of MI (adjusted HR 0.56, 95% CI 0.34–0.92) compared to normal weight patients. Underweight and obese patients had higher risk of CCF (underweight: adjusted HR 3.05, 95% CI 1.45–6.42; obese: adjusted HR 1.86, 95% CI 1.03–3.35) compared to normal weight patients.

Conclusion

Patients at the lower and upper extremes of BMI demonstrated higher risk of mortality, MI and CCF post-PCI.

Funding Acknowledgement

Type of funding sources: None.

Long term survival and disease burden from out-of-hospital cardiac arrest: a population-based cohort study

Background

Long-term outcomes of out-of-hospital cardiac arrest (OHCA) are important to evaluate the overall health burden of OHCA on society. The concept of disability-adjusted life years (DALY) have recently been utilised to measure disease burden in OHCA, but data in an Asian cohort remains limited. We aimed to quantify and identify predictors of long-term survival (up to 10 years follow up) in patients with OHCA, as well as to quantify the annual disease burden of OHCA estimated using DALY in a national multi-ethnic Asian cohort.

Methods

We conducted an open cohort study through the linkage of the Pan-Asian Resuscitation Outcomes Study and the Singapore Registry of Births and Deaths from 2010 to 2020 in Singapore [1]. We quantified long-term survival using the standardised mortality ratio (SMR) for each year of follow up and the annual disease burden using DALY. Predictors of long-term survival were identified using cox-proportional hazards models. Kaplan-Meier survival curves were constructed for the overall population, and by key characteristics. The proportion surviving (and 95% CI) was calculated for up to eight years post-OHCA.

Results

We included 802 cases in the analysis. The mean age was 56.0 (SD 17.8), 631 cases (78.7%) were male, and the majority (552 cases, 68.8%) were of Chinese ethnicity (Table 1). The proportion surviving at one year of follow up was 0.84 (95% CI: 0.81–0.87), at five years of follow up was 0.68 (95% CI 0.65–0.72), and at ten years of follow up was 0.62 (95% CI 0.57–0.67) (Figure 1). Age at arrest (HR 1.03, 95% CI: 1.02–1.04, p<0.001), shockable first arrest rhythm (HR 0.75, 95% CI: 0.52–0.93, p=0.015) and Cerebral Performance Category (CPC) (HR 4.62, 95% CI: 3.17–6.75, p<0.001) were independently associated with mortality (Figure 2, 3). At one year, the SMR was 14.9 (95% CI: 12.5–17.8), and this decreased to 1.2 (95% CI: 0.7–1.8) at three years, and 0.4 (95% CI: 0.2–0.8) at five years (Figure 4). The top three causes of death after OHCA based on ICD10 categories were pneumonia, chronic ischemic heart disease, and acute myocardial infarction. The total DALY increased from 304.1 in 2010 to 849.7 in 2015, followed by decreasing to 547.1 in 2018. The mean DALY decreased from 12.162 in 2010 to 3.599 in 2018.

Conclusions

Age at arrest and CPC category was independently associated with higher risk of mortality, while a shockable first arrest rhythm was independently associated with a lower risk of mortality in long-term OHCA survivors. Initial survivors of OHCA have an increased mortality rate compared to the general population for the first three years, but normalises to that of the general population subsequently, while the annual disease burden of OHCA quantified using DALY showed decreasing trends from 2010 to 2018. Further improvements in the surveillance and management of OHCA may be warranted to improve the long-term survivorship and decrease the burden of disease of OHCA globally.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Medical Research Council, Clinician Scientist Award, Singapore (NMRC/CSA/024/2010 and NMRC/CSA/0049/2013), Ministry of Health, Health Services Research Grant, Singapore (HSRG/0021/2012)

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.

Clonally expanded CD8 T cells characterize amyotrophic lateral sclerosis-4

Amyotrophic lateral sclerosis (ALS) is a heterogenous neurodegenerative disorder that affects motor neurons and voluntary muscle control¹. ALS heterogeneity includes the age of manifestation, the rate of progression and the anatomical sites of symptom onset. Disease-causing mutations in specific genes have been identified and define different subtypes of ALS¹. Although several ALS-associated genes have been shown to affect immune functions², whether specific immune features account for ALS heterogeneity is poorly understood. Amyotrophic lateral sclerosis-4 (ALS4) is characterized by juvenile onset and slow progression³. Patients with ALS4 show motor difficulties by the time that they are in their thirties, and most of them require devices to assist with walking by their fifties. ALS4 is caused by mutations in the senataxin gene (SETX). Here, using Setx knock-in mice that carry the ALS4-causative L389S mutation, we describe an immunological signature that consists of clonally expanded, terminally differentiated effector memory (T_EMRA) CD8 T cells in the central nervous system and the blood of knock-in mice. Increased frequencies of antigen-specific CD8 T cells in knock-in mice mirror the progression of motor neuron disease and correlate with anti-glioma immunity. Furthermore, bone marrow transplantation experiments indicate that the immune system has a key role in ALS4 neurodegeneration. In patients with ALS4, clonally expanded T_EMRA CD8 T cells circulate in the peripheral blood. Our results provide evidence of an antigen-specific CD8 T cell response in ALS4, which could be used to unravel disease mechanisms and as a potential biomarker of disease state.

Emergency drug use in a pandemic: Harsh lessons from COVID-19

The scientific and clinical communities have both experienced several harsh lessons on clinical care management and drug development during the COVID-19 pandemic. Here, we discuss several key lessons learned and describe a framework within which our two communities can work together and invest in to improve future pandemic responses.

The "histone mimicry" by pathogens

One of the defining characteristics of human and animal viruses is their ability to suppress host antiviral responses. Viruses express proteins that impair the detection of viral nucleic acids by host pattern-recognition receptors, block signaling pathways that lead to the synthesis of type I interferons and other cytokines, or prevent the activation of virus-induced genes. We have identified a novel mechanism of virus-mediated suppression of antiviral gene expression that relies on the presence of histone-like sequences (histone mimics) in viral proteins. We describe how viral histone mimics can interfere with key regulators of gene expression and contribute to the suppression of antiviral responses. We also describe how viral histone mimics can facilitate the identification of novel mechanisms of antiviral gene regulation and lead to the development of drugs that use histone mimicry for interference with gene expression during diseases.

Preclinical evaluation of the combination of mTOR and proteasome inhibitors with radiotherapy in malignant peripheral nerve sheath tumors

About one half of malignant peripheral nerve sheath tumors (MPNST) have Neurofibromin 1 (NF1) mutations. NF1 is a tumor suppressor gene essential for negative regulation of RAS signaling. Survival for MPNST patients is poor and we sought to identify an effective combination therapy. Starting with the mTOR inhibitors rapamycin and everolimus, we screened for synergy in 542 FDA approved compounds using MPNST cells with a native NF1 loss in both alleles. We further analyzed the cell cycle and signal transduction. In vivo growth effects of the drug combination with local radiation therapy (RT) were assessed in MPNST xenografts. The synergistic combination of mTOR inhibitors with bortezomib yielded a reduction in MPNST cell proliferation. The combination of mTOR inhibitors and bortezomib also enhanced the anti-proliferative effect of radiation in vitro. In vivo, the combination of mTOR inhibitor (everolimus) and bortezomib with RT decreased tumor growth and proliferation, and augmented apoptosis. The combination of approved mTOR and proteasome inhibitors with radiation showed a significant reduction of tumor growth in an animal model and should be investigated and optimized further for MPNST therapy.

Suppression of the antiviral response by an influenza histone mimic

Viral infection is commonly associated with virus-driven hijacking of host proteins. Here we describe a novel mechanism by which influenza virus affects host cells through the interaction of influenza non-structural protein 1 (NS1) with the infected cell epigenome. We show that the NS1 protein of influenza A H3N2 subtype possesses a histone-like sequence (histone mimic) that is used by the virus to target the human PAF1 transcription elongation complex (hPAF1C). We demonstrate that binding of NS1 to hPAF1C depends on the NS1 histone mimic and results in suppression of hPAF1C-mediated transcriptional elongation. Furthermore, human PAF1 has a crucial role in the antiviral response. Loss of hPAF1C binding by NS1 attenuates influenza infection, whereas hPAF1C deficiency reduces antiviral gene expression and renders cells more susceptible to viruses. We propose that the histone mimic in NS1 enables the influenza virus to affect inducible gene expression selectively, thus contributing to suppression of the antiviral response.