The association between troponin level and mortality in patients admitted to hospital with acute stroke (NIHR Health Informatics Collaborative TROP-STROKE study)

Introduction

Acute stroke accounts for significant morbidity and mortality globally. The role of troponin for risk stratification in stroke is unclear.

Purpose

The aims of this study were to assess the relationship between peak troponin and mortality in patients with ischaemic stroke, haemorrhagic stroke, or subarachnoid haemorrhage and to compare this with the predictive value of first troponin or dynamic troponin change.

Methods

A retrospective cohort study was carried out using the National Institute for Health Research Health Informatics Collaborative Cardiovascular dataset of all consecutive patients who had a troponin measured at five hospitals between 2010 and 2017. Patients with at least one troponin measurement and a primary diagnosis of ischaemic stroke, haemorrhagic stroke or subarachnoid haemorrhage during a hospital admission were included. The main exposure variables were first and peak troponin, and dynamic troponin change, and the main outcome was all-cause mortality. Results were analysed using multivariable adjusted restricted cubic spline Cox regression. Survival analyses were adjusted for troponin assay, assay sensitivity (standard or highly sensitive), number of troponin measurements, age, sex, C-reactive protein level, white blood cell count, platelet count, haemoglobin, estimated glomerular filtration rate, angiography during admission, acute coronary syndrome during admission, and cardiovascular history (history of diabetes mellitus, myocardial infarction, heart failure, hypertension, stroke or atrial fibrillation). Receiver Operator Characteristic (ROC) curves were used to assess the predictive value of each exposure variable.

Results

4,712 patients were included in the analysis (ischaemic stroke: 3,346; haemorrhagic stroke: 718; subarachnoid haemorrhage: 648). Peak troponin was above the upper limit of normal in 47.4% of ischaemic stroke patients, 52.8% of haemorrhagic stroke patients, and 57.1% of subarachnoid haemorrhage patients. Patients with elevated peak troponin were older and had more cardiovascular risk factors.

A direct positive relationship was seen between peak troponin level and mortality hazard ratio in all three stroke subtypes (Figure 1). This relationship was consistent when considering dynamic troponin fold change for ischaemic or haemorrhagic stroke. For all three stroke subtypes, there was no added predictive value of peak troponin or dynamic troponin change over first troponin in predicting mortality (Figure 2).

Conclusions

A positive peak troponin was associated with increased mortality in patients presenting with ischaemic stroke, haemorrhagic stroke, or subarachnoid haemorrhage. Overall, serial troponin measurements may not improve mortality prediction beyond a single measurement. These findings may have implications for risk stratification of patients with acute stroke syndromes.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): NIHR Imperial Biomedical Research Centre, as part of the NIHR Health Informatics Collaborative, and 2) British Heart Foundation

The prognostic significance of troponin level in patients with malignancy (NIHR Health Informatics Collaborative TROP-MALIGNANCY study)

Background

Cardiac troponin is commonly raised in patients with malignancy and may aid clinicians in risk prediction. The prognostic significance of raised troponin in these patients with known malignancies remains unclear.

Purpose

We sought to investigate the relation between troponin and mortality in a large, well characterised cohort of patients undergoing cardiac troponin testing with a concomitant malignancy.

Methods

A retrospective cohort study was carried out using the National Institute for Health Research Health Informatics Collaborative Cardiovascular dataset of all consecutive patients who had a troponin measured at five hospitals between 2010 and 2017. Patients with a primary inpatient diagnosis of malignancy who had at least one cTn measurement during their hospital stay were identified. Patients were classified into solid tumour or haematological malignancy subgroups. Survival analyses were performed using multivariate Cox regression analyses and Kaplan-Meier plots. Cox regression analyses were adjusted for age, gender, C-reactive protein, haemoglobin, platelet count, white cell count, acute coronary syndrome, diabetes mellitus, heart failure, chronic kidney disease, chronic obstructive pulmonary disease, atrial fibrillation and angiography. The peak cTn level (highest level measured), standardised to the upper limit of normal (ULN), was used for all analyses.

Results

5571 patients undergoing troponin testing had a primary diagnosis of malignancy and comprised of twenty-one different cancer types. 4649 patients were diagnosed with solid tumours and 922 patients were diagnosed with haematological malignancies. Patients with raised troponin had a higher burden of cardiovascular comorbidities compared to patients with a troponin level below the ULN. The median follow-up in the cohort was 14 months (interquartile range 2–39 months). At 1-year follow-up, 2495 (42%) of patients died.

Figure 1 shows Kaplan-Meier plots for patients stratified by troponin level. Patients with a troponin level ≥1xULN had a higher risk of death compared to patients with a troponin level <1xULN (Figure 1A). A similar trend was shown in cancer subtypes (Figure 1B, C). Raised troponin was an independent predictor of mortality in all patients with malignancy (adjusted hazard ratio 1.66, 95% confidence interval [CI] 1.52–1.81), in solid tumours (adjusted hazard ratio 1.63, 95% CI 1.48–1.81) and in haematological malignancy (adjusted hazard ratio 1.75, 95% CI 1.44 to 2.13) when compared to patients with a troponin level <1xULN.

Conclusion

A raised troponin was associated with an increased mortality risk in patients with malignancy regardless of cancer subtype. Stratification of mortality risk using troponin may help guide clinicians in making management decisions for patients with malignancy.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): NIHR Imperial Biomedical Research Centre, as part of the NIHR Health Informatics Collaborative, and 2) British Heart Foundation

Developing informatics infrastructure to curate datasets using electronic health record data from five hospitals for translational cardiovascular research

Introduction

It has been challenging for researchers to access granular electronic health record (EHR) data at scale. One emerging prospect is to use big data to traverse the translational spectrum from an early discovery phase to a later implementation phase.

Purpose

To create a research-ready dataset to support translational research in cardiovascular medicine, using routinely-collected EHR data from multiple hospitals. As an early discovery phase study, we estimated the effect of invasive versus non-invasive management on the survival of patients with non-ST elevation myocardial infarction (NSTEMI) aged 80 years or older (SENIOR-NSTEMI Study). As a later implementation phase study, we determined the relationship between the full spectrum of troponin level and mortality in patients in whom troponin testing was performed for clinical purposes (TROP-RISK Study).

Methods

Using Microsoft SQL we developed a dataset of 257948 consecutive patients who had a troponin measured between 2010 and 2017 at five hospitals. We extracted phenotypically detailed data, including demographics, blood tests, procedural data, and survival status.

For the SENIOR-NSTEMI Study, eligible patients were 80 years or older who were diagnosed with NSTEMI. We estimated mortality hazard ratios comparing invasive with non-invasive management. For the TROP-RISK Study, we modelled the relation between peak troponin level and all-cause mortality using multivariable adjusted restricted cubic spline Cox regression analyses.

Results

For the SENIOR-NSTEMI Study, 1500 patients with NSTEMI were included who had a median age of 86 (interquartile range (IQR) 82–89) years of whom (845 [56%]) received non-invasive management. During a median follow-up of 3 (IQR 1.2–4.8) years, the adjusted cumulative five-year mortality was 36% in the invasive and 55% in the non-invasive group (hazard ratio 0.68, 95% confidence interval 0.55–0.84).

For the TROP-RISK Study, during a median follow-up of 1198 days (IQR 514–1866 days), 55850 (21.7%) deaths occurred. There was an unexpected inverted U-shaped relation between troponin level and mortality in acute coronary syndrome (ACS) patients (n=120049) (Figure 1A). The paradoxical decline in mortality at very high troponin levels may be driven in part by the changing case mix as troponin levels increase; a higher proportion of patients with very high troponin levels received invasive management (Figure 1B).

Conclusion

Routine EHR data can be aggregated across multiple sites to create highly granular datasets for research. The SENIOR-NSTEMI Study showed a survival advantage of invasive compared with non-invasive management of elderly patients with NSTEMI, who were underrepresented in previous trials. The inverted U-shaped relationship between troponin and mortality in ACS patients in the TROP-RISK Study demonstrates that assembling sufficiently large datasets can cast light on patterns of disease that are impossible to adequately define in single centre studies.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): 1) NIHR Imperial Biomedical Research Centre, as part of the NIHR Health Informatics Collaborative, and 2) British Heart Foundation

The association between age, troponin level, and mortality in patients hospitalised with acute pulmonary embolism (NIHR Health Informatics Collaborative TROP-PE study)

Background

A positive cardiac troponin (cTn) is an independent predictor of short-term mortality in individuals presenting with acute pulmonary embolism (PE). However, there is limited evidence regarding the impact age has on the association between cTn levels and mortality in patients with PE.

Purpose

The aim of our study was to investigate the relationship between cTn level, age, and all-cause mortality, in hospitalised patients diagnosed with an acute PE.

Methods

A retrospective cohort study using the National Institute for Health Research Health Informatics Collaborative Cardiovascular dataset of all consecutive patients who had a troponin measured at five hospitals between 2010 and 2017. Patients admitted to hospital with a primary diagnosis of PE with at least one cTn measurement were included. We modelled the relation between peak troponin level and all-cause mortality using multivariable adjusted restricted cubic spline Cox regression analyses. Effect estimates were adjusted for age, gender, high-sensitivity troponin assay, C-reactive protein, haemoglobin, platelet count, white cell count, creatinine, sodium, potassium, diabetes, hypertension, hypercholesterolaemia, acute coronary syndrome, atrial fibrillation, heart failure, acute kidney injury, chronic kidney disease, obstructive lung disease, inflammatory disorders, pneumonia and malignancy. The peak cTn level (highest level measured), standardised to the upper limit of normal (ULN), was used for all analyses.

Results

1,477 patients with at least one cTn measurement and a diagnosis of acute PE were included. During a median follow-up of 34.8 months, there were 290 (19.6%) deaths. Elevated cTn (>1xULN) was associated with a hazard ratio (HR) of 3.29 (95% confidence interval [CI] 1.95–5.53) for 30-day mortality and 2.12 (95% CI 1.63–2.75) for 3-year mortality. Higher cTn levels were progressively associated with a higher mortality risk, reaching a maximum HR of 2.59 (95% CI 1.64–4.09) at 141xULN (Figure 1). Younger patients (<55 years), compared with those aged over 55, had the highest 3-year HR associated with a positive cTn of 2.94 (95% CI 1.48–5.82) despite having the lowest troponin levels (mean 7.01xULN) on admission (Figure 2).

Conclusion

Elevated cTn, at all ages, is associated with an increased mortality risk in patients presenting with PE, with increasing cTn levels conferring a progressively worse long-term prognosis. Elevated cTn, no matter how small, needs to be taken seriously, particularly in young patients with an acute PE.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): 1) NIHR Imperial Biomedical Research Centre, as part of the NIHR Health Informatics Collaborative, and 2) British Heart Foundation

Clinical characteristics with inflammation profiling of long COVID and association with 1-year recovery following hospitalisation in the UK: a prospective observational study

BACKGROUND

No effective pharmacological or non-pharmacological interventions exist for patients with long COVID. We aimed to describe recovery 1 year after hospital discharge for COVID-19, identify factors associated with patient-perceived recovery, and identify potential therapeutic targets by describing the underlying inflammatory profiles of the previously described recovery clusters at 5 months after hospital discharge.

METHODS

The Post-hospitalisation COVID-19 study (PHOSP-COVID) is a prospective, longitudinal cohort study recruiting adults (aged ≥18 years) discharged from hospital with COVID-19 across the UK. Recovery was assessed using patient-reported outcome measures, physical performance, and organ function at 5 months and 1 year after hospital discharge, and stratified by both patient-perceived recovery and recovery cluster. Hierarchical logistic regression modelling was performed for patient-perceived recovery at 1 year. Cluster analysis was done using the clustering large applications k-medoids approach using clinical outcomes at 5 months. Inflammatory protein profiling was analysed from plasma at the 5-month visit. This study is registered on the ISRCTN Registry, ISRCTN10980107, and recruitment is ongoing.

FINDINGS

2320 participants discharged from hospital between March 7, 2020, and April 18, 2021, were assessed at 5 months after discharge and 807 (32·7%) participants completed both the 5-month and 1-year visits. 279 (35·6%) of these 807 patients were women and 505 (64·4%) were men, with a mean age of 58·7 (SD 12·5) years, and 224 (27·8%) had received invasive mechanical ventilation (WHO class 7-9). The proportion of patients reporting full recovery was unchanged between 5 months (501 [25·5%] of 1965) and 1 year (232 [28·9%] of 804). Factors associated with being less likely to report full recovery at 1 year were female sex (odds ratio 0·68 [95% CI 0·46-0·99]), obesity (0·50 [0·34-0·74]) and invasive mechanical ventilation (0·42 [0·23-0·76]). Cluster analysis (n=1636) corroborated the previously reported four clusters: very severe, severe, moderate with cognitive impairment, and mild, relating to the severity of physical health, mental health, and cognitive impairment at 5 months. We found increased inflammatory mediators of tissue damage and repair in both the very severe and the moderate with cognitive impairment clusters compared with the mild cluster, including IL-6 concentration, which was increased in both comparisons (n=626 participants). We found a substantial deficit in median EQ-5D-5L utility index from before COVID-19 (retrospective assessment; 0·88 [IQR 0·74-1·00]), at 5 months (0·74 [0·64-0·88]) to 1 year (0·75 [0·62-0·88]), with minimal improvements across all outcome measures at 1 year after discharge in the whole cohort and within each of the four clusters.

INTERPRETATION

The sequelae of a hospital admission with COVID-19 were substantial 1 year after discharge across a range of health domains, with the minority in our cohort feeling fully recovered. Patient-perceived health-related quality of life was reduced at 1 year compared with before hospital admission. Systematic inflammation and obesity are potential treatable traits that warrant further investigation in clinical trials.

FUNDING

UK Research and Innovation and National Institute for Health Research.

Durable Polymer Drug Eluting Stent-Induced Kounis Syndrome and Eosinophilia Requiring Long-term Immunosuppression

There are no reports of systemic eosinophilic reactions to durable polymer coated drug eluting stents (DP-DES) and a consensus statement indicates that these devices should be considered in nickel allergy. We present a case of in-stent thrombosis, eosinophilia, and rash consistent with allergic myocardial infarction, a presentation of Kounis syndrome, in the context of metal allergy to DP-DES requiring long-term immunosuppression.

We present a case of in-stent thrombosis and eosinophilia consistent with Kounis syndrome, in the context of metal allergy to durable polymer coated drug eluting stents, requiring long-term immunosuppression.

4301Diastolic dysfunction is an independent predictor of adverse events in patients with systolic dysfunction. Insights from the MADIT-CRT trial

Background

Diastolic dysfunction (DD) is common in patients with heart failure with reduced ejection fraction (HFrEF). However, its prognostic relevance in HFrEF, on top of conventional risk factors including natriuretic peptides, is unknown

Purpose

To show the prognostic contribution of DD in HFrEF

Methods

We analyzed 1155 baseline echocardiograms (63% of all available exams) in the MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial With Cardiac Resynchronization Therapy) study, comprising HFrEF patients with LVEF≤30%, QRS duration ≥130 ms, and NYHA class I/II. We classified DD according to ASE 2016 classification, based on transmitral Doppler velocities, mitral annular Tissue Doppler velocities, pulmonary venous flow velocities, and left atrial volumes. Using Cox regression and C-statistics we assessed the independent prognostic value of DD for nonfatal HF or death. We also evaluated CART (Classification And Regression Tree) analysis

Results

Patients were 64±11 years-old, 24% females, and mean LVEF was 24±5%. While 45% had impaired relaxation, 33% had pseudo-normal filling, 12% restrictive patter, 6% had indeterminate diastolic function, and 4% were not classifiable due to missing data. During a mean follow-up of 2.1±1.0 years, there were 233 adverse events. After multiple adjustment, compared to patients with impaired relaxation, those with pseudo-normal and restrictive filling had greater risk of HF/death (respectively HR 1.76, 95% CI 1.16–2.66, p=0.007; HR 2.70, 95% CI 1.58–4.60, p<0.001), independently of assigned treatment (p-interaction 0.34). Adding DD to conventional markers of risk improved prediction (C-statistic 0.733, 95% CI 0.689–0.776 versus 0.708, 95% CI 0.663–0.753, p=0.024). Finally, at CART analysis DD was the first parameter to be considered to risk stratify patients (Figure)

Risk stratification tree

Conclusions

DD is a strong independent predictor of death or heart failure in HFrEF patients with mild symptoms and should be considered in assessment of risk in this population

6029Invasive versus medical management for non-ST elevation myocardial infarction in the elderly (SENIOR-NSTEMI study)

Background

Trials and registry studies suggest lower long-term mortality after invasive than medical management among patients with non-ST elevated myocardial infarction (NSTEMI), but elderly patients were underrepresented.

Purpose

To estimate the effect of invasive compared with medical management on survival in patients with NSTEMI aged ≥80 years, using routine clinical data.

Methods

We used National Institute for Health Research Health Informatics Collaborative data to identify eligible patients admitted during 2010–2017 at five tertiary centres. We compared patients who did and did not have invasive management within 3 days of their peak troponin level. To limit the effect of immortal time bias, follow-up started 3 days after peak troponin: deaths within three days were excluded. We conducted intention-to-treat analyses.

Propensity scores were derived from a logistic regression model based on pre-treatment variables: patient demographics, blood test results, cardiovascular risk factors, history of cardiovascular disease and other comorbidities. We modelled non-linear relationships using splines. Patients with high probability (based on propensity score) of medical or invasive intervention were excluded. We used Cox models to estimate hazard ratios (HR) comparing invasive with medical management. Three methods were used to control confounding; multivariable-adjusted, multivariable-adjusted additionally for continuous propensity score (primary analysis), and inverse-probability-of-treatment (IPT) weighting. Kaplan-Meier survival curves were plotted. The robustness of the results to unmeasured confounding was assessed in sensitivity analyses.

Results

The 2,239 patients (61.3% medical management) included in analyses had a median age of 85 (IQR 82–89) years. During a median follow-up of 32.1 (IQR 11.1–54.3) months, there were 1,015 (45.3%) deaths. At 3-years, cumulative survival was 78.9% and 50.3% in the invasive and medical management groups, respectively (Figure 1).

The crude HR comparing invasive with medical management was 0.34 (95% CI 0.29–0.40). The multivariable-adjusted HR was 0.44 (95% CI 0.36–0.53), was unchanged with additional adjustment for propensity score, and was 0.46 (95% CI 0.39–0.56) in the IPT-weighted model (all p<0.0001). The E-value for the point estimate was 2.91: this implies that residual confounding could explain the association if there is an unmeasured covariate with a relative risk of at least 2.91 for both mortality and undergoing invasive management. The highest mortality HR for comorbidities included in our model were aortic stenosis 1.66 (95% CI 1.28–2.14) and obstructive lung disease 1.50 (95% CI 1.16–1.94).

Figure 1. Kaplan-Meier survival curves

Conclusion

This study provides evidence that the survival advantage from invasive management may extend to elderly patients with NSTEMI. Future research should address the possibility of unmeasured confounding, including by post-admission prognostic factors that affect choice of invasive or medical management.

Acknowledgement/Funding

Funded by NIHR Imperial Biomedical Research Centre (BRC) using NIHR Health Informatics Collaborative data service, supported by OUH, GSTT & UCLH BRCs

P4345Supporting big data research in cardiovascular medicine using routinely-collected data

Background

Many of the data points required to support translational research are collected as a matter of routine, and should be available within electronic patient records. Variations in clinical and data recording practice can mean that the extraction and standardisation of this data, with the aim of producing a large-scale, research-ready dataset, presents a number of challenges.

Purpose

We set out to create a large-scale, research-ready dataset to support translational research in cardiovascular medicine, using routinely-collected data from five large university-hospital partnerships. As an initial focus, we selected those data points that would support an investigation of the relationship between test results and outcomes in acute coronary syndrome (ACS).

Methods

The National Institute of Health Research (NIHR) Health Informatics Collaborative (HIC) is a programme of infrastructure development aimed at increasing the quality and availability of routinely-collected data for collaborative, translational research. Eighteen university-hospital partnerships signed the data sharing agreement, and are working to facilitate the sharing and re-use of data across centres, for approved research purposes.

With support from the Directors of the NIHR Biomedical Research Centres (BRCs) within five of the largest partnerships, we established a clinical data collaboration, specifying a dataset and selecting an initial research question (Figure 1). The NIHR HIC team worked to extract data against this specification. With approval from an ethics committee, and from the information governance teams at each contributing centre, data was processed by one of the centres for standardisation and analysis.

Results

The specified dataset represented a longitudinal record for patients presenting with a suspected ACS, characterised by a request for a troponin test (Figure 1). The dataset included 156 data points, grouped into demographics, cardiovascular risk factor profile, emergency department attendance and inpatient episodes, blood tests, echocardiography and mortality. Data was extracted from the records of patients for whom a troponin test was requested between 2010 and 2017. A total of 257,948 records were standardised and analysed.

The collaboration has been successful, and an initial version of the combined dataset has been created. The size of the dataset has yielded new insights into the relationship between test results and outcomes, and publications are in preparation. An expanded dataset of over 800 data points has been agreed for the next phase of the collaboration, and three other centres have joined.

Figure 1. NIHR HIC dataset generation

Conclusion

It is perfectly feasible – in terms of governance and technology – to re-use routinely-collected data for collaborative, translational research in cardiovascular medicine. The resulting dataset will be large and complex enough to require big data tools and techniques, and will yield the kind of insights afforded only by big data in medicine.

Acknowledgement/Funding

Funded by NIHR Imperial Biomedical Research Centre (BRC) using NIHR Health Informatics Collaborative data service, supported by OUH, GSTT & UCLH BRCs

2231HsCRP predicts mortality beyond troponin in 102,337 patients with suspected acute coronary syndrome (CRP-RISK study)

Background

The incremental long-term prognostic value of high-sensitivity C-reactive protein (hsCRP) above troponin in a large real-world cohort of unselected patients presenting with suspected acute coronary syndromes (ACS) is unknown.

Purpose

We hypothesised that a mildly elevated hsCRP is associated with mortality risk in patients with suspected ACS, independent of troponin level.

Methods

We used the National Institute for Health Research Health Informatics Collaborative data of 257,948 patients who had a troponin measured at 5 cardiac centres. We excluded patients with clinically abnormal white cell counts and hsCRP >15 mg/L to try limiting the population to those without overt infections, malignancies or systemic inflammatory conditions that may confound our analyses. Patients were divided into four hsCRP groups (<2, 2–4.9, 5–9.9 and 10–15 mg/L) and the association between hsCRP levels and all-cause mortality assessed.

Results

There were 102,337 patients included in the analysis (hsCRP <2 mg/L (n=38,390), 2–4.9 mg/L (n=27,397), 5–9.9 mg/L (n=26,957) and 10–15 mg/L (n=9,593)). Figure 1A displays cumulative mortality per hsCRP group, revealing increasing mortality with each consecutive group. Figure 1B further stratifies the groups according to dichotomised peak troponin level as positive or negative. This shows the greatest mortality for patients in the highest hsCRP group who also had a positive troponin assay (36.0% at 3 years).

In Cox regression analysis with time-dependent covariates, even mildly raised hsCRP was an independent predictor of mortality over time, after adjusting for age, gender, haemoglobin, white cell count, platelet count, creatinine and troponin positivity. There was a positive and graded relationship between hsCRP level and mortality at baseline, which remained at 3-years (hazard ratio (95% CI) of 1.32 (1.18–1.48) for those with hsCRP 2.0–4.9mg/L, and 1.40 (1.26–1.57), and 2.00 (1.75–2.28) for those with hsCRP 5–9.9 mg/L and 10–15 mg/L, respectively.

We explored whether inclusion of hsCRP could better reclassify the population into at-risk mortality groups. The association with 30-day, 1-year and 3-year mortality was assessed using three different risk models (model 1: age, gender, haemoglobin, creatinine; model 2: model 1 plus troponin (positivity versus negativity); model 3: model 2 plus hsCRP groups. For cumulative mortality at each time point, each successive model was better able to discriminate risk than its precursor (p<0.0001); such that inclusion of troponin and hsCRP gave the most robust risk discrimination. Model 3 achieved an AUROC >0.8 at 30 days, 1-year and 3-year mortality, surpassing the use of troponin on its own.

Figure 1. Kaplan-Meier mortality curves

Conclusions

These multi-centre, real-world data from a large cohort of patients with suspected ACS identify hsCRP as a clinically meaningful prognostic marker in addition to troponin levels and point to its potential utility in selecting patients for novel treatments targeting inflammation.

Acknowledgement/Funding

Funded by NIHR Imperial Biomedical Research Centre (BRC) using NIHR Health Informatics Collaborative data service, supported by OUH, GSTT & UCLH BRCs

P3592Troponin level and mortality risk in an unselected population of over 250,000 patients (TROP-RISK study)

Background

Current evidence suggests a direct relationship between the magnitude of troponin elevation and mortality, albeit over a limited range of troponin levels, and clinicians generally work under the impression that higher troponins signify higher mortality in all age groups.

Purpose

The objective was to use big data to determine the relationship between the full spectrum of troponin level and mortality in patients in whom troponin testing has been performed for clinical purposes.

Methods

As part of the National Institute for Health Research Health Informatics Collaborative project, all troponin values measured during the study period (2010 to 2017) were assembled from five cardiovascular centres. Troponin concentrations were standardised as a multiple of each laboratory's 99th-percentile of the upper limit of normal (ULN). All patients were followed up until death or censoring on 1st April 2017. To model the relation between peak troponin level and all-cause mortality we used restricted cubic spline Cox regression analysis. Splines were adjusted for patient age, gender, haemoglobin, creatinine, white cell count and C-reactive protein.

Results

257,948 patients underwent troponin assessment. During a median follow-up of 1,198 (IQR, 514–1,866) days, there were 55,850 (21.7%) deaths. Using multivariable-adjusted restricted cubic spline Cox regression analysis, an inverted-U shaped relationship was observed between peak troponin level and mortality in all patients (Figure 1A). Among patients who were admitted to hospital, the recorded diagnostic code was acute coronary syndrome (ACS) in 14,468 patients and non-ACS in 120,049 patients.

The revascularisation rate within 3 months was 61.0% (n=8,820) in ACS versus 4.0% (n=4,793) in non-ACS patients. There was a very different rate of revascularisation across the spectrum of troponin. The rate was only 1.4% for troponins below 1 xULN, and 6.1% between 1 and 10 xULN. Beyond 10 xULN, rate of revascularisation rose rapidly to over 85% for greater than 10,000 xULN (Figure 1B). Stratifying patients by revascularisation, the restricted cubic spline Cox regression curve showed a progressive increase in mortality within both the revascularised and non-revascularised strata, even to very high peak troponin levels (Figure 1C). Overall, revascularisation was associated with lower hazard ratios across all troponin levels. A similar pattern was seen when patients were stratified by the presence or absence of ACS diagnosis.

Figure 1. Troponin level and mortality

Conclusions

An elevated troponin, even slightly above the ULN should be taken seriously. The inverted-U shaped mortality relationship with troponin occurred because patients with the highest troponin formed a different clinical subgroup who underwent different clinical management with a high revascularisation rate. These data on troponin level and mortality may help to inform clinical practice decisions and guide future risk stratification algorithms for patients with elevated troponin.

Acknowledgement/Funding

Funded by NIHR Imperial Biomedical Research Centre (BRC) using NIHR Health Informatics Collaborative data service, supported by OUH, GSTT & UCLH BRCs

Continuous-Flow Left Ventricular Assist Device Survival Improves With Multidisciplinary Approach

BACKGROUND

Continuous-flow left ventricular assist devices have revolutionized the management of advanced heart failure. Device complications continue to limit survival, but enhanced management strategies have shown promise. This study compared outcomes for HeartMate II recipients before and after implementation of a multidisciplinary continuous support heart team (HTMCS) strategy.

METHODS

Between January 2012 and December 2016, 124 consecutive patients underwent primary HeartMate II implantation at our institution. In January 2015, we instituted a HTMCS approach consisting of (1) daily simultaneous cardiology/cardiac surgery/critical care/pharmacy/coordinator rounds, (2) pharmacist-directed anticoagulation, (3) speed optimization echocardiogram before discharge, (4) comprehensive device thrombosis screening and early intervention, (5) blood pressure clinic with pulsatility-adjusted goals, (6) early follow-up after discharge and individual long-term coordinator/cardiologist assignment, and (7) systematic basic/advanced/expert training and credentialing of ancillary in-hospital providers. All patients completed 1-year of follow-up.

RESULTS

Demographic characteristics for pre-HTMCS (n = 71) and HTMCS (n = 53) groups, including age (55.8 ± 12.1 versus 52.5 ± 14.1 years, p = not significant), percentage of men (77.5% versus 71.7%, p = not significant), and Interagency Registry for Mechanically Assisted Circulatory Support class 3 (84.5% versus 83.0%, p = not significant), were comparable. One-year survival was 74.6% versus 100% for the pre-HTMCS and HTMCS groups, respectively (p = 0.0002). One-year survival free of serious adverse events (reoperation to replace device or disabling stroke) was 70.4% versus 84.9% for the pre-HTMCS and HTMCS groups, respectively (p = 0.059). Event per patient-year rates for disabling stroke (0.15 versus 0, p = 0.019), gastrointestinal bleeding (0.87 versus 0.51, p = 0.11), and driveline infection (0.24 versus 0.10, p = 0.18) were lower for the HTMCS group, whereas pump thrombosis requiring device exchange was higher (0.09 versus 0.18, p = 0.14).

CONCLUSIONS

Implementing a comprehensive multidisciplinary approach substantially improved outcomes for recipients of continuous-flow left ventricular assist devices.

WP1-6 The syndrome of the trephined

Objectives

Syndrome of the Trephined (SoT) or sinking skin flap syndrome is characterised by neurological deterioration occurring after a delay post-craniectomy, with or without a significant postural component, that may improve with cranioplasty. The symptoms and signs seen are heterogeneous and can be readily missed. With increasing numbers of patients surviving after decompressive craniectomies, and often a long delay before cranioplasty, we think it important that awareness of this potentially lethal but reversible condition is raised.

Design

Case Series.

Subjects

Cases with suspected SoT were identified retrospectively from all admissions to a Level 1 Neurorehabilitation Unit over 2 years.

Methods

Cases were identified by their treating clinicians. Their clinical features are described, and outcomes after cranioplasty are discussed.

Results

From 36 patients admitted after craniectomy over 2 years, 4 patients with suspected SoT were identified, with a latency of 4–12 months post-injury. Late neurological deterioriation included reduced alertness and mobility, cognitive decline and headache. Two patients had a clear postural component to their symptoms. Coexisting hydrocephalus was sometimes seen, and complicated neurosurgical management. All cases improved after cranioplasty.

Conclusions

SoT is an under-reported and under-recognised complication of craniectomy. It is a potentially reversible cause of significant late deterioration following craniectomy. Further research into the optimal timing for cranioplasty is needed.

Discovery of anti-microbial and anti-tubercular molecules from Fusarium solani: an endophyte of Glycyrrhiza glabra

AIMS

Glycyrrhiza glabra is a high-value medicinal plant thriving in biodiversity rich Kashmir Himalaya. The present study was designed to explore the fungal endophytes from G. glabra as a source of bioactive molecules.

METHODS AND RESULTS

The extracts prepared from the isolated endophytes were evaluated for anti-microbial activities using broth micro-dilution assay. The endophytic strain coded as A2 exhibiting promising anti-bacterial as well as anti-tuberculosis activity was identified as Fusarium solani by ITS-5.8S ribosomal gene sequencing technique. This strain was subjected to large-scale fermentation followed by isolation of its bioactive compounds using column chromatography. From the results of spectral data analysis and comparison with literature, the molecules were identified as 3,6,9-trihydroxy-7-methoxy-4,4-dimethyl-3,4-dihydro-1H-benzo[g]isochromene-5,10-dione (1), fusarubin (2), 3-O-methylfusarubin (3) and javanicin (4). Compound 1 is reported for the first time from this strain. All the four compounds inhibited the growth of various tested bacterial strains with MIC values in the range of <1 to 256 μg ml^-1 . Fusarubin showed good activity against Mycobacterium tuberculosis strain H37Rv with MIC value of 8 μg ml^-1 , whereas compounds 1, 3 and 4 exhibited moderate activity with MIC values of 256, 64, 32 μg ml^-1 , respectively.

CONCLUSIONS

To the best of our knowledge, this is the first study that reports significant anti-tuberculosis potential of bioactive molecules from endophytic F. solani evaluated against the virulent strain of M. tuberculosis. This study sets background towards their synthetic intervention for activity enhancement experiments in anti-microbial drug discovery programme.

SIGNIFICANCE AND IMPACT OF THE STUDY

Due to the chemoprofile variation of same endophyte with respect to source plant and ecoregions, further studies are required to explore endophytes of medicinal plants of all unusual biodiversity rich ecoregions for important and or novel bioactive molecules.

Transcatheter Valve-in-Valve Implantation: Failing Tricuspid Bioprosthesis in a Patient with Ebstein’s Anomaly

Transcatheter valve-in-valve (VIV) implantation has been recently proposed as an alternative to surgical reoperative aortic valve replacement in patients with a failing aortic bioprosthesis. Experience with transcatheter VIV implantation at other valve positions is very limited. Herein is reported the case of an 18-year-old man with Ebstein's anomaly and severe tricuspid valve (TV) regurgitation status after bioprosthetic valve replacement, who developed new dyspnea on exertion three years after the initial valve replacement. Transesophageal echocardiography showed a severely dilated right atrium and new TV stenosis with an immobile leaflet. The patient underwent successful VIV implantation of a 29-mm SAPIEN XT bioprosthetic valve, with resolution of symptoms and no residual TV regurgitation or stenosis at the two-year follow up. Video 1: Degenerative bioprosthetic tricuspid valve. TEE showing the degenerative bioprosthetic tricuspid valve, and color Doppler during systole showing severe tricuspid regurgitation. Video 2: Degenerative bioprosthetic tricuspid valve. Three-dimensional TEE showing stenosis with an immobile leaflet creating a coaptation defect, viewed from the right atrium. Video 3: Transcatheter VIV replacement with a 29-mm Edwards SAPIEN XT deployed within the tricuspid valve prosthesis. Final result after valve implantation, demonstrating a patent valve orifice, and appropriate apposition of transcatheter valve within a pre-existing surgical Carpentier-Edwards bioprosthetic valve, viewed from the right ventricle. Video 4: Transcatheter VIV replacement with a 29-mm Edwards SAPIEN XT deployed within the tricuspid valve prosthesis. Final result after valve implantation, demonstrating a patent valve orifice, and appropriate apposition of transcatheter valve within a pre-existing surgical Carpentier-Edwards bioprosthetic valve, viewed from the right atrium.

Abstract P2-01-14: circulating tumor cells in breast cancer exhibit dynamic changes in epithelial and mesenchymal cell composition

Epithelial to mesenchymal transition (EMT) has been postulated to contribute to the migration and dissemination of cancer cells, but supporting histopathological evidence is limited. We used a microfluidic device to isolate circulating tumor cells (CTCs), combined with multiplex fluorescent RNA-in-situ hybridization (ISH) and RNA sequencing, to quantify and characterize EMT in breast cancer cells within the bloodstream. Whereas only rare (0.1–10%) cells in the primary tumor expressed both mesenchymal and epithelial markers, such biphenotypic as well as purely mesenchymal cells were enriched among CTCs, across all histological subtypes of breast cancer. Analysis of the therapy response in 8 patients suggest an association of mesenchymal CTCs with disease progression. In an index patient followed longitudinally, fluctuation in epithelial and mesenchymal states was observed as a function of initial response and subsequent resistance to therapy. Mesenchymal markers were predominant in clusters of tumor cells, many of which had adherent platelets. Finally, RNA sequencing of mesenchymal CTC clusters identified TGF-B and other EMT-related signatures, which were absent from more epithelial CTCs. FOXC1, a known regulator of EMT, was abundantly expressed in mesenchymal CTCs and was detectable within localized regions of the primary breast tumor. Together, these data support a role for EMT in the blood-borne dissemination of breast cancer and point to the dynamic nature of this cell fate change.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-01-14.

Abstract P360: Temporal Variability in the ECG Manifestations of Cardiac Sarcoidosis

BACKGROUND: Temporal variability in ECG manifestations of cardiac sarcoidosis in patients with documented extra-cardiac sarcoidosis has not been previously reported.

METHODS: Six or more 12-lead ECGs were reviewed for each of 8 patients (6 females, 6 African Americans, 38-63 years old) with documented extra-cardiac sarcoidosis. Analyzed ECGs were obtained at intervals no longer than 12 months apart. PR and QT intervals and QRS duration were measured in each ECG lead and averaged for three consecutive beats per lead. The presence of PVCs, AV block, RBBB, and/or QT prolongation was recorded. Between ECG variability was analyzed with ANOVA for continuous data and chi-square analysis for categorical data.

RESULTS: Significant variability in ECG indicators of sarcoidosis activity, concurrent with clinical impression of sarcoidosis exacerbation, was detected in seven of eight patients. Most common were new QT prolongation (94%, p=0.031) and PR interval increase (87.5% of the analyzed ECGs, p=0.029). Concordant variability was noted for both in between visit and in between lead comparisons of PR duration, QT/QTc intervals, and QRS duration (p<0.0001 in 5 patients; p<0.001 in 2 patients). No PVCs were documented on the analyzed ECGs.

CONCLUSION: ECG abnormalities diagnostic of cardiac sarcoidosis have high temporal variability which parallels clinical impression of extra-cardiac disease activity. A 12-lead ECG is warranted at each visit in patients with documented extra-cardiac sarcoidosis. At the same time, 12-lead ECGs are probably not sufficiently sensitive to detect arrhythmias and/or PVCs in patients with documented extra-cardiac sarcoidosis.

Acute diverticulitis in the young: a 5-year retrospective study of risk factors, clinical presentation and complications

AIM

Acute diverticulitis in the young is considered to follow an aggressive course, but there is a paucity of data on factors that could determine a complicated course.

METHOD

All patients of 18-40 years of age diagnosed with acute diverticulitis from 1 January 2003 to 31 December 2008 were identified. Patients were included if they had computed tomography (CT) evidence of acute diverticulitis and at least one clinical feature. Demographics, body mass index, presenting symptoms/signs, CT location of diverticulitis and complications were noted. Fisher's exact test and a multivariate logistic regression analysis model were used to detect possible associations between clinical variables and complications.

RESULTS

There were 76 patients, of whom 23 (30.2%) had fever (>38°C) and 52 (68.4%) had leucocytosis (≥11000/mm(3)). The majority [48 (63.1%)] were obese. A total of 29 (38.1%) patients had complications, with perforation [18 (62%)] being the most common. Twelve (15.7%) required surgical or radiological intervention. Fever of ≥38.0°C and a body mass index of ≥25 were independently associated with complications (P=0.04 and P=0.03, respectively).

CONCLUSION

Fever (≥38°C) at presentation and a body mass index of ≥25 may help to predict a complicated course of acute diverticulitis in patients under 40 years of age.

Biomarkers in pulmonary arterial hypertension

Despite recent advances in medical treatment, pulmonary arterial hypertension (PAH) continues to be associated with high morbidity and mortality. While the diagnosis is established via a right heart catheterisation, current non-invasive measures of disease severity and response to treatment used in clinical practice are the 6-min walk distance and the World Health Organization functional class. Although both parameters correlate with disease severity and prognosis, they have significant limitations. A major shortcoming in assessing PAH is lack of standardised, non-invasive, objective parameters that function as biomarkers to help assess the severity and prognosis of disease and to follow patients' response to treatment. In this article, we will review current knowledge on potential biomarkers associated with diagnosis, prognosis and response to treatment of PAH. Most biomarkers are either being evaluated for potential use in clinical practice, or being used as research tools.

Cardiovascular activity of the n-butanol fraction of the methanol extract of Loranthus ferrugineus Roxb

We investigated the vascular responses and the blood pressure reducing effects of different fractions obtained from the methanol extract of Loranthus ferrugineus Roxb. (F. Loranthaceae). By means of solvent-solvent extraction, L. ferrugineus methanol extract (LFME) was successively fractionated with chloroform, ethyl acetate and n-butanol. The ability of these LFME fractions to relax vascular smooth muscle against phenylephrine (PE)- and KCl-induced contractions in isolated rat aortic rings was determined. In another set of experiments, LFME fractions were tested for blood pressure lowering activity in anesthetized adult male Sprague-Dawley rats (250-300 g, 14-18 weeks). The n-butanol fraction of LFME (NBF-LFME) produced a significant concentration-dependent inhibition of PE- and KCl-induced aortic ring contractions compared to other fractions. Moreover, NBF-LFME had a significantly higher relaxant effect against PE- than against high K+-induced contractions. In anesthetized Sprague-Dawley rats, NBF-LFME significantly lowered blood pressure in a dose-dependent manner and with a relatively longer duration of action compared to the other fractions. HPLC, UV and IR spectra suggested the presence of terpenoid constituents in both LFME and NBF-LFME. Accordingly, we conclude that NBF-LFME is the most potent fraction producing a concentration-dependent relaxation in vascular smooth muscle in vitro and a dose-dependent blood pressure lowering activity in vivo. The cardiovascular effects of NBF-LFME are most likely attributable to its terpenoid content.

Hydrodynamic gene delivery to the pig liver via an isolated segment of the inferior vena cava

Hydrodynamic gene delivery is an attractive option for non-viral liver gene therapy, but requires evaluation of efficacy, safety and clinically applicable techniques in large animal models. We have evaluated retrograde delivery of DNA to the whole liver via the isolated segment of inferior vena cava (IVC) draining the hepatic veins. Pigs (18-20 kg weight) were given the pGL3 plasmid via two programmable syringe pumps in parallel. Volumes corresponding to 2% of body weight (360-400 ml) were delivered at 100 ml s(-1) via a Y connector. The IVC segment pressure, portal venous pressure, arterial pressure, electrocardiogram (ECG) and pulse were monitored. Concurrent studies were performed in rats for interspecies comparisons. The hydrodynamic procedure generated intrahepatic vascular pressures of 101-126 mm Hg, which is approximately 4 times higher than in rodents, but levels of gene delivery were approximately 200-fold lower. Suprahepatic IVC clamping caused a fall in arterial pressure, with the development of ECG signs of myocardial ischaemia, but these abnormalities resolved rapidly. The IVC segment approach is a clinically acceptable approach to liver gene therapy. However, it is less effective in pigs than in rodents, possibly because of larger liver size or a less compliant connective tissue framework.

Cardiovascular function following acute volume overload for hydrodynamic gene delivery to the liver

Hydrodynamic gene delivery to the liver is a valuable experimental tool and an attractive option for nonviral gene therapy of liver disease. However, little attention has been paid to the major obstacle to clinical application: acute volume overload of the cardiovascular system. We delivered volumes of DNA solution (pGL3 plasmid) corresponding to 1, 2, 4, 6 and 8% of the body weight at 100 ml/min to the inferior vena cava (IVC) of DA strain rats. Central venous pressure (CVP), arterial pressure, pulse and electrocardiogram (ECG) were continuously recorded for subsequent analysis. Each volume produced a characteristic response, but all (including the 1% volume) caused severe falls in blood pressure and pulse within 1-2 s of the infusion, with ectopic beats and widening of the QRS complex in the ECG. The response to volumes of 4% and higher suggested that the liver acted as a volume sink, mitigating the immediate effects of volume overload. The 6 and 8% volumes caused profound and protracted falls in blood pressure and pulse, with a multitude of severe electrical abnormalities in the heart, including electromechanical dissociation. Vagal blockade with atropine, and the use of Ringer's solution to prevent electrolyte disturbances, did not ameliorate this picture.

Redox signalling involving NADPH oxidase-derived reactive oxygen species

Increased oxidative stress plays an important role in the pathophysiology of many diseases such as atherosclerosis, diabetes mellitus, myocardial infarction and heart failure. In addition to the well-known damaging effects of oxygen-free radicals, ROS (reactive oxygen species) also have signalling roles, acting as second messengers that modulate the activity of diverse intracellular signalling pathways and transcription factors, thereby inducing changes in cell phenotype. NADPH oxidases appear to be especially important sources of ROS involved in redox signalling. Seven NADPH oxidase isoforms, known as Noxs (NAPDH oxidases), are expressed in a cell- and tissue-specific fashion. These oxidases are thought to subserve distinct functions as a result of their tightly regulated activation (e.g. by neurohormonal and growth factors and mechanical stimuli) and their specific coupling with distinct downstream signalling pathways. In the present paper, we review the structure and mechanisms of activation of NADPH oxidases and consider their involvement in redox signalling, focusing mainly on the cardiovascular system.

Effect of fat distribution on endothelial-dependent and endothelial-independent vasodilatation in healthy humans

AIM

The present study aims to explore the relationship between inflammatory cytokines, plasma lipids, insulin, blood pressure (BP), total adiposity/markers of fat distribution and endothelial function in healthy people across a wide range of body fatness.

METHODS

Seventy-three healthy people (44 women; age range: 24-64 years) with body mass index (BMI) range of 18.6-73.1 kg/m2 were recruited. All participants underwent assessment of conduit artery endothelial-dependent vasodilatation by using flow-mediated vasodilatation (FMD) of the brachial artery and endothelial-independent vasodilatation to sublingual GTN. They had blood taken for measurement of plasma markers of glucose homeostasis (fasting insulin and glucose), systemic inflammation (interleukin-6 (IL-6), C-reactive protein (CRP) and tumour necrosis factor-alpha receptor 2 (TNF-alpha R2)) and lipids (low-density lipoprotein (LDL), high-density lipoprotein (HDL) and triglycerides). Morphometric assessment (waist circumference, BMI and waist-to-hip ratio (WHR)) and systolic and diastolic arterial pressure were also measured.

RESULTS

Markers of total body fat/fat distribution (waist circumference, BMI and WHR), inflammation (IL-6, CRP and TNF-alpha R2), metabolism (fasting insulin, HDL, LDL and triglycerides) and BP (systolic and diastolic) correlated with FMD. Among these measurements, WHR was the only independent predictor of FMD (r2 = 0.30; p = 0.0001).

CONCLUSIONS

WHR is an important marker of endothelial dysfunction in healthy people across a wide range of body fatness.

Moderate mitral stenosis in pregnancy: the haemodynamic impact of diuresis

A case of asymptomatic, newly diagnosed, moderate mitral stenosis in a 27 year old pregnant woman is described. A conservative management strategy with regular cardiac assessment was adopted and the patient remained well. Routine transthoracic echocardiography at 36 weeks' gestation showed the development of severe pulmonary hypertension with right ventricular pressure overload, which was successfully treated with oral diuretics resulting in rapid normalisation of pulmonary pressure. Mitral stenosis in pregnancy and its management in pregnancy are briefly discussed.

Predicting sudden death in patients with mild to moderate chronic heart failure

OBJECTIVES

To explore the relation between non-invasive measures of cardiac function and sudden cardiac death, as well as the development and utility of an index integrating these variables to identify patients at increased risk of this mode of death.

DESIGN

UK-HEART (United Kingdom-heart failure evaluation and assessment of risk trial) was a prospective study conducted between December 1993 and April 2000. The study was specifically designed to identify non-invasive markers of death and mode of death among patients with chronic heart failure.

SETTING

8 UK general hospitals.

MAIN OUTCOME MEASURES

Death and mode of death.

RESULTS

553 patients aged a mean (SD) of 63 (10) years, in New York Heart Association functional class 2.3 (0.02), recruited prospectively. After 2365 patient-years' follow up, 201 patients had died (67 suddenly). Predictors of sudden death were greater cardiothoracic ratio, QRS dispersion, QT dispersion corrected for rate (QTc) across leads V1-V6 on the 12 lead ECG, and the presence of non-sustained ventricular tachycardia. The hazard ratio and 95% confidence intervals (CI) of sudden death for a 10% increase in cardiothoracic ratio was 1.43 (95% CI 1.20 to 1.71), for a 10% increase in QRS dispersion 1.11 (95% CI 1.04 to 1.19), for the presence of non-sustained ventricular tachycardia 2.03 (95% CI 1.27 to 3.25), and for a 10% increase in QTc dispersion across leads V1-V6 1.03 (95% CI 1.00 to 1.07) (all p < 0.04). An index derived from these four factors performed well in identifying patients specifically at increased risk of sudden death.

CONCLUSIONS

Results show that an index derived from three widely available non-invasive investigations has the potential to identify ambulant patients with chronic heart failure at increased risk of sudden death. This predictive tool could be used to target more sophisticated investigations or interventions aimed at preventing sudden death.

Inspiratory muscle load and capacity in chronic heart failure

BACKGROUND

Although breathlessness is common in chronic heart failure (CHF), the role of inspiratory muscle dysfunction remains unclear. We hypothesised that inspiratory muscle endurance, expressed as a function of endurance time (Tlim) adjusted for inspiratory muscle load and inspiratory muscle capacity, would be reduced in CHF.

METHODS

Endurance was measured in 10 healthy controls and 10 patients with CHF using threshold loading at 40% maximal oesophageal pressure (Poes(max)). Oesophageal pressure-time product (PTPoes per cycle) and Poes(max) were used as indices of inspiratory muscle load and capacity, respectively.

RESULTS

Although Poes(max) was slightly less in the CHF group (-117.7 (23.6) v -100.0 (18.3) cm H(2)O; 95% CI -37.5 to 2.2 cm H(2)O, p = 0.1), Tlim was greatly reduced (1800 v 306 (190) s; 95% CI 1368 to 1620 s, p<0.0001) and the observed PTPoes per cycle/Poes(max) was increased (0.13 (0.05) v 0.21 (0.04); 95% CI -0.11 to -0.03, p = 0.001). Most of this increased inspiratory muscle load was due to a maladaptive breathing pattern, with a reduction in expiratory time (3.0 (5.8) v 1.1 (0.3) s; 95% CI 0.3 to 3.5 s, p = 0.03) accompanied by an increased inspiratory time relative to total respiratory cycle (Ti/Ttot) (0.43 (0.14) v 0.62 (0.07); 95% CI -0.3 to -0.1, p = 0.001). However, log Tlim, which incorporates the higher inspiratory muscle load to capacity ratio caused by this altered breathing pattern, was >/=85% predicted in seven of 10 patients.

CONCLUSIONS

Although a marked reduction in endurance time was observed in CHF, much of this reduction was explained by the increased inspiratory muscle load to capacity ratio, suggesting that the major contributor to task failure was a maladaptive breathing pattern rather than impaired inspiratory muscle endurance.

Bronchoscopic closure of bronchopleural fistula using gelfoam

Management of a persistent bronchopleural fistula (BPF) can be a therapeutic challenge. The etiological factors responsible for BPF include pulmonary tuberculosis, post-thoracic resection surgeries, trauma, malignancy, necrotising infections and rupture of lung abscess. The immediate management of BPF is drainage of the pleural cavity with insertion of an intercostal drainage tube. Patients with BPF may also require surgical intervention in the form of a wedge resection or lobectomy or muscle flap surgery. We report a case of a peripheral BPF secondary to a bacterial infection, which was successfully managed by the instillation of gelfoam via flexible bronchoscopy.

Pathophysiological implications of insulin resistance on vascular endothelial function

BACKGROUND

Insulin resistance is a key component of the insulin resistance syndrome and is a crucially important metabolic abnormality in Type 2 diabetes. Insulin-resistant individuals are at significantly increased risk of cardiovascular disease, although the underlying mechanisms remain incompletely understood. The endothelium is thought to play a critical role in maintaining vascular homeostasis, a process dependent on the balance between the production of nitric oxide, superoxide and other vasoactive substances. Endothelial dysfunction has been demonstrated in insulin-resistant states in animals and humans and may represent an important early event in the development of atherosclerosis. Insulin resistance may be linked to endothelial dysfunction by a number of mechanisms, including disturbances of subcellular signalling pathways common to both insulin action and nitric oxide production. Other potential unifying links include the roles of oxidant stress, endothelin, the renin angiotensin system and the secretion of hormones and cytokines by adipose tissue. Lifestyle measures and drug therapies which improve insulin sensitivity and ameliorate endothelial dysfunction may be important in delaying the progression to overt cardiovascular disease in at risk individuals.

METHODS

We conducted a literature search using Medline, restricted to articles published in the English language between 1966 and the present, and reviewed bibliographies of relevant articles. An initial search strategy employing combinations of the MeSH terms: insulin resistance; endothelium, vascular; insulin; nitric oxide or hyperinsulinaemia produced over 300 references. Focused searches using keywords relevant to the molecular aspects of endothelial function and insulin signalling, and lifestyle or pharmacological interventions relevant to insulin resistance or endothelial function, produced over 300 further references. Abstracts of all references were screened before selecting those relevant to this review.