Predictors of in-hospital mortality due to heart failure hospitalisation and trends of guideline-directed medical therapy usage

Background

The burden of heart failure (HF) is immense, from reducing quality of life (QoL) to increasing mortality risks and additional financial implications. The risk of adverse outcomes get higher with each HF hospitalisation (HFH).

Purpose

To look at predictors of in-hospital mortality outcomes during HFH and the prescription trends in conventional guideline-directed medical therapy (GDMT) for HF.

Methods

Retrospective analyses were performed for 7405 HFH cases admitted to our cardiology institution from 2009 to 2018, diagnosed based on the signs and symptoms of heart failure with NTProBNP≥300 at presentation.

Results

Most patients that required HFH were aged <65 years (53.5%), were males (72.8%) and had more diabetes mellitus (66%) and hypertension (75.1%). There were fewer other co-morbidities such as coronary artery disease (CAD) (26.9%), renal insufficiency (33.8%), atrial fibrillation (Afib) (23.9%), dyslipidaemia (40.3%), prior stroke/transient ischaemic attack (TIA) (5.6%), chronic obstructive pulmonary disease (11.6%), current/ex-smokers (45.5%). Most had presenting systolic blood pressure (SBP) >100 mmHg (88.8%), presenting heart rate ≥70 bpm (78.6%) and were in heart failure with reduced ejection fraction (HFrEF) <40% (74.8%). At presentation for HFH, 31.2% had 3 GDMTs (GDMT III) (angiotensin converting enzyme inhibitor / angiotensin receptor blocker / angiotensin receptor neprilysin inhibitor + beta blocker + mineralocorticoid receptor antagonist), 37% had either 2 GDMTs (GDMT II), 25% had only 1 GDMT (GDMT I), while 6.8% had none. The average in-hospital mortality rate was 5.2%. Independent predictors associated with increased in-hospital mortality were males, renal insufficiency, Afib, prior stroke/TIA, SBP ≤100 mmHg, serum sodium <135 mmol/L, uric acid ≥529 μmol/L, NTProBNP ≥6590, inpatient procedures i.e. dialysis, mechanical ventilation and cardiopulmonary resuscitation (CPR). Independent predictors associated with reduced inpatient mortality were hypertension, inpatient cardiac diagnostic procedures and presence of GDMT I, GDMT II and GDMT III at presentation (Figure 1). Throughout the 10 years, the proportion of GDMT prescription were similar; GDMT I (19.1–28.7%), GDMT II (35.1–41.6%), GDMT III (25.2–37.3%). The proportion of GDMT III across the CKD group stages were never more than 50% (Figure 2).

Conclusion

There remains significant in-hospital mortality risk for HFH. While some of these predictors are not modifiable, others are, especially when it comes to GDMT prescriptions. GDMTs provide better prognosis in patients living with HF. There are growing evidence that simultaneous / rapid sequence initiation of GDMTs are more beneficial than the conventional step wise approach. The analysis findings of GDMT proportions at presentation of HFH and also in the CKD group stages meant that many patients are still receiving suboptimal care for their HF and this clinician inertia mentality has got to change.

Funding Acknowledgement

Type of funding sources: None.

Development and validation of gender specific risk models in prediction of mortality for hospitalized heart failure patients in a multiethnic asian population

Funding Acknowledgements

Type of funding sources: None.

Background/Introduction

Heart failure carries substantial morbidity and mortality.  Female has different characteristics compared to male which may affect prognosis and are not represented well in many trials.  Multiple risk scores for in-hospital mortality have been created and validated such as ADHERE (Acute Decompensated Heart Failure National Registry) and GWTG (Get With The Guidelines).  However, these risk scores were in Western population and not gender specific.

Purpose

To develop and validate a gender specific risk model in predicting mortality amongst Asian patients admitted for acute decompensated heart failure (ADHF).

Methods

We analyzed data from our national centre’s ADHF registry.  Epidemiological, clinical, laboratory and imaging variables were ascertained.  Univariate and multivariate analysis using forward stepwise logistic regression were performed to identify predictors for all-cause in hospital mortality with emphasis on disparities between male and female. The accuracy of risk score was assessed using the concordance statistics while calibration was done using the Hosmer-Lemeshow method. The validity of the risk score was determined using separate gender validation cohorts.

Results

A total of 10148 patients admitted for ADHF were analyzed. 8262 patients admitted for ADHF from January 2009 to December 2018 (6008 males and 2254 females) were in the derivation cohort where as 1886 patients (1304 males and 582 females) were selected randomly from January 2019 to July 2021 for our validation cohort.  Female had better survival  (p value =0.04). There were 8 predictive variables for female cohort and 10 predictive variables for male cohort. Similar variables were low systolic blood pressure, loop diuretic use, dialysis, mechanical ventilation and CPR (cardiopulmonary resuscitation).  Interestingly, there were significant differences. For female, other variables that had impact on mortality were hypertension (AOR, 0.23; 95% CI,0.09–0.58), high urea (AOR, 3.32; 95% CI, 1.36–8.09) and hyponatremia (AOR, 2.87, 95% CI, 1.21–6.78).  However for male, the variables were renal insufficiency (AOR, 1.749; 95% CI, 1.13–2.72), history of stroke (AOR, 2.386, 95% CI, 1.22–4.65), LVEF less than 40% (AOR, 2.81; 95% CI, 1.40–5.63), absence of ARB/ACEi (AOR, 2.31; 95% CI, 1.48–3.60) and absence of beta blockers (AOR, 2.65; 95% CI, 1.73–4.05).  The AUC for the female derivation cohort was 0.97 (95% CI, 0.95–0.99) and 0.94 (95% CI, 0.92–0.96) for male derivation cohort.  AUC in the female validation cohort was 0.91 (95% CI, 0.83-0.98) and male was 0.90 (95% CI, 0.84–0.97). The risk scores showed good calibration (female; x²=8.88, p = 0.18 and male; x²=13.11, p = 0.07). 

Conclusion

A gender specific risk score for ADHF was developed and validated successfully in our Asian population. This will change our practice in providing valuable prognostic information in both female and male thereby guiding the need for more intensive treatment. Abstract Figure. ROC Curves (Female and Male)  Abstract Figure. Key Variables (Female and Male)

Mutant clones in normal epithelium outcompete and eliminate emerging tumours

Human epithelial tissues accumulate cancer-driver mutations with age1-9, yet tumour formation remains rare. The positive selection of these mutations suggests that they alter the behaviour and fitness of proliferating cells10-12. Thus, normal adult tissues become a patchwork of mutant clones competing for space and survival, with the fittest clones expanding by eliminating their less competitive neighbours11-14. However, little is known about how such dynamic competition in normal epithelia influences early tumorigenesis. Here we show that the majority of newly formed oesophageal tumours are eliminated through competition with mutant clones in the adjacent normal epithelium. We followed the fate of nascent, microscopic, pre-malignant tumours in a mouse model of oesophageal carcinogenesis and found that most were rapidly lost with no indication of tumour cell death, decreased proliferation or an anti-tumour immune response. However, deep sequencing of ten-day-old and one-year-old tumours showed evidence of selection on the surviving neoplasms. Induction of highly competitive clones in transgenic mice increased early tumour removal, whereas pharmacological inhibition of clonal competition reduced tumour loss. These results support a model in which survival of early neoplasms depends on their competitive fitness relative to that of mutant clones in the surrounding normal tissue. Mutant clones in normal epithelium have an unexpected anti-tumorigenic role in purging early tumours through cell competition, thereby preserving tissue integrity.

P252 Identifying predictors for all-cause mortality at admission, 1 and 3 years after admission for acute decompensated heart failure amongst patients with atrial fibrillation

Background

Heart failure (HF) and atrial fibrillation (AF) commonly co-exist, each, predisposing the other. AF may inflict haemodynamic disturbances, leading to reduced cardiac output and hence acute decompensation. Ultimately mortality risk is further increased. Identifying contributing factors is thus vital lest increasing risk of poor outcome.

Purpose

Identify predictors of all-cause mortality in AF patients after admission for acute decompensation HF (ADHF) at admission, 1 and 3 years. 

Methods

A retrospective observational study of 810 AF patients" first admission from 2009 to 2018, analysed using descriptive, ROC curve and Cox regression.

Results

Mortality at admission, 1 and 3 years following ADHF were 5.1%, 14.4% and 40.5% respectively. Majority of AF patients were male (64.7%) but there was no significant statistical difference between gender with associated mortality during those timelines. Using multivariate analysis, predictors associated with increased in-hospital mortality were Hyponatraemia, Na < 135mmol/L (adjusted Odds Ratio, aOR 2.49; 95% Confidence Interval, CI 1.91-5.20; p0.015), Uric Acid ≥ 675 (aOR 2.75; CI 1.31-5.79; p0.008), Ejection Fraction, EF < 40% (aOR 3.93; CI 1.63-9.49; p0.002). Medications on admission associated with reduced inpatient mortality were Angiotensin Converting Enzyme inhibitor (ACEi) / Angiotensin Receptor Blocker (ARB) + Beta Blocker (BB) + Mineralocorticoid Receptor Antagonist (MRA) (aOR 0.07; CI 0.02-0.30; p < 0.001). At 1 year, multivariate analysis showed an associated increase in mortality when NTProBNP ≥ 7500pg/ml (adjusted Hazard Ratio, aHR 1.64; CI 1.02-2.65; p0.042) and Urea > 7mmol/L (aHR 1.86; CI 1.04-3.32, p0.036). Medications on discharge comprising ACEi/ARB + BB + MRA were the only combination that showed a reduction in mortality (aHR 0.23; CI 0.09-0.60; p0.003). At 3 years, background coronary artery disease (aHR 1.72; CI 1.09-2.71; p0.02), hypernatraemia, Na > 145mmol/L (aHR 14.89; CI 3.17-69.86; p0.001), EF < 40% (aHR 2.00; CI 1.28-3.12; p0.002) were associated with increased mortality. Medications on discharge namely ACEi/ARB (aHR 0.14; CI 0.03-0.70; p0.013), BB (aHR 0.23; CI 0.10-0.51; p < 0.001), ACEi/ARB + BB (aHR 0.16; CI0.06-0.41; p < 0.001), ACEi/ARB + MRA (aHR 0.34; CI 0.14-0.85; p0.021), BB + MRA (aHR 0.38; CI 0.17-0.83; p0.016), ACEi/ARB + BB + MRA (aHR 0.193; CI 0.09-0.43; p < 0.001) showed an associated reduction in mortality.

Conclusions

In this single centre study, patients with AF who presented with ADHF had a variety of mortality predictors that influence at different timelines. They had higher risk of inpatient mortality with hyponatraemia, hyperuricaemia and EF < 40%. Elevated NTProBNP and Urea levels seemed to have more effect on mortality at 1 year compared to 3 years. Having 3 disease-modifying heart failure medications at discharge exerted the most benefit up to 3 years of follow up.

Abstract P252 Figure.

Development and Psychometric Evaluation of the Hypoglycemia Perspectives Questionnaire in Patients with Type 2 Diabetes Mellitus

AIMS

The aim of this study was to evaluate the factor structure and psychometric characteristics of the Hypoglycemia Perspectives Questionnaire (HPQ) assessing experience and perceptions of hypoglycemia in patients with type 2 diabetes mellitus (T2DM).

METHODS

HPQ was administered to adults with T2DM in a clinical sample from Cyprus (HYPO-Cyprus, n = 500) and a community sample in the United States (US, n = 1257) from the 2011 US National Health and Wellness Survey. Demographic and clinical data were collected. Analysis of HPQ data from two convenience samples examined item performance, factor structure, and HPQ measurement properties (reliability, convergent validity, known-groups validity).

RESULTS

Analyses supported three HPQ domains: symptom concern (six items), compensatory behavior (five items), and worry (five items). Internal consistency was high for all three domains (all ≥0.75), supporting reliability. Convergent validity was supported by moderate Spearman correlations between HPQ domain scores and the Audit of Diabetes-Dependent Quality of Life (ADDQoL-19) total score. Patients with recent hypoglycemia events had significantly higher HPQ scores, supporting known-group validity.

CONCLUSIONS

HPQ may be a valid and reliable measure capturing the experience and impact of hypoglycemia and useful in clinical trials and community-based settings.

Oral versus intravenous iron therapy in patients with inflammatory bowel disease and iron deficiency with and without anemia in Germany - a real-world evidence analysis

Background

Iron-deficiency anemia and iron deficiency are common comorbidities associated with inflammatory bowel disease (IBD) resulting in impaired quality of life and high health care costs. Intravenous iron has shown clinical benefit compared to oral iron therapy.

Aim

This study aimed to compare health care outcomes and costs after oral vs intravenous iron treatment for IBD patients with iron deficiency or iron deficiency anemia (ID/A) in Germany.

Methods

IBD patients with ID/A were identified by ICD-10-GM codes and newly commenced iron treatment via ATC codes in 2013 within the InGef (formerly Health Risk Institute) research claims database. Propensity score matching was performed to balance both treatment groups. Non-observable covariates were adjusted by applying the difference-in-differences (DID) approach.

Results

In 2013, 589 IBD patients with ID/A began oral and 442 intravenous iron treatment. After matching, 380 patients in each treatment group were analyzed. The intravenous group had fewer all-cause hospitalizations (37% vs 48%) and ID/A-related hospitalizations (5% vs 14%) than the oral iron group. The 1-year preobservation period comparison revealed significant health care cost differences between both groups. After adjusting for cost differences by DID method, total health care cost savings in the intravenous iron group were calculated to be €367. While higher expenditure for medication (€1,876) was observed in the intravenous iron group, the inpatient setting achieved most cost savings (€1,887).

Conclusion

IBD patients receiving intravenous iron were less frequently hospitalized and incurred lower total health care costs compared to patients receiving oral iron. Higher expenditures for pharmaceuticals were compensated by cost savings in other domains.

Cost-effectiveness of omalizumab add-on to standard-of-care therapy in patients with uncontrolled severe allergic asthma in a Brazilian healthcare setting

OBJECTIVE

Omalizumab add-on to standard-of-care therapy has proven to be efficacious in severe asthma patients for whom exacerbations cannot be controlled otherwise. Moreover, evidence from different healthcare settings suggests reduced healthcare resource utilization with omalizumab. Based on these findings, this study aimed to assess the cost-effectiveness of the addition of omalizumab to standard-of-care therapy in patients with uncontrolled severe allergic asthma in a Brazilian healthcare setting.

METHODS

A previously published Markov model was adapted using Brazil-specific unit costs to compare the costs and outcomes of the addition of omalizumab to standard-of-care therapy vs standard-of-care therapy alone. Model inputs were largely based on the eXpeRience study. Costs and health outcomes were calculated for lifetime-years and were annually discounted at 5%. Both one-way and probabilistic sensitivity analyses were performed.

RESULTS

An additional cost of R$280,400 for 5.20 additional quality-adjusted life-years was estimated with the addition of omalizumab to standard-of-care therapy, resulting in an incremental cost-effectiveness ratio of R$53,890. One-way sensitivity analysis indicated that discount rates, standard-of-care therapy exacerbation rates, and exacerbation-related mortality rates had the largest impact on incremental cost-effectiveness ratios.

LIMITATIONS

Assumptions of lifetime treatment adherence and rate of future exacerbations, independent of previous events, might affect the findings. The lack of Brazilian patients in the eXpeRience study may affect the findings, although sample size and baseline characteristics suggest that the modeled population closely resembles Brazilian severe allergic asthma patients.

CONCLUSION

Results indicate that omalizumab as an add-on therapy is more cost-effective than standard-of-care therapy alone for Brazilian patients with uncontrolled severe allergic asthma, based on the World Health Organization's cost-effectiveness threshold of up to 3-times the gross domestic product.

Systematic Literature Review of DPP-4 Inhibitors in Patients with Type 2 Diabetes Mellitus and Renal Impairment

INTRODUCTION

Dipeptidyl peptidase-4 (DPP-4) inhibitors are widely used in the management of patients with type 2 diabetes mellitus (T2DM) and renal impairment (RI). A systematic literature review was performed to compare the efficacy and safety of DPP-4 inhibitors in patients with T2DM and RI.

METHODS

We searched EMBASE, MEDLINE, and the Cochrane Central Register of Controlled Trials (cut-off, June 2015) to identify ≥12-week, randomized, placebo-controlled trials on DPP-4 inhibitors in ≥50 patients with T2DM and RI. Outcomes of interest included change in glycated hemoglobin (HbA1c), overall safety, and incidence of hypoglycemic events (HEs).

RESULTS

Seven trials of ≤52-54 weeks duration were retrieved, which included one study each on vildagliptin, saxagliptin, and sitagliptin, two on linagliptin, and the remaining two were extension studies of vildagliptin and saxagliptin. Majority of patients were on insulin at baseline (53-86%), except in the sitagliptin study, where approximately 11% received insulin during the placebo-controlled phase. After 52 weeks, vildagliptin and saxagliptin reduced HbA1c levels by 0.6-0.7% (baseline 7.8-8.4%) versus placebo in the overall population. HbA1c reductions were similar at weeks 12 and 52. In the 12-week, placebo-controlled phase, sitagliptin and linagliptin reduced mean HbA1c by approximately 0.4% (baseline 7.7-8.1%) versus placebo. Rates of HEs with DPP-4 inhibitors were not significantly different versus placebo in any study. Rates of adverse events (AEs) and changes involving renal function were similar in the active- and placebo-treated groups.

CONCLUSION

These results suggest that DPP-4 inhibitors have the potential to improve glycemic control in patients with RI without increasing the risk of HEs or overall AEs.

FUNDING

Novartis Pharma AG.

Prolactin-induced protein as a potential therapy response marker of adjuvant chemotherapy in breast cancer patients

Many studies are dedicated to exploring the molecular mechanisms of chemotherapy-resistance in breast cancer (BC). Some of them are focused on searching for candidate genes responsible for this process. The aim of this study was typing the candidate genes associated with the response to standard chemotherapy in the case of invasive ductal carcinoma. Frozen material from 28 biopsies obtained from IDC patients with different responses to chemotherapy were examined using gene expression microarray, Real-Time PCR (RT-PCR) and Western blot (WB). Based on the microarray results, further analysis of candidate gene expression was evaluated in 120 IDC cases by RT-PCR and in 224 IDC cases by immunohistochemistry (IHC). The results were correlated with clinical outcome and molecular subtype of the BC. Gene expression microarray revealed Prolactin-Induced Peptide (PIP) as a single gene differentially expressed in BC therapy responder or non-responder patients (p <0.05). The level of PIP expression was significantly higher in the BC therapy responder group than in the non-responder group at mRNA (p=0.0092) and protein level (p=0.0256). Expression of PIP mRNA was the highest in estrogen receptor positive (ER+) BC cases (p=0.0254) and it was the lowest in triple negative breast cancer (TNBC) (p=0.0336). Higher PIP mRNA expression was characterized by significantly longer disease free survival (DFS, p=0.0093), as well as metastasis free survival (MFS, p=0.0144). Additionally, PIP mRNA and PIP protein expression levels were significantly higher in luminal A than in other molecular subtypes and TNBC. Moreover significantly higher PIP expression was observed in G1, G2 vs. G3 cases (p=0.0027 and p=0.0013, respectively). Microarray analysis characterized PIP gene as a candidate for BC standard chemotherapy response marker. Analysis of clinical data suggests that PIP may be a good prognostic and predictive marker in IDC patients. Higher levels of PIP were related to longer DFS and MFS but not with OS.

Comparison of amlodipine/valsartan/hydrochlorothiazide single pill combination and free combination: adherence, persistence, healthcare utilization and costs

OBJECTIVES

To determine whether amlodipine/valsartan/hydrochlorothiazide single pill combination (SPC) is associated with improved persistence, adherence and reduced healthcare utilization and costs compared to the corresponding free combination (FC).

METHODS

Adult (≥18 years) patients covered by commercial and Medicare Supplemental insurance in the Truven MarketScan database with hypertension (HTN) diagnosis between October 2009 and December 2011 were included. At least two filled prescriptions for the SPC cohort or two periods of minimum 15 days of concurrent use of amlodipine, valsartan and hydrochlorothiazide (HCT) for the FC cohort were required. Cohorts were propensity score matched (PSM) to balance on important confounders. Outcomes included: 1) adherence (proportion of days covered [PDC] and medication possession ratio [MPR]); 2) persistence (treatment gap >30 days); 3) all-cause and HTN-specific healthcare utilization and costs at 12 months.

RESULTS

After cohort matching with PSM, patients taking SPC (N = 9221) exhibited better outcomes than FC (N = 1884): higher mean adherence (85.7% vs. 77.0%), mean PDC (73.8% vs. 60.6%) and persistence (46.8% vs. 23.6%) (all p < 0.0001). Patients taking SPC were associated with higher odds of persistence (OR: 3.51; 95% CI: 3.08-4.02), MPR ≥80% (OR: 2.72; 95% CI: 2.40-3.08) and PDC ≥80% (OR: 2.88; 95% CI: 2.55-3.26). After PSM, the SPC cohort exhibited statistically significantly lower mean number of resource utilization events compared to FC. Patients in the SPC cohort also had a statistically significantly (p < 0.05) lower percentage of patients with ≥1 all-cause hospitalization (15.0% vs. 18.2%), ≥1 all-cause emergency room (ER) visits (25.7 vs. 31.4%), and ≥1 ER HTN-specific visits (9.7% vs. 14.1%). The costs incurred by SPC cohort patients were 2.8% to 41.7% numerically lower than the FC cohort, statistically significant for all-cause ER costs ($430.6 vs. $549.5, p < 0.05).

CONCLUSIONS

Real-world data indicate an association of the amlodipine/valsartan/HCT SPC with improved adherence and persistence vs. FC with no difference in overall healthcare or hypertension specific costs between the cohorts.

Clinical trial simulation methods for estimating the impact of DPP-4 inhibitors on cardiovascular disease

Introduction

Dipeptidyl peptidase-4 (DPP-4) inhibitors are a class of oral antidiabetic agents for the treatment of type 2 diabetes mellitus, which lower blood glucose without causing severe hypoglycemia. However, the first cardiovascular (CV) safety trials have only recently reported their results, and our understanding of these therapies remains incomplete. Using clinical trial simulations, we estimated the effectiveness of DPP-4 inhibitors in preventing major adverse cardiovascular events (MACE) in a population like that enrolled in the SAVOR-TIMI (the Saxagliptin Assessment of Vascular Outcomes Recorded in Patients with Diabetes Mellitus – Thrombolysis in Myocardial Infarction) 53 trial.

Methods

We used the Archimedes Model to simulate a clinical trial of individuals (N=11,000) with diagnosed type 2 diabetes and elevated CV risk, based on established disease or multiple risk factors. The DPP-4 class was modeled with a meta-analysis of HbA_1c and weight change, pooling results from published trials of alogliptin, linagliptin, saxagliptin, sitagliptin, and vildagliptin. The study treatments were added-on to standard care, and outcomes were tracked for 20 years.

Results

The DPP-4 class was associated with an HbA_1c drop of 0.66% (0.71%, 0.62%) and a weight drop of 0.14 (−0.07, 0.36) kg. These biomarker improvements produced a relative risk (RR) for MACE at 5 years of 0.977 (0.968, 0.986). The number needed to treat to prevent one occurrence of MACE at 5 years was 327 (233, 550) in the elevated CV risk population.

Conclusion

Consistent with recent trial publications, our analysis indicates that DPP-4 inhibitors do not increase the risk of MACE relative to the standard of care. This study provides insights about the long-term benefits of DPP-4 inhibitors and supports the interpretation of the published CV safety trial results.

Pulse pressure and stroke risk: development and validation of a new stroke risk model

OBJECTIVE

This study aims to develop and validate a stroke risk model incorporating pulse pressure (PP) as a potential risk factor. Recent evidence suggests that PP, defined as the difference between systolic blood pressure (SBP) and diastolic blood pressure (DBP), could be an incremental risk factor beyond SBP.

METHODS

Electronic health records (EHRs) of hypertensive patients from a US integrated health delivery system were analyzed (January 2004 to May 2012). Patients with ≥ 1 PP reading and ≥ 6 months of observation prior to the first diagnosis of hypertension were randomly split into development (two-thirds of sample) and validation (one-third of sample) datasets. Stroke events were identified using ICD-9-CM 433.xx-436.xx. Cox proportional hazards models assessed time to first stroke event within 3 years of first hypertension diagnosis based on baseline risk factors, including PP, age, gender, diabetes, and cardiac comorbidities. The optimal model was selected using the least absolute shrinkage and selection operator (LASSO); performance was evaluated by the c-statistic.

RESULTS

Among 34,797 patients selected (mean age 59.3 years, 48% male), 4272 patients (12.3%) had a stroke. PP was higher among patients who developed stroke (mean [SD] PP, stroke: 02.0 [15.3] mmHg; non-stroke: 58.1 [14.0] mmHg, p < 0.001). The best performing risk model (c-statistic, development: 0.730; validation: 0.729) included PP (hazard ratio per mmHg increase: 1.0037, p < 0.001) as a significant risk factor.

LIMITATIONS

This study was subject to limitations similar to other studies using EHRs. Only patient encounters occurring within the single healthcare network were captured in the data source. Though the model was tested internally, external validation (using a separate data source) would help assess the model's generalizability and calibration.

CONCLUSIONS

This stroke risk model shows that greater PP is a significant predictive factor for increased stroke risk, even in the presence of known risk factors. PP should be considered by practitioners along with established risk factors in stroke treatment strategies.

Cost-effectiveness of metformin plus vildagliptin compared with metformin plus sulphonylurea for the treatment of patients with type 2 diabetes mellitus: a Portuguese healthcare system perspective

OBJECTIVE

To evaluate the cost-effectiveness of vildagliptin plus metformin vs generic sulphonylurea plus metformin in patients with type 2 diabetes mellitus, not controlled with metformin, from a Portuguese healthcare system perspective.

METHODS

A cost-effectiveness model was constructed using risk equations from the UK Prospective Diabetes Study Outcomes Model with a 10,000-patient cohort and a lifetime horizon. The model predicted microvascular and macrovascular complications and mortality in yearly cycles. Patients entered the model as metformin monotherapy failures and switched to alternative treatments (metformin plus basal-bolus insulin and subsequently metformin plus intensive insulin) when glycated hemoglobin A1c >7.5% was reached. Baseline patient characteristics and clinical variables were derived from a Portuguese epidemiological study. Cost estimates were based on direct medical costs only. One-way and probabilistic sensitivity analyses were conducted to test the robustness of the model.

RESULTS

There were fewer non-fatal diabetes-related adverse events (AEs) in patients treated with metformin plus vildagliptin compared with patients treated with metformin plus sulphonylurea (6752 vs 6815). Addition of vildagliptin compared with sulphonylurea led to increased drug acquisition costs but reduced costs of AEs, managing morbidities, and monitoring patients. Treatment with metformin plus vildagliptin yielded a mean per-patient gain of 0.1279 quality-adjusted life years (QALYs) and a mean per-patient increase in total cost of €1161, giving an incremental cost-effectiveness ratio (ICER) of €9072 per QALY. Univariate analyses showed that ICER values were robust and ranged from €4195 to €16,052 per QALY when different parameters were varied.

LIMITATIONS

The model excluded several diabetes-related morbidities, such as peripheral neuropathy and ulceration, and did not model second events. Patients were presumed to enter the model with no diabetes-related complications.

CONCLUSION

Treatment with metformin plus vildagliptin compared with metformin plus sulphonylurea is expected to result in a lower incidence of diabetes-related AEs and to be a cost-effective treatment strategy.

Costs associated with cardiovascular events in patients with hypertension in US managed care settings

Study quantified incremental cost of cardiovascular (CV) events in 6 high-risk and compelling indication subgroups: post-myocardial infarction (MI), diabetes, diabetic nephropathy, elderly, chronic kidney disease, and prior stroke. Based on claims data from privately insured individuals with 2+ hypertension (HTN) diagnoses in 2004-2006, we estimated regression-adjusted per-member-per-month healthcare costs after CVE. Costs were compared between patients with and without a CV events, and before and after CV events in each subgroup. The following CVevents were studied: acute MI, acute coronary syndrome, angina, ventricular arrhythmia, atrial arrhythmia, heart failure, coronary artery disease, left ventricular hypertrophy, stroke, and sinus tachycardia. Of 1,598,890 HTN patients, 510,118 had >/=1 CV event. Compared with controls, healthcare costs among patients with events were significantly greater across all cost components (inpatient, outpatient, and prescription drug). Acute MI and congestive heart failure generally had the largest incremental total healthcare costs. First-quarter post-event costs were attributable to inpatient costs. CV events are costly sequelae of hypertension in high-risk and CI subgroups.

An incremental approach to pigmented skin lesion segmentation with classification refinements in uncertain regions

Skin lesion segmentation in dermatoscopic images is difficult because there are large inter variations in shape, size, color, and texture between lesions and skin types. Hence, computational features learned from a training set of lesion images may not be applicable to other lesion images. In this paper, we propose an incremental method for lesion segmentation. It leverages the Expectation-Maximization algorithm to find an initial segmentation. A new adaptive method is proposed to define two types of segmented regions: the high-confident and the low-confident. We train a support vector machine, using computational features from the high-confident regions, to further refine segmentation and, hence, achieve improved results for the low-confident regions. Validation experiments of our proposed method are performed on 319 dermatoscopy images and we have achieved good results with precision and recall to be 0.864 and 0.875 respectively.

Resource utilization and costs following hospitalization of patients with chronic heart failure in the US

BACKGROUND

Despite advances in its management and the identification of preventable risk factors, heart failure (HF) is a growing health problem in the US. The objective of this study was to describe treatment patterns, medical resource utilization and costs following hospitalization for chronic HF for patients stratified by age.

METHODS

Patients with at least one hospitalization with chronic HF were identified in a US commercial insurance claims database from 2004-2008. Patients were followed from the 1st day of chronic HF hospitalization (index hospitalization) until disenrollment or end of data availability. Inpatient, outpatient and prescription drug utilization rates were calculated per person per month (PPPM). Costs included payments made by insurers and, where available, patient out-of-pocket payments and sick-leave costs were also calculated. Utilization rates and costs were stratified by patient age.

RESULTS

There were 7814 patients included in the study. Index hospitalization was the most resource intensive and expensive ($31,023 age <65, $12,426 age ≥ 65). The rate of outpatient visits was the highest within 3 months following index hospitalization (3.6/PPPM age <65, 4.1/PPPM age ≥ 65). For the older age group, rate of re-hospitalizations was highest (0.06/PPPM) within 3-6 months following index hospitalization, while the younger group had its highest rate (0.08/PPPM) during the first 3 months following index hospitalization. Prescription dispensing rates were similar between age groups; average reimbursement PPPM for cardiovascular drugs did not exceed $92 (age <65) and $221 (age ≥ 65), which represents less than 3% of hospitalization costs for both groups.

CONCLUSIONS

Treating chronic HF patients is resource intensive. The greatest burden occurs within 6 months after index hospitalization for both age groups; patients continue to be burdened after hospitalization by high inpatient and outpatient visit rates. Outpatient cardiovascular drug costs account for a small proportion of total healthcare costs.

Transradial percutaneous coronary intervention in acute ST elevation myocardial infarction and high-risk patients: experience in a single centre without cardiothoracic surgical backup

INTRODUCTION

Primary transradial percutaneous coronary intervention (TRI) is shown to be efficacious in stable patients with acute coronary syndrome. We aimed to evaluate the application of primary TRI for acute ST elevation myocardial infarction (STEMI), including among high-risk patients from our registry.

METHODS

This was a single-centre case series comprising 138 patients who underwent primary TRI for STEMI between May 2007 and June 2008. TRI was attempted with a 6-Fr guiding catheter in all patients regardless of Killip class status. Outcome measures were success rates of primary TRI, door-to-balloon time, procedure duration and volume of contrast used. All patients were followed up for major adverse cardiac events in-hospital, at 30 days and six months.

RESULTS

A total of 138 patients had primary TRI attempted for STEMI. Four patients failed primary TRI and required a femoral approach. The remaining 134 patients underwent primary TRI. The mean patient age was 56.4 years. Most patients with acute STEMI presented in Killip class I and II (91.8 percent). Only 8.2 percent were in Killip class III or IV on admission. 50 percent of patients presented with anterior STEMI. The median door-to-balloon time for this group was 92 (interquartile range [IQR] 77-121) minutes, with a median procedure time of 39 (IQR 29-51) minutes. The success rate of primary TRI was 97.1 percent.

CONCLUSION

Success rate, procedural and radiation time for TRI are comparable to those achieved via the femoral approach. Primary TRI is therefore a feasible and effective approach for acute STEMI, even in high-risk patients.

Effects on blood pressure and cardiovascular risk of variations in patients' adherence to prescribed antihypertensive drugs: role of duration of drug action

AIM

To determine the effects of imperfect adherence (i.e. occasionally missing prescribed doses), and the influence of rate of loss of antihypertensive effect during treatment interruption, on the predicted clinical effectiveness of antihypertensive drugs in reducing mean systolic blood pressure (SBP) and cardiovascular disease (CVD) risk.

METHOD

The effects of imperfect adherence to antihypertensive treatment regimens were estimated using published patterns of missed doses, and taking into account the rate of loss of antihypertensive effect when doses are missed (loss of BP reduction in mmHg/day; the off-rate), which varies between drugs. Outcome measures were the predicted mean SBP reduction and CVD risk, determined from the Framingham Risk Equation for CVD.

RESULTS

In patients taking 75% of prescribed doses (typical of clinical practice), only long-acting drugs with an off-rate of ∼1 mmHg/day were predicted to maintain almost the full mean SBP-lowering effect throughout the modelled period. In such patients, using shorter-acting drugs (e.g. an off-rate of ∼5-6 mmHg/day) was predicted to lead to a clinically relevant loss of mean SBP reduction of > 2 mmHg. This change also influenced the predicted CVD risk reduction; in patients with a baseline 10-year CVD risk of 27.0% and who were taking 75% of prescribed doses, a difference in off-rate from 1 to 5 mmHg/day led to a predicted 0.5% absolute increase in 10-year CVD risk.

CONCLUSIONS

In patients who occasionally miss doses of antihypertensives, modest differences in the rate of loss of antihypertensive effect following treatment interruption may have a clinically relevant impact on SBP reduction and CVD risk. While clinicians must make every effort to counsel and encourage each of their patients to adhere to their prescribed medication, it may also be prudent to prescribe drugs with a low off-rate to mitigate the potential consequences of missing doses.

Integrating spatial fuzzy clustering with level set methods for automated medical image segmentation

The performance of the level set segmentation is subject to appropriate initialization and optimal configuration of controlling parameters, which require substantial manual intervention. A new fuzzy level set algorithm is proposed in this paper to facilitate medical image segmentation. It is able to directly evolve from the initial segmentation by spatial fuzzy clustering. The controlling parameters of level set evolution are also estimated from the results of fuzzy clustering. Moreover the fuzzy level set algorithm is enhanced with locally regularized evolution. Such improvements facilitate level set manipulation and lead to more robust segmentation. Performance evaluation of the proposed algorithm was carried on medical images from different modalities. The results confirm its effectiveness for medical image segmentation.

ST segment elevation myocardial infarction following elective direct current synchronised cardioversion for atrial fibrillation

Atrial fibrillation is the most common arrhythmia in clinical practice. There is no difference in mortality, incidence of stroke or quality of life regardless of whether the rhythm control or rate control strategy is used. However, in certain circumstances, such as when rate control is inadequate, rhythm control is a viable option. We present a 74-year-old Eurasian man with a history of hypertension who presented with new-onset atrial fibrillation and sustained an ST segment elevation myocardial infarction following elective direct current cardioversion.

Accurate measurement of bone mineral density using clinical CT imaging with single energy beam spectral intensity correction

Although dual-energy X-ray absorptiometry (DXA) offers an effective measurement of bone mineral density, it only provides a 2-D projected measurement of the bone mineral density. Clinical computed tomography (CT) imaging will have to be employed for measurement of 3-D bone mineral density. The typical dual energy process requires precise measurement of the beam spectral intensity at the 80 kVp and 120 kVp settings. However, this is not used clinically because of the extra radiation dosage and sophisticated hardware setup. We propose an accurate and fast approach to measure bone material properties with single energy scans. Beam hardening artifacts are eliminated by incorporating the polychromatic characteristics of the X-ray beam into the reconstruction process. Bone mineral measurement from single energy CT correction is compared with that of dual energy correction and the commonly used DXA. Experimental results show that single energy correction is compatible with dual energy CT correction in eliminating beam hardening artifacts and producing an accurate measurement of bone mineral density. We can then estimate Young's modulus, yield stress, yield strain and ultimate tensile stress of the bone, which are important data for patient specific therapy planning.

Medical image segmentation using watershed segmentation with texture-based region merging

The use of the watershed algorithm for image segmentation is widespread because it is able to produce a complete division of the image. However, it is susceptible to over-segmentation and in medical image segmentation, this meant that that we do not have good representations of the anatomy. We address this issue by thresholding the gradient magnitude image and performing post-segmentation merging on the initial segmentation map. The automated thresholding technique is based on the histogram of the gradient magnitude map while the post-segmentation merging is based on the similarity in textural features (namely angular second moment, contrast, entropy and inverse difference moment) belonging to two neighboring partitions. When applied to the segmentation of various facial anatomical structures from magnetic resonance (MR) images, the proposed method achieved an overlap index of 92.6% compared to manual contour tracings. It is able to merge more than 80% of the initial partitions, which indicates that a large amount of over-segmentation has been reduced. Results produced using watershed algorithm with and without the proposed and proposed post-segmentation merging are presented for comparisons.

Issues in blood pressure control and the potential role of single-pill combination therapies

Hypertension (HTN) is a major risk factor for cardiovascular mortality, yet only a small proportion of hypertensive individuals receive appropriate therapy and achieve target blood pressure (BP) values. Factors influencing the success of antihypertensive therapy include physicians' acceptance of guideline BP targets, the efficacy and tolerability of the drug regimen, and patient compliance and persistence with therapy. It is now well recognised that most hypertensive patients require at least two antihypertensive agents to achieve their target BP. However, complicated treatment regimens are a major contributory factor to poor patient compliance. The use of combination therapy for HTN offers a number of advantages over the use of monotherapy, including improved efficacy, as drug combinations with a synergistic mechanism of action can be used. This additive effect means that lower doses of the individual components can be used, which may translate into a decreased likelihood of adverse events. The use of single-pill combination therapy, in which two or more agents are combined in a single dosage form, offers all the benefits of free combination therapy (improved efficacy and tolerability over monotherapy) together with the added benefit of improved patient compliance because of the simplified treatment regimen. The use of single-pill combination therapy may also be associated with cost savings compared with the use of free combinations for reasons of cheaper drug costs, fewer physician visits and fewer hospitalisations for uncontrolled HTN and cardiovascular events. Thus, the use of single-pill combination therapy for HTN should help improve BP goal attainment through improved patient compliance, leading to reduced costs for cardiovascular-related care.

Stonefish envenomation presenting to a Singapore hospital

INTRODUCTION

Stonefish, belonging to the genus Synanceia and classified under the Synanceiidae family, are commonly found in the shallow waters of the Indo-Pacific region and are considered the most dangerous and venomous of this family. The aim of the study was to describe the presenting features, clinical course and current management of this series of patients with stonefish envenomation presenting to a tertiary general hospital in Singapore.

METHODS

Data involving stonefish stings was retrospectively retrieved from the Singapore General Hospital Accident & Emergency Emerge Version 3.7.6 database from October 2004 to September 2006. Information, such as the patients' demographics, date and location of the incident, identity of the fish, local or systemic effects, pain score (upon arrival and after treatment), investigations and treatment as well as the outcome of the patients, were evaluated.

RESULTS

30 cases were identified. The median age of the patients was 28 years. The majority of patients were male (80 percent) and 47 percent of cases were foreign nationals. Most incidences occurred on weekends/public holidays (77 percent), with November having the highest number of cases (seven cases). The majority of cases (80 percent) arrived at the hospital within two hours of envenomation. Symptoms included extreme pain, swelling and redness of the affected limbs. 24 (80 percent) patients received hot water soak treatment and 27 (90 percent) patients received either intramuscular pethidine or diclofenac for analgesia, where nine patients (33 percent) required additional analgesics after a period of observation. 17 patients (58 percent) were treated and discharged, eight (26 percent) were referred to a specialist for follow-up and five (16 percent) were admitted for an average of three days. 13 out of 25 patients (52 percent) were discharged with antibiotics. One case complained of persistent pain and hyperalgesia five months post-envenomation. One patient required surgical intervention. No deaths and systemic symptoms were reported.

CONCLUSION

Cases of stonefish envenomation that presented to our hospital showed that the majority of patients were young male adults. Stonefish envenomation, though it rarely kills, can cause extreme pain, swelling and erythema, which can be managed with symptomatic treatment.

Automatic working area classification in peripheral blood smears without cell central zone extraction

In this paper we study automatic classification of working areas in peripheral blood smears using image analysis and recognition methods. Such automatic classification can provide objective and reproducible quality control for the evaluation of smears and smear maker devices. However, research in this filed has drawn little attention. Existing methods either can not differentiate correctly different cell distributions or rely on the extraction of the central pallor zones in cells for counting, which are not always observable. In contrast, we do not rely on the pallor zone extraction thus on more general basis. We introduce two generic parameters to measure the goodness of working areas, one for the degree of overlap, and the other for the spatial occupancy. We also propose a cascading classification network for the classification of different areas. The effectiveness of our method has been tested on over 150 labeled images acquired from three malaria-infected Giemsa-stained blood smears using an oil immersion 100 x objective.

Generalized negative binomial distribution: a promising statistical distribution for Oncomelania hupensis in the lake- and marsh-land regions of China

A new generalization of the negative binomial distribution (GNBD) is introduced and fitted to counts of Oncomelania hupensis, the intermediate host of Schistosoma japonicum, made, in areas of Chinese lakeland and marshland, early in the winter of 2005 and late in the spring of 2006. The GNBD was found to fit the snail data better than the standard negative binomial distribution (NBD) that has previously been widely used to model the distribution of O. hupensis. With two more parameters than the NBD, the GNBD can integrate many discrete distributions and is more flexible than the NBD in modelling O. hupensis. It also provides a better theoretical distribution for the quantitative study of O. hupensis, especially in building an accurate prediction model of snail density. The justification for adopting the GNBD is discussed. The GNBD allows researchers to broaden the field in the quantitative study not only of O. hupensis and schistosomiasis japonica but also of other environment-related helminthiases and family-clustered diseases that have, traditionally, been modelled using the NBD.

Spectrogram denoising and automated extraction of the fundamental frequency variation of dolphin whistles

Marine mammal vocalizations are often analyzed using time-frequency representations (TFRs) which highlight their nonstationarities. One commonly used TFR is the spectrogram. The characteristic spectrogram time-frequency (TF) contours of marine mammal vocalizations play a significant role in whistle classification and individual or group identification. A major hurdle in the robust automated extraction of TF contours from spectrograms is underwater noise. An image-based algorithm has been developed for denoising and extraction of TF contours from noisy underwater recordings. An objective procedure for measuring the accuracy of extracted spectrogram contours is also proposed. This method is shown to perform well when dealing with the challenging problem of denoising broadband transients commonly encountered in warm shallow waters inhabited by snapping shrimp. Furthermore, it would also be useful with other types of broadband transient noise.

The Cdc42 effector IRSp53 generates filopodia by coupling membrane protrusion with actin dynamics

The Cdc42 effector IRSp53 is a strong inducer of filopodia formation and consists of an Src homology domain 3 (SH3), a potential WW-binding motif, a partial-Cdc42/Rac interacting binding region motif, and an Inverse-Bin-Amphiphysins-Rvs (I-BAR) domain. We show that IRSp53 interacts directly with neuronal Wiskott-Aldrich syndrome protein (N-WASP) via its SH3 domain and furthermore that N-WASP is required for filopodia formation as IRSp53 failed to induce filopodia formation in N-WASP knock-out (KO) fibroblasts. IRSp53-induced filopodia formation can be reconstituted in N-WASP KO fibroblasts by full-length N-WASP, by N-WASPDeltaWA (a mutant unable to activate the Arp2/3 complex), and by N-WASPH208D (a mutant unable to bind Cdc42). IRSp53 failed to induce filopodia in mammalian enabled (Mena)/VASP KO cells, and N-WASP failed to induce filopodia when IRSp53 was knocked down with RNA interference. The IRSp53 I-BAR domain alone induces dynamic membrane protrusions that lack actin and are smaller than normal filopodia ("partial-filopodia") in both wild-type N-WASP and N-WASP KO cells. We propose that IRSp53 generates filopodia by coupling membrane protrusion through its I-BAR domain with actin dynamics through SH3 domain binding partners, including N-WASP and Mena.

Medical image segmentation using feature-based GVF snake

We propose a feature-based GVF snake for medical image segmentation here. Feature-based criteria are introduced for the GVF snake to stop its iterations. Without these criteria, the GVF snake might continue its iterations even though it has converged at the targeted object and result in longer computational time. The feature here is the area of the targeted object. Our proposed method comprises of two stages, namely the training stage and the segmentation stage. In the training stage, we acquire prior knowledge on the relative area of the targeted object from training data. In the segmentation stage, the proposed feature-based GVF snake is applied to segment the object from the image after computing the estimated area of the targeted object. In our proposed method, the GVF snake stops its iterations when the area bounded by its propagation is approximately equal to the estimated area and when it undergoes little change over two consecutive iterations. To illustrate the effectiveness of our proposed method, we applied it to the segmentation of the masseter muscle, which is the strongest jaw muscle, from 2-D magnetic resonance (MR) images. Numerical evaluation done indicates good agreement between the computerized and manual segmentations, with mean overlap of 92%.

Masseter segmentation using an improved watershed algorithm with unsupervised classification

The watershed algorithm always produces a complete division of the image. However, it is susceptible to over-segmentation and sensitivity to false edges. In medical images this leads to unfavorable representations of the anatomy. We address these drawbacks by introducing automated thresholding and post-segmentation merging. The automated thresholding step is based on the histogram of the gradient magnitude map while post-segmentation merging is based on a criterion which measures the similarity in intensity values between two neighboring partitions. Our improved watershed algorithm is able to merge more than 90% of the initial partitions, which indicates that a large amount of over-segmentation has been reduced. To further improve the segmentation results, we make use of K-means clustering to provide an initial coarse segmentation of the highly textured image before the improved watershed algorithm is applied to it. When applied to the segmentation of the masseter from 60 magnetic resonance images of 10 subjects, the proposed algorithm achieved an overlap index (kappa) of 90.6%, and was able to merge 98% of the initial partitions on average. The segmentation results are comparable to those obtained using the gradient vector flow snake.

New insights into image processing of cortical blood flow monitors using laser speckle imaging

Laser speckle imaging has increasingly become a viable technique for real-time medical imaging. However, the computational intricacies and the viewing experience involved limit its usefulness for real-time monitors such as those intended for neurosurgical applications. In this paper, we propose a new technique, tLASCA, which processes statistics primarily in the temporal direction using the laser speckle contrast analysis (LASCA) equation, proposed by Briers and Webster. This technique is thoroughly compared with the existing techniques for signal processing of laser speckle images, including, the spatial-based sLASCA and the temporal-based modified laser speckle imaging (mLSI) techniques. sLASCA is an improvement of the basic LASCA technique. In sLASCA, the derived contrasts are further averaged over a predetermined number of raw speckle images. mLSI, on the other hand, is the technique in which temporal statistics are processed using the equation described by Ohtsubo and Asakura. tLASCA preserves the original image resolution similar to mLSI. tLASCA outperforms sLASCA (window size M = 5) with faster convergence of K values (5.32 versus 20.56 s), shorter per-frame processing time (0.34 versus 2.51 s), and better subjective and objective quality evaluations of contrast images. tLASCA also outperforms mLSI with faster convergence of K values (5.32 s) compared to N values (10.44 s), shorter per-frame processing time (0.34 versus 0.91 s), smaller intensity fluctuations among frames (8%-10% versus 15%-35%), and better subjective and objective quality evaluations of contrast images. As laser speckle imaging becomes an important tool for real-time monitoring of blood flows and vascular perfusion, tLASCA is proven to be the technique of choice.

3D statistical models for tooth surface reconstruction

This paper presents a method to reconstruct the 3D surface of a tooth given partial information about its shape. A statistical model comprising a mean shape and a series of deformation modes is obtained offline using a set of specimens. During reconstruction, rigid registration is performed to align the mean shape with the target. The mean shape is then deformed to approximate the target by minimizing the sum of squared distances between the two surfaces according to the deformation modes. The method is shown to be efficient for the recovery of tooth shape given crown information.

Heterogeneous meshing and biomechanical modeling of human spine

We aim to develop a patient-specific biomechanical model of human spine for the purpose of surgical training and planning. In this paper, we describe the development of a finite-element model of the spine from the VHD Male Data. The finite-element spine model comprises volumetric elements suitable for deformation and other finite-element analysis using ABAQUS. The mesh generation solution accepts segmented radiological slices as input, and outputs three-dimensional (3D) volumetric finite element meshes that are ABAQUS compliant. The proposed mesh generation method first uses a grid plane to divide the contours of the anatomical boundaries and its inclusions into discrete meshes. A grid frame is then built to connect the grid planes between any two adjacent planes using a novel scheme. The meshes produced consist of brick elements in the interior of the contours and with tetrahedral and wedge elements at the boundaries. The nodal points are classified according to their materials and hence, elements can be assigned different properties. The resultant spine model comprises a detailed model of the 7 cervical vertebrae, 12 thoracic vertebrae, 5 lumbar vertebrae, and S1. Each of the vertebrae and intervertebral disc has between 1200 and 6000 elements, and approximately 1200 elements, respectively. The accuracy of the resultant VHD finite element spine model was good based on visual comparison of volume-rendered images of the original CT data, and has been used in a computational analysis involving needle insertion and static deformation. We also compared the mesh generated using our method against two automatically generated models; one consists of purely tetrahedral elements and the other hexahedral elements.

A study on shape determinative slices for the masseter muscle

In this paper, we localize the shape-determinative slices of the masseter, which plays a critical role in the mastication system, from magnetic resonance (MR) data sets for clinical purposes. Shape-based criteria were used to locate the candidates for determinative slices from training data. The localization process involves tracking of the centroid and detecting the locations where the structure of the masseter undergoes an abrupt change in orientation. Having determined all the candidates which satisfy the criteria, fuzzy-c-means (FCM) clustering technique was used to establish the determinative slices. Localization of these slices will facilitate the building of more accurate models. It will also allow for more accurate computerized extraction of the masseter from MR data. In our work here, a hybrid method to shape-based interpolation is used to build the masseter model from magnetic resonance (MR) data sets, and the mean overlap index (¿) achieved is 87.7%. Extraction of the masseter was carried out using our earlier proposed method and the mean ¿ achieved is 8.9%. This indicates good agreement between the results obtained using computerized technique and those contained using manual contour tracing.

Knowledge-driven 3-D extraction of the masseter from MR data

In this paper, we propose a knowledge-driven highly automatic methodology for extracting the masseter from magnetic resonance (MR) data sets for clinical purposes. The masseter is a muscle of mastication which acts to raise the jaw and clench the teeth. In our initial work, we designed a process which allowed us to perform 2-D segmentation of the masseter on 2-D MR images. In the methodology proposed here, we make use of ground truth to first determine the index of the MR slice in which we will carry out 2-D segmentation of the masseter. Having obtained the 2-D segmentation, we will make use of it to determine the region of interest (ROI) of the masseter in the other MR slices belonging to the same data set. The upper and lower thresholds applied to these MR slices, for extraction of the masseter, are determined through the histogram of the 2-D segmented masseter. Visualization of the 3-D masseter is achieved via volume rendering. Our methodology has been applied to five MR data sets. Validation was done by comparing the segmentation results obtained by using our proposed methodology against manual contour tracings, obtaining an average accuracy of 83.5%

Computational biomechanical modelling of the lumbar spine using marching-cubes surface smoothened finite element voxel meshing

There is a need for the development of finite element (FE) models based on medical datasets, such as magnetic resonance imaging and computerized tomography in computation biomechanics. Direct conversion of graphic voxels to FE elements is a commonly used method for the generation of FE models. However, conventional voxel-based methods tend to produce models with jagged surfaces. This is a consequence of the inherent characteristics of voxel elements; such a model is unable to capture the geometries of anatomical structures satisfactorily. We have developed a robust technique for the automatic generation of voxel-based patient-specific FE models. Our approach features a novel tetrahedronization scheme that incorporates marching-cubes surface smoothing together with a smooth-distortion factor (SDF). The models conform to the actual geometries of anatomical structures of a lumbar spine segment (L3). The resultant finite element analysis (FEA) at the surfaces is more accurate compared to the use of conventional voxel-based generated FE models. In general, models produced by our method were superior compared to that obtained using the commercial software ScanFE.

Computer-based extraction of the inferior alveolar nerve canal in 3-D space

Computed tomography (CT) is increasingly employed in orthodontic treatment. One of the most successful applications is in dental implantology, in which an artificial root is surgically inserted into the jawbone to provide anchorage for a dental prosthesis. For successful implant surgery, it is crucial to locate internal structures such as the inferior alveolar nerve canal (IAC). This paper presents a computerized technique for extracting the IAC. To facilitate the extraction, we first generate panoramic CT images (panoramics) by reformatting the original CT images. The panoramics are a series of cross-sectional images along curved planes through the mandible (lower jawbone). Hollow canals are subsequently detected by analyzing the voxel intensities and 3-D gradient orientations in the panoramics. The axis of the IAC is then traced out by a novel 3-D line-tracking technique. The method is effective for extracting the IAC despite the open structure of the surrounding bone.

Tooth segmentation of dental study models using range images

The accurate segmentation of the teeth from the digitized representation of a dental study model is an important component in computer-based algorithms for orthodontic feature detection and measurement and in the simulation of orthodontic procedures such as tooth rearrangement. This paper presents an automated method for tooth segmentation from the three-dimensional (3-D) digitized image captured by a laser scanner. We avoid the complexity of directly processing 3-D mesh data by proposing the innovative idea of detecting features on two range images computed from the 3-D image. The dental arch is first obtained from the plan-view range image. Using the arch as the reference, a panoramic range image of the dental model can be computed. The interstices between the teeth are detected separately in the two range images, and results from both views are combined for a determination of interstice locations and orientations. Finally, the teeth are separated from the gums by delineating the gum margin. The algorithm was tested on 34 dental models representing a variety of malocclusions and was found to be robust and accurate.

The WRP component of the WAVE-1 complex attenuates Rac-mediated signalling

WAVE-1, which is also known as Scar, is a scaffolding protein that directs actin reorganization by relaying signals from the GTPase Rac to the Arp2/3 complex. Although the molecular details of WAVE activation by Rac have been described, the mechanisms by which these signals are terminated remain unknown. Here we have used tandem mass spectrometry to identify previously unknown components of the WAVE signalling network including WRP, a Rac-selective GTPase-activating protein. WRP binds directly to WAVE-1 through its Src homology domain 3 and specifically inhibits Rac function in vivo. Thus, we propose that WRP is a binding partner of WAVE-1 that functions as a signal termination factor for Rac.

Personality of males charged with outrage of modesty

Outrage of modesty (OOM) is considered a serious crime in Singapore and offenders are often charged with a period of imprisonment with or without a fine and caning. Previous studies have indicated that non-violent sexual offenders tend to have a socially inhibited personality. No published study has yet been conducted to investigate the personality of OOM offenders. The purpose of the current study was to assess the personality of males charged with outrage of modesty and compare them to a group of males charged with theft using the 16 Personality Factors questionnaire (16PF; Cattell, Eber, and Tatsuoka, 1970). Participants were selected over a two-year study period from a cohort of prisoners serving sentence at Changi Prison. A total of 30 OOM and 22 theft offenders completed the 16PF. All OOM subjects had been charged for molesting an adult female. Unexpectedly, planned comparisons revealed that OOM subjects had marginally higher scores on Factor H (boldness) compared to theft subjects. Exploratory analyses revealed no other significant differences between OOM and theft subjects. Implications of findings and limitations of the study are discussed.

Sprouty2 inhibits the Ras/MAP kinase pathway by inhibiting the activation of Raf

Several genetic studies in Drosophila have shown that the dSprouty (dSpry) protein inhibits the Ras/mitogen-activated protein (MAP) kinase pathway induced by various activated receptor tyrosine kinase receptors, most notably those of the epidermal growth factor receptor (EGFR) and fibroblast growth factor receptor (FGFR). Currently, the mode of action of dSpry is unknown, and the point of inhibition remains controversial. There are at least four mammalian Spry isoforms that have been shown to co-express preferentially with FGFRs as compared with EGFRs. In this study, we investigated the effects of the various mammalian Spry isoforms on the Ras/MAP kinase pathway in cells overexpressing constitutively active FGFR1. hSpry2 was significantly more potent than mSpry1 or mSpry4 in inhibiting the Ras/MAP kinase pathway. Additional experiments indicated that full-length hSpry2 was required for its full potency. hSpry2 had no inhibitory effect on either the JNK or the p38 pathway and displayed no inhibition of FRS2 phosphorylation, Akt activation, and Ras activation. Constitutively active mutants of Ras, Raf, and Mek were employed to locate the prospective point of inhibition of hSpry2 downstream of activated Ras. Results from this study indicated that hSpry2 exerted its inhibitory effect at the level of Raf, which was verified in a Raf activation assay in an FGF signaling context.

ShcA and Grb2 mediate polyoma middle T antigen-induced endothelial transformation and Gab1 tyrosine phosphorylation

Middle T antigen (PymT) is the principal transforming component of polyomavirus, and rapidly induces hemangiomas in neonatal mice. PymT, a membrane-associated scaffold, recruits and activates Src family tyrosine kinases, and, once tyrosine phosphorylated, binds proteins with PTB and SH2 domains such as ShcA, phosphatidylinositol 3-kinase (PI3K) and phospholipase Cgamma-1 (PLCgamma-1). To explore the pathways required for endothelial transformation in vivo, we introduced PymT mutant forms into mice. PymT variants unable to bind PI3K and PLCgamma-1 directly induced hemangiomas similarly to wild type, but a mutant unable to bind ShcA was transformation compromised. Requirement for a ShcA PTB domain- binding site was suppressed by replacing this motif in PymT with YXN sequences, which bind the Grb2 SH2 domain upon phosphorylation. Surprisingly, PymT recruitment of ShcA and Grb2 correlated with PI3K activation. PymT mimics activated receptor tyrosine kinases by forming a ShcA-Grb2-Gab1 complex, thus inducing Gab1 tyrosine phosphorylation, which itself is associated with PI3K. Therefore, PymT activation of ShcA-Grb2 signaling is critical for endothelial transformation, and PymT can stimulate Grb2 signaling to both the MAP kinase and PI3K pathways.

Structural basis for autoinhibition of the Ephb2 receptor tyrosine kinase by the unphosphorylated juxtamembrane region

The Eph receptor tyrosine kinase family is regulated by autophosphorylation within the juxtamembrane region and the kinase activation segment. We have solved the X-ray crystal structure to 1.9 A resolution of an autoinhibited, unphosphorylated form of EphB2 comprised of the juxtamembrane region and the kinase domain. The structure, supported by mutagenesis data, reveals that the juxtamembrane segment adopts a helical conformation that distorts the small lobe of the kinase domain, and blocks the activation segment from attaining an activated conformation. Phosphorylation of conserved juxtamembrane tyrosines would relieve this autoinhibition by disturbing the association of the juxtamembrane segment with the kinase domain, while liberating phosphotyrosine sites for binding SH2 domains of target proteins. We propose that the autoinhibitory mechanism employed by EphB2 is a more general device through which receptor tyrosine kinases are controlled.

Gene dosage-dependent functions for phosphotyrosine-Grb2 signaling during mammalian tissue morphogenesis

BACKGROUND

The mammalian Grb2 adaptor protein binds pTyr-X-Asn motifs through its SH2 domain, and engages downstream targets such as Sos1 and Gab1 through its SH3 domains. Grb2 thereby couples receptor tyrosine kinases to the Ras-MAP kinase pathway, and potentially to phosphatidylinositol (PI) 3'-kinase. By creating a null (Delta) allele of mouse Grb2, we have shown that Grb2 is required for endoderm differentiation at embryonic day 4.0.

RESULTS

Grb2 likely has multiple embryonic and postnatal functions. To address this issue, a hypomorphic mutation, first characterized in the Caenorhabditis elegans Grb2 ortholog Sem-5, was engineered into the mouse Grb2 gene. This mutation (E89K) reduces phosphotyrosine binding by the SH2 domain. Embryos that are compound heterozygous for the null and hypomorphic alleles exhibit defects in placental morphogenesis and in the survival of a subset of migrating neural crest cells required for branchial arch formation. Furthermore, animals homozygous for the hypomorphic mutation die perinatally because of clefting of the palate, a branchial arch-derived structure. Analysis of E89K/Delta Grb2 mutant fibroblasts revealed a marked defect in ERK/MAP kinase activation and Gab1 tyrosine phosphorylation following growth factor stimulation.

CONCLUSIONS

We have created an allelic series within mouse Grb2, which has revealed distinct functions for phosphotyrosine-Grb2 signaling in tissue morphogenesis and cell viability necessary for mammalian development. The placental defects in E89K/Delta mutant embryos are reminiscent of those seen in receptor tyrosine kinase-, Sos1-, and Gab1-deficient embryos, consistent with the finding that endogenous Grb2 is required for efficient RTK signaling to the Ras-MAP kinase and Gab1 pathways.

Docking protein FRS2 links the protein tyrosine kinase RET and its oncogenic forms with the mitogen-activated protein kinase signaling cascade

The receptor tyrosine kinase RET functions as the signal transducing receptor for the GDNF (for "glial cell-derived neurotrophic factors") family of ligands. Mutations in the RET gene were implicated in Hirschsprung disease (HSCR), multiple endocrine neoplasia type 2 (MEN 2), and thyroid carcinomas. In this report we demonstrate that the docking protein FRS2 is tyrosine phosphorylated by ligand-stimulated and by constitutively activated oncogenic forms of RET. Complex formation between RET and FRS2 is mediated by binding of the phosphotyrosine-binding domain of FRS2 to pY1062, a residue in RET that also functions as a binding site for Shc. However, overexpression of FRS2 but not Shc potentiates mitogen-activated protein (MAP) kinase activation by RET oncoproteins. We demonstrate that oncogenic RET-PTC proteins are associated with FRS2 constitutively, leading to tyrosine phosphorylation of FRS2, MAP kinase stimulation, and cell proliferation. However, loss-of-function HSCR-associated RET mutants exhibit impaired FRS2 binding and reduced MAP kinase activation. These experiments demonstrate that FRS2 couples both ligand-regulated and oncogenic forms of RET, with the MAP kinase signaling cascade as part of the response of RET under normal biological conditions and pathological conditions, such as MEN 2 and papillary thyroid carcinomas.