Follow-up study of morphology and cardiac function in rats undergoing induction of supravalvular aortic stenosis

OBJECTIVE: To characterize the follow-up of an experimental model of left ventricular hypertrophy (LVH) induced by supravalvular ascending aortic stenosis in young rats. METHODS: Wistar rats were submitted to thoracotomy and aortic stenosis was created by placing a clip on the ascending aorta (AoS group, n=12). Age-matched control animals underwent a sham operation (C group, n=12). Cardiac function was analysed by echocardiograms performed 6, 12, and 21 weeks after aortic banding. Myocardial morphological features and myocardial hydroxyproline concentration (HOP) were evaluated 2, 6, 12, and 21 weeks after surgery in additional animals. RESULTS: Aortic banding promoted early concentric LVH and a progressive increase in HOP. Under light microscopy, we observed myocyte hypertrophy and wall thickening of the intramural branches of the coronary arteries due to medial hypertrophy. Cardiac function was supranormal after 6 weeks (percentage of fractional shortening - EAo6: 70.3±10.8; C6: 61.3±5.4; p<0.05), and depressed in the last period. Diastolic dysfunction was detected after 12 weeks (ratio of early-to-late filling velocity - EAo12: 4.20±3.25; C12: 1.61±0.16; p<0.05). CONCLUSION: Ascending aortic stenosis promotes concentric LVH with myocardial fibrosis and minimal histological changes. According to the period of evaluation, cardiac function may be improved, normal, or depressed. The model is suitable and useful for studies on pathophysiology and treatment of the different phases of cardiac hypertrophy.

Protective Effect of Aortic Stenosis on the Coronary Arteries. Hypothetic Considerations to an Old Enigma

Abstract A literature overview of angiographic studies has shown that the prevalence of significant coronary disease in patients with aortic stenosis (AS) varies from 20 to 60%. Early necropsy studies suggested that patients with AS had a lower than expected incidence of coronary artery disease (CAD), originating the concept of a protective effect of AS on the coronary arteries. The myth of AS protection against CAD would be better explained as endothelium-myocardial interaction (crosstalk) protection triggered by left ventricular overload. Therefore, the cGMP/NO pathway induced by the AS overload pressure would explain the low incidence of CAD, which is compatible with the amazing natural long-term evolution of this cardiac valve disease.

Exploring Determinants of Urban Motorcycle Accident Severity: The Case of Barcelona

Public authorities and road users alike are increasingly concerned by recent trends in road safety outcomes in Barcelona, which is the European city with the highest number of registered Powered Two-Wheel (PTW) vehicles per inhabitant,. In this study we explore the determinants of motorcycle and moped accident severity in a large urban area, drawing on Barcelona’s local police database (2002-2008). We apply non-parametric regression techniques to characterize PTW accidents and parametric methods to investigate the factors influencing their severity. Our results show that PTW accident victims are more vulnerable, showing greater degrees of accident severity, than other traffic victims. Speed violations and alcohol consumption provide the worst health outcomes. Demographic and environment-related risk factors, in addition to helmet use, play an important role in determining accident severity. Thus, this study furthers our understanding of the most vulnerable vehicle types, while our results have direct implications for local policy makers in their fight to reduce the severity of PTW accidents in large urban areas.

Reasons why emergency department providers do not rely on the pneumonia severity index to determine the initial site of treatment for patients with pneumonia.

BACKGROUND: Many emergency department (ED) providers do not follow guideline recommendations for the use of the pneumonia severity index (PSI) to determine the initial site of treatment for patients with community-acquired pneumonia (CAP). We identified the reasons why ED providers hospitalize low-risk patients or manage higher-risk patients as outpatients. METHODS: As a part of a trial to implement a PSI-based guideline for the initial site of treatment of patients with CAP, we analyzed data for patients managed at 12 EDs allocated to a high-intensity guideline implementation strategy study arm. The guideline recommended outpatient care for low-risk patients (nonhypoxemic patients with a PSI risk classification of I, II, or III) and hospitalization for higher-risk patients (hypoxemic patients or patients with a PSI risk classification of IV or V). We asked providers who made guideline-discordant decisions on site of treatment to detail the reasons for nonadherence to guideline recommendations. RESULTS: There were 1,306 patients with CAP (689 low-risk patients and 617 higher-risk patients). Among these patients, physicians admitted 258 (37.4%) of 689 low-risk patients and treated 20 (3.2%) of 617 higher-risk patients as outpatients. The most commonly reported reasons for admitting low-risk patients were the presence of a comorbid illness (178 [71.5%] of 249 patients); a laboratory value, vital sign, or symptom that precluded ED discharge (73 patients [29.3%]); or a recommendation from a primary care or a consulting physician (48 patients [19.3%]). Higher-risk patients were most often treated as outpatients because of a recommendation by a primary care or consulting physician (6 [40.0%] of 15 patients). CONCLUSION: ED providers hospitalize many low-risk patients with CAP, most frequently for a comorbid illness. Although higher-risk patients are infrequently treated as outpatients, this decision is often based on the request of an involved physician.

Prospective validation of the Pulmonary Embolism Severity Index. A clinical prognostic model for pulmonary embolism

Practice guidelines recommend outpatient care for selected patients with non-massive pulmonary embolism (PE), but fail to specify how these low-risk patients should be identified. Using data from U.S. patients, we previously derived the Pulmonary Embolism Severity Index (PESI), a prediction rule that risk stratifies patients with PE. We sought to validate the PESI in a European patient cohort. We prospectively validated the PESI in patients with PE diagnosed at six emergency departments in three European countries. We used baseline data for the rule's 11 prognostic variables to stratify patients into five risk classes (I-V) of increasing probability of mortality. The outcome was overall mortality at 90 days after presentation. To assess the accuracy of the PESI to predict mortality, we estimated the sensitivity, specificity, and predictive values for low- (risk classes I/II) versus higher-risk patients (risk classes III-V), and the discriminatory power using the area under the receiver operating characteristic (ROC) curve. Among 357 patients with PE, overall mortality was 5.9%, ranging from 0% in class I to 17.9% in class V. The 186 (52%) low-risk patients had an overall mortality of 1.1% (95% confidence interval [CI]: 0.1-3.8%) compared to 11.1% (95% CI: 6.8-16.8%) in the 171 (48%) higher-risk patients. The PESI had a high sensitivity (91%, 95% CI: 71-97%) and a negative predictive value (99%, 95% CI: 96-100%) for predicting mortality. The area under the ROC curve was 0.78 (95% CI: 0.70-0.86). The PESI reliably identifies patients with PE who are at low risk of death and who are potential candidates for outpatient care. The PESI may help physicians make more rational decisions about hospitalization for patients with PE.

Treatment of congenital aortic valve stenosis: impact of the Ross operation.

GOAL: To evaluate the impact of the Ross operation, recently (1997) introduced in our unit, for the treatment of patients with congenital aortic valve stenosis. METHODS: The period from January 1997 to December 2000 was compared with the previous 5 years (1992-96). Thirty-seven children (< 16 yrs) and 49 young adults (16-50 yrs) with congenital aortic valve stenosis underwent one of these treatments: percutaneous balloon dilatation (PBD), aortic valve commissurotomy, aortic valve replacement and the Ross operation. The Ross operation was performed in 16 patients, mean age 24.5 yrs (range 9-46 yrs) with a bicuspid stenotic aortic valve, 7/10 adults with calcifications, 2/10 adults with previous aortic valve commissurotomy, 4/6 children with aortic regurgitation following PBD, and 1/6 children who had had a previous aortic valve replacement with a prosthetic valve and aortic root enlargement. RESULTS: PBD was followed by death in two neonates (fibroelastosis); all other children survived PBD. Although there were no deaths, PBD in adults was recently abandoned, owing to unfavourable results. Aortic valve commissurotomy showed good results in children (no deaths). Aortic valve replacement, although associated with good results (no deaths), has been recently abandoned in children in favour of the Ross operation. Over a mean follow-up of 16 months (2-40 months) all patients are asymptomatic following Ross operation, with no echocardiographic evidence of aortic valve regurgitation in 10/16 patients and with trivial regurgitation in 6/16 patients. CONCLUSIONS: The approach now for children and young adults with congenital aortic valve stenosis should be as follows: (1) PBD is the first choice in neonates and infants; (2) Aortic valve commissurotomy is the first choice for children, neonates and infants after failed PBD; (3) The Ross operation is increasingly used in children after failed PBD and in young adults, even with a calcified aortic valve.

Cognitive and emotional effects of carotid stenosis.

PRINCIPLES: Patients with carotid artery stenosis (CAS) are at risk of ipsilateral stroke and chronic compromise of cerebral blood flow. It is under debate whether the hypo-perfusion or embolism in CAS is directly related to cognitive impairment. Alternatively, CAS may be a marker for underlying risk factors, which themselves influence cognition. We aimed to determine cognitive performance level and the emotional state of patients with CAS. We hypo-thesised that patients with high grade stenosis, bilateral stenosis, symptomatic patients and/or those with relevant risk factors would suffer impairment of their cognitive performance and emotional state. METHODS: A total of 68 patients with CAS of ≥70% were included in a prospective exploratory study design. All patients underwent structured assessment of executive functions, language, verbal and visual memory, motor speed, anxiety and depression. RESULTS: Significantly more patients with CAS showed cognitive impairments (executive functions, word production, verbal and visual memory, motor speed) and anxiety than expected in a normative sample. Bilateral and symptomatic stenosis was associated with slower processing speed. Cognitive performance and anxiety level were not influenced by the side and the degree of stenosis or the presence of collaterals. Factors associated with less co-gnitive impairment included higher education level, female gender, ambidexterity and treated hypercholesterolemia. CONCLUSIONS: Cognitive impairment and increased level of anxiety are frequent in patients with carotid stenosis. The lack of a correlation between cognitive functioning and degree of stenosis or the presence of collaterals, challenges the view that CAS per se leads to cognitive impairment.

Mean platelet volume in the early phase of acute ischemic stroke is not associated with severity or functional outcome.

Background: Previous studies reported an increase of mean platelet volume (MPV) in patients with acute ischemic stroke. However, its correlation with stroke severity has not been investigated. Moreover, studies on the association of MPV with functional outcome yielded inconsistent results. Methods: We included all consecutive ischemic stroke patients admitted to CHUV (Centre Hospitalier Universitaire Vaudois) Neurology Service within 24 h after stroke onset who had MPV measured on admission. The association of MPV with stroke severity (NIHSS score at admission and at 24 h) and outcome (Rankin Scale score at 3 and 12 months) was analyzed in univariate analysis. The chi(2) test was performed to compare the frequency of minor strokes (NIHSS score </=4) and good functional outcome (Rankin Scale score </=2) across MPV quartiles. The ANOVA test was used to compare MPV between stroke subtypes according to the TOAST classification. Student's two-tailed unpaired t test was performed to compare MPV between lacunar and nonlacunar strokes. MPV was generated at admission by the Sysmex XE-2100 automated cell counter (Sysmex Corporation, Kobe, Japan) from EDTA blood samples. Results: There was no significant difference in the frequency of minor strokes (p = 0.46) and good functional outcome (p = 0.06) across MPV quartiles. MPV was not associated with stroke severity or outcome in univariate analysis. There was no significant difference in MPV between stroke subtypes according to the TOAST classification (p = 0.173) or between lacunar and nonlacunar strokes (10.50 +/- 0.91 vs. 10.40 +/- 0.81 fl, p = 0.322). Conclusions: MPV, assessed within 24 h after ischemic stroke onset, is not associated with stroke severity or functional outcome.

An Introduction to parametric and non-parametric models for bivariate positive insurance claim severity distributions

We present a real data set of claims amounts where costs related to damage are recorded separately from those related to medical expenses. Only claims with positive costs are considered here. Two approaches to density estimation are presented: a classical parametric and a semi-parametric method, based on transformation kernel density estimation. We explore the data set with standard univariate methods. We also propose ways to select the bandwidth and transformation parameters in the univariate case based on Bayesian methods. We indicate how to compare the results of alternative methods both looking at the shape of the overall density domain and exploring the density estimates in the right tail.

Estimation of parametric and nonparametric models for univariate claim severity distributions - an approach using R

This paper presents an analysis of motor vehicle insurance claims relating to vehicle damage and to associated medical expenses. We use univariate severity distributions estimated with parametric and non-parametric methods. The methods are implemented using the statistical package R. Parametric analysis is limited to estimation of normal and lognormal distributions for each of the two claim types. The nonparametric analysis presented involves kernel density estimation. We illustrate the benefits of applying transformations to data prior to employing kernel based methods. We use a log-transformation and an optimal transformation amongst a class of transformations that produces symmetry in the data. The central aim of this paper is to provide educators with material that can be used in the classroom to teach statistical estimation methods, goodness of fit analysis and importantly statistical computing in the context of insurance and risk management. To this end, we have included in the Appendix of this paper all the R code that has been used in the analysis so that readers, both students and educators, can fully explore the techniques described

French version of the addiction severity index (5th Edition): validity and reliability among Swiss opiate-dependent patients. French validation of the Addiction Severity Index.

OBJECTIVE: The aim of the study was to validate a French adaptation of the 5th version of the Addiction Severity Index (ASI) instrument in a Swiss sample of illicit drug users. PARTICIPANTS AND SETTING: The participants in the study were 54 French-speaking dependent patients, most of them with opiates as the drug of first choice. Procedure: Analyses of internal consistency (convergent and discriminant validity) and reliability, including measures of test-retest and inter-observer correlations, were conducted. RESULTS: Besides good applicability of the test, the results on composite scores (CSs) indicate comparable results to those obtained in a sample of American opiate-dependent patients. Across the seven dimensions of the ASI, Cronbach's alpha ranged from 0.42 to 0.76, test-retest correlations coefficients ranged from 0.48 to 0.98, while for CSs, inter-observer correlations ranged from 0.76 to 0.99. CONCLUSIONS: Despite several limitations, the French version of the ASI presents acceptable criteria of applicability, validity and reliability in a sample of drug-dependent patients.