Population-based detection of systolic and diastolic dysfunction with amino-terminal pro-B-type natriuretic peptide

Background: There is limited information regarding the clinical utility of amino-terminal pro-B-type natriuretic peptide (NT-proBNP) for the detection of left ventricular (LV) dysfunction in the community. We evaluated predictors of circulating NT-proBN

What motivates senior clinicians to teach medical students?

BACKGROUND: This study was designed to assess the motivations of senior medical clinicians to teach medical students. This understanding could improve the recruitment and retention of important clinical teachers. METHODS: The study group was 101 senior medical clinicians registered on a teaching list for a medical school teaching hospital (The Canberra Hospital, ACT, Australia). Their motivations to teach medical students were assessed applying Q methodology. RESULTS: Of the 75 participants, 18 (24%) were female and 57 (76%) were male. The age distribution was as follows: 30–40 years = 16 participants (21.3%), 41–55 years = 46 participants (61.3%) and >55 years = 13 participants (17.3%). Most participants (n = 48, 64%) were staff specialists and 27 (36%) were visiting medical officers. Half of the participants were internists (n = 39, 52%), 12 (16%) were surgeons, and 24 (32%) were other sub-specialists. Of the 26 senior clinicians that did not participate, two were women; 15 were visiting medical officers and 11 were staff specialists; 16 were internists, 9 were surgeons and there was one other sub-specialist. The majority of these non-participating clinicians fell in the 41–55 year age group. The participating clinicians were moderately homogenous in their responses. Factor analysis produced 4 factors: one summarising positive motivations for teaching and three capturing impediments for teaching. The main factors influencing motivation to teach medical students were intrinsic issues such as altruism, intellectual satisfaction, personal skills and truth seeking. The reasons for not teaching included no strong involvement in course design, a heavy clinical load or feeling it was a waste of time. CONCLUSION: This study provides some insights into factors that may be utilised in the design of teaching programs that meet teacher motivations and ultimately enhance the effectiveness of the medical teaching workforce

Validation of diffusion tensor MRI measurements of cardiac microstructure with structure tensor synchrotron radiation imaging.

Background Diffusion tensor imaging (DTI) is widely used to assess tissue microstructure non-invasively. Cardiac DTI enables inference of cell and sheetlet orientations, which are altered under pathological conditions. However, DTI is affected by many factors, therefore robust validation is critical. Existing histological validation is intrinsically flawed, since it requires further tissue processing leading to sample distortion, is routinely limited in field-of-view and requires reconstruction of three-dimensional volumes from two-dimensional images. In contrast, synchrotron radiation imaging (SRI) data enables imaging of the heart in 3D without further preparation following DTI. The objective of the study was to validate DTI measurements based on structure tensor analysis of SRI data. Methods One isolated, fixed rat heart was imaged ex vivo with DTI and X-ray phase contrast SRI, and reconstructed at 100 μm and 3.6 μm isotropic resolution respectively. Structure tensors were determined from the SRI data and registered to the DTI data. Results Excellent agreement in helix angles (HA) and transverse angles (TA) was observed between the DTI and structure tensor synchrotron radiation imaging (STSRI) data, where HADTI-STSRI = −1.4° ± 23.2° and TADTI-STSRI = −1.4° ± 35.0° (mean ± 1.96 standard deviation across all voxels in the left ventricle). STSRI confirmed that the primary eigenvector of the diffusion tensor corresponds with the cardiomyocyte long-axis across the whole myocardium. Conclusions We have used STSRI as a novel and high-resolution gold standard for the validation of DTI, allowing like-with-like comparison of three-dimensional tissue structures in the same intact heart free of distortion. This represents a critical step forward in independently verifying the structural basis and informing the interpretation of cardiac DTI data, thereby supporting the further development and adoption of DTI in structure-based electro-mechanical modelling and routine clinical applications

Mapping cardiac microstructure of rabbit heart in different mechanical states by high resolution diffusion tensor imaging: A proof-of-principle study

Myocardial microstructure and its macroscopic materialisation are fundamental to the function of the heart. Despite this importance, characterisation of cellular features at the organ level remains challenging, and a unifying description of the structure of the heart is still outstanding. Here, we optimised diffusion tensor imaging data to acquire high quality data in ex vivo rabbit hearts in slack and contractured states, approximating diastolic and systolic conditions. The data were analysed with a suite of methods that focused on different aspects of the myocardium. In the slack heart, we observed a similar transmural gradient in helix angle of the primary eigenvector of up to 23.6°/mm in the left ventricle and 24.2°/mm in the right ventricle. In the contractured heart, the same transmural gradient remained largely linear, but was offset by up to +49.9° in the left ventricle. In the right ventricle, there was an increase in the transmural gradient to 31.2°/mm and an offset of up to +39.0°. The application of tractography based on each eigenvector enabled visualisation of streamlines that depict cardiomyocyte and sheetlet organisation over large distances. We observed multiple V- and N-shaped sheetlet arrangements throughout the myocardium, and insertion of sheetlets at the intersection of the left and right ventricle. This study integrates several complementary techniques to visualise and quantify the heart’s microstructure, projecting parameter representations across different length scales. This represents a step towards a more comprehensive characterisation of myocardial microstructure at the whole organ level

Acute mountain sickness.

Acute mountain sickness (AMS) is a clinical syndrome occurring in otherwise healthy normal individuals who ascend rapidly to high altitude. Symptoms develop over a period ofa few hours or days. The usual symptoms include headache, anorexia, nausea, vomiting, lethargy, unsteadiness of gait, undue dyspnoea on moderate exertion and interrupted sleep. AMS is unrelated to physical fitness, sex or age except that young children over two years of age are unduly susceptible. One of the striking features ofAMS is the wide variation in individual susceptibility which is to some extent consistent. Some subjects never experience symptoms at any altitude while others have repeated attacks on ascending to quite modest altitudes. Rapid ascent to altitudes of 2500 to 3000m will produce symptoms in some subjects while after ascent over 23 days to 5000m most subjects will be affected, some to a marked degree. In general, the more rapid the ascent, the higher the altitude reached and the greater the physical exertion involved, the more severe AMS will be. Ifthe subjects stay at the altitude reached there is a tendency for acclimatization to occur and symptoms to remit over 1-7 days

Prevalence of Heart Failure and systolic ventricular dysfunciton in Older Australians: the Canberra Heart Study

Objective: To estimate the prevalence of heart failure (HF) and left ventricular (LV) systolic dysfunction in a population-based sample of older Australians. Design, setting and participants: A cross-sectional survey of 2000 randomly selected residents of Canberra, aged 60-86 years, conducted between February 2002 and June 2003. Participants were assessed by history, physical examination by a cardiologist, and echocardiography. Main outcome measures: Age- and sex-specific prevalence rates of clinical HF and LV systolic dysfunction (defined as LV ejection fraction ≤ 50%). Results: Of 1846 people eligible for our study, 1388 (75%) agreed to participate and 1275 completed all investigations (mean age, 69.4 years; 50% men). In the study sample, 72 subjects (5.6%; 95% Cl, 4.4%-7.1%) had clinical HF that had been previously diagnosed and was confirmed by our assessment. A further 0.6% (95% Cl, 0.3%-1.2%) had undiagnosed clinical HF (ie, evidence of structural heart disease and symptoms/signs of cardiac insufficiency without a previous diagnosis of clinical HF). Thus, the overall prevalence of clinical HF in the sample was 6.3% (95% Cl, 5.0%-7.7%). Clinical HF increased in prevalence with advancing age (a 4.4-fold increase from the 60-64-years age group to the 80-86-years age group; P < 0.0001). Of the 75 subjects (5.9%; 95% Cl, 4.7%-7.3%) with LV systolic dysfunction, 44 (59%) were in the preclinical stage of disease. Conclusion: Diagnosed HF cases represent the "tip of the iceberg" for the national burden of HF and LV systolic dysfunction. Clinically identifiable HF cases can remain undiagnosed, and the majority of people with LV systolic dysfunction are in a preclinical stage of the disease

Prognostic efficacy of cardiac biomarkers for mortality in dialysis patients

Background: The high prevalence of cardiovascular mortality in the end-stage renal disease population is well established. The aim of this current study was to document the relative prognostic significance of established cardiac biomarkers troponin T (TnT), troponin I (TnI), B-type natriuretic peptide (BNP) and N-terminal pro-BNP (NT-pro-BNP) in this population. Methods: A prospective cohort study of dialysis patients undertaken in a single tertiary centre in Australia. Relevant clinical and biochemical information was collected at entry and all patients followed up prospectively without any loss to follow up. End-point of interest was all-cause mortality. Statistical analysis using Cox proportional hazards was used to study relationship between competing covariates and outcome. A total of 143 patients with a mean age of 59.67 ± 15.49 years was followed up for a median duration of 30 months. Of these patients, 89.3% were white Australians of European ancestry. Twenty-seven per cent had an established diagnosis of diabetes mellitus. The mean concentrations (±SD) of TnT, TnI, BNP and N-terminal peptide pro-BNP (NT-pro-BNP) were 0.08 ± 0.04g/L, 0.09 ± 0.2g/L, 270 ± 117 ng/L and 1434 ± 591 ng/L respectively. Results: Twenty-eight subjects died during the period of follow up. By univariate analysis, all cardiac markers (TnT, TnI, BNP, NT-pro-BNP and C-reactive protein) were significantly associated with an increase in mortality. On Cox proportionate hazards analysis, only albumin and NT-pro-BNP showed a significant association with mortality, with hazard ratios of 0.834, 95% confidence interval (CI) 0.779-0.893, P < 0.001, and 1.585, 95%CI 1.160-20165, P = 0.004 respectively. Conclusion: In patients with end-stage renal failure on dialysis NT-pro-BNP provides greater prognostic information compared with TnT and TnI