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Biomedical subjects

John Chambers

Publications and source records attributed to John Chambers.

At least 19 recordsLinked to original sources
PubMed2007

Measurement of pulse wave velocity: site matters.

BACKGROUND: Aortic pulse wave velocity (PWV) predicts mortality from cardiovascular disease, ischaemic heart disease and stroke. However, a comparison of associations between PWV measured at different sites and atherosclerosis in coronary, carotid and femoral arteries has not been made. METHODS: In 159 men (ages 45-82 years) with and without known coronary artery disease, PWV measurements were made between carotid-femoral, carotid-radial and femoral-posterior tibial sites, using an ultrasound technique. Coronary artery calcification (CAC) scores were measured by multislice computed tomography. Carotid and femoral intima-media thickness (IMT) and presence of plaque were determined by ultrasound. Known coronary artery disease was confirmed by angiography. Participants were grouped into four categories of CAC score: 0-10, 11-100, 101-400, > 400 Hounsfield Units (HU). Measurements of blood pressure, heart rate and fasting bloods were made in all individuals. RESULTS: Carotid-femoral PWV correlated positively with CAC score and increased with incremental coronary calcification category (median carotid-femoral PWV 16.8 m/s in those with CAC score > 400 HU and 13.8 m/s in those with CAC score < 10 HU; P = 0.003). Carotid-femoral PWV also correlated with carotid and femoral IMT (P < 0.001, P = 0.004, respectively) and with carotid and femoral plaque (P = 0.001, P = 0.038, respectively). Increased carotid-femoral PWV also correlated with increasing age (P < 0.001), systolic blood pressure (P < 0.001), mean arterial pressure and pulse pressure (P < 0.001). Carotid-radial and femoral-posterior tibial PWV were not significantly associated with CAC score, carotid or femoral IMT or carotid plaque. CONCLUSIONS: Carotid-femoral PWV is a better indicator of atherosclerosis than either carotid-radial or femoral-posterior tibial PWV, and should be used preferentially in studies of atherosclerosis and in stratifying risk in clinical settings.

Adult↗
PubMed2006

Mitral valve repair for severe mitral regurgitation: the way forward?

Severe primary mitral regurgitation (MR) has a poor outcome if left uncorrected. Successful mitral valve repair has the unique potential to restore normal life expectancy and is superior to valve replacement. Despite this, mitral repair is performed relatively infrequently and many patients with potentially reparable valves have a replacement instead, subjecting them to unnecessary risk. Surgery in asymptomatic patients is a particularly difficult issue with some units advocating surgery irrespective of symptoms, based purely on the severity of regurgitation. This strategy cannot be widely adopted with the current patchy provision of high-quality valve repair surgery. Misplaced enthusiasm for early operation runs the risk of a failed repair and the hazards of a mechanical prosthesis. To ensure optimal treatment for patients with MR, cardiologists must be aware of the indications for valve repair and ensure that patients with potentially reparable valves are referred to surgeons with proven expertise, even if this means a shift from established practice. Surgical units need to promote subspecialization and rigorously audit their outcomes. There are currently no agreed standards for best practice in mitral valve repair and this is an area where professional societies may wish to take a role.

Coronary Care Units↗
PubMed2005

Identification of a sex pheromone from male yellow mealworm beetles, Tenebrio molitor.

The sex pheromone released by the adult female Tenebrio molitor, 4-methyl-1-nonanol, is well known. In addition, there is evidence that adult males release a pheromone that attracts females. The purpose of the present study was to isolate and identify male-released pheromone(s). Emissions from virgin adult males and females were collected on filter paper and extracted with pentane. Extracts were analyzed by gas chromatography-mass spectrometry. One male-specific compound was detected and identified as (Z)-3-dodecenyl acetate (Z3-12:Ac). In arena bioassays, E3-12:Ac was attractive to females only, at 1 and 10 microg doses. E3-12:Ac was also attractive to females at a 10-microg dose. The presence of both male and female pheromones, each attracting the opposite sex, may contribute to maintaining a high-density population of both sexes.

Acetates↗
PubMed2005

Acupuncture for subacute stroke rehabilitation: a Sham-controlled, subject- and assessor-blind, randomized trial.

BACKGROUND: Any adjunctive therapy that may reduce persistent disability after stroke should be considered. Acupuncture is used for this purpose, but there is conflicting evidence on its effectiveness. METHODS: Patients with a recent (<4 weeks) episode of stroke were randomized to receive 12 sessions of either real or sham acupuncture during 2 weeks. The primary outcome was the change in Barthel activities of daily living score at the end of treatment. Secondary outcome measures included National Institutes of Health Stroke Scale score, motoricity index, and quality of life (EQ-5D [ EuroQoL-5 Dimensional form] and EQ-VAS [EuroQoL-Visual Analog Scale]). Assessments were carried out by blinded physicians. RESULTS: A total of 116 patients (56 in the real acupuncture group and 60 in the sham group) were randomized, and 98 (real, 48; sham, 50) completed treatment and the 2-week assessment. Patient blinding by means of the sham acupuncture device was successful. Acupuncture was well tolerated except for 1 seizure during a real acupuncture session. The improvements in the Barthel scores were 4 points (interquartile range [IQR], 0-8) vs 3 points (IQR, 0-7) in the real and sham acupuncture groups, respectively (P = .38). The secondary outcome measures also essentially showed no significant effect of acupuncture. Post hoc analysis by baseline severity showed a greater improvement in leg function in the subgroup with baseline Barthel score less than the median (median score, 6): 22 points (IQR, 0-37) vs 0 [corrected] points (IQR, 0-4) in the acupuncture and sham control groups, respectively (P = .02). CONCLUSIONS: Acupuncture is not superior to sham treatment for recovery in activities of daily living and health-related quality of life after stroke, although there may be a limited effect on leg function in more severely affected patients.

Activities of Daily Living↗
PubMed2005

Aortic stenosis.

Explore the source record for details and available documents.

Aortic Valve Stenosis↗
PubMed2005

Exercise testing to stratify risk in aortic stenosis.

AIMS: The aims of this study were to assess the accuracy of exercise testing in predicting symptom onset within 12 months in patients with asymptomatic aortic stenosis and to establish the criteria that define a positive test. METHODS AND RESULTS: A total of 125 patients with aortic stenosis [effective orifice area (EOA) 0.9+/-0.2 cm2] were assessed by Specific Activity Scale (SAS) classification, transthoracic echocardiography, and treadmill exercise testing using the modified Bruce protocol. During follow-up, 36 patients (29%) developed spontaneous symptoms within 12 months. Of these, 26 (72%) had had symptoms revealed by exercise testing and 24 (67%) had severe stenosis (EOA < or = 0.8 cm2). Exercise-limiting symptoms were the only independent predictors of outcome at 12 months, and an abnormal blood pressure response or ST segment depression did not improve the accuracy of the exercise test. The positive predictive accuracy for exercise-induced symptoms was 57% in the whole population and 79% for patients aged <70 in SAS Class I. The negative predictive accuracy was 87% in the whole population and 86% in the subgroup. CONCLUSION: A significant proportion of patients with apparently asymptomatic aortic stenosis experience limiting symptoms on treadmill exercise testing. The subsequent development of spontaneous symptoms is strongly related to the severity of stenosis and to limiting symptoms on exercise testing, but less so to an abnormal blood pressure response or ST segment depression.

Aged↗
PubMed2005

The peak to mean pressure decrease ratio: a new method of assessing aortic stenosis.

BACKGROUND: The ratio of peak to mean pressure decrease is a new measure of transaortic continuous waveform shape that could be useful for grading aortic stenosis. METHODS: We retrospectively analyzed echocardiograms in 163 patients with all grades of aortic stenosis as assessed by the continuity equation. RESULTS: The peak to mean pressure decrease ratio was 1.75 (0.14) in mild stenosis, 1.66 (0.13) in moderate stenosis, 1.56 (0.10) in severe stenosis, and 1.57 (0.07) in severe aortic stenosis with left ventricular ejection fraction less than 40%. Receiver operating characteristic curve analysis showed that a threshold of less than 1.50 gave a specificity of 94% against continuity area whereas a ratio less than 1.75 gave a sensitivity of 96%. CONCLUSION: The peak to mean pressure decrease ratio is a simple and quick cue to the likelihood of severe aortic stenosis in patients with low left ventricular ejection fraction when transaortic pressure decreases appear only moderate.

Aged↗