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Biomedical subjects

M Metcalfe

Publications and source records attributed to M Metcalfe.

At least 19 recordsLinked to original sources
PubMed2006

Is it possible to identify a population in which the incidence of future development of AIS is greatly increased when compared to the normal population?

For future research of predictors of AIS, it would be advantageous to identify a general population in which the development of AIS is greatly increased when compared to the normal population. The probability of predicting future development of AIS among younger relatives of current patients based on the probability of AIS incidence was assessed from the research literature. Although there is considerable literature relating to familial relationships of the probability of developing AIS or having AIS, the probability is relatively low in most cases. Even with the best of predicted probabilities, the identification of patients with a high probability of developing AIS remained low. The identification of people among the general population who have a high probability of developing AIS based on the probabilities expressed in the literature is not possible.

Adolescent↗
PubMed2005

Direct observation of dynamical bifurcation between two driven oscillation states of a Josephson junction.

We performed a novel phase-sensitive microwave reflection experiment which directly probes the dynamics of the Josephson plasma resonance in both the linear and the nonlinear regime. When the junction was driven below the plasma frequency into the nonlinear regime, we observed for the first time the transition between two different dynamical states predicted for nonlinear systems. In our experiment, this transition appears as an abrupt change in the reflected signal phase at a critical excitation power. This controlled dynamical switching can form the basis of a sensitive amplifier, in particular, for the readout of superconducting qubits.

Journal Article↗
PubMed2005

Myocardial perfusion scintigraphy in the UK: insights from the British Nuclear Cardiology Society Survey 2000.

BACKGROUND: The National Institute for Health and Clinical Excellence (NICE) has recently published a very positive technology appraisal of myocardial perfusion scintigraphy (MPS). This has important implications for service provision within the National Health Service, and an accurate knowledge of the current level of MPS activity is necessary. METHODS: A postal questionnaire was sent to 207 nuclear medicine departments in the UK, requesting information about nuclear cardiology facilities, activity, and practice. Non-responding departments were sent a second questionnaire, followed where necessary by a telephone call. RESULTS: A response rate of 61% was achieved; 52% of departments performed MPS, and these tended to have more gamma cameras than those which did not (median (25th-75th centile) 2.0, 1.5-2.5 v 1.0, 0.5-1.5; p = 0.02). The median number of studies performed was 256 (144-460). The estimated rate of MPS in the UK for the year 2000 was 1200 per million population. The median (25th-75th centile) waiting time for MPS was 16 (9-24) weeks. Pharmacological stress was used in 77% of studies, and a technetium-99m based radiopharmaceutical in 60% (two day protocol in 75%). Tomographic rather than planar imaging was performed in 88% of studies, of which 22% were ECG gated. A cardiologist was involved in reporting in 35% of studies. CONCLUSIONS: MPS activity in the UK remains low, and it tends to be provided as a low volume service with unacceptably long waiting times and a lack of involvement by cardiologists. The recent NICE appraisal may provide an impetus for further resourcing and development.

Coronary Disease↗
PubMed2004

RF-driven Josephson bifurcation amplifier for quantum measurement.

We have constructed a new type of amplifier whose primary purpose is the readout of superconducting quantum bits. It is based on the transition of a rf-driven Josephson junction between two distinct oscillation states near a dynamical bifurcation point. The main advantages of this new amplifier are speed, high sensitivity, low backaction, and the absence of on-chip dissipation. Pulsed microwave reflection measurements on nanofabricated Al junctions show that actual devices attain the performance predicted by theory.

Journal Article↗
PubMed2004

Systematic review of the effectiveness and cost-effectiveness, and economic evaluation, of myocardial perfusion scintigraphy for the diagnosis and management of angina and myocardial infarction.

OBJECTIVES: To assess the effectiveness and cost-effectiveness of single photon emission computed tomography (SPECT) myocardial perfusion scintigraphy for the diagnosis and management of angina and myocardial infarction (MI). DATA SOURCES: Major electronic databases. REVIEW METHODS: Two reviewers independently extracted data and assessed study quality. A decision tree model was used to model the diagnosis decision and a Markov model was developed for the management of patients with suspected coronary artery disease. Costs for the treatments and interventions within strategies were derived from the literature and expressed in 2001-02 pounds sterling. Quality-adjusted life-year (QALY) weights for the different Markov model states were also obtained from the literature. RESULTS: Twenty-one diagnostic and 46 prognostic studies were included, plus two studies comparing SPECT with electrocardiography (ECG)-gated SPECT and one study comparing SPECT with attenuation-corrected SPECT. The diagnostic values of SPECT were generally higher than those of stress ECG, indicating that SPECT provided a better diagnostic performance. SPECT also provided higher positive and lower negative likelihood ratios than stress ECG but heterogeneity was evident among studies. The subgroup of studies including patients with previous MI tended to report a better diagnostic performance for SPECT than stress ECG, but there were too few studies to assess this reliably. The extent and size of the perfusion defect, and whether reversible or fixed, were important factors in predicting future cardiac events such as cardiac death or non-fatal MI. SPECT may be able to identify lower risk patients for whom coronary angiography (CA) might be avoided. Normal SPECT scans were associated with a benign prognosis and the option of medical rather than invasive management. Four studies of patients post-MI reported SPECT to be valuable in stratifying patients into at-risk groups for further cardiac events. The two studies comparing SPECT with ECG-gated SPECT, one diagnostic and the other prognostic, found in favour of gated SPECT. The study comparing SPECT with attenuation-corrected SPECT reported the latter to be more accurate. The systematic review of economic evaluations indicated that strategies involving SPECT were likely either to be dominant or to produce more QALYs at an acceptable cost. There was less agreement about which of the strategies involving SPECT was optimal. The model suggested that, for low prevalence, the incremental cost per unit of output (true positives diagnosed, accurate diagnosis, QALY) for the move from stress ECG-SPECT-CA and from stress ECG-CA to SPECT-CA might be considered worthwhile. Even after allowing for different values for sensitivity or specificity, the least costly and least effective strategy was stress ECG-SPECT-CA. The sensitivity analysis suggested that the cost-effectiveness of SPECT-CA improved if it was assumed that SPECT results allowed for the adoption of a management strategy without recourse to CA. As the time horizon reduced, the incremental cost per QALY increased (as the cost of initial diagnosis and treatment were not offset by survival and quality of life gains). CONCLUSIONS: There was a considerable variability in terms of measurement of outcomes, management, setting and patient characteristics, however the direction of evidence tended to favour SPECT in terms of test sensitivity, although these conclusions are based on a relatively small number of diagnostic studies. SPECT, in a variety of settings and patient populations, provided valuable independent and incremental prognostic information to that provided by stress ECG and/or CA that helped to risk-stratify patients and influence the way in which their condition was managed. However, all of the prognostic studies were observational studies and may be biased by unknown confounding factors. Although the ECG-gated and attenuation-corrected SPECT findings seem promising, it is difficult to draw conclusions from so few studies. Further research is needed on the effectiveness and cost-effectiveness, diagnostically and prognostically, of (a) gated and attenuation-corrected SPECT compared with standard SPECT, (b) standard SPECT compared with stress echocardiography and (c) the uncertainty surrounding the results presented in the cost-effectiveness analysis.

Angina Pectoris↗
PubMed2003

Facilitation of open spigelian hernia repair by laparoscopic location of the hernial defect.

A spigelian hernia is an uncommon entity. The diagnosis and location of this disorder often is difficult. We present a case in which the hernia could not be located at the time of operation, despite exploration. Laparoscopy performed subsequently enabled location and repair of the hernia under direct visualization, with good results. Laparoscopy is advocated as an adjunct to the diagnosis and treatment of spigelian hernia.

Adult↗
PubMed2002

Elbow fistulas using autogeneous vein: patency rates and results of revision.

BACKGROUND: The provision and maintenance of vascular access remains a major cost to end stage renal failure programmes. There are few reports regarding the surgical revision of the failing native elbow arteriovenous fistula (AVF). PATIENTS AND METHODS: A retrospective case note review was performed on all patients identified from the hospital vascular access database as having undergone construction of an autogeneous vein elbow AVF. Over a seven year period 282 autogeneous vein AVFs were fashioned in 232 patients using the brachial artery as the in-flow conduit. Of these 208 were brachiocephalic fistulas, or a variant thereof, and 74 were fashioned using the transposed autologous basilic vein (136 male: 96 female; median age 60 years, range 14-94 years). RESULTS: Of 282 elbow fistulas 197 were successfully used for dialysis (70%). Cumulative primary patency of elbow fistulas using autogeneous vein in this series was 68%, 54%, and 44% at one, two, and three years respectively. A further 34 revision procedures were performed on 28 fistulas to maintain fistula function, and cumulative secondary patency after surgical revision was 75%, 60%, and 46% at one, two, and three years. Overall 21 out of 34 procedures (62%) successfully restored fistula function and cumulative primary patency of the revised fistulas was 56% at one year. Eighteen AVFs (brachiocephalic, n=12; autologous basilar vein, n=6) required revision for access dysfunction secondary to a short stenoses within 4 cm of the arteriovenous anastomoses. Of these 18 AVFs eight were revised by excision of the stenosed segment and either primary anastomoses of the two cut ends of arterialised vein or reanastomoses of the proximal venous limb proximally on the brachial artery. In another nine fistulas the excised segment was replaced with a short interposition graft (polytetrafluoroethylene, n=7; native basilic vein, n=1; bovine carotid artery, n=1). One fistula with postanastomotic stenoses and a more proximal needle site stenoses was revised using two vein patches. Overall 100% were patent at 24 hours, 13 provided successful dialysis (72%), and cumulative primary patency was 67% and 50% at six months and one year respectively. CONCLUSIONS: Successful surgical revision of failing native elbow fistulas can restore patency and improve cumulative secondary patency with potential benefits in terms of patient morbidity and mortality. These results compare favourably to published patency rates after fistula salvage using interventional radiological techniques.

Adolescent↗
PubMed2001

Influence of aspirin on early allograft thrombosis and chronic allograft nephropathy following renal transplantation.

BACKGROUND: Primary thrombosis and chronic allograft nephropathy are important causes of early and late graft loss, respectively, following renal transplantation. This study examined the potential for aspirin therapy to reduce these complications. METHODS: A consecutive series of 105 cadaveric renal transplants treated with aspirin 150 mg daily for the first 3 months after transplantation was compared with an untreated historical control group (n = 121). Protocol needle-core biopsies were performed on all transplants in both groups at 1 week and 12 months after transplantation. Needle-core allograft biopsies were performed at 3, 6 and 12 months after transplantation, and serum creatinine was measured at each outpatient attendance for the duration of follow-up. RESULTS: There was a significantly lower rate of primary allograft thrombosis in patients treated with aspirin (none of 105) compared with that in the control group (six (5 per cent) of 121; P = 0.03). There were no differences in renal function or 2-year allograft survival between the two groups. Aspirin-treated patients had a lower incidence of chronic allograft nephropathy at 1 year than controls although this did not reach statistical significance (16 versus 26 per cent; P = 0.075). There were no major bleeding complications in either group in association with peptic ulcer disease or following renal transplant biopsy. CONCLUSION: Aspirin reduced the rate of early graft thrombosis of renal transplants in this series but did not improve renal function or graft survival. A trend towards a lower rate of chronic allograft nephropathy was noted with aspirin treatment. These findings require confirmation in a prospective randomized trial.

Aspirin↗
PubMed2000

The accuracy of non-invasive methods for the detection of obstructive coronary artery disease in the presence of left ventricular hypertrophy.

In the hypertensive patient with electrocardiographic and/or echocardiographic evidence of left ventricular hypertrophy, exercise electrocardiography lacks sensitivity and specificity for the detection of obstructive coronary artery disease and should be avoided. In comparative studies both myocardial perfusion imaging and stress echocardiography are significantly more sensitive and specific for the detection of significant obstructive coronary artery disease, in the presence of left ventricular hypertrophy, and are the investigations of choice.

Coronary Disease↗
PubMed1995

Activation of the micturition reflex by NK2 receptor stimulation in the anaesthetized guinea-pig.

1. The mechanisms underlying stimulation of bladder contractions and bronchoconstriction by the selective NK2 receptor agonist, [beta-Ala8]NKA(4-10), were examined in the anaesthetized guinea-pig. 2. Atropine, alpha,beta-methylene-ATP and ganglion blocking agents were used to examine the contribution of reflex arc activation and/or potentiation of efferent mechanisms to the NK2 receptor-mediated responses seen in these two tissues. 3. [beta-Ala8]NKA(4-10)-induced bronchoconstriction was immediate, dose-dependent and was unaffected by pretreatment with ganglion blockers (hexamethonium or chlorisondamine), blockade of muscarinic receptors by atropine, or desensitization of P2 purinoceptors by alpha,beta-methylene-ATP. 4. At does of 5 micrograms kg-1 and above, [beta-Ala8]NKA(4-10) induced bladder contractions that appeared to be of an 'all-or-nothing' nature. These contractions occurred after a delay of 10 to 30 s and were often biphasic, comprised of an initial rapid component followed by a slower tonic component. 5. Pretreatment of the animals with either atropine or the desensitizing purinoceptor agonist alpha,beta-methylene-ATP, resulted in partial inhibition of bladder contractile responses to [beta-Ala8]NKA(4-10). The combination of atropine and alpha,beta-methylene-ATP pretreatment resulted in additive inhibition leading to complete blockade of the response. 6. The bladder responses to [beta-Ala8]NKA(4-10) (5 micrograms kg-1) were inhibited by pretreatment with the ganglion blockers, hexamethonium and chlorisondamine, indicating a preganglionic mechanism of action. 7. These findings demonstrate the indirect nature of the bladder contractions induced by activation of NK2 receptors in the anaesthetized guinea-pig. Contractions occur secondary to the release of endogenous cholinergic and NANC transmitters by activation of neuronal NK2 receptors located at apreganglionic site, possibly on capsaicin-sensitive sensory afferent nerves, where NK2 sites have been demonstrated autoradiographically. In contrast, [beta-Ala8]NKA(4- 10)-induced bronchoconstriction in the anaesthetized guinea-pig is a direct smooth muscle contractile response that is unaffected by ganglionblockade or blockade of muscarinic receptors.

Animals↗
PubMed1994

Childhood sexual experiences with adults: adult male psychiatric patients and general practice attenders.

BACKGROUND: Sexual abuse of male children is now believed to be common, and there may be links to adult psychiatric disorders. METHOD: Recollections of sexual experiences with adults in childhood were studied systematically in 115 men attending general practice surgeries and 100 male psychiatric patients. RESULTS: The latter reported more frequent and more serious events before the age of 13 than the general practice attenders. No significant difference was detected for events between the ages of 13 and 15. CONCLUSIONS: Childhood sexual abuse before the age of 13 may be associated with later psychiatric disorders, although the nature of the association remains uncertain. The possible significance of such experiences should be considered when assessing men with mental disorders.

Adolescent↗
PubMed1992

Small cell carcinoma with two paraendocrine syndromes.

Simultaneous elevated levels of ectopic arginine vasopressin (AVP) and ectopic adrenocorticotropin (ACTH) were found in a patient with small cell carcinoma (SCC). The finding of one of these paraendocrine syndromes at the time of diagnosis is common; however, the simultaneous presence of both syndromes has been reported in the literature only on four occasions in the past 25 years. This is the only report in which elevated plasma levels of both hormones are documented in a patient who simultaneously fulfills the criteria for the syndrome associated with each ectopically produced peptide. In the English-language literature, this is the first case that demonstrates by immunohistochemical staining the presence of both of these hormones in the patient's neoplasm. In addition to the use of radiographs, the presence of paraendocrine disorders can provide a method of monitoring the patient's response to therapy. The levels of ACTH and AVP were assayed during this patient's course and correlated with disease refractory to therapy, resulting in poor survival.

ACTH Syndrome, Ectopic↗
PubMed1991

Attitudes toward nurses discussing sexual concerns with patients.

Attitudes toward nurses discussing sexual concerns with clients were examined in 73 healthy subjects using Section A of the Sexual Adjustment Questionnaire. The variables of age, sex, race, occupation, educational level, marital status, importance of sexual activity, frequency of discussing sexual relationship with partner, and number of others with whom sexual concerns are discussed were examined to determine influence on subject's attitudes. Ninety-two per cent of subjects thought that nurses should discuss sexual concerns with clients. Weighted least squares analysis showed that only two variables (number of others with whom sexual concerns are discussed and race) were significant predictors of attitudes.

Adult↗
PubMed1990

Childhood sexual experiences reported by male psychiatric patients.

One hundred adult male psychiatric patients were investigated concerning their recollections of defined sexual activities occurring with adults before the age of sixteen. Twenty-three subjects reported such events. The events were remembered as having been mostly distressing at the time but their later significance is unclear.

Adolescent↗