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Biomedical subjects

G Jackson

Publications and source records attributed to G Jackson.

At least 109 records · Page 6Linked to original sources
PubMed2000

When is an aortic valve prosthesis too small? The need for dobutamine stress echocardiography.

We describe a patient who had undergone aortic valve replacement with a small prosthesis 10 years previously and who presented with exertional breathlessness. The resting transaortic pressure gradient was only 30 mmHg but increased to 165 mmHg on dobutamine stress. Conventional resting echocardiography may fail to demonstrate abnormal prosthetic aortic valve function; in the presence of symptoms, dobutamine stress echocardiography should be considered.

Adult↗
PubMed2000

The role of statins in acute coronary syndromes: managing the unmet need.

Coronary heart disease is the major cause of death in the industrialised world. As the prevalence increases with advancing age, coronary heart disease will be a growing problem as the average age of the population increases. The cost of treatment following an acute coronary syndrome is considerable and there is a substantial risk of further episodes. However, there is much evidence that the disease is a dynamic and reversible process and further episodes are preventable. Numerous trials have shown the efficacy of statins in coronary heart disease. The most recent studies have shown efficacy in secondary prevention when statin therapy was started early (hours/days) after an acute episode. Although guidelines recommend that statin therapy should be initiated following an acute coronary syndrome, prescription rates seem to be static at around 40%. A number of measures need to be taken to improve the situation. Firstly, each hospital and coronary care unit should implement a clearly defined protocol delineating patient management following hospital admission. Provision of comprehensive discharge information should be a key feature of this communication. Secondly, regular audit of prescribing habits is essential to assess the situation. Finally, patient adherence to their regimen should be improved by collaborative involvement of doctor and patient in planning and implementing the treatment regimen.

Anticholesteremic Agents↗
PubMed1999

Effects of sildenafil citrate on human hemodynamics.

Nitric oxide (NO) induces the formation of intracellular cyclic guanosine monophosphate (cGMP) by guanylate cyclase. Sildenafil, which selectively inhibits phosphodiesterase type 5 (PDE5) found predominantly in the corpora cavernosa of the penis, effectively blocks the degradation of cGMP and enhances erectile function in men with erectile dysfunction. The NO-cGMP pathway also plays an important role in mediating blood pressure. It is, therefore, possible that the therapeutic doses of sildenafil used to treat erectile dysfunction may have clinically significant effects on human hemodynamics. Three studies were undertaken to assess the effects of intravenously, intra-arterially, and orally administered doses of sildenafil on blood pressure, heart rate, cardiac output, and forearm blood flow and venous compliance in healthy men. A fourth study evaluated the hemodynamic effects of intravenous sildenafil in men with stable ischemic heart disease. In healthy men, significant (p <0.01) decreases in supine systolic and diastolic blood pressures were observed with intravenous sildenafil (20, 40, and 80 mg) at the end of the infusion period when plasma levels of sildenafil were highest (mean decreases from baseline of 7.0/6.9 and 9.2/6.7 mm Hg, for the 40- and 80-mg doses, respectively). These changes were transient and not dose related. Modest reductions in systemic vascular resistance also were observed (maximum decrease 16%), although heart rate was not affected by sildenafil administration when compared with placebo. Single oral doses of sildenafil (100, 150, and 200 mg) produced no significant changes in cardiac index from 1-12 hours postdose between placebo- and sildenafil-treated subjects. The approved dosage strengths of sildenafil citrate are 25 mg, 50 mg, and 100 mg. The 80-mg intravenous dose and the 200-mg oral dose of sildenafil produced comparable plasma levels at twice the maximum therapeutic dose (recommended range, 25-100 mg). After brachial artery infusion of sildenafil (up to 300 microg/min), there was a modest vasodilation of resistance arteries and a reversal of norepinephrine-induced preconstriction of forearm veins. These hemodynamic effects were similar to but smaller in magnitude than those of nitrates. In a small pilot study of men with ischemic heart disease, decreases from baseline in pulmonary arterial pressure (-27% at rest and -19% during exercise) and cardiac output (-7% at rest and -11% during exercise) were observed after 40-mg intravenous doses of sildenafil. Sildenafil was well tolerated by subjects and patients in all studies, with headache and other symptoms of vasodilation the most commonly reported adverse effects of treatment. Modest, transient hemodynamic changes were observed in healthy men after single intravenous or oral doses of sildenafil even at supratherapeutic doses. In men with stable ischemic heart disease, sildenafil produced modest effects on hemodynamic parameters at rest and during exercise.

Administration, Oral↗
PubMed1999

Investigation of variant Creutzfeldt-Jakob disease and other human prion diseases with tonsil biopsy samples.

BACKGROUND: Prion diseases are associated with the accumulation of an abnormal isoform of cellular prion protein (PrPSc), which is the principal constituent of prions. Prions replicate in lymphoreticular tissues before neuroinvasion, suggesting that lymphoreticular biopsy samples may allow early diagnosis by detection of PrPSc. Variant Creutzfeldt-Jakob disease (variant CJD) is difficult to distinguish from common psychiatric disorders in its early stages and definitive diagnosis has relied on neuropathology. We studied lymphoreticular tissues from a necropsy series and assessed tonsillar biopsy samples as a diagnostic investigation for human prion disease. METHODS: Lymphoreticular tissues (68 tonsils, 64 spleens, and 40 lymph nodes) were obtained at necropsy from patients affected by prion disease and from neurological and normal controls. Tonsil biopsy sampling was done on 20 patients with suspected prion disease. Tissues were analysed by western blot to detect and type PrPSc, by PrP immunohistochemistry, or both. FINDINGS: All lymphoreticular tissues obtained at necropsy from patients with neuropathologically confirmed variant CJD, but not from patients with other prion diseases or controls, were positive for PrPSc. In addition, PrPSc typing revealed a consistent pattern (designated type 4t) different from that seen in variant CJD brain (type 4) or in brain from other CJD subtypes (types 1-3). Tonsil biopsy tissue was positive in all eight patients with an adequate biopsy sample and whose subsequent course has confirmed, or is highly consistent with, a diagnosis of variant CJD and negative in all patients subsequently confirmed to have other diagnoses. INTERPRETATION: We found that if, in the appropriate clinical context, a tonsil biopsy sample was positive for PrPSc, variant CJD could be diagnosed, which obviates the need for a brain biopsy sample to be taken. Our results also show that variant CJD has a different pathogenesis to sporadic CJD.

Adolescent↗
PubMed1999

Risk of hepatitis B transmission after amniocentesis in chronic hepatitis B carriers.

OBJECTIVE: To measure the risk of perinatal transmission of HBV in chronic carriers who undergo amniocentesis. METHODS: This was a prospective, longitudinal study from 1990 to 1995 of women who were HBV carriers and underwent amniocentesis. The infants of these women were followed from birth to one year of age. Maternal data examined included HBV antigen and antibody status, liver function tests (LFTs) and the amniocentesis report. RESULTS: Twenty-eight women were identified. Two of 28 neonates were stillborn unrelated to hepatitis. Five infants were lost to follow-up leaving 21 mother-child pairs to evaluate. All 21 women were chronic HBV carriers at the time of amniocentesis for delivery. No mother had abnormal LFTs, and only one of 21 women was positive for hepatitis B e antigen (HBeAg). Thirteen amniocenteses were for advanced maternal age, and four were for abnormal maternal serum alphafetoprotein (MSAFP) screening. None of the amniocenteses were recorded as bloody, and the placenta was anterior in 6 of 21 procedures. None of the 21 infants (95% CI: 0-16.8%) were positive for HbsAg during the first month of life or at 12 months of age. All infants received HBV vaccine and HBIG immunoprophylaxis. CONCLUSION: The risk of transmission of HBV to the fetus after amniocentesis in women who are HBV carriers is low. Immunoprophylaxis in these infants was successful.

Amniocentesis↗
PubMed1999

Use of a skin explant model for predicting GVHD in HLA-matched bone marrow transplants - effect of GVHD prophylaxis.

Over the last decade we have successfully evaluated the use of a human skin explant assay for predicting acute GVHD in HLA-matched sibling transplants. In the present study, we modified GVHD prophylaxis on an individual patient basis depending on the GVHD outcome predicted by the skin explant model. We have summarised our previous data describing how the skin explant assay results correctly predict GVHD occurrence and severity in 45/56 patients (80%); P< 0.0001, chi2 19.97, df = 1. In a further cohort of 19 patients, all were predicted to develop grade II or above GVHD. These patients were given increased GVHD prophylaxis with the addition of methotrexate and a significant reduction in the expected incidence of GVHD was observed (P = 0.02; chi2 7.7, df = 1; Fisher exact test P = 0.04). The results from these studies suggest that modifying GVHD prophylaxis, based on skin explant assay results, may reduce the expected incidence and severity of GVHD. We suggest that the technique might be used for selective GVHD prophylaxis in T cell non-depleted HLA matched sibling transplants.

Adolescent↗
PubMed1999

A randomized placebo-controlled trial of fluvastatin for prevention of restenosis after successful coronary balloon angioplasty; final results of the fluvastatin angiographic restenosis (FLARE) trial.

BACKGROUND: The 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors competitively inhibit biosynthesis of mevalonate, a precursor of non-sterol compounds involved in cell proliferation. Experimental evidence suggests that fluvastatin may, independent of any lipid lowering action, exert a greater direct inhibitory effect on proliferating vascular myocytes than other statins. The FLARE (Fluvastatin Angioplasty Restenosis) Trial was conceived to evaluate the ability of fluvastatin 40 mg twice daily to reduce restenosis after successful coronary balloon angioplasty (PTCA). METHODS: Patients were randomized to either placebo or fluvastatin 40 mg twice daily beginning 2-4 weeks prior to planned PTCA and continuing after a successful PTCA (without the use of a stent), to follow-up angiography at 26+/-2 weeks. Clinical follow-up was completed at 40 weeks. The primary end-point was angiographic restenosis, measured by quantitative coronary angiography at a core laboratory, as the loss in minimal luminal diameter during follow-up. Clinical end-points were death, myocardial infarction, coronary artery bypass graft surgery or re-intervention, up to 40 weeks after PTCA. RESULTS: Of 1054 patients randomized, 526 were allocated to fluvastatin and 528 to placebo. Among these, 409 in the fluvastatin group and 427 in the placebo group were included in the intention-to-treat analysis, having undergone a successful PTCA after a minimum of 2 weeks of pre-treatment. At the time of PTCA, fluvastatin had reduced LDL cholesterol by 37% and this was maintained at 33% at 26 weeks. There was no difference in the primary end-point between the treatment groups (fluvastatin 0.23+/-0.49 mm vs placebo 0.23+/-0.52 mm, P=0.95) or in the angiographic restenosis rate (fluvastatin 28%, placebo 31%, chi-square P=0.42), or in the incidence of the composite clinical end-point at 40 weeks (22.4% vs 23.3%; logrank P=0.74). However, a significantly lower incidence of total death and myocardial infarction was observed in six patients (1.4%) in the fluvastatin group and 17 (4.0%) in the placebo group (log rank P=0.025). CONCLUSION: Treatment with fluvastatin 80 mg daily did not affect the process of restenosis and is therefore not indicated for this purpose. However, the observed reduction in mortality and myocardial infarction 40 weeks after PTCA in the fluvastatin treated group has not been previously reported with statin therapy. Accordingly, a priori investigation of this finding is indicated and a new clinical trial with this intention is already underway.

Angioplasty, Balloon, Coronary↗
PubMed1999

Pacemaker-induced superior vena cava obstruction: bypass using the intact azygous vein.

Superior vena cava thrombosis due to pacemaker leads is an uncommon but well-recognized complication. Its pathogenesis remains unclear and it is usually a benign condition. Superior vena cava occlusion can be successfully treated by thrombolysis and anticoagulation if the occlusion is recent, balloon venoplasty and stenting, and surgery. We describe a case of superior vena cava obstruction successfully bypassed using the intact native azygous vein, a technique that has not been described before, with excellent long-term results.

Humans↗
PubMed1999

Why patients do not attend cardiac rehabilitation: role of intentions and illness beliefs.

OBJECTIVE: Many patients fail to attend cardiac rehabilitation. Attempts to identify sociodemographic or clinical predictors of non-attendance have not been very successful; therfore, this study aimed to determine whether the illness beliefs held during hospitalisation by patients who had suffered acute myocardial infarction or who had undergone coronary artery bypass graft surgery could predict cardiac rehabilitation attendance. SUBJECTS AND METHODS: 152 patients were prospectively studied of whom 41% had attended cardiac rehabilitation at six months. RESULTS: In addition to being older, less aware of their cholesterol values, and less likely to be employed, non-attenders were less likely to believe their condition was controllable and that their lifestyle may have contributed to their illness. CONCLUSION: It should now be determined whether interventions aimed at optimising certain perceptions could promote cardiac rehabilitation uptake among those patients who could benefit the most.

Age Factors↗
PubMed1999

The needs of neurology patients after discharge.

Patients discharged from neurosciences units and their carers often express a range of needs. Patients' needs relate to the illness and its physical effects. Carers experience mainly psychosocial effects. Needs can be met through planning and co-operation between the statutory and voluntary sectors and the use of liaison nurses.

Continuity of Patient Care↗