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Biomedical subjects

W Whitaker

Publications and source records attributed to W Whitaker.

At least 19 recordsLinked to original sources
PubMed1999

Localization of the type VI voltage-gated sodium channel protein in human CNS.

The cellular distribution of the type VI human voltage-gated sodium channel (Type VI) was examined in selected human brain regions. Antibodies designed to be specific to rat and human Type VI were raised against a synthetic peptide from the predicted NH2-terminal of the protein, and used for an immunohistochemical investigation. Immunoblot experiments showed that purified antibodies specifically detected the presence of Type VI in transfected cells and human brain membrane preparations. Immunohistochemistry on perfusion fixed human tissue revealed a predominantly somato-dendritic distribution of Type VI in major output neurons of the cerebellum, cerebral cortex and hippocampus. The observed localisation of this channel may reflect an important role in the integration of synaptic input in the human CNS.

Animals↗
PubMed1984

The effects of long-term physical training in patients with coronary heart disease.

A previous trial was completed in 24 patients with coronary heart disease, randomly assigned to a group who undertook a 6-month exercise training programme (5BX/XBX) and a control (no training) group. It was shown that the patients in the training group were able to achieve during exercise a higher heart rate at ST segment depression of 0.1 mV (HR/ST threshold) and that the patients in the control group showed a reduction in the threshold as well as symptomatic deterioration; the results indicated that the training programme had resulted in a reduction in the severity of myocardial ischaemia. In the present trial 9 patients of the previous training group were followed up to examine the effect of long-term maintenance training (up to 4.5 years). The same methods were used to examine the effect of maintenance training in a further group of 8 patients with coronary heart disease, 6 of whom were on beta-blocker therapy. By the end of the study, the heart rate achieved during exercise in the 17 patients was still significantly greater (P less than 0.0004) by 12.1 +/- 2.85 beats/min (mean +/- SEM) than that at the beginning of the trial; similar results were obtained in the 6 patients on beta-blocker therapy. Therefore a maintenance exercise training programme in patients with coronary heart disease can result in a sustained improvement in the form of a reduction in the severity of myocardial ischaemia, and this can occur in patients on beta-blocker therapy.

Adrenergic beta-Antagonists↗
PubMed1984

Use of the exercise maximal ST segment/heart rate slope in assessing the results of coronary angioplasty.

A new exercise test was used to assess the effects of coronary angioplasty in 22 patients. Twenty five angioplasty procedures were performed and the exercise maximal ST segment/heart rate slope was measured before and after operation on 23 occasions; in two patients treated for unstable angina the slope was measured only after the two procedures. Successful angioplasty (23 of the 25 procedures) resulted in a significant reduction of the maximal ST/HR slope, usually falling by the equivalent of single vessel disease according to previously published criteria. When angioplasty produced little angiographic change (two of the 25 procedures) the maximal ST/HR slope was not significantly altered. A second, and successful, angioplasty for these two patients led to a significant reduction of the maximal ST/HR slope. Twelve patients were restudied by coronary angiography and exercise testing approximately six months after angioplasty. Of these, six had experienced recurrent chest pain, and the exercise test successfully identified the three who had restenoses and the three who did not. Thus the maximal ST/HR slope was useful as a non-invasive and accurate method for following the progress of individual patients after coronary angioplasty.

Adult↗
PubMed1982

Accurate detection of coronary heart disease by new exercise test.

The ability of a new exercise test accurately to detect the presence and severity of coronary heart disease has been examined in 206 patients with anginal pain, including patients on beta blockers or with concomitant cardiac lesions. From recordings of 13 electrocardiographic leads during exercise, the maximal rate of progression of ST segment depression relative to increased in heart rate (maximal ST/HR slope) was obtained and used as an index of myocardial ischaemia. The maximal ST/HR slope and results of coronary arteriography were independently obtained and the two sets of data compared the ranges of the maximal ST/HR slopes in the 38 patients with no significant disease, 49 with single vessel, 75 with double vessel, and 44 patients with triple vessel disease were different from each other and there was no overlap in the data between adjacent groups; there were no false positive, false negative, or indeterminate results. It is concluded that the maximal ST/HR slope can be used reliably to predict the presence of absence and severity of coronary heart disease in individual patients presenting with anginal pain in a hospital population.

Adrenergic beta-Antagonists↗
PubMed1980

Effects of physical training on myocardial ischaemia in patients with coronary artery disease.

The effects of a simple physical training programme were investigated in a prospective and randomised trial in patients with stable angina pectoris using a modified exercise test. Twenty-four patients with ischaemic heart disease and an ischaemic response to conventional exercise electrocardiography were randomised into two groups: 12 patients took part in a training programme and 12 patients were allocated to a control group (no training). Exercise testing was performed sequentially at entry to the study and six months afterwards. At both studies we determined the heart rate at the same level of ischaemic ST segment depression (HR/ST threshold), the duration of the test, and relation of heart rate to the exercise load. The HR/ST threshold increased only in patients who underwent the exercise programme, suggesting indirectly that training resulted in the ability to do more work and attain a higher degree of myocardial oxygen consumption at the same level of myocardial ischaemia. In addition, training led to an increase in the duration of the test and to a reduction in heart rate at any level of submaximal exercise load. It is concluded that physical training in anginal patients results in an enhancement of myocardial oxygen availability.

Adult↗
PubMed1980

Multiple valve replacement with pericardial xenograft. Clinical and haemodynamic study.

Multiple valve replacement with pericardial xenografts (sizes 17 to 31) was undertaken in 76 patients. The incidence of early and late deaths was 10.5 and 3.9 per cent, respectively. ACtuarially it is predicted that 94.7 +/- 3.9 per cent of hospital survivors will be alive at three and a half years after valve replacement. Though long-term anticoagulants were not used, thrombotic valve obstruction was not seen in this series. A systemic embolus occurred early in one case only (0.95 episodes/100 patient years). Mechanical dysfunction of the pericardial xenograft has not been seen. Haemodynamic studies were performed in seven patients, eight to 21 months after valve replacement. The transvalvular gradients were negligible across the aortic pericardial xenografts. Gradients across mitral and tricuspid xenografts were small. The calculated surface areas ranged from 1.0 to 1.4 cm2 for aortic, 1.7 to 2.1 cm2 for mitral, and 2.0 to 2.4 cm2 for tricuspid valves. These results after multiple valve replacement are comparable to those reported with isolated mitral or aortic pericardial xenografts over a similar period of observation.

Adult↗
PubMed1979

Diagnostic value of routine exercise testing in hospital patients with angina pectoris.

A group of patients with angina pectoris were investigated prospectively using a simple and well-recognised exercise test protocol, and S-T segment displacements during exercise were correlated with the results of coronary arteriography. Definitive exercise results in 100 patients correlated well with findings on coronary angiograms: 69 out of 70 patients with positive exercise test results had significant coronary disease on angiography, while 23 out of 30 with negative exercise test results had no significant coronary disease. In six patients a period of physical training changed indeterminate initial tests to definitive ones after the training. These results show that the use of a widely available exercise test and a light physical training programme, with rigid adherence to the protocol, can reduce the overall demand on coronary arteriography.

Adult↗
PubMed1978

Long-term haemodynamic evaluation of aortic pericardial xenograft.

Haemodynamic studies were performed in 30 patients at a mean interval of 43.4 (range 27 to 59) months after aortic valve replacements with pericardial xenografts. Five valve sizes--19, 21, 23, 25, and 27 mm annulus diameter--were used. Of these 30 patients, 16 had preoperative haemodynamic investigations. Comparison of the pre- and postoperative data showed a marginal but significant increase in cardiac output (P less than 0.05). There was a significant reduction in the pulmonary wedge and left ventricular end-diastolic pressures at rest and on exercise (P less than 0.05 and P less than 0.01). At the postoperative study the mean peak systolic gradient was 8.3 mmHg at rest and 12.3 mmHg on exercise in patients with the smallest xenograft inserted (19 mm) and decreased with each corresponding increase in graft size, so that across the 27 mm graft it was hardly measurable. The calculated xenograft surface area ranged from 1.1 to 2.1 cm2 at rest and 1.3 to 2.4 cm2 during exercise. Aortic root angiography showed competent valves in all 30 patients, but a grade 1 to 2 perivalvular leak was shown in 8 patients. This long-term study has indicated significant circulatory improvement and very small transvalvular gradients in patients with aortic pericardial xenografts.

Adult↗
PubMed1975

Congenital intrapericardial aneurysms of the left atrium.

A patient with congenital intrapericardial aneurysm/diverticulum of the left atrium diagnosed preoperatively is described. A review of the 16 previously reported cases revealed that the majority of the patients present with palpitation and are found to have an abnormal cardiac shadow on chest radiography, as did this patient. The aneurysm appears to cause systemic emboli and paroxysmal or persistent atrial tachyarrhythmias which are often resistant to medical therapy. The presence of the aneurysm is suggested by an abnormal contour of the left cardiac border in the postero-anterior chest radiograph and this can be confirmed by angiocardiography. Surgical excision of the aneurysm is indicated in all patients to prevent the occurrence or recurrence of systemic emboli and atrial arrhythmias. Our patient has remained free of symptoms since her operation 14 months ago.

Adult↗
PubMed1975

Clinical and hemodynamic results of mitral valve replacement with autologous fascia lata grafts. Studies in patients with competent prostheses.

Nine patients with severe mitral disease were studied before and six months after mitral valve replacement with a three-cusp stented prosthesis using fresh autologous fascia lata tissue. Only patients in whom there was no auscultatory and angiographic evidence of incompetence of the replaced valve were selected for restudy. All patients claimed a marked improvement in their exercise capacity after operation and there was a significant reduction in radiographic heart size. The cardiac output at rest and the response to exercise were both reduced before operation and were unchanged after valve replacement. The elevated pulmonary arterial and wedge pressures were significantly reduced after operation in all patients both at rest and during exercise, but in no instance were the postoperative exercise values within normal limits. Left ventricular end-diastolic pressure was within normal limits at rest and during exercise in all patients after valve replacement but the average pressure gradient across the fascia lata valve was 6+/-1 mm Hg at rest and 18+/-3 mm Hg during exercise. These findings indicate that altough replacement of the diseased mitral valve with a competent fascia lata prosthesis afforded substantial symptomatic relief, reduction of cardiac enlargement and a lowering of the pulmonary vascular pressures, this artificial valve offered a significant obstruction to left ventricular diastolic filling, particularly during exercise.

Adult↗
PubMed1975

Pulmonary veno-occlusive disease.

Pulmonary veno-occlusive disease has recently been recognized as a distinct pathological entity and a cause of pulmonary arterial hypertension. Twenty previously reported cases and a new patient are here reviewed. The majority presented with breathlessness and in the early stages of the disease, when the abnormal signs were not striking, some patients were wrongly diagnosed as suffering from an anxiety state. The condition usually has an insidious onset but is remorselessly progressive and since no effective treatment is available at present, invariably fatal and the majority of patients have died within two years. The fully developed clinical picture is dominated by symptoms and signs of pulmonary arterial hypertension, similar to those found with other diseases causing a raised pulmonary arterial blood pressure. However, some patients with pulmonary veno-occlusive disease show, in addition, signs of pulmonary venous and capillary hypertension, which can lead to its clinical recognition when associated with a normal left atrial blood pressure. In this condition the pulmonary wedge pressure would appear to be unreliable as a record of the left atrial blood pressure. Pulmonary angiography and lung scanning will differentiate pulmonary veno-occlusive disease from massive thromboembolic pulmonary arterial hypertension but not from primary pulmonary arterial hypertension or micro thromboembolism. Although in some patients it should now be possible to recognise pulmonary veno-occlusive disease in life, there will be others where, even after full investigation, it will still be impossible to differentiate the condition from primary pulmonary arterial hypertension or micro thromboembolism and in these the diagnosis will only be made when the distinctive histological pattern of the disease is demonstrated. In pulmonary veno-occlusive disease there is a widespread occlusion of the pulmonary veins and venules by a loose intimal fibrosis which is often basophilic. Recanalization of the occluded veins is common and in some cases may be very striking. These occlusive lesions in the pulmonary veins lead to an elevation of pulmonary arterial pressure with associated disease of these vessels, and are also responsible for chronic oedema of the elveolar walls with subsequent development of interstitial pulmonary fibrosis. In the present case organised thrombi were present in the pulmonary arteries in addition to the pulmonary venous lesions.

Adolescent↗
PubMed1973

Comparison of adrenergic beta-receptor antagonists in angina pectoris.

The symptomatic, electrocardiographic, and circulatory effects of intravenous and oral preparations of propranolol, oxprenolol, and practolol were compared in 16 patients with uncomplicated angina pectoris precipitated by exertion. The method of study included treadmill exercise, double-blind assessment, single-blind analysis, with placebo control and randomized serial comparison of each drug in each patient. The doses used were selected to give the same near-maximum suppression of the heart rate response to exercise. The symptomatic, electrocardiographic, and circulatory response of each patient to both preparations of each of the three drugs was similar. Exercise tolerance was increased in two-thirds, unchanged in one-sixth, and significantly worsened in one-sixth of the studies. Electrocardiographic evidence of myocardial ischaemia was conspicuously reduced by all three drugs in most studies irrespective of their symptomatic effects. Though the exclusive choice of patients, the single dose design of the trial, and the treadmill method of assessment limit the general application of these results, they do clearly indicate that in doses that induce equal suppression of the exercise heart rate these three drugs have similar distinct anti-anginal activity. Their ancillary pharmacological properties are probably of little importance in this respect. Equally, the similarity in the symptomatic, circulatory, and electrocardiographic response to the intravenous and oral preparations suggests that metabolic breakdown products are probably of therapeutic importance only in so far as they antagonize beta-receptor activity.

Acetanilides↗