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Biomedical subjects

J B Stoker

Publications and source records attributed to J B Stoker.

At least 37 records · Page 2Linked to original sources
PubMed1982

Detection of severity of coronary artery disease by the ST segment/heart rate relationship in patients on beta-blocker therapy.

Many patients presenting with anginal pain are on beta-blocker therapy and it has been suggested that noninvasive exercise tests for coronary artery disease are adversely affected by such therapy. Recently a new exercise test has been introduced claiming the ability accurately to detect the presence and severity of coronary heart disease in patients with anginal pain; the claim was based on results obtained in patients not undergoing beta-blocker therapy. Therefore using this test, the maximal rate of progression of ST segment depression relative to increases in heart rate during exercise (maximal ST/HR slope) as an index of the severity of myocardial ischaemia, 60 patients on beta-blocker therapy were studied and the results compared with results of coronary arteriography independently obtained. There was a complete agreement, without false results, between the maximal ST/HR slope and the number of significantly diseased coronary arteries. In 21 of these 60 patients the maximal ST/HR slopes obtained before and after beta-blockade were compared; the maximal ST/HR slopes after beta-blockade were not different from those before. It is concluded, that the maximal SR/HR slope can be used reliably to detect the pressure and the severity of coronary heart disease in patients with angina pectoris who are already on beta-blocker therapy.

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↗
PubMed1981

Clinical cardiovascular experiences with iopamidol: a new non-ionic contrast medium.

Iopamidol, a new non-ionic water-soluble contrast medium, has been compared with standard ionic media in a number of cardiovascular applications. It is stable in aqueous solution, is much less viscous and only slightly more osmolar than metrizamide. Compared to sodium meglumine diatrizoate in a series of 40 coronary arteriograms, it produced a consistent and highly significant decrease in the incidence and severity of hypotension and bradycardia following intracoronary injection. In the same group and in 62 children undergoing ventricular or great vessel angiocardiography, a subjective assessment of patient reaction showed that iopamidol was better tolerated than the ionic medium. There was a very strong patient preference for iopamidol in a group of 20 of the adult patients who had also consented to femoral artery injections of both media. Throughout these series there was no detectable difference in arterial image quality between the media. Venous phase opacification during arterioportography was assessed in 11 cases comparing iopamidol with sodium meglumine iothalamate. No significant difference was found. We conclude that iopamidol is clearly preferable to ionic media for routine cardiovascular applications.

Angiocardiography↗
PubMed1980

Long-term comparison of metoprolol and methyldopa in the treatment of hypertension.

The effect of the cardioselective beta-adrenoreceptor blocking compound, metoprolol, was compared with methyldopa in the long-term management of hypertension. Thirty patients given metoprolol and twenty-six given methyldopa were treated for 2 years. The maximum dose of metoprolol was 200 mg twice daily (average 308 mg) and of methyldopa 1,000 mg twice daily (average 1,120 mg). Blood pressure was similar at entry to the study (metoprolol 177/110 mmHg and methyldopa 181/111 mmHg). After 2 years of treatment the blood pressure levels were again similar (metoprolol 149/91 mmHg and methyldopa 148/91 mmHg). Erect pressures were lower in the methyldopa group, but there was no difference between supine and erect blood pressure levels in those on metoprolol. At an exercise load of 300 and 600 kpm the increase in systolic pressure was significantly less in the metoprolol group. The proportional increase in systolic and diastolic pressure in response to a standardized stress situation was reduced by treatment with metroprolol but not by methyldopa. Tolerance to therapy did not develop in either group. The main difference between metoprolol and methyldopa was in the incidence and severity of side effects. Four patients were withdrawn from the metoprolol group. Seventeen were withdrawn from the methyldopa mainly because of side effects including drowsiness, depression, skin rash, and impotence. Six patients on metoprolol and seventeen on methyldopa continued on therapy although side effects were present. It is concluded that metoprolol and methyldopa lower blood pressure to the same extent, but metoprolol is advantageous because of a lower incidence of side effects.

Adult↗
PubMed1980

Physical training after heart valve replacement.

A controlled trial was undertaken to examine the efficacy of physical training in patients recovering from the replacement of a single heart valve. Patients were allocated to a test or control group two weeks after operation. Each patient performed a submaximal exercise test at entry, and 12 and 24 weeks after this test. The Canadian Air Force exercise programme was undertaken by the test group, while the control group continued normal activities for the 24 weeks between the first and last exercise group. A regression line of submaximal heart rate on oxygen consumption was calculated from the data of each exercise test in each patient. Alterations in this line were used as an "index" of changes in "cardiorespiratory fitness". The individual results showed a consistent improvement in "cardiorespiratory fitness" over the first 12 weeks in both groups. Only patients in the test group continued to improve between 12 and 24 weeks. Thus the exercise programme modified the recovery of "cardiorespiratory fitness" after operation. Results in patients who developed clinical complications, and were excluded from the trial, predicted a deteriorating clinical condition. This finding suggested that sequential exercise tests are of value after cardiac surgery.

Adolescent↗
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↗
PubMed1979

Effect of exercise in hypertension controlled with metoprolol or methyldopa.

1. The adequacy of the control of essential hypertension during exercise was studied in patients whose resting blood pressure had been controlled for 1 year with either metoprolol or methyldopa. 2. Systolic blood pressure increased with exercise in both groups, the increase being significantly less in the metoprolol group than in the methyldopa group.

Adult↗
PubMed1979

Effects of 4 beta-adrenoceptor blocking drugs on blood pressure and exercise heart rate in hypertension.

The effects of 4 beta-adrenoceptor blocking drugs on blood pressure and on exercise tachycardia were compared in a within-patient study of patients with uncomplicated essential hypertension. Twelve patients were treated with propranolol, practolol and atenolol and 7 of the same patients also received oxprenolol. Each patient received each drug separately, withdrawing each drug before starting the next, and each patient was titrated to the lowest attainable blood pressure and heart rate with each compound. All 4 drugs caused reductions in both systolic and diastolic blood pressure and in the heart rate induced by exercise. The maximum reduction by each drug in both systolic and diastolic blood pressure was the same. There were small but significant differences in the effects on heart rate between those drugs which had intrinsic sympathomimetic activity and those which did not have this property.

Adrenergic beta-Antagonists↗
PubMed1976

Histocompatibility antigens and myocardial infarction.

The incidence of histocompatibility (HLA) antigens in 100 men with myocardial infarction was compared with the incidence in 500 healthy controls. No significant difference was found, providing no support for either a genetic or an immunological basis for myocardial infarction.

Adult↗
PubMed1975

The assessment of acid-base disturbance in man by the use of carbon dioxide titration curves.

1. Carbon dioxide titration curves were determined in vivo in dog and man at various degrees of acute non-respiratory acidaemia and alkalaemia. 2. The slope of the CO2 titration curve (delta log Pco2/delta pH) was found to increase with the severity of the acute non-respiratory alkalaemia the slope (delta log Pco2/delta pH) tended towards unity. 3. A simple scheme based on the CO2 titration curves determined in vivo has been proposed for the assessment of acute acid-base disturbances in man. 4. Carbon dioxide titration curves were also determined in vivo in patients with chronic respiratory and non-respiratory acidaemia and it was found that these curves were not significantly different from those obtained in states of acute acid-base disturbances. It is therefore suggested that the scheme described in this paper is applicable to all acid-base disturbances.

Acid-Base Equilibrium↗
PubMed1975

The influence of aortic baroreceptors on venous tone in the perfused hind limb of the dog.

1. The aortic arch and both carotid sinuses were vascularly isolated and perfused. A hind limb was vascularly isolated and blood was pumped at constant flows into the femoral artery and the central end of a superficial metatarsal vein. 2. Large increases in aortic arch pressure resulted in decreases in arterial blood pressure, heart rate and femoral arterial perfusion pressure. The average response of the vein was a decrease of 11% in the pressure gradient between the perfused vein and the femoral vein. Similar responses were obtained when carotid sinus pressure was increased. 3. Crushing or cooling the lumbar sympathetic trunk caused responsed similar to those induced by increasing baroreceptor perfusion pressure. Stimulation at 1 HZ resulted in venous responses four times as great as the average reflex response, whereas frequencies of 2-5 Hz were required to produce changes in arterial resistance as great as those induced reflexly. 4. These experiments indicate, that although the large superficial veins of the dog's hind limb participate in the baroreceptor reflexes, the activities in the nerves supplying arterioles and veins must have been different.

Animals↗
PubMed1974

Blockade of peripheral vascular responses to isoprenaline by three beta-adrenoceptor antagonists in the anaesthetized dog.

1 A dog's hind limb was vascularly isolated by strong nylon snares and its sympathetic nerve supply interrupted. Blood was perfused at constant flow into the femoral artery and drained from the femoral vein. In some dogs the cardiac nerves were cut.2 Isoprenaline infused intravenously caused an increase in heart rate and a decrease in arterial resistance.3 Practolol (2 mg/kg) effectively blocked heart rate responses to isoprenaline infused at up to 10 mug/min but was relatively ineffective in blocking arterial responses. ICI 66082 (2 mg/kg) reduced vasomotor responses and propranolol (0.5 mg/kg) abolished vasomotor responses.4 Small cumulative doses of beta-adrenoceptor antagonists were given to some dogs. Practolol blocked heart rate responses in lower doses than were required to block vasomotor responses. Propranolol preferentially blocked vasomotor responses and ICI 66082 was intermediate between the other two in its effects.

Acetamides↗