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Biomedical subjects

M A James

Publications and source records attributed to M A James.

At least 91 records · Page 5Linked to original sources
PubMed1989

The relationship of symptoms to performance in paced patients with breathlessness.

Eighteen adult patients presenting with breathlessness associated with bradycardia, and whose breathlessness was diminished or abolished by permanent pacing, were studied at least one month after this procedure in order to examine the relationship between symptoms and exercise performance. All were pacing-dependent at rest and were studied over successive two-weekly periods at set rates of 50, 70 and 90 beats min-1 in a double-blind, balanced and randomized trial. The degree of breathlessness was closely related to exercise capacity judged by 6-min walk testing, effort scores and weekly pedometer distance. Overall results were worse at 50 beats min-1 than the two faster rates. For a given individual, changing of ventricular rate caused parallel alterations in symptoms and performance. The 6-min walking test was a useful guide to disability in these patients, tightly linked to the symptoms of effort and breathlessness, and may be of clinical value in assessing mild heart failure. The pedometer readings were influenced more by the patients' walking habits than by fitness.

Adult↗
PubMed1989

Improved control of atrial fibrillation with combined pindolol and digoxin therapy.

This study has compared the effect on heart rate control of the addition of pindolol 15 mg bd or verapamil 40 mg tds to maintenance digoxin therapy in 12 patients with chronic atrial fibrillation. The study was performed in a randomized cross-over fashion. Treatment effects were assessed by 24-h ambulatory electrocardiography and symptomatic improvement by symptom scores. The results show that the combination of pindolol and digoxin provides better control of atrial fibrillation. With an attenuation of daytime tachycardia, prevention of nocturnal bradycardia and reduction in the length of nocturnal pauses in rhythm. Overall heart rate variability was significantly less with digoxin and pindolol (523 beats min-1 h-1) than with digoxin and verapamil (745 beats min-1 h-1). We conclude that, in the dosages employed, combined digoxin and pindolol therapy is superior to either digoxin and verapamil in combination or digoxin alone for the treatment of atrial fibrillation.

Adult↗
PubMed1989

Computed body tomography with a new nonionic contrast agent. Comparison of ioversol with sodium/meglumine diatrizoate.

The authors undertook a double-blind parallel group comparative study of 80 adult patients to examine the efficacy, safety, and tolerance of ioversol and sodium/meglumine diatrizoate in patients undergoing computed body tomography (CT). All procedures were considered diagnostic, although the scan quality of four procedures enhanced with sodium/meglumine diatrizoate was rated fair. Both contrast media induced clinically insignificant postprocedure decreases in mean systolic and diastolic blood pressure. There were no statistically significant differences between the two contrast media in their effects on these or other vital signs. Ioversol was better tolerated, as evidenced by significantly lower pain and heat scores. There was a remarkable difference in adverse side effects induced by ioversol (n = 0) and sodium/meglumine diatrizoate (n = 14 [35%], including six of moderate severity). Ioversol is a safe and effective nonionic contrast agent for contrast-enhanced body CT.

Adult↗
PubMed1989

Ioversol clinical safety summary.

The authors evaluated double-blind comparative and open-label clinical trials in 1,186 patients who received ioversol to evaluate the safety and efficacy of ioversol, a new nonionic low-osmolality contrast medium, at iodine concentrations of 32%, 24%, and 16%. The results indicate that ioversol was well tolerated in all patients and showed fewer adverse effects than conventional ionic agents. The diagnostic efficacy of ioversol was comparable to both conventional and other nonionic agents with respect to diagnostic quality. However, the improved patient tolerance may contribute to higher quality radiographs. The effects on renal function were monitored at 24, 48, 72, and 96 hours and did not reveal any clinically or statistically significant changes.

Adolescent↗
PubMed1989

Ventricular arrhythmia in untreated newly presenting hypertensive patients compared with matched normal population.

There is evidence to suggest that hypertensive patients are at increased risk of sudden death. However, to date this evidence is restricted to treated hypertensives and it is not clear whether this risk is due to the hypertension itself, its treatment, or its long-term consequences. This study has investigated, by 24-h ambulatory electrocardiography, a total of 58 newly diagnosed hypertensive patients who have never previously been treated and compared the first 50 of them with 50 matched control subjects. The results show that there is an increased prevalence of ventricular arrhythmia in hypertensive patients, compared with normal controls, and that this arrhythmia is present from the outset and thus not dependent on treatment or the development of long-term complications. Multivariate analysis showed that age (positive correlation) and potassium (negative correlation) made the most important independent contributions to the prevalence of arrhythmia in these patients, but even so only accounted for about 33% of the observed arrhythmia. This suggests that the precursors of arrhythmia in hypertension are multifactorial. One other factor appeared to make an important contribution to ventricular arrhythmia in these patients. In contrast to recent evidence from the study of treated hypertensives, the prevalence of ventricular arrhythmia was significantly lower in patients exhibiting electrocardiographic evidence of left ventricular hypertrophy. However, left ventricular hypertrophy did also appear to sensitize the myocardium to the arrhythmogenic effect of low serum potassium levels. These findings may help to explain some of the previous confusion surrounding treatment, hypertension and ventricular arrhythmia.

Adult↗
PubMed1989

Combined anti-arrhythmic therapy with class 1 and class 3 drugs.

This study was designed to investigate the differences in efficacy between 3 different combinations of amiodarone and a class 1 anti-arrhythmic drug (one from each class). The purpose was to determine whether the known differing electrophysiological properties of class 1 drugs result in any particular one making a superior combination with the class 3 drug amiodarone. Eight patients were studied in a randomized single blind cross-over trial. Amiodarone and flecainide proved to be the superior combination producing a significantly greater reduction in mean ectopic counts/24 hours than the amiodarone/mexilitene combination (1,286 vs 3,243; P less than 0.05) or the amiodarone/disopyramide combination (3,795; P less than 0.05). All 3 combinations reduced mean ectopic counts from the baseline value (8,729), but this was only significant for amiodarone/flecainide (P less than 0.01) and amiodarone/mexilitene (P less than 0.05). In addition the amiodarone/flecainide combination produced a significant reduction in complex forms of arrhythmia with ventricular tachycardia abolished in all cases, which was not achieved by any other combination.

Adult↗
PubMed1987

Polymorphous ventricular tachycardia due to alpha-blockade.

We report a case of polymorphous ventricular tachycardia caused by treatment with the post-synaptic alpha-blocking agent indoramin. This has not been reported with indoramin previously, nor to our knowledge with any other alpha-blocker. This pro-arrhythmic effect appears to be related to its class 3 anti-arrhythmic properties (QT interval prolongation) which is dose dependent, occurring only at large doses.

Arrhythmias, Cardiac↗
PubMed1987

Fundamental differences between the standard 12-lead electrocardiograph and the modified (Mason-Likar) exercise lead system.

A comparison of the standard 12-lead electrocardiograph with the Mason-Likar lead system widely used for exercise stress testing shows that the two are not 'essentially identical' as was originally claimed. Placement of the limb electrodes onto the torso distorts the electrocardiograph causing a rightward shift of the mean QRS axis, a significant reduction in R-wave amplitude in leads I and aVL, and a significant increase in R-wave amplitude in leads II, III and aVF; the R-wave amplitude of the chest leads is also altered. The so-called 'inferior' leads on the exercise electrocardiography are probably modified anterior/inferior leads, since their R-wave amplitudes correlate closely with those of antero-lateral chest leads. The inferior surface of the heart is not represented in isolation on the exercise electrocardiograph, thus explaining the reported inability of the exercise test to predict the location of coronary artery disease and high incidence of false negative tests in patients with ischaemia limited to the inferior cardiac surface.

Coronary Disease↗
PubMed1987

Towards improved control of atrial fibrillation.

Patients with atrial fibrillation frequently show a wide variation in heart rate with digoxin therapy. We have compared the effect on heart rate variability, of doubling the digoxin dosage or adding verapamil 120 mg daily in a randomized cross-over study in 14 patients. Twenty-four hour ambulatory electrocardiographic recordings, six minute walking tests and palpitation and breathlessness scores were obtained on each regime. All patients exhibited a diurnal pattern in heart rate variability. Both treatments significantly lowered heart rate but high dose digoxin lowered minimum heart rate significantly more than digoxin and verapamil, causing more night time bradycardia. Overall, digoxin with verapamil produced significantly less heart rate variability than digoxin alone. Day time but not night time pauses were prolonged by digoxin and verapamil but were prolonged more by high dose digoxin. Five (36%) patients had serum digoxin levels in the toxic range when taking high dose digoxin. Palpitations were significantly reduced by both treatments but most improvement occurred with digoxin and verapamil. No significant effect was found on six minute walking distances or breathlessness scores. In conclusion, the addition of verapamil to digoxin was superior to increasing the dose of digoxin alone, producing significantly better control of heart rate variability with less night time bradycardia.

Aged↗
PubMed1987

Simple anatomical basis for surface electrocardiographic changes during selective coronary arteriography.

The relationship between surface electrocardiographic changes during selective coronary arteriography and coronary artery anatomy was examined in 185 consecutive patients. When both major arteries were patent, two distinct patterns of electrocardiographic changes occurred. Electrocardiogram leads reflecting the areas supplied by the injected vessels showed a change we have termed the 'perfusion response', while electrocardiogram leads reflecting regions not supplied by the injected vessel simultaneously showed a pattern we have termed the 'reciprocal response'. These changes were reproducible on serial injections, and occurred whether or not coronary artery or valvular heart disease was present. A third type of electrocardiographic change--termed a 'biphasic response' and comprising a reciprocal followed by a perfusion response--was observed in leads reflecting a collateral-dependent region of viable myocardium. This response was seen in the inferior surface leads with left coronary artery injection when the right coronary artery was occluded, but not in leads I and aVL with right coronary artery injection when a branch of the left coronary artery was occluded, where chest leads may be needed for its detection. The biphasic response was also seen in the inferior leads with left coronary artery injection in patients in whom this artery was dominant. Thus, the distribution of electrocardiographic changes during arteriography is dependent on native coronary artery anatomy, collateral vessels and myocardial viability. Changes relate to the site of coronary lesions only where vessels are occluded, but may be of practical value when the viability of (and thus suitability for bypass grafting to) a myocardial region is in doubt.

Contrast Media↗
PubMed1987

Antigenic relationship between Plasmodium falciparum and Babesia bovis: reactivity with antibodies to culture-derived soluble exoantigens.

Antigenic similarities between Plasmodium and Babesia parasites of the phylum Apicomplexa have been previously demonstrated primarily by the serological cross reactivity observed in the indirect fluorescent antibody (IFA) test. We have now studied the antigenic relationship between the human malaria parasite, Plasmodium falciparum, and the hemoparasitic agent of cattle, Babesia bovis, using rabbit monospecific antibodies produced against individual culture-derived P. falciparum polypeptides and bovine polyspecific antibodies to B. bovis exoantigens. These respective antibodies were found to be distinctly cross reactive in the IFA test using infected erythrocytes (squirrel monkey--P. falciparum; bovine--B. bovis) as antigen substrates. Immunofluorescence was shown to be highly specific for parasite surfaces. Additionally, the degree of reactivity with soluble exoantigens contained in Plasmodium and Babesia culture supernatants was monitored by a two-site enzyme immunoassay employing the cross-reactive antibodies. Further evidence for antigenic cross reactivity between P. falciparum and B. bovis parasites was shown with the in vitro inhibition assay. Antibodies to P. falciparum and B. bovis were found to be highly inhibitory for the in vitro growth of P. falciparum in human erythrocytes.

Animals↗
PubMed1987

Pathologic changes associated with fatal Plasmodium falciparum infection in the Bolivian squirrel monkey (Saimiri sciureus boliviensis).

Fatal cases of experimental Plasmodium falciparum (Indochina I) in Bolivian squirrel monkeys (Saimiri sciureus boliviensis) were examined by histologic and ultrastructural methods. Gross lesions were characterized by hepatosplenomegaly and interstitial pulmonary changes. Histologically, there was marked diffuse reticuloendothelial hyperplasia, pulmonary alveolar septal thickening, mesangioproliferative glomerulonephropathy, sequestration of parasitized erythrocytes in deep vascular beds, degenerative parenchymal changes in the liver and myocardium, and in one case retinal and cerebral hemorrhage. These data indicate that the Bolivian squirrel monkey is a good model for studying pathologic changes associated with human falciparum malaria.

Animals↗
PubMed1987

Correlative clinical biochemistry and hematological profiles of laboratory-bred Bolivian squirrel monkeys (Saimiri sciureus).

Twenty-five clinical and biochemical parameters were determined on 17 normal, male, laboratory-bred Bolivian squirrel monkeys (Saimiri sciureus). Parallel hematologic parameters were conducted. The correlation of biochemical and hematological observations and the distribution characteristics, range, and standard error of the mean were determined. The purpose of the present communication is to establish baseline biochemical values for laboratory-bred squirrel monkeys and to present a correlative comparison between selected cellular elements and major blood electrolytes.

Animals↗
PubMed1987

Failure of a negative exercise test to reassure patients with chest pain.

Seventy-two patients with chest pain and negative exercise tests were observed. Twenty-one (29 per cent) became pain free but 51 (71 per cent) continued to complain of chest pain. Patients with persistent pain were significantly more anxious and depressed at presentation and later compared with those who had become pain free. Anxiety and particularly depression, at presentation and later, were significantly associated with severe symptoms. Patients with chest pain associated with neurosis and depression are not reassured by physiological stress testing because their physical symptoms are a feature of underlying psychiatric disease.

Adult↗