Mycoplasma arthritidis mitogen. V beta engaged in mice, rats, and humans, and requirement of HLA-DR alpha for presentation.

OBJECTIVE. Mycoplasma arthritidis mitogen (MAM) is mitogenic for mouse, rat, and human T cells, and behaves as a superantigen in mice through its capacity to bind to the alpha chain of I-E molecules and engage entire sets of T cells expressing specific V beta. Here, we have attempted to fully characterize the V beta-engaging activities of MAM in mice, and define similar activities in rats and humans. METHODS. Multiprobe RNase-protection assays and mice transgenic for human DR alpha, DR beta, and DR alpha beta were utilized for this purpose. RESULTS. MAM-reactive V beta in the mouse included not only the previously reported V beta 6, V beta 8.1, V beta 8.2, and V beta 8.3, but also V beta 5.1. In the rat, engagement of V beta 5.1, V beta 6, V beta 8.1, and V beta 8.2, but not V beta 8.3, was documented, whereas in humans, the engaged V beta included primarily V beta 19.1 (alternatively termed V beta 17.1) and, to a lesser extent, V beta 3.1, V beta 11.1, V beta 12.1, and V beta 13.1. In DR transgenic E alpha- E beta- mice, presentation of MAM and engagement of specific V beta was effected by DR alpha. CONCLUSIONS. Homologous V beta are engaged by MAM in mice, rats, and humans, presumably through a binding site similar to that proposed previously for other superantigens. MAM presentation primarily via the nonpolymorphic DR alpha makes it unlikely that there is involvement of such a superantigen in the pathogenesis of autoimmune diseases known to be associated with certain DR haplotypes. The possibility cannot be excluded, however, that superantigen-activated T cells may lead to disease by cross-reactions with self-antigens presented by particular DR haplotypes.     

Effect of cardiac rehabilitation on functional outcomes after coronary revascularization

Background Current guidelines recommending cardiac rehabilitation (CR) after coronary revascularization are largely based on early studies that evaluated only a subset of the population and failed to assess the impact of CR on a patient's perception of their functional status. The main objective of this study was to evaluate the impact of CR in a diverse contemporary population on patient functional outcomes. Methods We studied the effect of CR on 6-month SF-36 Physical Functioning (PF) in 700 patients (mean age 67 ± 11 years, 37% women) who underwent coronary bypass grafting or percutaneous intervention from August 1998 to July 2000. Results Overall CR participation was 24%. At baseline, CR participants had higher PF (mean 62.5 vs 52.5, P < .001). After adjusting for baseline clinical variables and PF score, CR was associated with significant improvement in 6-month PF (+5.0, 95% CI 1.0-9.0). This improvement was observed in all patient subgroups, but tended to be greater in magnitude in men versus women, patients aged <70 years versus ≥70 years, and patients with coronary bypass grafting versus patients with percutaneous intervention. CR participants also tended to be more likely to engage in regular exercise (63% vs 55%, P = .06) and modify their diet (82% vs 73%, P = .07). Rates of rehospitalization and repeat revascularization were similar among CR participants and nonparticipants. Conclusions CR after coronary revascularization is associated with improved functional outcomes and adoption of secondary preventive measures. Innovative strategies to facilitate CR enrollment and tailoring programs to better address the needs of all patient subgroups would extend these benefits to more eligible patients. (Am Heart J 2003;145:445-51.)     

Effect of flestolol on ventricular rate during atrial fibrillation in Wolff-Parkinson-White syndrome

The ultrashort-acting beta blocker flestolol was studied during atrial pacing and atrial fibrillation (AF) in 10 patients with Wolff-Parkinson-White syndrome. Flestolol was given as a 100-micrograms/kg bolus followed by a 10-micrograms/kg/min infusion for 15 minutes. The drug did not alter the antegrade effective refractory period of the accessory pathway or the atrial paced cycle length at which block occurred in the accessory pathway. After flestolol, the percent of preexcited QRS complexes during AF increased (60 +/- 10 vs 87 +/- 5%, p = 0.01). Despite this, the ventricular rate slowed, with increases in mean RR interval (382 +/- 20 vs 416 +/- 22 ms, p = 0.02) and in the shortest interval between preexcited QRS complexes (251 +/- 18 vs 270 +/- 17 ms, p less than 0.01). The effect of isoproterenol 3 to 5 micrograms/min was studied in 5 patients. During atrial pacing, isoproterenol decreased the antegrade refractory period and the atrial paced cycle length of block in the accessory pathway (p less than or equal to 0.05). During AF, it decreased the percent of preexcited QRS complexes, mean RR interval and shortest interval between preexcited QRS complexes (p less than 0.05). Flestolol reversed the effects of isoproterenol both during atrial pacing and AF. Thus, flestolol does not alter conduction over the accessory pathway during atrial pacing, but during AF it slows conduction over the accessory pathway and prevents isoproterenol-mediated increases in ventricular rate. This suggests that in patients with Wolff-Parkinson-White syndrome sympathetic stimulation after the onset of AF enhances conduction over the accessory pathway and is an important determinant of ventricular rate.     

Psychometric validation of the Stoma-QOL questionnaire in a Canadian cross-sectional sample of colostomy and ileostomy patients

Objectives: The Stoma-QOL questionnaire is a patient-reported outcome (PRO) used to measure quality of life in patients with ileostomy or colostomy. This study assesses the Stoma-QOL’s overall and item-level psychometric characteristics in patients with temporary stomas, and whether stoma-related quality of life differs by demographic characteristics.

Materials and methods: Analysis of cross-sectional observational PRO data from hospitals in Vancouver, Canada. Patients registered for elective ileostomy or colostomy closure, over the age of 18, and able to read English were eligible for participation. Emergent and cancer-related cases were excluded. One-way analysis of variance was used to test for demographic differences in Stoma-QOL scores. Cronbach’s alpha was used for reliability, and Rasch item-response theory was used to assess overall and item characteristics.

Results: 120 patients were included. No statistically significant difference in Stoma-QOL scores was found by age, sex, or socioeconomic status. Reliability was 0.93. Mean item responses ranged from 1.77 to 3.55 and item-total correlation ranged from 0.51 to 0.77. The Rasch item-response theory model demonstrated significant misfit, likely due to the misfit of item 9, which asks about sexuality, and high residual correlations between item pairs 6 and 8 about fatigue, and items 16 and 17 about social relationships.

Conclusions: The Stoma-QOL questionnaire is a well-designed PRO for measuring stoma-related quality of life. Demographic variables do not appear to have a strong influence on Stoma-QOL scores. Item 9 demonstrated misfit but removal likely does not improve the instrument. Future research should focus on revising items 6, 8, 16, and 17.     

The safety of performing diagnostic cardiac catheterizations in a mobile catheterization laboratory at primary care hospitals

The benefits of mobile cardiac catheterization laboratories include keeping patients closer to their families, communities, local hospitals, and primary care physicians while receiving services comparable to those available at tertiary centers. However, there are very few studies regarding the safety of performing cardiac catheterization in mobile laboratories at remote locations. Thus, the authors performed an observational study of 1,775 consecutive patients undergoing a diagnostic cardiac catheterization in a mobile catheterization laboratory at primary care hospitals served by the Appleton Heart Institute (AHI) from August 1, 1991, to December 31, 1998. Twenty-three percent (1,775/7,637) of all AHI diagnostic cases in this time period were performed in the mobile catheterization laboratory. Urgent transfer to the tertiary care facility via ambulance or helicopter was used for 2.3% of patients (n = 41). The overall complication rate was 1.2% (n = 21). Of the patients who underwent cardiac catheterization in the mobile laboratory, 32.6% (n = 579) were subsequently referred for interventional or surgical revascularization. There were no deaths. Cardiac catheterizations can be performed safely in a mobile laboratory at primary care hospitals, provided that immediate transfer is available for those in need of urgent intervention or revascularization and that unstable patients are not studied in the mobile laboratory.     

Reflex heart rate control via specific aortic nerve afferents in the rabbit.

Reflex bradycardia was elicited in rabbits via repetitive electrical stimulation of the central end of the sectioned left aortic nerve. Supramaximal stimulation produced a 16.9 plus or minus 1.3% (SE) increase in the R-R interval when vagal and sympathetic efferent pathways were intact. Reducing the stimulation voltage allowed selective stimulation of the myelinated (A) fibers, and polarizing electrodes placed central to the stimulus site permitted A fiber blockade and selective stimulation of the unmyelinated (C) fibers. When afferent A fibers were selectively stimulated, 64% of the maximum response was obtained; selective C fiber activation elicited 63% of the maximum observed response. Selective stimulation of A or C fibers after either vagotomy or stellectomy indicated that A fiber afferents elicit heart rate responses via both vagal and sympathetic efferents, whereas C fiber afferent information is mediated predominantly via vagal efferents. This afferent-efferent specificity of the aortic baroreceptor pathways suggests baroreceptor mechanisms normally used to modulate heart rate. Small increments in blood pressure would activate low-threshold A fibers and result in reciprocal changes in vagal and sympathetic efferent activity. More substantial increases in blood pressure would activate afferent C fibers and produce additional heart rate effects via vagal efferents.     

Association of ankle-brachial index with severity of angiographic coronary artery disease in patients with peripheral arterial disease and coronary artery disease

The ankle-brachial index (ABI) was correlated with the severity of coronary artery disease (CAD) in 273 patients, mean age 71 years, with peripheral arterial disease and angiographically obstructive CAD (> 50% occlusion). Of 155 patients with an ABI < 0.40, 130 (84%) had 3- or 4-vessel CAD, 17 (11%) had 2-vessel CAD and 8 (5%) had 1-vessel CAD. Of 80 patients with an ABI of 0.40-0.69, 37 (46%) had 3- or 4-vessel CAD, 33 (41%) had 2-vessel CAD and 10 (13%) had 1-vessel CAD. Of 38 patients with an ABI of 0.70-0.89, 10 (26%) had 3- or 4-vessel CAD, 16 (42%) had 2-vessel CAD and 12 (32%) had 1-vessel CAD. The lower the ABI, the higher the prevalence of 3- or 4-vessel CAD and the lower the prevalence of 1-vessel CAD.     

Successful partial excision of an intramural fibroma of the left ventricle.

A report of the only surviving adult to undergo partial excision of an intramural cardiac left ventricular fibroma is presented. Good results were obtained by relieving outflow tract obstruction through partial excision of the tumor from the septum and left ventricle. The need for conservative surgical treatment of patients with this rare, benign tumor is emphasized.