Biomedical subjects

N R Niles

Publications and source records attributed to N R Niles.

At least 19 recordsLinked to original sources

PubMed1988

Idiopathic dilated cardiomyopathy. Role of programmed electrical stimulation and Holter monitoring in predicting those at risk of sudden death.

The prognostic role of programmed electrical stimulation and Holter monitoring was evaluated in 21 patients with idiopathic dilated cardiomyopathy who had no prior history of ventricular tachyarrhythmias. During a mean follow-up period of 23 months, sudden death or ventricular fibrillation occurred in four (20 percent). One patient died of complications of sepsis, and one underwent cardiac transplantation. Programmed electrical stimulation (PES) resulted in five or more beats of induced ventricular tachycardia in seven patients (33 percent), but was a poor predictor of sudden death (sensitivity = 20 percent). Thirteen patients (62 percent) had complex ventricular ectopy (Lown class 4A or 4B) by ambulatory monitoring. This was a sensitive (80 percent) but not specific (31 percent) marker for sudden death. The predictive value of a negative Holter monitor study was high (80 percent) for identifying those at low risk of sudden death. The results of this prospective study suggest that programmed ventricular stimulation and routine ambulatory monitoring are poor predictors of sudden death in this population.

Adult↗

PubMed1987

Exercise induced augmentation of cellular and humoral autoimmunity associated with increased cardiac dilatation in experimental autoimmune myocarditis.

To determine the effects of exercise in experimental autoimmune myocarditis, guinea pigs immunised with heterologous heart protein (rat heart), Freund's complete adjuvant, and pertussis vaccine (treated group) were exercised on a treadmill for a total of 11 weeks and compared with non-exercise treated animals. In vivo heart rates and pressures, in vitro left ventricular pressure-volume relations, myocardial histology, circulating antiheart antibody, and in vitro lymphocyte stimulation were determined. Exercise resulted in increased cardiac dilatation in treated animals as assessed by in vitro left ventricular pressure-volume relations compared with non-exercise treated animals (at 8 mmHg 1.41(0.17) ml.kg-1 vs 1.20(0.17) ml.kg-1 respectively, p less than 0.005). Exercise also resulted in increased concentrations of circulating antiheart antibody as assessed by radioimmunoassay (0.14(0.04) microgram vs 0.10(0.03) microgram respectively, p = 0.01), and increased lymphocyte activation to specific antigen (stimulation index 3.7(0.07) vs 2.4(1.0) respectively, p less than 0.001). Despite the associated augmentation of autoimmunity with cardiac dilatation, there were no differences in the histopathological findings between the exercised treated and the non-exercised treated animals either qualitatively or quantitatively (number of inflammatory cell microaggregates). This finding suggests that, although the immune system is important in experimental autoimmune myocarditis, the amount of inflammation and necrosis does not appear to correlate with the degree of left ventricular dilatation and presumed dysfunction.

Animals↗

PubMed1986

Unexpected myocardial disease in patients with life threatening arrhythmias.

It is not unusual for an individual without recognisable clinical heart disease to have a life threatening arrhythmia. This report describes the results of endomyocardial biopsy in twelve patients who presented with life threatening arrhythmias and normal or near normal cardiac function. The eight men and four women (mean age 35) presented with ventricular tachycardia or fibrillation (nine cases), high grade heart block with inadequate ventricular escape (two cases), and dangerous ventricular extrasystoles (Lown grade 4, one case). In ten of the twelve patients symptoms had been present for less than or equal to 6 months at presentation. No patient had a normal electrocardiogram. Electrophysiological testing confirmed the clinical arrhythmia in all but three patients. Endomyocardial biopsy demonstrated lymphocytic myocarditis in two patients, granulomatous myocarditis in two patients, small vessel vasculitis in one patient, and cardiomyopathic changes in six patients. In one patient the biopsy specimen was normal. Endomyocardial biopsy is a valuable diagnostic tool in patients with unexplained life threatening arrhythmias. In this study half the patients had a treatable form of heart muscle disease.

Adult↗

PubMed1986

Granulomatous myocarditis. Diagnosis by endomyocardial biopsy and response to corticosteroids in two patients.

Granulomatous involvement of the myocardium is of uncertain etiology, rarely diagnosed premorbidly, and the response to therapy is unknown. We report two patients with granulomatous disease apparently isolated to the myocardium, one presenting with cardiac arrest secondary to ventricular tachycardia, one with heart block. In both cases, the clinical rhythm was substantiated by electrophysiologic studies and neither case had evidence of significant myocardial dysfunction. In both, treatment was instituted with orally administered prednisone. One patient died suddenly two months following onset of therapy. Limited autopsy demonstrated no evidence of granulomatous involvement of the myocardium. The other patient is alive without clinical arrhythmias on amiodarone therapy; however, inducible ventricular tachycardia persists. Repeat endomyocardial biopsy in this patient demonstrated no granulomatous disease. These cases are discussed and the literature reviewed.

Adult↗

PubMed1986

Clinical, hemodynamic and endomyocardial biopsy findings in idiopathic restrictive cardiomyopathy.

Restrictive cardiomyopathy is uncommon and in its overt form is associated with heart failure, characterized primarily by abnormalities in diastolic function and preserved or nearly preserved systolic function. It may be associated with amyloidosis, hemochromatosis or endomyocardial fibrosis. We describe five patients with restrictive cardiomyopathy, ages ranging from 35 to 71 (mean 49), three of whom were men. Fatigue, dyspnea on exertion and chest pain were the most frequent symptoms. Only one patient had overt heart failure, and three had normal or near-normal hemodynamics at rest that became greatly abnormal with exercise. Four of the five patients are alive now 9 to 77 (mean 33) months following the onset of symptoms. Despite prior emphasis on specific causes, restrictive cardiomyopathy in this series had no definable cause. Moreover, the presence of a "latent" form of restriction (abnormalities only with exercise) suggests that the incidence of the disease may be higher than previously appreciated.

Adult↗

PubMed1985

Lack of objective improvement in ventricular systolic function in patients with myocarditis treated with azathioprine and prednisone.

Six patients with myocarditis documented by biopsy, after a baseline right heart catheterization and echocardiogram, underwent treatment with azathioprine and prednisone. After 3 months of treatment, biopsy, right heart catheterization and echocardiogram were repeated. In addition to the immunosuppressive therapy, most patients received additional conventional medications for heart failure between evaluation periods (mean number of cardiac drugs increased from 1.7 +/- 1.0 to 2.7 +/- 0.05, p = 0.041). Mean heart rate decreased (105 +/- 14 to 84 +/- 13 beats/min, p = 0.016), as did pulmonary wedge pressure (23 +/- 8 to 12 +/- 4 mm Hg, p = 0.012). There were no significant changes in cardiac index (3.1 +/- 0.8 to 2.9 +/- 1.0 liters/min), end-diastolic dimension (62 +/- 13 to 62 +/- 12 mm) or fractional shortening (11 +/- 6 to 12 +/- 3%) with treatment. Complications from immunosuppressive therapy included severe soft tissue infection, acute psychosis and adrenal insufficiency in one patient each. The benefits from prednisone and azathioprine in this group of patients have not been demonstrated. Although heart rate and pulmonary wedge pressure decreased, these changes could be ascribed to increases in the conventional therapy for heart failure. Finally, there is a high incidence of side effects from prednisone and azathioprine therapy. These findings suggest that this unproven therapy for myocarditis should be limited to experimental protocols.

Adult↗

PubMed1985

Experimental autoimmune myocarditis in the guinea pig.

Male and female guinea pigs underwent immunisation with heterologous heart protein (rat heart), complete Freund's adjuvant and pertussis vaccine (immunised) or normal saline (control) at weekly intervals for 6 weeks, and were subsequently studied. In vivo intracardiac pressures, cardiac outputs, blood volumes, in vitro pressure-volume relations, left ventricular collagen contents, light microscopy, direct immunofluorescence, lymphocyte stimulation studies, and serology for circulating anti heart antibody (haemagglutination and radioimmunoassay) were performed. Immunised guinea pigs studied between 5 and 8 weeks following the immunisation protocol demonstrated a 44% increase in LVEDP (p less than 0.005), an increase in right atrial pressure (p less than 0.001), although no change in aortic pressure or cardiac output when compared with controls. Left ventricular weight was increased 20% (p less than 0.001), and in vitro left ventricular volume by 34% (at 8 mmHg distending pressure, p less than 0.001). Lung wet weight was increased 44% (p less than 0.005), and left ventricular collagen content increased 60% (p less than 0.001). Cultured lymphocytes from treated guinea pigs demonstrated a 1.5- to 4.5-fold (dependent upon proximity to last immunisation) increase in radiolabelled thymidine uptake when incubated with guinea pig heart protein compared to controls (p less than 0.001), and circulating anti guinea pig heart antibodies were detected by haemagglutination and radioimmunoassay. Histological examination of the left ventricles revealed inflammatory cell infiltration and myocyte increase to varying degrees in 15 of the 18 treated animals. We conclude that inflammatory, probably immune-mediated, chronic myocarditis can be produced in the guinea pig.

Animals↗

PubMed1973