Peripheral circulatory adaptations to pump failure of the heart

Pathophysiology of heart failure update: the role of neurohumoral activation in the progression of heart failure

Understanding the pathophysiologic mechanisms responsible for producing heart failure is necessary before effective treatments can be developed that increase survival and improve quality of life. Recent advances in the treatment of heart failure can be traced directly to improved appreciation of the role of neurohumoral activation in the pathophysiology of heart failure. Initially adaptive, neurohumoral activation ultimately results in a series of overadjustments that actively participate in the progression of heart failure. In this article, the role of neurohumoral activation, ventricular remodeling, and various peripheral vascular abnormalities in the pathophysiology of heart failure are explored.

Medium-term effectiveness of L-thyroxine treatment in idiopathic dilated cardiomyopathy

BACKGROUND

In dilated cardiomyopathy, short-term administration of L-thyroxine (100 micrograms/ day) improves cardiac and exercise performance without changing the heart's adrenergic sensitivity. The aim of this study was to test the medium-term (3 months) efficacy of L-thyroxine (10 patients) compared with placebo (10 patients) and to find out whether later effects are obtainable.

METHODS

Echocardiographic parameters in the control state and during acute changes of left ventricular afterload, cardiopulmonary exercise test, and hemodynamic parameters, including cardiac beta 1 responses to dobutamine, were obtained before and at the end of treatment.

RESULTS

Significant (P < 0.05) changes were observed only with the active drug. After L-thyroxine, patients did not show evidence of chemical hyperthyroidism, despite the increase in thyroxine and the reduction in thyroid-stimulating hormone plasma levels. Cardiac performance improved, as shown by the increase in the left ventricular ejection fraction and rightward shift of the slope of the relation left ventricular ejection fraction/end-systolic stress. Resting cardiac output increased, and the left ventricular diastolic dimensions and systemic vascular resistances decreased. The responses of cardiac output and heart rate to dobutamine infusion were also enhanced. Functional capacity markedly improved, together with an increase in peak exercise cardiac output.

CONCLUSION

L-thyroxine does not lose its beneficial effects on cardiac and exercise performance on medium-term administration and does not induce adverse effects. In addition to the short-term study, the left ventricular diastolic dimensions were decreased. An upregulation of beta 1 receptors might explain the cardiac response to dobutamine.

Improved quality of life in chronic heart failure patients following local endurance training with leg muscles

BACKGROUND

Despite reported benefits of exercising for chronic heart failure patients, limited data are available on quality of life and the effects of different modes of training. This study assessed the effects of local endurance training with knee extensor muscles on exercise tolerance and health-related quality of life in male patients with moderate, chronic heart failure.

METHODS AND RESULTS

Twenty-one patients (mean age, 60 years; range, 43-73 years) in New York Heart Association functional classes II-III (ejection fraction, 28 +/- 11%) were randomized to two training groups and one control group. Both training groups performed the same relative quantity of dynamic work with knee extensor muscles 3 days a week for 8 weeks. However, the quantity of muscle mass trained at one time and, consequently, the load on the integrated circulation differed between the groups (two-and one-leg training). Exercise capacity and perceived quality of life were assessed before and after the training or control period. Exercise tolerance increased (P < .01) in both training groups with significantly (P < .01) better improvement in submaximal exercise capacity in the two-leg group. There was no improvement in the control group. Coping capacity did not differ from the reference range and did not change during the study. Global health-related quality of life was depressed at baseline. Training improved (P < .05) health-related quality of life. Compared with the control group, the improvement of health-related quality of life subscales was more pronounced in the two-leg training group (P < .02-.005) as compared to the one-leg training group (not significant to P < .05).

CONCLUSIONS

Local muscle endurance training has beneficial effects on exercise tolerance and health-related quality of life in patients with moderate, chronic heart failure. As two-leg training showed a tendency toward better improvement in submaximal exercise capacity and in quality of life than one-leg training, the effects on quality of life appear to be exercise-related in addition to a possible placebo-related effect. Also, the effect appears to be related to the extent of muscle trained at one time.

Skeletal muscle fiber composition and capillarization in patients with chronic heart failure: relation to exercise capacity and central hemodynamics

Patients with chronic heart failure have structural and metabolic changes in skeletal muscle, which may be of importance for symptomatology. The origin of these changes are still unknown. The relationship between fiber composition and capillarization in skeletal muscle with exercise capacity and central hemodynamic variables was examined. Biopsies from the lateral vastus muscle were taken in 12 patients with chronic heart failure. Samples from eight normal subjects served as control samples. All patients underwent maximal exercise tests. Central hemodynamic variables were measured during exercise in five patients. The patients had a higher percentage of type II B fibers (P = .03) and fewer capillaries per fiber (P = .02) than the controls subjects. VO2 max correlated with the percentage of type I fibers, whereas the correlation with the type II A fibers was inverse. Cardiac index and pulmonary capillary wedge pressure at submaximal and maximal exercise were related to fiber type composition and relative fiber areas. Skeletal muscle fiber type composition and capillarization was changed in patients with chronic heart failure. These changes might influence exercise capacity. There were relationships between central hemodynamic variables and skeletal muscle changes. What the cause and effects were need further investigation.