Exercise training as therapy for chronic heart failure

Heart failure accompanied by sick euthyroid syndrome and exercise training

Sick euthyroid syndrome is defined as the decrease of serum free triiodothyronine with normal free L-thyroxin and thyrotropin. Its appearance in patients with chronic heart failure is an indicator of severity. Exercise training through a wide variety of mechanisms reverses sick euthyroid syndrome (normalization of free triiodothyronine levels) and improves the ability to exercise. There is a connection during exercise among dyspnea, hyperventilation, fatigue, catecholamines, a decrease in the number and function of beta-blocker receptors, and elevation of serum free triiodothyronine. It is not known whether sick euthyroid syndrome contributes to the development of heart failure or is only an attendant syndrome.

The management of congestive heart failure

Despite the remarkable advances in cardiovascular therapeutics over the past four decades, little impact has been made on either the incidence or mortality rate of congestive heart failure and it remains a major clinical and public health problem. Recent practice audits have suggested that proven efficacious therapies are not maximally applied in patients with this condition. An approach to the patient with congestive heart failure is presented, emphasizing the two distinct syndromes of systolic dysfunction and diastolic dysfunction. Treatment recommendations are derived from consideration of the underlying pathophysiology and the evidence from randomised clinical trials.

Determinants of perceived health in patients with left ventricular dysfunction: a structural modeling analysis

OBJECTIVE

Few studies have evaluated the determinants of perceived health in patients with chronic illness. The present study was designed to evaluate the role of biomedical, demographic, and psychosocial influences on global subjective health by means of a structural equation modeling approach.

METHOD

A conceptual model of perceived health was tested in a subsample of patients (N = 146) from the multicenter Studies of Left Ventricular Dysfunction (SOLVD) trial. Domain-specific quality of life constructs (emotional status, social support, and physical functioning), were assessed by means of multiple indicators. These latent (mediating) variables, along with six single-indicator biomedical and background variables, were modeled as predictors of a composite index of perceived health.

RESULTS

A satisfactory fit was obtained for the proposed model, with practical fit indices ranging from .89 to .95. High levels of perceived health were associated with low levels of emotional distress and high levels of physical functioning. Social support was positively correlated with physical functioning and negatively associated with emotional distress. Among the background variables, no direct associations were observed between any of the single-indicator variables and perceived health. Several background variables (eg, age, income, walk-test scores) had indirect effects via associations with the latent variables of physical functioning and emotional distress.

CONCLUSIONS

These findings support the use of a structural modeling approach in assessing determinants of perceived health in patients with congestive heart failure. Further research is needed to evaluate the utility of the model in other patient populations.

Exercise for patients with congestive heart failure

Congestive heart failure is a widely prevalent sequel to myocardial infarction and other chronic conditions (including ischaemia without infarction, hypertension, various infections, toxic metabolic and endocrine disorders). Exercise tolerance is severely limited; the cardiac ejection fraction is often less than 20% and the peak oxygen intake may be less than 10 ml/kg x min, with a resulting deterioration in the quality of life. Possible factors contributing to the poor tolerance of exercise include: (i) disturbances of myocardial function (damage to the ventricular wall; decreased inotropic response, mitral valve regurgitation and increased diastolic pressures); (ii) peripheral vascular factors (decreased metaboreceptor discharge, reduced vasodilator response, increased activity of sympathetic afferents and less efficient distribution of cardiac output); (iii) hormonal disturbances (increases of catecholamines, renin/angiotensin/aldosterone, antidiuretic and natriuretic factors, endothelin and decreased endothelium-relaxing factor); (iv) impaired muscle function (loss of lean tissue, increase of type II fibres, increased impedance to perfusion, enzyme changes); (v) ventilatory disturbances (increased oxygen cost of activity, pulmonary congestion, increased ventilatory drive, mismatching of ventilation and perfusion, increased anaerobic effort); and (vi) psychological factors (anxiety, depression and iatrogenic limitation of effort). The prognosis with conventional treatment is poor, but patients with stable congestive heart failure respond favourably to a progressive exercise programme. Reported gains depend on the cause of congestive failure, initial status, study duration and compliance, and the type of training programme. Most studies to date have been short term (4 to 16 weeks), and relatively few have adopted a randomised controlled design. Suggested bases for the enhancement of aerobic performance of up to 20% include an increased intensity of peak effort, an enhanced matching of ventilation to perfusion, improved cardiac function, a strengthening of skeletal muscle and an increase of aerobic enzyme activity in the muscles. A few studies have continued for a year or longer and it appears that the gains realised over the first 16 weeks of training can be sustained for this period; the quality of life is enhanced, but data are as yet insufficient to judge effects upon mortality rates. Useful clinical information can be obtained from a 6-minute walk, but the choice for more precise evaluation lies between a measurement of ventilatory threshold or peak oxygen intake. Given initial muscle wasting, prescribed exercise should include both aerobic activity and resisted muscle exercises.

Exercise intolerance in patients with chronic heart failure

Patients with chronic heart failure (CHF) experience significant morbidity because of dyspnea and fatigue with activities of daily living. Although central hemodynamic abnormalities are the hallmark of this disorder, investigators have not shown a relationship between left ventricular ejection fraction or exercise pulmonary capillary wedge pressure and exercise intolerance in this disorder. Recent studies have focused on the contributions of pulmonary abnormalities and alterations in peripheral vasomotor control and skeletal muscle in exercise intolerance in this disorder. Early anaerobic metabolism occurs in patients with CHF and appears to be caused by a combination of reduced skeletal muscle blood flow and decreased aerobic enzyme content in skeletal muscle. Atrophy in skeletal muscle and alterations in skeletal muscle fiber typing are accompanied by alterations in contractile function in skeletal muscle. These results suggest that exercise intolerance in patients with CHF is multifactorial, and that research efforts must consider central hemodynamic abnormalities, pulmonary abnormalities, and alterations in peripheral blood flow and skeletal muscle biochemistry and histology. The present review will explore current research in this area and develop a model for understanding exercise intolerance in CHF.

Nonpharmacologic therapy improves functional and emotional status in congestive heart failure

PURPOSE

To compare the effects of a multimodal nonpharmacologic intervention to digoxin and to placebo in patients with congestive heart failure receiving background therapy with angiotensin-converting enzyme inhibitors.

DESIGN

Randomized, parallel assignment to three treatment groups of 20 patients with congestive heart failure (New York Heart Association Class II and III).

INTERVENTION

Nonpharmacologic treatment program included the following: (1) graduated exercise training, three to five times per week; (2) structured cognitive therapy and stress management; and (3) dietary intervention aimed at salt reduction and weight reduction in the overweight. Digoxin was titrated to achieve a blood level between 0.8 and 2.0 ng/ml. Placebo and digoxin were administered in a randomized, double-blind fashion.

RESULTS

Echocardiographic ejection fraction improved (p < 0.05) in the digitalis group (change = +4.4 +/- 6.5) compared with both placebo (change = -3.2 +/- 3.9) and nonpharmacologic therapy (change = -3.2 +/- 3.9). The nonpharmacologic treatment program was well tolerated by all patients and resulted in significant improvement (p < 0.05) in exercise tolerance (digoxin = +51 +/- 50 s, placebo = +91 +/- 76, nonpharmacologic therapy = +182 +/- 139), as well as Beck Depression Inventory score (digoxin = +1.2 +/- 4.4, placebo = +2.0 +/- 4.2, nonpharmacologic therapy = -5.0 +/- 4.2), Hamilton Scale scores of anxiety (digoxin = +3.0 +/- 6.8, placebo = +6.0 +/- 2.6, nondrug therapy = -5.2 +/- 5.4), and depression (digoxin = +1.0 +/- 4.9, placebo = +5.0 +/- 5.0, nonpharmacologic therapy = -6.6 +/- 10.1). In addition, weight loss was significantly greater with nonpharmacologic therapy (digoxin = +0.32 +/- 1.76 kg; placebo = -1.35 +/- 1.44 kg; nonpharmacologic therapy = -4.37 +/- 4.50 kg) compared with both digoxin and placebo.

CONCLUSIONS

Nonpharmacologic therapy improved functional capacity, body weight, and mood state in patients with congestive heart failure. In contrast, digoxin improved ejection fraction without corresponding changes in exercise tolerance or quality of life.

Why do we eat?

The urge to eat is the main apparent issue underlying obesity. Although vast information regarding the physiology and psychology of eating behavior has been accumulated, a comprehensive concept is still missing. The model presented suggests that feeding behavior is ultimately controlled by the rate of work performed in the muscle or in an as yet unidentified compartment. It suggests a novel approach of a dynamic set-point weight and explains why diets usually fail to resolve the disorder while physical activity is beneficial in losing excess weight. Obesity is presented as a syndrome of high efficiency of energy conversion resulting in a variety of symptoms of which over-weight is only the more apparent. Other symptoms manifested in the predisposition to a variety of illnesses constitute the main health problem and can prevail in the obese subject even without the excess weight. Therefore, resolution of the disorder requires developing approaches which directly affect the efficiency of energy conversion.

Medical advances in the treatment of congestive heart failure

The increased incidence and prevalence of congestive heart failure place a high priority on novel treatment strategies. Left ventricular ejection fraction remains the single most valuable measurement providing both diagnostic and prognostic insights. The most systematic approach to heart failure involves an objective assessment of functional disability, to include exercise tests such as a 6-minute walk under standardized conditions. Left ventricular dysfunction incites a host of neurohumoral compensations that are of fundamental importance in the heart failure syndrome expression. Both vasoconstrictor and vasodilator neurohormones are stimulated and provide new therapeutic opportunities. The therapeutic approach to heart failure begins with a strong emphasis on prevention, patient education, and self-participation in therapy with respect to both its monitoring and adjustment. Diuretics remain a mainstay of therapy but, in the face of severe heart failure, may become ineffectual, requiring constant infusion of loop-active diuretics, combination diuretics, or diuretics in association with concomitant low-dose dopamine infusion. Vasodilator therapy has been an important advance: combination hydralazine and nitrate therapy was initially shown to be efficacious in improving survival, and more recently, angiotensin-converting enzyme (ACE) inhibitors, in the form of enalapril, have shown incremental benefit on survival over this combination. Interestingly, there is now evidence from both SOLVD and SAVE to demonstrate an unexpected and, as yet, unexplained reduction in the frequency of both unstable angina and myocardial infarction. Although, on balance, the weight of evidence concerning the long-term efficacy of inotropic agents has been disappointing, especially as it relates to their unfavorable effects on survival, recent information on vesnarinone, an agent with a complex and diversified mechanism of action, suggests that with appropriate doses, improved symptoms and survival are possible. A substantial amount of new information from randomized placebo-controlled trials attests to the symptomatic relief, hemodynamic improvement, and gain in exercise performance achieved by digoxin. A long-term survival study is ongoing to assess its effects on mortality. beta-Blockers, especially metoprolol, appear beneficial in some patients with heart failure, possibly related to their reduction in sympathetic nervous activity and restoration of beta-receptor population, with resultant improved contractile performance, enhanced myocardial relaxation, and overall increase in cardiac efficiency. Based on available evidence, the best contemporary approach to treatment involves the use of ACE inhibitors coupled with diuretic therapy, either continuous or intermittent, to relieve central or peripheral congestion. The addition of digoxin or a hydralazine nitrate combination is a logical next step, with commencement of low-dose beta-blocker a reasonable option.(ABSTRACT TRUNCATED AT 400 WORDS)