Controlled trial of physical training in chronic heart failure. Exercise performance, hemodynamics, ventilation, and autonomic function

Time course of haemodynamic changes after maximal exercise

The haemodynamic changes during 4 h following maximal upright bicycle exercise were evaluated in six normals in a randomized controlled crossover design. Total peripheral resistance was reduced to 2 h (-6.7 mmHg min l-1, P < 0.05); exercising and non-exercising vascular beds were vasodilated for 2 h (-24.1 and -23.8 mmHg min ml-1 100 ml-1 tissue, respectively, P < 0.05), associated with reductions in systolic (-5.8 mmHg, P < 0.05) and diastolic pressure (-8.3 mmHg, P < 0.05). Rise in cardiac index for 1 h (+0.51 min-1 m-2, P < 0.05) was accounted for by an elevated heart rate (+14.4 beats min-1, P < 0.01) as stroke volume was unchanged. Body temperature was elevated until 40 min (+0.20 degrees C, P < 0.05). The return of all haemodynamic variables to control by 3 h suggests a 3 h limit for a hypotensive effect of exercise. Rise in body temperature is not the only factor responsible for the hypotension.

The nutrition implications of cardiac cachexia

Weight loss is a frequent sequela in patients with congestive heart failure and is commonly referred to as cardiac cachexia. This weight loss is unlike that seen in simple starvation because it preferentially involves the depletion of lean body mass. In addition, the presence of cardiac cachexia can have profound clinical implications for patients in terms of complications, clinical outcome, and overall cost. The mechanism for the alterations in body composition is multifactorial, but a major cause may be the cytokine-mediated host response to the underlying disease. This article reviews the syndrome of cardiac cachexia in light of recent evidence regarding the role of cytokines, as well as potential therapies.

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.

Baroreflex sensitivity: methods, mechanisms, and prognostic value

A large bulk of data collected over the last 25 years links reflex autonomic activation during acute myocardial ischemia with risk of developing lethal arrhythmias. Specifically, evidence obtained in an experimental preparation in chronically infarcted dogs supported the concept that sympathetic hyperactivity enhances likelihood for ventricular tachyarrhythmias, vagal activation exerts protective effects. Based on this knowledge, it was first proposed by our group that analysis of autonomic control of heart rate could provide information relevant to risk stratification in post-myocardial infarction individuals. Among several possibilities, baroreflex sensitivity was evaluated by correlating blood pressure rise induced by bolus injections of phenylephrine with the consequent beat to beat R-R interval lengthening. Experimental studies involving direct recordings from single neural vagal fibers directed to the heart documented that baroreflex sensitivity closely reproduces cardiac vagal activity. In a large group of conscious dogs it was shown that a depressed baroreflex sensitivity was highly predictive of the risk for ventricular, fibrillation during acute myocardial ischemia. The clinical prognostic value of baroreflex sensitivity has already been confirmed in pilot studies conducted by different groups of investigators. Overall, the phenylephrine test has been performed in several hundred patients with no reports of side effects. An ongoing multicenter study, the ATRAMI (Autonomic Tone and Reflexes After Myocardial Infarction) is aimed to definitively assess the predictive value of baroreflex sensitivity and heart rate variability in patients with a prior myocardial infarction. While the enrollment is still ongoing, this study has already provided an important methodological information about the possibility of using non invasive technique to record blood pressure by means of FINAPRES, to evaluate baroreflex sensitivity. Comparison among 142 tests performed with simultaneous recording from an intraarterial line and from FINAPRES indicated a strong correlation (r = 0.9) between the two methods. ATRAMI is expected to close the enrollment in the near future. To data, baroreflex sensitivity appears to be a safe and non-invasive test likely to provide meaningful information on autonomic balance and consequently on risk profile of patients with a prior myocardial infarction.

Clinical aspects of sympathetic activation and parasympathetic withdrawal in heart failure

Proposed reflex mechanisms for generalized neurohumoral activation in heart failure include decreased input from inhibitory baroreceptor afferent vessels and increased input from excitatory afferent vessels arising from arterial chemoreceptors, skeletal muscle metaboreceptors or the lungs. Not all subjects with left ventricular dysfunction have increased sympathetic nerve activity, but the magnitude of sympathoneural activation appears to independently predict survival. This association suggests both a causative mechanism linking sympathetic activation with adverse outcome and a therapeutic opportunity to improve the prognosis of such patients by inhibiting central sympathetic outflow. Generalized sympathetic activation is not unique to heart failure, and its functional consequences appear to be both organ- and condition-specific. Sympathetic activation is present in other disorders such as mild hypertension, cirrhosis and aging that do not share the dim prognosis of congestive heart failure. The adverse effects of adrenergic activation on the diseased myocardium may be a function of the magnitude and time course of increases in cardiac sympathetic nerve activity, the mechanical and electrophysiologic consequences of nonuniform abnormalities of sympathetic innervation in the failing heart and the absence of specific countervailing mechanisms present in other conditions also characterized by increased sympathetic traffic. The hypotheses that activation of adrenergic drive to the diseased myocardium is the causative mechanism linking sympathoexcitation to adverse outcome and that interventions that inhibit sympathetic outflow to the heart will improve the prognosis of patients with congestive heart failure have not been specifically tested. Greater understanding of the mechanisms responsible for the heterogeneity of sympathetic activation in response to ventricular dysfunction, for cardiac-specific and generalized activation of the sympathetic nervous system and for the stimulation or suppression of countervailing mechanisms capable of resisting its adverse effects is fundamental to the development of better therapies for congestive heart failure.

Factors contributing to the exercise limitation of heart failure

Exertional intolerance is a major clinical problem in ambulatory patients with chronic heart failure and is associated with both muscle fatigue and dyspnea. The increased muscle fatigability is most likely caused by a combination of muscle underperfusion and muscle deconditioning; patients frequently exhibit skeletal muscle atrophy, altered muscle metabolism and reduced mitochondrial-based enzyme levels, consistent with deconditioning. The muscle underperfusion is largely due to impaired arteriolar vasodilation within exercising muscle. Exertional dyspnea appears to be due to increased respiratory muscle work mediated by excessive ventilation and decreased lung compliance. Both excessive carbon dioxide production, secondary to increased muscle lactate release, and increased lung dead space contribute to the excessive ventilation. Decreased lung compliance is caused by chronic pulmonary congestion and fibrosis. Optimal management of exercise intolerance in patients with heart failure requires an understanding of the role of these multiple potential contributors to exertional fatigue and dyspnea.

Exercise rehabilitation in chronic heart failure

In acute heart failure with pulmonary edema, rest is a useful adjunct to pharmacologic treatment because it increases urinary flow and enhances the effectiveness of diuretic drugs. In chronic heart failure, however, there is increasing evidence that avoiding exercise can lead to deconditioning changes in skeletal muscle and in the peripheral circulation that may actually impair exercise tolerance. Exercise training was introduced as part of postinfarction rehabilitation in the 1960s, but it was not tested in patients with heart failure until well into the 1980s. Several reports have now shown considerable improvements in exercise capacity after physical training in patients with stable chronic nonedematous heart failure. Many of the peripheral abnormalities described in chronic heart failure have been shown to be at least partially reversible after physical training. These include abnormalities of skeletal muscle, respiratory gas exchange and autonomic nervous control of the circulation. Controversy still exists as to whether training may have beneficial prognostic effects in chronic heart failure and how soon after myocardial infarction it is safe to commence training. In addition, little information exists as to the most appropriate form of exercise therapy and the proper criteria for patient selection into training programs. Exercise training seems set to become a popular and beneficial adjunct to the management of patients with chronic heart failure. It has been shown to have a beneficial effect on symptoms, exercise performance and a host of pathophysiologic changes characteristic of chronic heart failure. Whether it improves prognosis is not known.

Time and frequency domain assessment of heart rate variability: a theoretical and clinical appreciation

Non-invasive techniques for assessing heart rate variability can be used either diagnostically, as in identification of autonomic neuropathy associated with diabetes mellitus or tissue rejection following cardiac transplantation, or as a prognostic indicator in coronary artery disease. The methodology is based upon calculation of successive R-R intervals from an electrocardiogram, which can then be plotted as a frequency histogram (time domain analysis), undergo power spectral analysis to yield information in the frequency domain or be applied to chaos theory. In this review, several parameters are discussed which can be derived to quantify heart rate variability in the time and frequency domains; the latter providing information on autonomic balance. In the frequency domain up to three peaks may be observed, with the peak below 0.15 Hz being mediated by sympathetic and parasympathetic activity and peaks above 0.15 Hz being of vagal origin. The effects of different physiological and pathophysiological conditions on various indices of heart rate variability, and the use of heart rate variability analysis as a pharmacological method to assess the impact of drug therapy on sympathovagal balance are discussed.