Usefulness of exercise tests in the evaluation of the effects of treatment in chronic cardiac insufficiency
Zannad, F.
La Revue du Praticien 40(23 Suppl): 31-35
1990
ISSN/ISBN: 0035-2640 PMID: 2267563 Document Number: 367261
Before it reaches the decompensation stage, heart failure is characterized by symptoms which occur only during exercise. It is therefore rational to believe that the effectiveness of treatments of heart failure should be evaluated by the improvement they produce in tolerance to stress. This tolerance can be evaluated by exercise tests which may take different forms. The most common is a progressive load test on bicycle ergometer or treadmill. Among the indices used to assess tolerance to stress, the total duration of the exercise test until symptoms develop is a variable subject to fluctuations which may be independent of the patient's cardiovascular state. Measurement of oxygen consumption at peak exercise level is usually preferred, being unrelated to the nature of the stress and much more reproducible and sensitive to changes. Among the pharmacological treatments of heart failure, only chronic vasodilator therapy, notably with angiotensin-converting enzyme inhibitors, has proved constantly effective on the various ergometric indices. In the literature, the effects of digitalis compounds, dihydralazine and alpha-blockers are inconstant. Among the new treatments of heart failure, phosphodiesterase inhibitors may improve tolerance to stress, as does Corwin which may prolong the total duration of exercise. Its effect on oxygen consumption has not yet been evaluated. Performance at exercise is almost never improved by acute treatment with any pharmacological agent, and the same remarks applies to short-term heart transplantation. The reason for this is that heart failure is associated with a physical deconditioning syndrome due to abnormalities of the arterial dilatation capacity in skeletal muscles, and with muscular metabolic abnormalities due to a defective oxygen utilization by these muscles.