Exercise as a means of assessing heart failure and its response to treatment.

Exercise testing was originally applied to healthy subjects and to patients who had, or were suspected of having, ischemic heart disease. Its extension as a means to evaluate heart failure and the response to treatment was logical. Unfortunately, interpreting these tests when done on patients with heart failure is considerably more complicated, being greatly affected by the severity of heart failure, the exercise protocol employed and numerous other factors. An ideal exercise test for use in evaluating heart failure has not yet been designed. Expired gas analysis adds objectivity to the test, but interpretation is more complex than originally thought.