In the presence of heart failure the exercise ECG fulfils essentially two functions:

1. Establishment of the patient's exercise tolerance

2. Discovery of exercise-induced heart rhythm disturbances.
The case presented on the left is an example of this kind: at rest we find monomorphic ventricular extrasystoles (in the Lown classification assigned to Lown class II), during exercise (see under "pathological") there are bursts of both ventricular and supraventricular extrasystoles. Independently of this, if coronary heart disease is present in addition, the exercise ECG fulfils its diagnostic function in detection of ischemia.

It should also be noted that in NYHA III patients the exercise-tolerance test should be carried out with greater caution, while in NYHA stage IV this test is contraindicated.