Evolving role of cardiopulmonary exercise testing in cardiovascular disease. 
CPX testing allows for the objective assessment of aerobic capacity, anaerobic threshold, and the ventilatory response to exercise in patients with cardiovascular disease.  These results can be used to assess severity of disease, its progression over time, prognosis, candidacy for transplantation, and response to therapy.  CPX testing can also serve to distinguish cardiac from ventilatory causes of exertional dyspnea.