[ ] [CK] CPET indicaiton(MEDSCAPE)

Cardiopulmonary exercise testing

Cardiopulmonary exercise testing (CPET) combines exercise testing with ventilation gas analysis. Like post-MI exercise testing, it is performed in accordance with ACC/AHA guidelines.

Class I applications of CPET are as follows:

• For evaluation of exercise capacity and response to therapy in patients with heart failure who are being considered for heart transplantation
• For assistance in differentiating cardiac limitations from pulmonary limitations as a cause of exercise-induced dyspnea or impaired exercise capacity when the cause is uncertain

Class IIa applications are as follows:

• For evaluation of exercise capacity when indicated for medical reasons in patients with unreliable estimates of exercise capacity from exercise test time or work rate

Class IIb applications are as follows:

• For evaluation of the patient’s response to specific therapeutic interventions in which improvement of exercise tolerance is an important goal or end point
• For determination of the intensity for exercise training as part of comprehensive cardiac rehabilitation

Class III applications are as follows:

• For routine use to evaluate exercise capacity

CPET is a useful adjunctive tool for the assessment of patients with cardiovascular and pulmonary disease. It involves measurements of gas exchange, primarily oxygen uptake (ie, VO₂), carbon dioxide output (VCO₂), minute ventilation, and anaerobic (lactic acid) threshold. Patients usually wear a nose clip and breathe through a nonrebreathing valve that separates expired air from room air.

VO₂ at maximal exercise (peak VO₂) is considered the best index of aerobic capacity and cardiorespiratory function. Estimation of maximal aerobic capacity by using published formulas based on exercise time or work rate without direct measurement is limited by physiologic and methodologic inaccuracies.

According to data acquired from patients with heart failure who have undergone cardiopulmonary stress testing with this method, subsequent analysis is reliable and important and has been shown to benefit this subgroup of patients the most.

Such data are only partly influenced by resting left ventricular dysfunction. Maximal exercise capacity does not necessarily reflect the daily activities of patients with heart failure. Use of this technique to stratify patients with ambulatory heart failure has improved the clinician’s ability to identify those with the poorest prognosis, who should be considered for heart transplantation.

Abnormal ventilatory and chronotropic responses to exercise are also predictors of outcome in patients with heart failure. ^[24] In addition, evaluation of the rate of VO₂ decline during exercise recovery (VO₂kinetics) may provide additional information regarding the functional state in patients with heart failure. Compared with normal oxygen kinetics, prolonged recovery time of VO₂ has been correlated with poorer exercise tolerance, lower peak VO₂, and a lower cardiac index.

Most investigators conclude that measurement of peak VO₂ yields the best prognostic information in patients with heart failure. Evaluation of submaximal and recovery ventilatory responses may be particularly useful when exercise to near-maximal levels (respiratory exchange ratio greater than 1) is not achieved.