Invited commentary

The article by Simms et al (1) opens up what should be a healthy discussion on the type of exercise testing that can safely and reasonably be done in cardiac rehabilitation without physician supervision. The American Association of Cardiovascular and Pulmonary Rehabilitation (AACVPR) and the American College of Sports Medicine (ACSM) have not endorsed a standard exercise tolerance test (ETT) as of yet (2–4), and perhaps this paper will lead to further research into this area.

A possible problem with the protocol is that the peak metabolic equivalents (METs) level was only 5.4 METs. Many younger patients may exceed that level and require longer-duration testing. However, if the patient can safely achieve over 5 METs, it would increase the value-added time for the initial exercise sessions. For example, a 45-year-old patient routinely exercised at 9 METs after 10 sessions but spent the first five getting from 3.6 to 5.2 METs. A simple ETT could have saved this patient 5 hours of doing far less than he was capable of.

One question that comes up regarding the data analysis is, Was any distinction made between those who started the program early and those who started late? Anecdotally, it is known that the patient 6 months postoperatively is far different from the patient 4 weeks postoperatively. It would be interesting to see if the ETT is sensitive enough to pick up differences in early versus late starters.

Some final questions: With regard to the protocol, were the patients monitored using a 12-lead electrocardiogram, the standard cardiac rehabilitation telemetry (3-lead), or just heart rate monitoring? What resting heart rate was used? Often, patients have anxiety before the test or before beginning cardiac rehabilitation, which can lead to an increased heart rate at rest. Was the test stopped at 10 minutes even if none of the endpoints were achieved? What is the age range of the subjects? How many subjects completed the protocol?

Graded exercise testing is widely used for diagnostic evaluation in cardiac patients. In order to attain this data, the patient or subject must be pushed to a maximal endpoint. This type of testing requires, in most cases, direct physician supervision, is labor intensive, and can be expensive to the patient if not reimbursed by insurance. Cardiac rehabilitation programs may or may not have a physician who can be dedicated to supervising the new entrant population as well as the patients who are completing the program. For the purposes of beginning cardiac rehabilitation, the program simply needs an objective measure of functional status. Many of these patients have already undergone that type of testing with their primary cardiologist. A submaximal functional test will establish a threshold to which a patient can be safely exercised and an exercise prescription can be developed. If the patient completes the protocol without difficulty, that at least tells the staff that he or she can safely start exercising at a higher level.

The 6-minute walk test has been successfully used in pulmonary rehabilitation and heart failure research, yet it tends to be a low-level test that may not be applicable to the cardiac rehabilitation setting. It would be possible to calculate a gross rate of oxygen consumption for the 6-minute walk, which can be converted to METs, but there is no way to extrapolate that information to predict the maximal rate of oxygen consumption. Without that information, it would be difficult to establish a proper exercise prescription. However, the 6-minute walk is a validated test of improvement that does not require physician supervision, and if one of the goals is to increase patient motivation, it might be considered for potential inclusion in a battery of functional assessments.

Cardiac rehabilitation programs are often criticized for lacking hard data related to patient improvement and outcomes. Improvement is seen daily in patients, but it is usually not well quantified. By incorporating a standardized ETT that does not require physician supervision and will provide quality data, cardiac rehabilitation programs could use it to justify their existence in the hospital setting.

With regard to physician supervision, the AACVPR and ACSM recommend that high-risk patients be supervised by a physician during the test. Proper risk stratification is vital to avoid negative responses. The type of testing that is recommended by the study seems to push the patients only to a level that would be accomplished during a regular rehabilitation exercise session. If the patient has been referred to the program to exercise without continuous physician supervision, this test seems reasonable.

Getting the exercise prescription right can be a difficult task without preliminary ETT data. The fact that the standard maximum heart rate prediction equation has inherent error included and most patients are on beta-blockers, which renders that equation questionable, the cardiac rehabilitation programs tend to waste the first few sessions just setting the work rate. An ETT would solve much of the problem of wasted sessions. This could be done during the first or second regular exercise session, which solves the problem of nonpayment.

A study by Joo et al (5) looked at prescribing exercise based on the resting heart rate plus 20. It found that many of the participants were exercising below the physiological range in which they would experience benefit. In this case, the range was safe but not necessarily beneficial. The same study also found that using the rate of perceived exertion level of 11 to 13 led to some subjects exercising at too high an intensity.

Simms et al concluded that this test would be a minimal test, and a more challenging test may be necessary. This should be pursued with some caution. A potential problem with a more advanced type of test is that some highly motivated overachievers would try to perform at a level beyond what they are capable of and would get into trouble. Staff need to recognize this potential problem and establish the ground rules with the patient before the test begins.

For this type of test to be successfully utilized, several criteria must be met.

• The test must be safe. The patient must always be top priority. The AACVPR and ACSM should encourage and support research in this area. If there is one thing that can put a cardiac rehabilitation program at risk for closure, it is the appearance that the program is not safe.

• Physician supervision should not be required. Obviously, the program staff would have the option to call in a physician if a shaky patient was enrolling. The staff should run the tests and forward the results to the referring physician.

• In many centers, coronary patients are tested in the exercise lab by technicians rather than physicians. A member of the rehabilitation team, who has worked in the exercise lab and has become knowledgeable in exercise physiology, can safely perform a near-maximal test.