ALTERNATIVE APPROACHES TO CARDIAC REHABILITATION
In carefully selected patients, alternatives to the traditional supervised (group or individual) cardiac rehabilitation program have been examined. These alternatives, which are applicable primarily to very low-risk patients, include the following options:
Ø Home-based cardiac rehabilitation (effective and safe)
Ø Exercise with transtelephonic monitoring/surveillance
CARDIAC REHABILITATION IN PATIENTS WITH HEART FAILURE
Heart rate recovery (HRR) following maximal exercise has been found to be a predictor of all-cause mortality. In a 2006 study, Streuber and colleagues hypothesized that aerobic exercise training could improve HRR in patients who have suffered heart failure, because athletes are known to have accelerated HRR, while cardiac rehabilitation has been shown to positively effect such recovery in patients with coronary artery disease (CAD).
The authors conducted a retrospective study of 46 patients with heart failure who had completed a phase 2 aerobic cardiac rehabilitation program with entry and exit maximal stress tests. The results indicated that in patients with heart failure who have low exercise capacity, even short-term aerobic training can aid HRR.
EXERCISE TESTING AND EXERCISE PRESCRIPTION
INDICATIONS
Cardiac rehabilitation initially was designed for low-risk cardiac patients. Now that the efficacy and safety of exercise have been documented in patients previously stratified to the high-risk category, such as those with congestive heart failure (CHF), the indications have been expanded to include such patients.
Exercise training benefits persons with the following cardiac conditions:
Recent myocardial infarction
Coronary bypass
Valve surgery
Coronary angioplasty
Cardiac transplantation
Angina
Compensated CHF
Exercise prescription depends on the results of exercise testing, which often includes cardiopulmonary exercise (CPX) testing.
MODIFICATIONS OF EXERCISE
Patients with limitations due to chronic obstructive pulmonary disease (COPD), peripheral vascular disease (PVD), stroke, and orthopedic conditions still can be trained in the exercises through special techniques and adaptive equipment (eg, use of arm-crank ergometer).
CONTRAINDICATIONS
Cardiac rehabilitation services are contraindicated in patients with the following conditions:
Ø Severe residual angina
Ø Uncompensated heart failure
Ø Uncontrolled arrhythmias
Ø Severe ischemia, LV dysfunction, or arrhythmia during exercise testing
Ø Poorly controlled hypertension
Ø Hypertensive or any hypotensive systolic blood pressure response to exercise
Ø Unstable concomitant medical problems (eg, poorly controlled or "brittle" diabetes, diabetes prone to hypoglycemia, ongoing febrile illness, active transplant rejection)
In such patients, every effort should be made to correct these abnormalities through optimization of medical therapy, revascularization by angioplasty or bypass surgery, or electrophysiologic testing and subsequent antiarrhythmic drug or device therapy.
Patients should then undergo retesting for exercise prescription.
EXERCISE TESTING
Two forms of exercise tests are performed in patients following an acute cardiac event: submaximal exercise testing and symptom-limited exercise testing.
Furthermore, CPX also may be performed, particularly in patients with cardiomyopathy or CHF, to determine objectively the patient's exercise capacity.
v Submaximal exercise testing
o In this strategy, the patients exercise enough to achieve 70% of maximum predicted heart rate for their age (ie, 70% of 220 minus age in years).
o This test is commonly performed prior to discharge and is followed by maximal exercise testing 6-8 weeks later (when patients aim to achieve 90% of maximum predicted heart rate).
v Symptom-limited exercise testing
o The patients exercise soon after a cardiac event.
o A representative schedule might begin exercise at intervals, such as 7-21 days following uncomplicated acute myocardial infarction (MI), 3-10 days following angioplasty, or 14-28 days after bypass surgery.
Submaximal exercise testing is not necessarily safer than symptom-limited testing. In fact, the submaximal strategy may have certain disadvantages; it can lead to inappropriate limitation in the patient's routine activities and exercise training and to a significant delay in the patient's return to work.
The use of submaximal exercise may also result in a failure to elicit important factors in prognosis, such as ischemia, cardiac dysfunction, and arrhythmia.
CPX testing
Ø Incremental exercise is employed, using modified Naughton protocol for treadmill or modified protocols on a bicycle ergometer.
Ø Concomitant minute-to-minute breath analysis and measurement of oxygen consumption and elimination of carbon dioxide are performed to determine VO2 max, which is the most objective method of determining functional capacity in patients with cardiac dysfunction, valvular disease, or recent acute cardiac event.
Ø Modified Bruce or Naughton protocols typically are used during the testing phase, because the standard Bruce protocol has been modified to avoid too abrupt an increase in METs (by 2-3 METs per stage).
Ø The modified Naughton protocol starts at a lower MET workload and increases by 1 MET per stage, thus allowing better-tolerated gradual progression in exercise and a more accurate assessment of exertional capacity.
Ø The usual symptomatic endpoints are fatigue and breathlessness.
Ø Severe abnormalities found on stress testing may contraindicate exercise training until they have been corrected. Less severe abnormalities, such as the development of the above symptoms at high workloads, may not necessarily contraindicate exercise training; however, certain modifications and closer surveillance may be required, including ECG monitoring.
Ø Some reports have questioned early exercise training following acute anterior MI, suggesting that it may lead to abnormal scar formation. Nonetheless, evidence is strong that moderate exercise training is not associated with worsening LV function in patients following acute anterior MI.
EXERCISE PRESCRIPTION AND SURVEILLANCE
Phase 2 of a cardiac rehabilitation program is initiated based on the result of the exercise testing, and the exercise prescription is individualized.
Three main components of an exercise training program are as follows:
Frequency - The minimum frequency for exercising to improve cardiovascular fitness is 3 times weekly.
Time - Patients usually need to allow 30-60 minutes for each session, which includes a warm-up of at least 10 minutes
Intensity - The intensity prescribed is in relation to one's target heart rate. Aerobic conditioning is emphasized in the first few weeks of exercise. Strength training is introduced later.
The Borg scale of Rate of Perceived Exertion (RPE) is used. Patients usually should exercise at an RPE of 13-15.
Borg scale of perceived exertion
6
7 - Very, very light
8
9 - Very light
10
11 - Light
12
13 - Somewhat hard
14
15 - Hard
16
17 - Very hard
18
19 - Very, very hard
20 - Exhaustion
EXERCISE INITIATION
Exercise sessions should begin with 10 minutes of warm-up, during which light calisthenics and muscular stretching are performed to avoid muscle injury and to bring about a graded increase in heart rate. This warm-up period is followed by 40 minutes of aerobic exercise (eg, walking, jogging, bicycling) and a final 10 minutes of cool-down period involving muscular stretching.
The cool-down period is very important. Gradual cool-down prevents ventricular arrhythmias, which may occur in patients with coronary disease on abrupt cessation of exercise.
PROGRESSION
The patient's peak heart rate is noted. The target is, subsequently, increased by 5-10% of the peak heart rate until the patient is able to exercise at 85% of the peak heart rate. Most patients are able to do so by 2-3 months. A follow-up treadmill test should be performed at 4-8 weeks after the patient starts the program, and the result should be used to fine-tune the exercise training.
SPECIAL CONSIDERATIONS
In patients with myocardial ischemia, exercise training still can be performed safely. The maximal heart rate should be kept 10 beats per minute (bpm) lower than the heart rate at which ischemia occurred. Closer surveillance and ECG monitoring are recommended in patients following myocardial ischemia. Patients with arrhythmias also need ECG monitoring. Patients with CHF require a much more modified exercise program.