Statistical Analysis

The questionnaire data were analyzed using descriptive statistics (frequency, counts, percentages, means, and ranges). Comparison statistics were not performed. The data presented is for descriptive purposes only.

Clinical Characteristics

Patients who had received a percutaneous coronary intervention (PCI) were described as being the most common patient population to utilize cardiac rehabilitation, followed by those who had suffered a myocardial infarction (MI), then by those with coronary artery bypass graft (CABG) (see Table 2 for clinical characteristics data). Very few clinics reported patients with valve disease. All CR programs admitted patients with heart failure into their programs. The number of exercise training sessions scheduled prior to the start of the CR programs ranged from 9 to 36 sessions, with the full 36 sessions coverage by Medicare occurring in 57% of CR programs.

TABLE 2. Cardiac rehabilitation program characteristics.

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Table 2 lists CR program characteristics. Almost 75% of enrolled patients graduated from phase II CR programs. Forty-four percent of CR programs set specific patient functional capacity (FC) goals upon graduation. Exercise prescriptions were written by clinical exercise physiologists (81%) in the majority of surveyed clinics. Other healthcare professionals writing prescriptions included nurses (56%), respiratory therapists (12%), and other clinicians (18%). The “other clinicians” category included cardiologists, physical therapists, and those described as exercise therapists or exercise technicians. Further, 68% of CR programs did not require their clinicians to have a certification from an established clinical agency (i.e., ACSM, AACVPR). Performing baseline stress tests before writing an exercise prescription occurred in 33% of CR programs. Reasons for not performing baseline stress tests included doctor's choice, cost, and the test considered not helpful or not a common practice. Several clinics reported using the 6-minute walk test to evaluate fitness.

Aerobic Exercise Training

Table 3 presents information on aerobic training. Aerobic exercise training was prescribed 3 days per week in most CR programs, with some treating patients 2 days per week. The most frequently reported measure for aerobic exercise prescription was RPE; however, 67% of CR programs used more than one measurement to prescribe intensity. Other measures included %HRR, METs, and heart rate max. Target intensity ranges for first aerobic session were: 11–15 on the RPE scale (Borg scale); and 30%–80% for %HRR; 50%–85% for HRmax. When prescribing initial exercise intensity without performing a baseline stress test, the most common variable used was RPE (11–14). Other intensity markers used were 20 b·min⁻¹ above resting HR, blood pressure, and many used combination prescription techniques. Thirty-four percent of clinics used other intensity measures, including 20–40 b·min⁻¹, 85% HRmax, common sense, and trial and error.

TABLE 3. Aerobic exercise prescription principles.

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The reported durations of the aerobic training session, from most often to least often used, were 40 min, 30 min, between 30–50 min, and 60 min. All CR programs used treadmills with their patients along with other modes (see Table 3). Most programs used continuous aerobic training, and almost 70% utilized interval training. All CR programs progressed patients using a combination of intensity and duration. Only a few programs set calorie expenditure goals for their patients (not reported in Table 3).

Strength Exercise Training

Strength training (see Table 4) was used in most programs, with sessions performed 1 to 3 days per week. The majority of clinics used a trial-and-error approach for determining intensity with additional reported methods of RPE, and %1RM. Among the clinics that used RPE, intensity range was 11–15 (6–20 Borg scale; data not in Table 4). The range was 50%–80% for 1 RM (data not in Table 4). All CR programs monitored HR during strength-training exercise as well as blood pressure (BP) checked before and after exercise sessions. Few programs monitored BP during the session, citing monitoring only occurred if a BP reading was high during the earlier aerobic session or if the patient had hypertension. The most reported number of sets of resistance exercise was 1. All clinics reported a range between 6–12 exercises per session for their respective patients. Clinics used a variety of exercise equipment, which included free weights, elastic bands, resistance machines, and bodyweight exercises. All CR programs progressed patients by the amount of resistance being used in combination with RPE.

TABLE 4. Resistance exercise prescription principles.

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Clinical Characteristics

The Centers for Medicare and Medicaid Services (CMS) have recently expanded coverage for cardiac rehabilitation services to include those with stable chronic heart failure (4). Prior to this expansion, the CMS permitted coverage to beneficiaries who experienced one or more of the following: acute MI within the preceding 12 months, CABG, current stable angina pectoris, heart valve repair or replacement, PCI or coronary stenting, or a heart or heart-lung transplant (4). Studies show that utilization rates of cardiac rehabilitation programs are low for covered diagnoses such as MI or CABG (5) and for recent coverage expansion of stable chronic heart failure (6). Yet more studies that assess utilization rates of all currently covered diagnoses are needed. From our findings, post-PCI patients were described as the most common patient population at CR sites, followed by those who had suffered an MI, and then CABG patients. Encouragingly, all CR programs were treating patients with heart failure. Many factors have been identified as barriers to participating in CR, including logistics, age, gender, race, socioeconomic status, education level, and the presence of comorbidities (5). While these factors were not assessed in the current analysis, we found that the average graduation rate for the 58 CR programs was 73%, but the range was 15%–95%, further substantiating a lack of patient adherence to cardiac rehabilitation. Recently, Ades and colleagues (7) created a valuable roadmap outlining specific strategies for increasing cardiac rehabilitation participation to 70%, which would save an estimated 25,000 lives and prevent 180,000 hospitalizations. The framework for achieving this goal was centered on patient referral, enrollment, and adherence. Several adherence strategies were presented, such as incentives, text messaging, and gender-tailored programming. While the graduation rates reported in the current analysis reflect adherence, types of strategies employed to maintain patient attendance were not collected. In addition, both referrals and enrollment are unknown in the surveyed clinics.

Various healthcare professionals are involved in exercise-based cardiac rehabilitation. Our findings showed that clinical exercise physiologists are primarily involved with writing exercise prescriptions. Interestingly, 32% of the facilities require that their exercise staff obtain clinical certification from highly respected organizations such as ACSM or AACVPR. A large effort has been made by these organizations to establish set criteria and examinations to substantiate the positions of clinical exercise physiologists. In the United States, Louisiana is the only state that licenses clinical exercise physiologists as a means of governing the practices and define the scope of services provided to the public by clinical exercise physiologists (8). In the remaining 49 states, anyone can claim to be an exercise physiologist (8). In addition, ACSM has established undergraduate and graduate educational program accreditation similar to that in other fields of study (e.g., physical therapy, physician assistant). An important indication for program success is students sitting for and passing certification exams. Based on this current study, additional efforts are needed to raise the level of training and certifying of clinical exercise personnel.

Graded exercise tests—often referred to as stress tests—may be used for diagnostic, prognostic, and therapeutic purposes (9). The importance of the stress test for cardiac rehabilitation is to accurately prescribe exercise intensity. We found that 67% of the CR facilities surveyed did not conduct a baseline stress test before writing an exercise prescription. Reasons for not performing baseline stress tests included physician's choice, cost, and that it was considered not helpful or not a common practice. Failure of being reimbursed may also be reason for not performing baseline stress tests. Those eligible for CR programs are often at high-risk, so it was surprising to find so many CR facilities not performing baseline stress tests. Disparities among facilities could be due to the influence of organizational internal factors. Ideally, to accurately assess the safety and effectiveness of an exercise prescription, a test-retest methodology is needed.

Subsequently, if a baseline stress test is not conducted prior to developing an exercise prescription, other measurements could potentially be used to establish exercise workload. Among the clinics surveyed, RPE (most commonly used), 20 b·min⁻¹ above resting HR, ≥85% of age predicted maximal heart rate, blood pressure, common sense, and trial and error were being used. Variability exists due to multitude of patient types (e.g., CABG, MI, PCI), characteristics (e.g., age, health history), and condition (e.g., exercise tolerance, exercise history). Therefore, it is essential to train exercise clinicians in a variety of prescription techniques in the absence of a baseline stress test.