Timeline for Peak Improvements During 52 Weeks of Outpatient Cardiac Rehabilitation

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1 c e Timeline for Peak Improvements During 52 Weeks of Outpatient Cardiac Rehabilitation Larry F. Hamm, PhD; Terence Kavanagh, MD, FRCP; Robin B. Campbell, MS; Donald J. Mertens, MD; Joseph Beyene, PhD; Johanna Kennedy, RN; Roy J. Shephard, MD, PhD PURPOSE: Cardiac rehabilitation is an integral component of comprehensive care for patients with coronary heart disease. Although the typical programmatic delivery of outpatient cardiac rehabilitation services often involves 36 sessions over 12 weeks, that format is based more on historical practice than on outcome data. This study aimed to determine the point at which during 52 weeks of outpatient cardiac rehabilitation, patients achieved peak values for selected outcomes, and whether the number of supervised exercise sessions had any effect on these outcomes. METHODS: In this study, 623 male patients with coronary heart disease admitted to an outpatient cardiac rehabilitation program were randomized to one of two 52-week program formats. One format (CR1) used one supervised exercise session per week over 52 weeks, and the second format (CR2) used weekly supervised sessions for 26 weeks followed by one supervised session per month for the remaining 26 weeks. Both formats used four unsupervised, documented exercise sessions per week. Selected clinical, physiologic, and psychological variables were measured at baseline, then at 4, 12, 26, 38, and 52 weeks. The program costs for both the CR1 and CR2 formats were calculated from known expenses. RESULTS: Because there were no significant intercohort differences between CR1 and CR2 and no significant interaction (time group), data from the two cohorts were pooled for statistical analysis. Peak oxygen intake (V O 2peak ) significantly increased by 4.4 ml/kg per minute at 38 weeks, and the greatest percentage of patients (30.1%) also achieved their highest V O 2peak at this time. The largest gain in Medical Outcomes Survey Short Form 36 role physical scores was from baseline to 38 weeks (52.4 versus 85.2), and the highest percentage of patients (72%) with role physical scores in the excellent category occurred at 38 weeks. Clinical depression at baseline (Beck Depression Inventory score 10) had no significant effect on the dropout rate or the gain in VO 2peak with exercise training. Program costs for these alternative formats of service were similar to the cost for a standard program format of 36 sessions. CONCLUSIONS: Patients achieved their highest functional capacity after 38 weeks of outpatient cardiac rehabilitation using a program format of only 29 to 38 supervised exercise sessions. The results of this study show that an outpatient cardiac rehabilitation program combining supervised with unsupervised exercise sessions and continuing for 38 weeks results in the greatest improvement in these selected outcomes. K E Y W O R D S cardiac rehabilitation patient outcomes program format From the Department of Exercise Science, School of Public Health and Health Services, The George Washington University Medical Center, Washington, DC (Dr Hamm); Toronto Rehabilitation Institute,* Toronto, Canada (Dr Hamm, Dr Kavanagh, Mr Campbell, Dr Mertens, Ms Kennedy, and Dr Shephard); University of Toronto, Toronto, Canada (Dr Kavanagh, Mr Campbell, Dr Beyene, and Dr Shephard). *Formerly Toronto Rehabilitation Centre. This study was supported by a research grant from the Canadian Cardiac Rehabilitation Foundation. Address correspondence to: Larry F. Hamm, PhD, National Rehabilitation Hospital, 102 Irving Street, NW, Washington, DC ( Larry.F.Hamm@Medstar.net). 374 / Journal of Cardiopulmonary Rehabilitation 2004;24:

2 Cardiac rehabilitation, recognized as effective in reducing subsequent mortality, 1 is an essential component of comprehensive care in the treatment of coronary heart disease (CHD). 2-4 In the United States, it is generally accepted that outpatient cardiac rehabilitation services are covered by third-party payers to a maximum of 36 visits spread over a 12-week period. 5 On the other hand, in countries where medical services are funded by the government, the trend has been to recommend a longer duration of rehabilitation services. 6 As early as 1978, Saunamaki 7 continued exercisebased cardiac rehabilitation for 12 months after myocardial infarction. Another early cardiac rehabilitation study from Finland used a comprehensive cardiac rehabilitation approach for as long as 3 years with patients recovering from myocardial infarction. 8 Hedbeck et al 9 combined supervised and home exercise training over 2 years for patients who had experienced a myocardial infarction. A 6-month program that combined aerobic and strength training for patients recovering from coronary bypass surgery was reported by Wosornu et al. 10 In fact, the Cardiac Rehabilitation Clinical Practice Guideline recommends additional research regarding alternative delivery systems for cardiac rehabilitation services. 3 To date, however, there has been little empirical evaluation to determine the merits of a program with more than 12 weeks of structured cardiac rehabilitation or, for that matter, for the optimal number of supervised exercise sessions. Therefore, this study examined selected patient outcomes at 4 weeks and at 3-month intervals over the course of an exercise-based cardiac rehabilitation program that continued for 52 weeks. Clinical, physiologic, psychological, and program cost data were collected and analyzed. Finally, an attempt was made to determine whether outcomes were influenced by the frequency of attendance at supervised rehabilitation sessions. METHODS Background and Study Sample The setting for this study was an outpatient cardiac rehabilitation center in Toronto, Canada. The study protocol was approved by the program s Medical Advisory Committee, and written informed consent was obtained from all participants before baseline assessment. Clinical care remained the responsibility of the patient s primary physician. The initial sample consisted of 623 men with a diagnosis of CHD referred for rehabilitation. The standard program, described previously, 11,12 calls for 5 exercise sessions per week: 1 supervised at the rehabilitation center and 4 unsupervised away from the center. For the purpose of this study, the patients were randomly assigned to one of two groups. The first group (CR1) was offered the standard program for 52 weeks (a total of 50 supervised exercise sessions), and the second group (CR2) attended the standard program for 26 weeks, and thereafter attended once a month (a total of 32 supervised exercise sessions), with all other exercise sessions carried out away from the center. Exercise Rehabilitation Program The method used to develop the individual s exercise prescription has been described previously. 11 The patients were prescribed a walking or, where appropriate, a walk-jog program (1 supervised on-site session and 4 unsupervised off-site sessions) that specified both the duration and intensity of exercise to be performed 5 times per week. The participants returned weekly exercise logs documenting the type and duration of exercise, the distance walked or jogged, the ratings of perceived exertion (Borg scale range, 6-20), 13 pre- and post-exercise heart rates, and any symptoms experienced during exercise performed away from the center. These exercise logs were reviewed regularly by the patient s exercise supervisor every time the patients returned to the center for their next supervised session. Compliance with the program was defined as completion of at least 75% of the supervised exercise sessions and 70% or more of the unsupervised sessions. These percentages were calculated by dividing the number of sessions actually completed by the expected number of sessions. This definition of compliance has been used in the program for many years. Clinical and Physiologic Data Physiologic data were obtained initially and after 12, 26, 38, and 52 weeks. Baseline physiologic assessment included measurements of height and body mass, calculation of body mass index, estimated percentage of body fat based on 3 skinfold measurements, 14 and a 12- lead resting electrocardiogram. A multistage, progressive cardiopulmonary cycle ergometer exercise test also was administered to all the patients. 11 In brief, the power output on an electricallybraked cycle ergometer (Ergoline 800S; Ergoline Europa, Bitz, Germany) was increased by 16.7 watts (100 kpm) every minute until either voluntary fatigue or the occurrence of clinical indications for the test to be terminated. 15 A 3-lead (CM5, III, and V1) electrocardiogram (Case 8000; GE Marquette Medical Systems, Milwaukee, Wis) was monitored continuously throughout exercise and during a minimum 4 minutes of recovery. Expired air was analyzed every 20 seconds using a Sensor-Medics 2900 metabolic cart (Sensor-Medics, Yorba Linda, Calif). Timeline for Peak Improvements / 375

3 Psychological Questionnaires Two psychological questionnaires were administered initially, and then at 4, 12, 26, 38, and 52 weeks. General quality of life was assessed with the Medical Outcomes Study Short Form (MOS SF-36) 16 using 36 items to measure health and function within the general categories of functional status, well-being, and general health perception. With the MOS SF-36, total scores are rated as poor to fair (0-25), fair to good (26-61), good to very good (62-84), and excellent (85-100). Depression was assessed by the 21-question Beck Depression Inventory, 17 on which a score exceeding 10 indicates clinical depression. Program Costs Program costs were calculated from budgetary expense reports during the time the study was conducted. Cumulative costs, totaled for 12, 26, 38, and 52 weeks, consisted of administrative and medical staff salaries and the cost of exercise testing, electrocardiographic telemetry, Holter monitoring, office and medical supplies, and utilities. Statistical Analysis Data were described using means SDs for continuous measurements and proportions for categorical variables. Physiologic and psychological end points were analyzed by two-way analysis of variance (ANOVA) using group and time as well as an interaction effect. Times to peak values were determined and compared using a 2 test. The statistical significance level was set at a P value less than.05, and SAS Statistical Software, version 8.2 (SAS Institute, Cary, NC) was used for the analysis. RESULTS Clinical and Physiologic Data During the course of the study, there were 185 dropouts (29.7% of the initial enrollment): 85 (27.5%) from the CR1 and 100 (31.8%) from the CR2 cohorts. Medical problems accounted for 57 (CR1, 25; CR2, 32) and nonmedical problems for 128 (CR1, 60; CR2, 68) of all the dropouts. Therefore, complete data throughout the 52 weeks were collected for 438 subjects (CR1, 224; CR2, 214), all of whom met the previously stated attendance requirement for compliance. There were no significant differences between the characteristics of the patients who dropped out and those who completed the study. The baseline characteristics for the two cohorts and the total sample are presented in Table 1, and the change over the course of the study is shown in Table 2. There were no significant differences in baseline characteristics between CR1 and CR2, except for peak oxygen intake (V O 2peak ): ml/kg per minute for CR1 versus ml/kg per minute for CR2 (P.04). Two-way ANOVA showed neither significant intercohort differences nor significant interaction (time group) for any of the continuous variables during the course of the trial. It was therefore determined that for the purposes of analysis, data from the two cohorts could be pooled. Table 1 BASELINE CLINICAL AND PHYSIOLOGIC DATA FOR THE TWO COHORTS AND TOTAL SAMPLE (MEAN SD) CR1 CR2 Total Variable n 309 n 314 P* N 623 Age, y ns Height, cm ns Body mass, kg ns Body mass index, kg/m ns Resting HR, beats min ns Peak HR, beats min ns Resting systolic BP, mm Hg ns Resting diastolic BP, mm Hg ns Peak systolic BP, mm Hg ns Peak diastolic BP, mm Hg ns Peak RER ns Peak Borg rating ns Peak power output, W ns Peak oxygen intake, ml kg 1 min HR, heart rate; BP, blood pressure; RER, respiratory exchange ratio; W, watts; ns, no significant difference. *CR1 versus CR / Journal of Cardiopulmonary Rehabilitation 2004;24:

4 Initially, the patients walked an average distance of 2.4 km (1.5 miles) at a pace of 11.2 minutes/km (18 minutes/mile). Over the year of rehabilitation, this increased to 5.4 km (3.4 miles) at a pace of 9.5 minutes/ km (15 minutes/mile) during each exercise session. This represents a 126% increase in distance and a 17% increase in pace over the course of the rehabilitation program. All clinical and physiologic variables improved significantly over the course of the 52 weeks, with the exception of resting systolic and peak diastolic blood pressures (Table 2). Figure 1 illustrates the training response for V O 2peak over time. It shows a statistically and clinically significant increase of 4.4 ml/kg per minute that continued in exponential fashion to the testing at 38 weeks. The greatest percentage of patients (30.4%) achieved their highest V O 2peak at 38 weeks (Table 3). Psychological Data Baseline and 52-week data on the psychological questionnaires are presented in Table 4 for both patient groups and Table 5 for the total sample. The average initial MOS SF-36 scores showed that the patients were above the median score for role physical and general health and at or below the median score for all the other domains. With regard to changes during the 52 weeks of the program, the largest gains were in measures of role physical, with exponential increments continuing to 38 weeks (52.4 versus 85.2; Fig. 2). Furthermore, the percentage of patients scoring 86 to 100 for role physical (ie, excellent) increased from 33% at baseline to 72% at 38 weeks, with no further increase at assessments conducted at 52 weeks (Fig. 3). By the same token, the percentage of those with lower scores decreased over the same period. Table 3 DISTRIBUTION OF TIME (IN WEEKS) WHEN PEAK OXYGEN INTAKE REACHED A MAXIMUM VALUE Week CR1 (%) CR2 (%) Total Initial 8 (3.6) 4 (1.9) 12 (2.7) (15.6) 41 (19.2) 76 (17.4) (23.2) 46 (21.5) 98 (22.4) (30.8) 64 (29.9) 133 (30.4) (26.8) 59 (27.6) 119 (27.2) Patients The Beck Depression Inventory showed that 18.7% of the sample initially was clinically depressed (score, 10). This depression did not significantly affect the dropout rate (P.09). Furthermore, there was no significant difference between the depressed patients and those who were not depressed with respect to initial V O 2peak (P.78) or the change in VO 2peak attributable to exercise training over the course of the study (P.30). With regard to MOS SF-36 role physical, there was a highly significant difference (P.001) between the depressed patients and those who were not depressed at baseline according to Beck Depression Inventory scores, in that the more depressed patients had lower role physical scores. However, the change in role physical scores over the course of the study did not differ significantly (P.81) between patients who are depressed and patients who are not depressed. Program Costs The cost of operating the program was calculated at $33.84 (US) per patient for each supervised session. The per patient cost of providing program services ranged from $406 at 12 weeks for both CR1 and CR2 to $1692 (CR1) or $1083 (CR2) at 52 weeks (Table 6). Table 2 CLINICAL AND PHYSIOLOGIC VARIABLES AT BASELINE AND AFTER 52 WEEKS OF REHABILITATION (N 438, MEAN SD) Variable Baseline 52 Weeks P Body mass, kg Body mass index, kg/m Resting HR, beats min Peak HR, beats min Resting systolic BP, mm Hg Resting diastolic BP, mm Hg Peak systolic BP, mm Hg Peak diastolic BP, mm Hg Peak RER Peak Borg rating Peak power output, W Peak oxygen intake, ml kg 1 min HR, heart rate; BP, blood pressure; RER, respiratory exchange ratio; W, watts. Timeline for Peak Improvements / 377

5 Figure 1. Peak V. O 2 at each assessment (n 438). DISCUSSION The study data demonstrate that the combination of supervised and unsupervised exercise sessions in a 52- week rehabilitation program was effective in improving both clinical and psychosocial outcomes. The peak improvement in measured exercise capacity and role physical scores from the MOS SF-36 occurred at 38 weeks. These gains were achieved with an average of 33 supervised sessions (combining the CR1 and CR2 models) in addition to prescribed workouts performed away from the center. This total number of supervised sessions during 38 weeks is comparable with the standard 36-session program often used in the United States. Thirty-eight weeks of outpatient rehabilitation, using either program format, resulted in program costs theoretically similar to or less than the costs for 36 supervised sessions (CR1 $1286 [US] and CR2 $914 versus $1218 for a theoretical 36-session program). Because the peak benefits for several important outcome variables occurred at 38 weeks, extending supervised sessions over a longer period (ie, 38 weeks) appears to have a positive effect. The added benefits at little or no increased cost observed at 38 weeks, as compared with 12 weeks, of rehabilitation call into question the practice of terminating outpatient programs at 12 weeks. The opportunity for patients to maximize their oxygen intake is an important outcome. The Figure 2. MOS-SF 36 role physical scores at each assessment (n 438). Figure 3. Percent of patients by role physical categories at each assessment (n 438). authors earlier research demonstrated that individuals who enter the program with a low level of aerobic fitness gain 1.8 years of survival for each 1 ml/kg per minute of increase in measured V O 2peak. 18 The CR1 model resulted in a total of 50 supervised exercise training sessions at the center. Clearly, this model, with its relatively intensive supervision over 52 weeks, would require more program resources than the traditional or tapered (CR2) model used in this study. However, the CR2 program format used only 32 supervised sessions over 52 weeks (4 fewer sessions than currently allowed by Medicare), but the patients had weekly or monthly contact with the program staff over the entire year, as compared with 12 weeks in a traditional model. Recently, other studies have reported further gains in functional capacity or psychosocial measures when outpatient cardiac rehabilitation is extended beyond the traditional 12 weeks. Verrill et al 19 reported an additional 10% increase in the 6-minute walk test distance after 24 weeks, as compared with 12 weeks of rehabilitation. In another study, Carlson et al 20 used a modified outpatient rehabilitation protocol in which patients received a decreased number of supervised exercise sessions and electrocardiographic monitoring and performed an increased amount of unsupervised exercise for 25 weeks. Self-efficacy scores were significantly higher for the patients enrolled in this modified protocol than for the patients in a traditional 12-week protocol. In a companion editorial to the Carlson article, Roitman and LaFontaine 21 discussed the potential values of extended timelines and modified formats for outpatient cardiac rehabilitation in this age of decreased hospital lengths of stay, measured program outcomes, and evidence-based medicine. It thus appears that consideration should be given to modifying the standard 12-week program format to one that increases the program time and incorporates a combination of supervised and unsupervised exercise sessions. Previously, an argument against prolonging the time for outpatient rehabilitation services has been cost, but the current economic data show that the costs associated with the modified 38-week protocols are 378 / Journal of Cardiopulmonary Rehabilitation 2004;24:

6 Table 4 BASELINE PSYCHOLOGICAL CHARACTERISTICS FOR THE TWO COHORTS AND THE TOTAL SAMPLE (MEAN SD) CR1 CR2 Total Variable n 309 n 314 P * N 623 MOS SF-36 Physical function ns Role physical ns Bodily pain ns General health ns Vitality ns Social functioning ns Role emotional ns Mental health ns BDI ns MOS SF-36, Medical Outcomes Study Short Form-36; BDI, Beck Depression Inventory; ns, no significant difference. *CR1 versus CR2. essentially comparable with the projected cost of the model that uses 36 sessions in a shorter period. It is interesting that during the period from 26 to 52 weeks, there was little difference in response between the CR1 and CR2 formats, indicating that further economies of cost might be realized by introducing a progressive tapering of supervision, as was used in the CR2 model. This study reported data only for patients who complied with 52 weeks of structured outpatient cardiac rehabilitation, but one issue related to extending the duration of these services is that compliance rates have been shown to decline with longer program duration. According to one analysis, approximately 20% to 25% of patients drop out within the first 3 months, and 40% to 50% drop out in 6 to 12 months. 22 However, much of the data leading to this conclusion were collected during a time when outpatient cardiac rehabilitation content, delivery, and goals were different from contemporary programming. 3 In addition to exercise training, Table 5 PSYCHOLOGICAL CHARACTERISTICS AFTER 52 WEEKS OF REHABILITATION (N 438, MEAN SD) Variable Baseline 52 Weeks P MOS SF-36 Physical function Role physical Bodily pain General health Vitality Social functioning Role emotional Mental health BDI MOS SF-36, Medical Outcomes Study Short Form-36; BDI, Beck Depression Inventory. outpatient cardiac rehabilitation programs currently incorporate a wide range of risk reduction and secondary prevention services, 4,23 which may be more effective if patients are involved in the program for a longer period. Other authors have reported exercise compliance rates of 63% to 94% over 6 months 10,24 and 70% during 12 months of rehabilitation. 25 In fact, Merz and Rozanski 26 stated that successful risk factor modification may require a minimum of 12 months for beneficial changes to be effected, and the challenge to cardiac rehabilitation programs is to offer convenient and affordable long-term risk factor modification services. The CR2 program model is one possible way to achieve this goal. In summary, the greatest percentage of patients achieved their highest peak oxygen intake and role physical scores on the SF-36 at the testing completed after 38 weeks of outpatient cardiac rehabilitation. Yet, during these 38 weeks, patients received only 29 supervised exercise sessions in the CR2 group or 38 sessions in the CR1 group. These data indicate that a combination of supervised and home exercise sessions for 38 weeks yielded a greater improvement in these variables than that attained at testing conducted after either 12 or 24 weeks of rehabilitation. These findings suggest that extending the outpatient rehabilitation process to Table 6 CR1 AND CR2 PROGRAM COSTS PER PATIENT AT 12, 26, 38, AND 52 WEEKS CR1 Format CR2 Format 12 weeks $406 $ weeks $880 $ weeks $1,286 $ weeks $1,692 $1,083 Note. Costs were originally in Canadian dollars but were converted to equivalent US dollars. Timeline for Peak Improvements / 379

7 incorporate weekly or less frequent supervised sessions over 38 weeks results in a higher functional capacity than that of more traditional program models. Acknowledgments The authors thank Drs Bev Evans, Abdul Elzawi, Victor Matosevic, and Rodica Rudner. They also thank Patricia Baskey, BScN (Project Coordinator) and Ed Strohm, MSc, for laboratory quality control, and exercise supervisors Gunnel Brandkvist, OT, Susan Marzolini, BPHE, Diane Nixon, RN, Marilyn Pieper, RN, Paul Sawyer, BPHE, Joanne Scott, RN, and Lesley Thacker, MAOT, as well as Minnie Bhagi, BE, for assisting with data collection. The authors also express appreciation to Ms. Janet Will for her efforts in preparing this manuscript. References 1. Jolliffe JA, Rees K, Taylor RS, et al. Exercise-based rehabilitation for coronary heart disease. Cochrane Review. In: The Cochrane Library. Issue 4. Chichester, UK: John Wiley; Balady GJ, Fletcher BJ, Froelicher ES, et al. Cardiac rehabilitation programs: a statement for healthcare professionals from the American Heart Association. Circulation. 1994;90: Wenger NK, Froelicher ES, Smith LK, et al. Clinical Practice Guideline No. 17: Cardiac Rehabilitation. Rockville, Md: US Department of Health and Human Services; AHCPR publication no Ades PA. Cardiac rehabilitation and secondary prevention of coronary heart disease. N Engl J Med. 2001;345: Medicare Coverage Issues Manual, Medical Procedures, Section 25-35, Cardiac Rehabilitation Programs. Centers for Medicare and Medicaid Services (Formerly the Health Care Financing Administration); Baltimore, MD Vanhees L, McGee HM, Dugmore, LD, Vuori I, Pentilla UR. The Carinex Survey. Current Guidelines and Practices in Cardiac Rehabilitation. Leuven: Uitgeverij Acco; Saunamaki KI. Feasibility and effect of physical training with maximum intensity in men after myocardial infarction. Scand J Rehabil Med. 1978;10: Kallio V, Hamalainen H, Hakkila J, Luurila OJ. Reduction in sudden deaths by a multifactorial intervention programme after acute myocardial infarction. Lancet. 1979;2(8152): Hedbeck B, Perk J, Perski A. Effect of a postmyocardial infarction rehabilitation program on mortality, morbidity, and risk factors. J Cardiopulm Rehabil. 1985;5: Wosornu D, Bedford D, Ballantyne D. A comparison of the effects of strength and aerobic exercise training on exercise capacity and lipids after coronary artery bypass surgery. Eur Heart J. 1996;17: Hamm LF, Kavanagh T. The Toronto Cardiac Rehabilitation and Secondary Prevention Program: 1968 into the new millennium. J Cardiopulm Rehabil. 2000;20: Kavanagh T. Take Heart! A Proven Step-By-Step Program to Improve Your Heart s Health. Toronto: Key Porter; Borg GAV. Perceived exertion as an indicator of somatic stress. Scand J Rehabil Med. 1970;2: Durnin J, Womersley J. Body fat assessment from total body density and its estimation from skinfold thickness: measurements on 481 men and women aged years. Br J Nutr. 1974;32: American College of Sports Medicine. In: Franklin BA, Whaley MH, Howley ET, eds. ACSM s Guidelines for Exercise Testing and Prescription. 6th ed. Philadelphia: Lippincott Williams & Wilkins; 2000: Stewart AL, Hays RD, Ware JE. The MOS Short Form General Health Survey: reliability and validity in a patient population. Med Care. 1988;26: Beck A. The Beck Depression Inventory. Philadelphia: Center for Cognitive Therapy; Kavanagh T, Mertens DJ, Hamm LF, et al. Prediction of long-term prognosis in 12,169 men referred for cardiac rehabilitation. Circulation. 2002;106: Verrill D, Lippard M, Barton C, Beasley W. Six-minute walk performance improves up to 6 months participation in North Carolina cardiac rehabilitation programs (abstract). J Cardiopulm Rehabil. 2002;22: Carlson JJ, Norman GJ, Feltz DL, Franklin BA, Johnson JA, Locke SK. Self-efficacy, psychosocial factors, and exercise behaviour in traditional versus modified cardiac rehabilitation. J Cardiopulm Rehabil. 2001;21: Roitman JL, LaFontaine T. Modified protocols for cardiovascular rehabilitation and program efficacy. J Cardiopulm Rehabil. 2001;21: Oldridge NB, Guyatt GH, Fischer ME, Rimm AA. Cardiac rehabilitation after myocardial infarction: combined experience of randomized trials. JAMA. 1988;260: American Association of Cardiovascular and Pulmonary Rehabilitation. Guideline for Cardiac Rehabilitation and Secondary Prevention Programs. 4th ed. Champaign: Human Kinetics; 2004: Belardinelli R, Paolini I, Cianci G, et al. Exercise training intervention after coronary angioplasty: the ETICA trial. J Am Coll Cardiol. 2001;37: Hambrecht R, Walther C, Mobius-Winkler S, et al. Percutaneous coronary angioplasty compared with exercise training in patients with stable coronary artery disease: a randomized trial. Circulation. 2004;109: Merz NB, Rozanski A. Remodeling cardiac rehabilitation into secondary prevention programs. Am Heart J. 1996;132: / Journal of Cardiopulmonary Rehabilitation 2004;24: