Exercise Therapy After Coronary Artery Bypass Graft Surgery: A Randomized Comparison of a High and Low Frequency Exercise Therapy Program

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1 Exercise Therapy After Coronary Artery Bypass Graft Surgery: A Randomized Comparison of a High and Low Exercise Therapy Program Inge D. van der Peijl, MS, Thea P. M. Vliet Vlieland, MD, PhD, Michel I. M. Versteegh, MD, Judith J. Lok, PhD, Marten Munneke, MS, and Robert A. E. Dion, MD, PhD Departments of Physical and Occupational Therapy, Cardiothoracic Surgery, and Medical Statistics, Leiden University Medical Center, Leiden, the Netherlands Background. Postoperative exercise therapy aims at recovering, as soon as possible, independence in the basic physical activities; but the type, intensity, and therefore the costs of the programs, vary widely. The aim of this study was to compare the effectiveness of a low frequency (once daily, not in the weekend) program with a high frequency (twice daily, including the weekend) one and to assess whether the latter would yield sufficient benefit for the patient to justify higher costs in material and personnel (physiotherapists) after uncomplicated coronary artery bypass graft (CABG) surgery. Methods. Two-hundred and forty-six patients were randomly allocated to either a low or high frequency exercise program. Endpoints were the functional level as measured by the achievement of five activity milestones, the patient s independence (functional independence measures [FIM]) as assessed by a structured interview, the amount of daily physical activity (activity monitor), and patient satisfaction (questionnaire). Except for patient satisfaction, all measurements were done in the first week after surgery. Results. Patients with the high frequency exercise program achieved functional milestones faster than patients with the low frequency exercise program (p 0.007). The frequency of the exercise program had no influence on functional independence as measured with the FIM or quantity of physical activity. The satisfaction degree was greater in the high frequency group (p 0.032), although the low frequency group was not dissatisfied. Conclusions. A high frequency exercise program leads to earlier performance of functional milestones and yields more satisfaction after uncomplicated CABG surgery and this should lead to an earlier discharge. On the other hand, if the shortage of physiotherapists remains unchanged or even increases, the low frequency program also yields excellent functional results, albeit at the cost of a somewhat longer hospital stay: but it would allow a sensible redistribution of the physiotherapists activity towards complicated and, therefore, more demanding patients. (Ann Thorac Surg 2004;77: ) 2004 by The Society of Thoracic Surgeons Coronary artery bypass graft (CABG) surgery is one of the most frequently performed surgical procedures [1]. Supervised exercise programs have been recommended to facilitate recovery immediately after surgery [1, 2]. The goals of these programs are to prevent the detrimental effects of prolonged bed rest, to enhance cardiac function, to improve physical tolerance and skills for the basic activities of daily life, and to strengthen the patient s self-confidence with the ultimate aim of reducing length of stay [3 8]. The onset, intensity, duration, and frequency of the exercise training vary widely. Frequencies varying from once or twice [1, 4, 7, 9, 10] to three or four times daily have been reported [3, 11], but their respective influence on the functional outcome remains unclear. Accepted for publication Oct 28, Address reprint requests to Dr van der Peijl, Department of Physical and Occupational Therapy (H-0-Q), Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, the Netherlands; i.d.van_der_peijl@lumc.nl. The aim of this study was to compare the effectiveness of two early postoperative cardiac exercise programs during the admission period in the surgical hospital, one with a low frequency (once a day and not in the weekend) and one with a high frequency (twice a day including the weekend) in patients who underwent CABG surgery, and to investigate whether the latter would yield sufficient clinical benefit for the patient to justify higher costs in material and personnel (physiotherapists). Patients and Methods Study Design The study featured a prospective single blinded, randomized trial comparing the functional relevance of two standardized exercise programs (high and low frequency) executed during the early postoperative course in patients undergoing uncomplicated CABG surgery. The study protocol was approved by the local medical 2004 by The Society of Thoracic Surgeons /04/$30.00 Published by Elsevier Inc doi: /j.athoracsur

2 1536 VAN DER PEIJL ET AL Ann Thorac Surg EXERCISE THERAPY AFTER CABG SURGERY 2004;77: Fig 1. Randomization and time table of the trial. (HF high frequency group; LF low frequency group.) ethics committee. All patients were informed about the study protocol and gave written informed consent. Randomization Procedure During 12 periods of 30 days each the patients benefited from a standardized exercise program of either high frequency (6 periods) or low frequency (6 periods) (Fig 1). The sequence of the periods was randomized by means of a computer with a random digit generator, with at least two different periods per three months. Randomization was done by period and not by patient to ensure homogeneity of the two programs. A washout interval of one week separated each treatment period. The order of the periods was known by only one independent person (MM), who then informed the physiotherapists. Exercise Protocol The two exercise programs included range of motion, muscle strengthening and coordination exercises, walking, and stair climbing (Table 1). The intensity increased from 1.0 metabolic equivalent (MET: the volume of oxygen utilized per kilogram of body weight per minute of rest) [1, 12] initially to a maximum of 3.5 MET at discharge. The high frequency exercise program was performed twice a day, including the weekend, starting the first day after surgery, regardless of the day of the week. The low frequency program was given once a day, not during the weekend, and started the first weekday. The patient was encouraged to repeat the exercises on his(her) own. Patient Population Patients were recruited between April 2000 and July Excluded were patients with concomitant surgical procedures, severe comorbidity interfering with daily life, an insufficient mastering of the Dutch language, and mental disorders. Postoperative complications jeopardizing the standardized exercise program also led to exclusion. Of the 482 patients considered for the study, 309 patients were initially included. Fourteen did not meet the inclusion criteria, 12 refused to participate, 56 underwent emergency CABG-surgery, and 91 were operated on in a washout period (Fig 2). Of all patients who were included, sociodemographic (sex, age) and disease characteristics (New York Heart Association [NYHA]-class, main features of cardiovascular disease, previous myocardial infarction, previous Table 1. The Exercise Therapy Program for the High and Low Group After Uncomplicated CABG Surgery High Exercise Program Low Exercise Program Start: First day after surgery. First weekday after surgery. : 2 a day, including weekend. 1 a day, not in the weekend. Day 1: Day 2: MET s Active ROM and muscle strengthening exercises for upper and lower extremities bed in 60 angle. Shoulder: flexion extension, abduction adduction, internal and external rotation. Elbow: flexion and extension, pronation and supination. Hand and wrist: flexion and extension, abduction and adduction. Hip and knee: flexion extension, abduction adduction, internal external rotation. Ankle and foot: flexion and extension, foot circling. Each joint motion was performed 5 times. HF 2: same as morning sitting on the side of the bed Active ROM and muscle strengthening exercises for upper and lower extremities transfer bed to chair. HF 2: transfer bed to chair active ROM and muscle strengthening exercises while sitting in the chair. Day 3: Walking in the room and if possible a longer distance on the ward. 2.0 HF 2: walking on the ward and active ROM and muscle strengthening exercises 2.0 while sitting in the chair. Day 4: 20 minute exercise group. 2.0 HF 2: walking on the ward. 2.0 Day 5: 20 minutes exercise group climbing stairs (20 steps) HF 2: 15 minutes exercise group 2.0 Day 6 and following days until discharge: same as day 5 but with increased intensity HF 2 second exercise time for the high frequency group on the same day; MET metabolic equivalent: 1 MET equals to the volume of oxygen utilized per kilogram of body weight per minute at rest. Exercise is expressed as multiples of MET s; ROM range of motion.

3 Ann Thorac Surg VAN DER PEIJL ET AL 2004;77: EXERCISE THERAPY AFTER CABG SURGERY 1537 Fig 2. Trial profile. (CABG coronary artery bypass graft; HF high frequency group; LF low frequency group; WE including the weekend; WE not in the weekend.) CABG), presence of coexisting illnesses (diabetes mellitus, chronic obstructive pulmonary disease [COPD], peripheral or central vascular disease), hypertension, and smoking history were listed from the medical record. Moreover, the type of CABG (on pump, off-pump, or first or re-cabg), left ventricular function [13] determined by angiography or echo, number and type of grafts and anastomoses, occurrence of rethoracotomy, the day of extubation, and length of hospital stay after surgery (LOS) were determined. Within 3 days after surgery, 63 of the initial 309 patients were excluded, because of hemodynamic complications (22 patients), concomitant cardiothoracic surgery (16), pulmonary complications (5), cardiac complications (4), rethoracotomy with prolonged need for ventilation (6), and combinations with other noncardiothoracic surgery (3). Four patients died during, or early after surgery. The 63 patients who were excluded after surgery were significantly older and had more severe angina pectoris according to the NYHA classification (results not shown). Of the remaining 246 patients, 134 were allocated to the high frequency and 112 to the low frequency programs. At baseline, there were no significant differences between patients in the two programs, except for a significantly larger proportion of patients with hypertension in the high frequency group (Table 2). Endpoints: Functional Level A. Five functional milestones were recorded daily: sitting in a chair; walking in the room; walking in the ward; group exercise therapy; and climbing stairs (20 steps). Degree of dependence was also evaluated: no help; some

4 1538 VAN DER PEIJL ET AL Ann Thorac Surg EXERCISE THERAPY AFTER CABG SURGERY 2004;77: Table 2. Preoperative Demographic and Clinical Characteristics of 246 Patients Who Underwent CABG Surgery and Were Assigned to a Postoperative Low or High Exercise Program Variables n (%) Low n 112 High n 134 p Value Sex male 87 (78%) 107 (80%) female 25 (22%) 27 (20%) Age (yrs) (mean, sd) 62.0 (10.2) 63.2 (10.2) NYHA class I 0 (0%) 2 (2%) II 14 (13%) 14 (10%) III 71 (63%) 81 (60%) IV 27 (24%) 37 (28%) Main stem lesion ( 50%) 23 (21%) 27 (20%) Prior myocardial infarct 54 (48%) 66 (49%) Hypertension 37 (33%) 63 (47%) b Diabetes mellitus 21 (19%) 25 (19%) COPD 7 (6%) 16 (12%) Peripheral vascular 6 (5%) 12 (9%) disease a Prior CVA/TIA a 13 (12%) 15 (11%) Prior CABG-surgery 4 (4%) 10 (8%) Smoke till surgery 21 (19%) 25 (19%) a No hindrance for performing the exercise program. b p COPD chronic obstructive pulmonary disease; CVA cerebrovascular accident; n number of patients; NYHA New York Heart Association; TIA transient ischemic attack. help (one person or walking aid); or much help (two persons). Moreover, every patient gave a score for fatigue and for dyspnea per milestone on the rating of perceived exertion (RPE) scale. This scale ranges from 0 (not at all) to 10 (maximal), with a descriptive verbal anchor at every odd number [14, 15]. The RPE scale has been shown to be reliable and a valid indicator of the level of physical exertion [16]. B. One day before surgery, and on the sixth postoperative day (or the day before transfer to another hospital), a semistructured interview was performed in which to determine the selfcare, transfers, and locomotion scales of the functional independent measure (FIM) scores [17, 18]. C. The quantity of physical activity measuring over 10 hours was assessed by a portable activity monitor, the Dynaport (Mc Roberts BV, The Hague, Netherlands), on the sixth postoperative day (or the day before transfer to another hospital). The following four parameters were used: time spent on locomotion, standing, sitting, and lying (in percentages). Patient Satisfaction Patient satisfaction was assessed by means of a selfdeveloped questionnaire. The questionnaire comprised four domains that were considered to be relevant: treatment parameters such as timing, intensity, and duration (6 questions); information (4 questions); empathy (6 questions); and collaboration (2 questions). Every question was answered with yes (satisfied) or no (not satisfied). Finally, the patient rated the entire exercise treatment on a scale from 0 to 10, with 0 being not satisfied at all. The satisfaction questionnaire was completed and sent back by post within 3 weeks after discharge. All assessments were carried out by a single assessor (IvdP), who was blinded for the patient s allocation status. Patients were instructed not to discuss the frequency of the exercise program with the assessor. The full randomization remained concealed until completion of the primary analysis. Statistical Analysis Measures with a Gaussian distribution are described as means and standard deviation (SD), otherwise medians and ranges are presented. Patients sociodemographic and disease characteristics at baseline were compared using the 2 -test for categorical variables, whereas for continuous variables unpaired t-tests or Mann Whitney tests were used. The pace with which the clinical activity milestones were achieved in both groups was analyzed with Kaplan- Meier curves. Differences in the pace of the achievement of the milestones between the groups were examined by the log rank test, both for all available data as with a cut-off at five days postoperatively accounting for differences in the average LOS among countries. Cox regression was used for the fifth milestone to explore the impact of the following factors on the effectiveness of the two exercise programs for subgroups of patients: age, gender, preoperative risk, NYHA class, myocardial infarction, left ventricular function, number and type of grafts, and off-pump CABG. The change scores of the semi-structured interview (FIM), the results of the activity monitor, and the report mark of the satisfaction questionnaire were compared between the two groups by the independent samples t-tests. The other variables of the patient satisfaction questionnaire were analyzed with the 2 -test. All statistical analyses were performed using SPSS for Windows, Version (SPSS Inc, Chicago, IL). The level of significance was set at p less than 0.05, two-sided. The Cox-regression was done with the software package Egret from Cytel Software Corporation. Results Postoperative Course One hundred and seventy-six patients were discharged home and 68 were moved to another hospital for social or medical reasons (not influencing physical functioning). Significantly more patients in the low frequency group had a rethoracotomy (Table 3). Two patients had a prolonged ( 2 weeks) hospital stay due to mediastinitis. Median length of stay was 7 days for both the high and low frequency group (range, from 5 to 11 and from 5 to 18, respectively) (p 0.510). The mean number of exercise sessions was 10 (SD 3.1) in the high frequency and 4 (SD 1.6) in the low frequency groups.

5 Ann Thorac Surg VAN DER PEIJL ET AL 2004;77: EXERCISE THERAPY AFTER CABG SURGERY Table 3. Postsurgery Characteristics of 246 Patients With CABG Surgery Assigned to a Low or High Exercise Program Variables Low n 112 High n 134 p Value Type of surgery: CABG 82 (73%) 90 (67%) off-pump a 25 (22%) 35 (26%) re-cabg b 5 (5%) 9 (7%) Number of anastomoses 3 (1.2) 3 (1.2) (mean, sd) Only arterial anastomoses 77 (69%) 78 (58%) Arterial venous 33 (13%) 54 (40%) anastomoses Only venous anastomoses 2 (2%) 2 (1%) Rethoracotomy 16 (14%) 7 (5%) c LVF Good (EF 50%) 99 (88%) 110 (82%) Moderate (EF 30% 50%) 11 (10%) 22 (16%) Poor (EF 30%) 2 (2%) 2 (2%) Day of extubation 1(0 9) 1 (0 9) (median, range) Length of stay after surgery (median, range) 7(3 18) 7 (4 15) a Off-pump CABG-surgery without extra corporal circulation. b re- CABG prior CABG-surgery. c p LVF left ventricular function; EF ejection fraction; n number of patients. Clinical Milestones The high frequency group achieved the first four clinical activity milestones significantly faster than the low frequency group (Fig 3). The same trend was observed for the fifth milestone (stairs climbing), but this was not statistically significant (p 0.056). As the average LOS may be kept to 5 days in other countries, the analysis was repeated by using only the data available up to, and including, the fifth postoperative day, which yielded the same results (data not shown). The mean RPE scores for fatigue and dyspnea related to the five milestones did not differ significantly between the two groups. In univariate analysis, age (p 0.001), sex (p 0.02), off-pump CABG surgery (p 0.002), NYHA class (p 0.001), and left ventricular function (p 0.03) were significantly related to the pace of achieving the fifth milestone, whereas history of myocardial infarction (p 0.11) and number of grafts (p 0.17) were not. Multivariate analysis resulted in a model in which only age and NYHA class contributed significantly (p 0.009), whereas neither of these two factors had a significant influence on the difference in effectiveness between the high and low frequency program (p 0.49 and p 0.34). FIM Score The FIM scores are presented in Table 4. On the sixth postoperative day, patients in both groups deteriorated with respect to self-care and transfers, whereas locomotion improved after surgery. However, there were no significant differences between the two groups. Physical Activity Physical activity, as measured by means of the activity monitor, is presented in Table 5. One hundred eightyone patients were assessed on the sixth day postoperatively. Transfer to another hospital and technical failure were responsible for the missing data. In both groups, patients were sitting or lying most of the day. There was no significant difference in the percentages of time spent on any activities between the high and the low frequency group. Patient Satisfaction The questionnaire was completed by 106 patients (79%) in the high frequency group and 108 patients (96%) in the low frequency group. With regard to treatment variables (p 0.05 for 4 out of 6 questions), information (p 0.05 for 3 out of 4 questions), and empathy (p 0.05 for 2 out of 6 questions), there were more satisfied patients in the high frequency group. The overall appreciation of the exercise program on a scale from 0 to 10 was significantly higher in the high frequency group (8.3 vs 7.6, respectively) (p 0.032). Seventy-nine percent of patients in the low frequency group would have preferred to have exercise treatment in the weekend. On the other hand, 61% of the patients in the high frequency group would have preferred to have less treatments in the weekend. Comment 1539 The patients in the high frequency group achieved four out of five clinical milestones significantly faster than the patients in the low frequency group. There were, however, no differences in other measures of functional independence and physical activity as assessed on the sixth postoperative day. Patients satisfaction was significantly higher in the high frequency group, although the low frequency group was not dissatisfied. The difference between the two groups in achieving the milestones was already significant within five days. This indicates that similar results might be expected in places where LOS is reduced. As under the constraints of cost reduction LOS is inclined to decrease further with time worldwide, the question is whether we should not favor the high frequency program. The decision regarding this question will be dependent on whether the benefits of the high frequency program counterbalance the higher costs. For that purpose, the quicker achievement of clinical milestones needs to be mirrored by a decreased need of medical and nursing care with a shorter LOS as a result. In our study we did, however, not try to demonstrate that the higher the frequency of exercise therapy, the shorter the LOS. We aimed rather at investigating whether the low frequency protocol would clinically perform as well as the high frequency one, for the sake of saving costs and adapting to a shortage of physiotherapists. Now that the clinical benefits of the intensive program appear to be superior to those of the low intensity program, the gain in efficiency of the intensive treatment strategy needs to be further determined.

6 1540 VAN DER PEIJL ET AL Ann Thorac Surg EXERCISE THERAPY AFTER CABG SURGERY 2004;77: Fig 3. Results of the HF and LF groups for the five clinical activity milestones: bed to chair (A), walking in the room (B), walking at the ward (C), taking part in exercise group (D), and climbing stairs (E). (HF high frequency group [straight line]; LF low frequency group [dashed line].) Apart from the intensity of physical therapy, the achievement of clinical milestones in the early postoperative phase depends on several factors. The results of the present study are in agreement with the results of other controlled trials, in which age appeared to be related to the recovery of physical functioning [19, 20]. In addition to age, the preoperative severity of angina pectoris had a significant effect on the postoperative outcome, similar to the results of previous studies [21]. There were no differences regarding the evolution of FIM scores between the two groups. Overall, the observed changes of the FIM scores were very small, and Table 4. Clinical Outcomes of the Semi-structured Interview of Which FIM Scores Can Be Determined of 246 Patients Before and After Surgery, After a Low Versus High Exercise Program Variables Group Presurgery Postsurgery Change Score (95% CI) Treatment effect (95% CI) Selfcare Low Freq ( ) 0.2 ( ) High Freq ( ) Transfers Low Freq ( ) 0.5 ( ) High Freq ( ) Locomotion Low Freq ( ) 0.5 ( ) High Freq ( ) Values are shown as mean SD. CI confidence interval.

7 Ann Thorac Surg VAN DER PEIJL ET AL 2004;77: EXERCISE THERAPY AFTER CABG SURGERY Table 5. Results (Mean Values and SD) for the Activities of the Day Before Discharge Measured by the Activity Monitor for the Group as a Whole and the Low and High Group Variables Whole Group n 170 Low Group n 85 High group n 85 p Value Locomotion Standing Sitting Lying ADL-monitor: time spent (% of 10 hours). n number of patients. one should question whether the responsiveness of FIM scores is sufficient to detect differences in this specific patient group. The activity monitor has been used before in patients with cardiac disease [22], but not in surgical patients. The results of our study indicate that patients were rather inactive (sitting) most of the time. Fatigue as a consequence of anesthesia, surgery, and pre-existing poor condition may have been the most important reason for inactivity. The intensity of physiotherapy did not affect the degree of physical activity 6 days after surgery. Patients were evidently more satisfied with the high frequency exercise program: more time is available for communication and answering questions. Empathy is indeed known as a determinant factor for the outcome of rehabilitation programs [2]. Exercise therapy treatment in the weekend has been a controversial issue for our patients. Most patients of the low frequency group would have preferred to have exercise therapy in the weekend, while most of the high frequency group would have preferred to have less exercise therapy in the weekend. We might conclude that once a day in the weekend would yield unanimity. In conclusion, a high frequency exercise program leads to earlier performance of functional milestones and yields more satisfaction after uncomplicated CABGsurgery and this should lead to an earlier discharge. On the other hand, if the shortage of physiotherapists remains unchanged or even increases the low frequency program also yields excellent functional results, albeit at the cost of a somewhat longer hospital stay: it would allow a sensible redistribution of the physiotherapists activity towards complicated, and therefore, more demanding patients. We thank the physical therapists and medical and nursing staff of the cardiothoracic surgery team of the LUMC for their assistance with the recruitment and treatment of the patients and with data collection. The study was financially supported by Vereniging Academische Ziekenhuizen and the Leiden University Medical Center, the Netherlands. Health Insurance Board (College voor Zorgverzekeringen) (Grant number 99221). References Ungerman-deMent P, Bemis A. Exercise program for patients after cardiac surgery. Arch Phys Med Rehab 1986;67: Wenger NK. Supervised versus unsupervised exercise training following myocardial infarction and myocardial revascularization procedures. Ann Acad Med 1992;21: Dion WF, Grevenow P, Pollock ML, et al. Medical problems and physiologic responses during supervised inpatient cardiac rehabilitation: the patient after coronary artery bypass grafting. Heart Lung 1982;11: Alling-Berne L. The nurse s role: early supervised exercise following coronary artery bypass surgery. Focus Crit Care 1987;14: Wenger NK. Rehabilitation of the coronary patient: status Prog Cardiovasc Dis 1986;29: American Heart Association. Risk factors and coronary heart disease a statement for physicians. Circulation 1980;62:445a. 7. Silvidi GE, Squires RW, Pollock ML, et al. Hemodynamic responses and medical problems associated with early exercise and ambulation in coronary artery bypass graft surgery patients. J Cardiac Rehab 1982;2: Juneau M, Geneau S, Marchand C, Brosseau R. Cardiac rehabilitation after coronary bypass surgery. In: Waters DD, Bourassa MG, eds. Care of the patient with previous coronary bypass surgery. Philadelphia: FA Davis, 1991: Shaw DK, Deutsch DT, Schall PM, Bowling RJ. Physical activity and lean body mass loss following coronary artery bypass graft surgery. J Sport Med Phys Fit 1991;31: Pollock ML. Exercise regimens after myocardial revascularization surgery: rationale and results. In: Wenger NK, ed. Exercise and the heart. Philadelphia: FA Davis, second edition, 1985: Goodwin MJ, Bissett L, Mason P, Kates R, Weber J. Early extubation and early activity after open heart surgery. Crit Care Nurse 1999;19: Fox EL, Bowers RW, Foss ML. The physiological basis of physical education and athletics. Dubuque: Brown, fourth edition, 1990: Nashef SAM, Roques F, Michel P, Gauducheau E, Lemeshow S, Salamon R, and the EuroSCORE study group. European system for cardiac operative risk evaluation (EuroSCORE). Eur J Cadiothorac Surg 1999;16: Borg GAV. Psychophysical bases of perceived exertion. Med Sci Sport Exer 1982;14: Noble BJ, Borg GAV, Jacobs I, Ceci R, Kaiser P. A category ratio perceived exertion scale: relationship to blood and muscle lactates and heart rate. Med Sci Sport Exer 1983;15: Eston RG, Williams JG. Reliability of ratings of perceived effort regulation of exercise intensity. Brit J Sport Med 1988;22: Kong K, Kevorkian CG, Rossi CD. Functional outcomes of patients on a rehabilitation unit after open heart surgery. J Cardiopulm Rehabil 1996;16: Sansone GR, Alba A, Frengley JD. Analysis of FIM instrument scores for patients admitted to an inpatient cardiac rehabilitation program. Arch Phys Med Rehab 2002;83: Redeker NS, Wykpisz E. Effects of age on activity patterns after coronary artery bypass surgery. Heart Lung 1999;28: Finkelmeier BA, Kaye GM, Saba YS, Parker MA. Influence of age on postoperative course in coronary artery bypass patients. J Cardiovasc Nurs 1993;7: Allen JK. Physical and psychosocial outcomes after coronary artery bypass graft surgery: review of literature. Heart Lung 1990;19: Fredriksen PM, Ingjer E, Thaulow E. Physical activity in children and adolescents with congenital heart disease: aspects of measurements with an activity monitor. Cardiol Young 2000;10: