Effects of Cardiac Rehabilitation and Exercise Training in Obese Patients With Coronary Artery Disease

Effects of Cardiac Rehabilitation and Exercise Training in Obese Patients With Coronary Artery Disease* Carl f. Lavie, MD, FCCP; and Richard V. Milani , MD 1 Study objective: To determine the effects of cardiac rehabilitation and exercise training in obese coronary patients. Design: We compared data before and after cardiac rehabilitation between obese and nonobese patients. Setting: Two large teaching institutions. Patients: 116 obese (body mass index [BMI] ~27.8 kglm 2 for men and :::::::27.3 kglm 2 for women; mean, 31.2±3.2 kglm 2 ] and 198 (mean BMI, 24.6:::+::2.1 kglm2 ) nonobese patients with recent cardiac events. Interventions: A 3-month (36-session) formal, outpatient phase 2 cardiac rehabilitation and supervised exercise training program. Measurements and results: At baseline, obese patients had higher levels of total cholesterol (p
HDL-C (+6%; p<0.001), and LDL-C/HDL-C ratio (-10%; p
obesity has significant adverse effects on various coronary heart disease (CHD) risk factors , including increasing a1terial pressure, promoting development of left ventlicular hype1trophy (LVH ), wars-

able to indicate that weight reduction with dietary therapy or exercise improves lipid profiles (particularly leading to increases in HDL-C) and reduces insulin resistance,8-12 and that weight reduction in severe obesity reduces both arterial pressure and LVH,13 ,1 4 limited d ata are available on the effects of vigorous risk factor intervention in obese patients with knmvn CHD. Cardiac rehabilitation and exercise training have been proven to have beneficial effects on CHD risk factors , including improving plasma lipids, insulin sensitivity, obesity indices, and exercise capacity and favorably affecting psychosocial function, behavioral characteristics, and overall quality of life .15 -19 Recent studies also have indicated significant effects of cardiac rehabilitation on reducing subsequent hospitalization costs following major CHD events,20 and pooled data from several randomized studies indicate significant reductions in subsequent major CHD events, cardiac mortality, and all-cause mortality. 21 ,22 However, the effects of cardiac rehabilitation and exercise training in obese patients with CHD havf' not hf'en well studied.

For editorial comment see page 3 erring insulin resistance, adversely affecting plasma lipids (particularly increasing levels of triglycerides and reducing levels of high-density lipoprotein cholesterol (HDL-C ), and leading to a more sedentary lifestyle.l-5 Despite adversely affecting all of these 1isk factors , some studies suggest that obesity is an independent risk factor for CHD events. 6' 7 Although data are avail*From the Department of Intern al Medicine, Section on Cardiovasculm· Diseases, Cardiovasculm· Health Center of Ochsner Heart and Vascular Institute, New Orleans. 1 Previously at Massachusetts General Hospital, Boston. Presented in part at the Annual Scientific Assembll' of the American Association of Cardiovascular and Pulmonary Rehabilitation, Orlando, Fla, October 1993. Manuscript received February 7, 1995; revision accepted Tune 21. Reprint requests: Dr. Lavie, Ochsner Hemt and Vascular Institute, 1514 Jefferson Highu;ay, New Orleans, LA 70121

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BMI=body mass index; CHD=coronary heart disease; HDL-C=high-density lipoprotein cholesterol; LDL=Iowdensity lipoprotein; LDL-C=Iow-density lipoprotein cholesterol; LVH=Ieft ventricular hypertrophy; METs=metaholic equivalent units

Key words: cardiac rehabilitation; coronary artery disease; exercise; obesity

Clinical Investigations

We studied the effects of outpatient phase 2 cardiac rehabilitation and exercise training programs in 116 consecutive obese patients and compared the benefits in these patients with those observed in 198 consecutive patients not classified as obese. Patients

M ETHODS

\Vp revi ewed data in 314 consecutive pati ents (160 from Massachusetts General Hospital and 154 from Ochsner Medical Institutions) who were referred to, attended, and completed outpatient phase 2 c radiac rehabilitation and exercise training programs. A subgroup of 116 patients were classified as obese by body mass index (BMI) criteria (BMI 2::27.8 kglm2 in men and ::=:27.3 kglm2 in women) as previously desc1ibed. 23 These obese patients were compared with the 198 patients not classified as obese. All patients were referred after a major cardiac event, including acute myocardial infarction, coronary artery bypass grafting, or percutaneous balloon angioplasty for an acute ische mic syndrome. Patients treated with lipid-lowering medications were excluded from the study, and other m edications which may affect lipid levels in some studies (such as estrogens, beta adrenergic blockers, diuretics, alph a blockers, and calcium channel blockers) were given at stable doses for 4 weeks or more before study entry and doses of these medications were not latered during the program.

Protocol

All patients were enrolled in an outpatient phase 2 cardiac rehabilitation and exercise training program. In general, these programs lasted for 3 to 4 months and consisted of 36 education and exercise training sessions, although occasionally the duration of the program was altered by the patient's ability to progress in altering risk f actors and in developing independence in performing and monitoring th e prescribed exercise program. At Ochsner, all patients completed the 36 sessions in an average of 14 weeks for both obese and nonobese subjects. Each exercise session consisted of a 10-min warm-up of calisthenics and stretching exercise, 30 to 40 min of continuous upright dynamic exe rcise ( usually a ocmbination of walking, jogging, and bicycling) combined with light isometric exercises such as those with hand weights, and a 10-min cooldown of calisthenics and stretching exercise. The intensity of exercise was prescribed on an individual basis sothat the e xercise heart rate was 70 to 85% of the maximal h eart rate obtained b yexercise testing, or 10 to 15 beats per minute below the levelof any exercise-induced symptomatic or silent ischemia. In addition, patients were e ncouraged to exercise one to three times p er week outside the supervised exercise program. Each exercise prescription was adjusted p eriodically to ensure agradual increase in exercise performance. All pati ents were instructed on the phase 1 diet of the American Heart Association and the National Cholesterol Education program, which included caloric recommendations to help patients achieve and maintain an ideal body weight. The di etary instruction was individualized, and monthly return visits with the dietitian were routine, particularly for obese patients and those who were less compliant \vith the diet. All patients were frequently encouraged by physicians, dietitians, exercise physiologists, and nurses to comply with both the dietmy and exerci se portions of the program, and weekly weights were charted. Although educational sessions dealt with psychosocial function, stress, and behavioral modification, presentation of specific programs in these areas was not routin e. Data Colle~tion

Body weight, BMI, percentage of body fat (by the sum of the skin fold method), plasma lipids (including fasting total cholesterol, triglycerides, HDL-C, low-density lipoprotein cholesterol [LDLC], and LDL-C/HDL-C ratio), and estimated metabolic equivalent

units (METs) were tested at baseline ( 4 to 8 weeks after a major cardiac event; average, 6 weeks ) and again vvithin 1 week of completing the phase 2 cardiac rehabilitation and exercise training program . In addition, th e prevalence of patients continuing to smoke or with a p ersonal history of di abetes m ellitus or systemic hypertension was assessed b yquestionnaire. Finally, the prevalence of obesity ( described previously) and severe obesity (BMk35 kg! mz) was also determined. Before enteling th e cardiac rehabilitation program, pati ents underwent symptom-limited, graded exercise testing. The majority of patients at both institutions exercised u sing a standard Bruce protocol treadmill test. although about 30% of patients underwent graded stress testing using another treadmill protoc'Ol or b y up1ight bicycle ergometlic testing. Patients were instructed to refrain from holding the treadmill handrail during exercise testing. Fo!lO\\~ng cardiac r ehabilitation and exercise training programs, similar protocols were repeated in each patient, and functional capacity was estimated in METs from standard formulas based on workload and exercise time.24 Statistical Analysis

The results are expressed as m aen ± 1 SD. Baseline characteristics of the obese and nonobese patients werecompared by nonpaired t test and x2 analysis. Baseline and post-cardiac rehabilitation data were compared in the entire cohOtt and in both groups by paired t tests, and changes in data between groups were analyzed with a two-factor (pre/ post and obesity status) repeated measures analysis of variance with repeated measures in one fac.t or (pre/post data). RE SU LTS

The effects of cardiac rehabilitation and exercise training in the entire cohort are demonstrated in Table l. Follmving cardiac rehabilitation, significant improvements were noted in triglycerides ( -11 %; p<0.0001 ), HDL-C ( +7%; p
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Table !-Improvement in Lipids, Obesity Indices, and Exercise Capacity Following Cardiac Rehabilitation and Exercise Training in the Total Cohort (n=314) Rehabilitation Parameter Total cholesterol, mgldL Triglycerides, mgldL HDL-C, mgldL LDL-C, mgldL LDL-/HDL-C ratio Weight, lbs BMI, kglm 2 Body fat,% Exercise capacity, est METs*

Before

After

207:!:42 167:!:88 38.4:!:10.7 137:!:35 3.75:!:1.32 178:!:30 27.0:!:4.1 24.4:!:6.3 6.9:!:2.8

202:!:39 148:!:80 41.1:!:11.0 133:!:33 3.42:!:1.22 176:!:26 26.6:!:3.9 23.0:!:5.9 9.0:!:3.3

% Change -2

-11 +7 -3 -9 -1 - 1.5 -6 +31

Probability Value 0.05 <0.0001 <0.0001 0.07 <0.0001 0.07 <0.0001 <0.0001 <0.0001

*1 MET=3.5 mL oxygen/kg/min.

and diabetes mellitus. Following cardiac rehabilitation and exercise training (Table 3), the obese patients had significant improvements in exercise capacity (+24%; p
Limited data are available regarding the effects of cardiac rehabilitation and exercise training in obese patients with CHD. The present report demonstrates Table 2-Baseline Differences Between Obese and Nonobese Coronary Patients* Parameter

Obese (n=ll6)

Non obese (n=198)

Probability Value

BMI, kglm 2 Age, yr Currently smoking Diabetes mellitus Systemic hypertension Total cholesterol, mgldL LDL-C, mgldL LDL-/HDL-C ratio Body fat ,%

31.2:!:3.2 58:!:9 10% 27% 71% 216:!:44 144:!:40 4.0:!: 1.4 25.5:!:6.7

24.6:!:2.1 62:!:11 10% 22% 60% 202:!:36 132:!:33 3.6:!:1.2 23.5:!:5.9

<0.0001 <0.001 NS NS <0.05 <0.01 <0.01 <0.01 <0.02

*Both groups were statistically similar regarding gender, exercise capacity, HDL-C, and triglycerides. NS=not significant.

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modest but significant improvements in obesity indices, plasma lipids, and exercise capacity in a large cohort of obese coronary patients. However, although obese patients had statistically greater relative improvement in indices of obesity following cardiac rehabilitation programs than nonobese patients, they had significantly less improvement in exercise capacity. Many studies have discussed the adverse effects of obesity on the total CHD risk profile. 1-14 Obesity increases arterial pressure and is a strong independent risk factor for the development of LVH. 1-4 It also has adverse effects on plasma lipids, particularly in reducing levels of HDL-C, and may lead to an increase in triglycerides and a slight increase in LDL-C. 1-6 Finally, obesity plays a major role in ~romoting insulin resistance and diabetes mellitus. Despite all of these known adverse effects on the overall CHD proflle, several studies have indicated that obesity is
Table 3--Effects of Cardiac Rehabilitation and Exercise Training Program on Exercise Capacity, Lipids, and Obesity Indices in Obese Coronary Patients (n=l16)* Rehabilitation C haracte ristic Exercise capacity, est METs Total cholesterol, mgldL Triglycerides, mgldL HDL-C , mgldL LDL-C, mgldL LDL-/HDL-C ratio Weight, lbs BMI, kglm 2 Body fat ,%

Before

Afte r

% Change

Probability Value

7.0::'::2.6 216::':: 44 175::'::82 38.0::'::10.0 144 ::':: 40 40 ::':: 1.4 206::':: 33 31.2 ::'::3.2 25.5::'::6.7

8.7::'::3.2 211::'::43 164::'::77 40.4::'::10.6 138::'::37 3.6::'::1.3 202::'::33 30.2::'::3.6 24.2::'::6.5

+24 -2 -6 +6 -4 -10 -2 -3 -5

<0.001 0.10 0.11 <0.01 0.07 <0.01 <0.0001 <0.0001 <0.001

*BMI ~ 27 . 8 kglm 2 in men and ~27.3 kglm 2 in women.

Several studies suggest that overall exercise and fitness levels may be very important risk factors for CHD,29-33 and improvement in exercise capacity and fitness predicts improvement in all-cause mortality. 33 Although all of these coronary patients had statistically similar functional capacity at baseline, in comparison to the nonobese patients, we were disappointed that the relative response to training, at least regarding improving exercise capacity, was less in the obese patients. The reason for the relative lack of improvement in exercise capacity in obese patients with CHD is speculative. During the exercise and educational sessions, attendance and compliance of both groups of patients appeared similar, as did their ability to follow the proposed exercise prescription. However, we did not precisely measure exercise capacity or effort by cardiopulmonary exercise assessment and instead estimated work capacity ~ workload and time on the treadmill or bicycle.34•3 Therefore, it is possible that the overall exercise effort may have differed in the two groups. In addition, we did not assess exercise or dietary recall outside of the formal exercise sessions. Finally, although improvements in obesity indices were statistically significant in our obese patients, the overall clinical improvement can be considered modest, at best. In addition, the obese patients had statistically higher levels of LDL-C and LDL-C/HDL-C

ratio at baseline than the nonobese patients. We have previously demonstrated that high baseline levels of these lipid levels are the strongest predictors of greater relative improvement following cardiac rehabilitation and exercise training programs.l 8 However, in the present study, the improvements in LDL-C and LDL-C/HDL-C ratio in the obese patients were statistically similar to those in the non obese patients who had lower baseline values. It seems likely that considerably greater improvements in obesity indices would have translated into greater rel;ttive improvements in both lipids and exercise capacity in these obese patients. Several other study limitations deserve mention. This study was retrospective and relatively short-term, and selection and referral biases may be present. Second, a control group was not included,16-18·36,37 although the primary purpose of this study was to compare the relative benefits of cardiac rehabilitation in obese and nonobese coronary patients. Third, we did not assess glucose metabolism and insulin resistance. Fourth, detailed evaluation of dietary adherence and exercise outside of the formal cardiac rehabilitation program was not available. Finally, as we discussed above, exercise capacity was estimated rather than precisely measured by gas exchange, and we did not assess HDL-C subfractions or LDL heterogeneity.

Table 4-Effects of Cardiac Rehabilitation Program on Exercise Capacity, Lipids, and Obesity Indices in Coronary Patients Not Classified as Obese (n=198)* Rehabilitation Characteristic Exe rcise capacity, est METs Total cholesterol, mgldL Triglyce rides, mgldL HDL-C, mgldL LDL-C, mgldL LDL-/HDL-C ratio Weight, lb BMI, kglm 2 Body fat, %

Before

After

% Change

Probability Value

6.8 ::':: 2.8 202 ::'::36 159::'::93 39.0::':: 11 132::'::33 3.6::':: 1.2 162::'::24 24.6::'::2.1 23.5 ::'::5.9

9.2::'::3.3 199::'::32 137::'::75 41.4::'::11.6 129::'::28 3.3::':: l.l 161::'::26 24.5::'::2.2 22.1 ::'::5.2

+36 -1.5 - 14 +6 -2 -8 0 0 -6

<0.0001 NS <0.001 <0.0001 NS <0.001 NS NS <0.0001

*BMI <27.8 kg/m 2 in men and <27.3 kglm 2 in women. NS=not significant. CHEST I 109 I 1 I JANUARY, 1996

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Despite these limitations, the present study demonstrates the effects of formal cardiac rehabilitation and exercise training programs on exercise capacity, plasma lipids, and obesity indices in obese palients with CHD. Although statistically significant improvements were noted in obesity indices in these obese patients, the clinical improvement can be considered modest at best. It seems likely that more signific
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