A COMPARISON OF EQUATIONS FOR THE PREDICTION OF VO_2max IN ELDERLY CARDIAC PATIENTS

Robert Lowe; Mark Williams; James Bryan; University of Central Florida, Orlando

McConnell et al (JCR 1998;18:458-463) recently have provided support for not requiring a graded exercise test (GXT) prior to beginning cardiac rehabilitation. Such measures could lead to considerable cost savings to our overburdened healthcare system. In addition, Ainsworth et al (MENH 1993:75-82) recently developed a gender-specific regression equation to predict maximal oxygen uptake (VO_2max) in apparently healthy adults. The purpose of this study was to examine the validity of this equation when applied to an elderly cardiac population. Prior to performing a GXT, 24 consecutive cardiac patients (19 male and 5 female; age 59 +/- 8 years) were asked how many times in the past 7 days they had performed vigorous exercise. The predicted VO_2max (PRED) was then compared to three VO_2max prediction equations (Bruce cardiac, CARDIAC; Bruce active, ACTIVE; and Bruce inactive, INACTIVE) as described by Milani et al (JCR 1996;16:394-401). Data was analyzed by two-way ANOVA with repeated measures across prediction equations (CARDIAC, ACTIVE, INACTIVE, and PRED). No significant differences between males and females were observed (P > .05). The pooled results indicated that VO_2max predicted by CARDIAC (32.2 +/- 3.9 mL/kg/min) was significantly less (P < .05) than VO_2max predicted by ACTIVE (36.2 +/- 5.6 mL/kg/min), INACTIVE (37.1 +/- 6.4 mL/kg/min), or PRED (36.7 +/- 6.1 mL/kg/min). These results suggested that PRED produced similar results to ACTIVE and INACTIVE. However, PRED significantly overestimated VO_2max compared to CARDIAC. In light of Milani and colleagues' (1996) conclusion that only CARDIAC accurately predicts VO_2max in cardiac patients, the validity of using PRED in an elderly cardiac population must be questioned and warrants further study.

SIX-MINUTE WALK TEST EARLY POSTCARDIAC SURGERY: PARAMETERS INFLUENCING WALKING DISTANCE

Piero Clavario; Francesco Copello; Alberto Camerini; Daniele Silvestri; Maria Luisa Biorci; Elena Michelis; Elisabetta Capurro; Sergio Ferrari; Cristina Barbara; Pasqualina Calisi; Raffaele Griffo; U.O. Cardiologia Riabilitativa

Introduction:

Because of its safety, reproducibility, and low costs, the 6-minute walk test (6MWT) has been proposed in the cardiac rehabilitation field. Reference equations in healthy adults have been described, but these are able to explain only about 40% of the walking variance and the confidence intervals are wide, practically covering the entire usual walking range. Even more frustrating is trying to set walking ranges in patients with cardiac diseases.

Purpose:

To evaluate, in a population of early postoperative patients undergoing in hospital cardiac rehabilitation, if any of the clinical parameters could be predictive of a 10% walking distance improvement compared with the baseline test.

Material and Methods:

360 patients (98 women, 262 men, abnormal ejection fraction 27%) referred to our rehabilitation center within 20 days after their cardiac surgery performed two 6MWT, one at baseline and the other before discharge. Stepwise regression was used to identify any parameter influencing the walking distance at baseline and logistic regression was done to search the factors predicting a 10% or more improvement in the walking distance at the discharge test.

Results:

As expected, the stepwise regression indicated that only age was negatively predictive of the walking distance at the baseline test and explained only 27% of the variance. The logistic regression was able to identify that increasing age was associate with an 1.1 odds ratio and depressed ejection fraction with an 1.5 odds ratio of not reaching the 10% increase target (see table).

Table. No caption available.

Conclusions:

Walking is a complex phenomenon too difficult to describe through simple clinical variables, therefore it is very difficult to build reliable reference equations. Moreover, in the clinical practice scenario-even for the single patient-it is difficult to predict performance improvements using the usually available clinical data.

RESTING METABOLIC RATE-LEAN BODY MASS RELATIONSHIP IN MEN WITH CORONARY ARTERY DISEASE

Helena Santa-Clara, PhD; L. Sardinha; B. Fernhall, FACSM; T. Manafaia; J. Almeida; Exercise and Health Laboratory, Human Faculty of Movement-Technical University of Lisbon, Portugal; Syracuse University, NY

Lean body mass (LBM) is not an energetically homogeneous compartment of whole body composition. Visceral organs have a higher metabolic rate than appendicular lean soft tissue. Resting metabolic rate (RMR) decreases with age, primarily as a result of presumed reductions in LBM. These relationships have not been extensively studied in patients with coronary artery disease (CAD). The aim of the present study was to analyze the relationship between RMR and total, trunk, and appendicular LBM. Twenty-five men with CAD from phase 3 cardiac rehabilitation program, aged 42 to 71 years (57.5 +/- 9.1 years; height 1.72 +/- 0.07 cm; weight 80.9 +/- 11.3 kg; BMI 27.2 +/- 3.1) were examined. RMR was measured in the morning after a 12-hour fast by indirect calorimetry (ventilated hood techniques) and the LBM was determined by dual-energy x-ray absorptiometry (DXA). Relative RMR (2.05 +/- 0.25 mL/kg/min) was not associated (P > .05) with LBM, while with aging decreased (r = -0.45, P < .05). The absolute RMR (0.16 +/- 0.03 L/min) showed positive associations with total LBM (r = 0.68, P < .001), trunk LBM (r = 0.51, P < .005), and appendicular LBM (r = 0.67, P < .001). Similar inverse association with age was also observed (r = -0.56, P < .005). These data indicate that RMR is dependent on age and LBM in patients with CAD, consistent with data on other populations. Furthermore, the decline in RMR is partially due to a reduction in LBM in this population, suggesting that training methods aimed at increasing LBM, such as resistance training, should play a prominent role in cardiac rehabilitation programs.

NASAL CALCITONIN SPRAY DOES NOT PREVENT GLUCOCORTICOID-INDUCED VERTEBRAL OSTEOPOROSIS IN HEART TRANSPLANT RECIPIENTS

Randy W. Braith, PhD; Peter M. Magyari, PhD; Juan M. Aranda, MD; Michael N. Fulton, MD; Clem F. Lisor; James A. Hill, MD; University of Florida, Gainesville, FL

Rationale:

Immunosuppression regimens utilizing bolus glucocorticoids cause loss of bone mineral density (BMD) and osteoporosis in heart transplant recipients (HTR) early in the post-transplant period. There is no standard therapeutic intervention to prevent osteoporosis in HTR.

Objectives:

To determine the efficacy of nasal spray calcitonin in preventing bone resorption in HTR early after transplantation.

Methods:

A group of HTR (n = 14) received 200 units of calcitonin intra-nasally once a day with the aid of an inhaler, beginning 48 to 72 hours posttransplant and continuing for 2 months. A second group of HTR (n = 18) did not receive calcitonin or other antiosteoporosis therapy. BMD of the total body, femur neck, and lumbar spine was measured before transplantation (mean = 12 weeks prior to transplant) and at 2 months after transplant using dual energy x-ray absorptiometry.

Results:

At 2 months posttransplant regional BMD of the total body (-2.9%), femur neck (-5.31%), and lumbar spine (-12.8%) were significantly decreased from baseline in the control group. In the nasal calcitonin group, BMD decreases from baseline were significantly attenuated in the total body (-1.4%) and femur neck (-2.2%) scans, when compared to the control group. However, changes from baseline in lumbar spine BMD in the calcitonin group (-12.6%) were not significantly different from changes in the control group.

Conclusion:

Nasal calcitonin administered early in the posttransplant period attenuates bone resorption in the total body and femur neck but does not prevent trabecular bone loss from the lumbar spine. Our results suggest that an osteogenic stimulus, such as mechanical loading, may be necessary to prevent glucocorticoid-induced osteoporosis of the axial skeleton in HTR.

EFFECT OF LAWN MOWING ON STERNAL INTEGRITY SOON AFTER CORONARY ARTERY BYPASS GRAFT SURGERY

Jenny Adams, PhD; Pamala Stafford, RN; Gwen Pullum, LVN; Nava Hanners, RN; Julie O'Bryan, MS

Exercise prescriptions are often conservative following coronary artery bypass graft (CABG) surgery due to uncertainty regarding adequate healing of the fractured sternum. For low-risk patients (eg, ejection fraction >= 45%, nondiabetic, nonobese, normotensive blood pressure, no ST-segment depression or serious ventricular arrhythmias, metabolic level >= 5) iso-dynamic exercise (eg, carpentry, circuit weight training) has been recommended as soon as 3 weeks after CABG surgery. However, lawn mowing (a necessary activity for many independent patients), is often targeted as a dangerous post-CABG activity. The purpose of this study was to determine if lawn mowing activity compromises sternal integrity when performed 3 to 6 weeks after CABG surgery. Ten post-CABG patients performed a simulated lawn mowing activity during 59 experimental trials. During each work trial a cable simulating a lawn mower start cord (force pounds >= 46) was pulled three times and a simulated lawn mower (force pounds >= 36) was pushed for 20 minutes. Resting and peak heart rate, blood pressure, and electrocardiograph measurements were obtained during each trial. Sternal integrity was evaluated by use of radiography and sternal palpation. One failure of patient sternal integrity following the lawn mowing activity was determined an endpoint to the study. The probability of zero failures in 59 trials was .82 ([alpha] = .18). Sternal integrity was not compromised in any patients during the 59 lawn mowing trials. If sample size were increased to 80 trials, a more acceptable power of .80 would be achieved. Preliminary findings indicate lawn mowing might be a safe activity for low-risk patients 3 to 6 weeks after CABG surgery. However, more trials are needed to support these preliminary results.

SIX-MINUTE WALK PERFORMANCE IMPROVES UP TO 6 MONTHS PARTICIPATION IN NORTH CAROLINA CARDIAC REHABILITATION PROGRAMS

D. Verrill, M. Lippard, NorthEast Medical Center, Concord, NC; C. Barton, W. Beasley, Davidson College Psychology Department, Davidson, NC

Rationale:

While there is a plethora of research looking at the short-term effects of supervised cardiac rehabilitation (CR), little is known about the long-term effects of CR on functional capacity changes in patients across multiple programs.

Objective:

The 6-minute walk (6MW) test is a valid and reliable predictor of functional capacity in patients with cardiovascular disease. In 1999, the North Carolina Cardiopulmonary Rehabilitation Association developed a registry to collect ongoing data to assess the effectiveness of long-term CR participation on 6MW performance and other functional outcomes statewide.

Methods:

For this project, 2502 patients aged 40 to 89 years from 23 hospital outpatient and free-standing CR programs performed 6MW tests following standardized instructions prior to and immediately following 12 weeks, 24 weeks, and 52 weeks of supervised CR participation. Six-minute walk distance (feet) at each time period was compared pre- and post-CR participation with repeated measures analysis of variance. Differences in scores were determined by post hoc t test analysis.

Results:

Mean 6MW scores at 12 weeks (1681.5 +/- 378.7; n = 2325) were greater than at CR entry (1433.1 +/- 342.5;P = .001). Mean 6MW scores at 24 weeks (1849.7 +/- 439.3; n = 134) were greater than entry and 12-week scores (P = .001). Mean 6MW scores at 52 weeks (1808.8 +/- 339.2; n = 43) were not significantly different than at 24 weeks (P = .386), but were greater than at both entry and 12 weeks (P < .001).

Conclusions:

Functional capacity, when assessed by the 6MW test, improves progressively in men and women across programs for up to 24 weeks of CR participation. A fitness "plateau" may occur in patients following 24 weeks of participation, or they may have simply reached peak walking distance. It is prudent to encourage participation in supervised CR for at least 24 weeks to promote continued improvements in physical performance.