Peak exercise capacity prediction from a submaximal exercise test in coronary artery disease patients

Submaximal Exercise Testing in Cardiovascular Rehabilitation Settings (BEST Study)

Background

This study compared changes in measured versus predicted peak aerobic power (V̇O_2peak) following cardiovascular rehabilitation (CR). Peak cardiopulmonary exercise testing (CPET) results were compared to four V̇O_2peak estimation methods: the submaximal modified Bruce treadmill, Astrand-Ryhming cycle ergometer, and Chester step tests, and the Duke Activity Status Index (DASI).

Methods

Adults with cardiovascular disease (CVD) who completed a 12-week CR program were assessed at baseline and 12 weeks follow-up. CPET, the DASI and three subsequent submaximal exercise tests were performed in a random order.

Results

Of the 50 adults (age: 57 ± 11 years) who participated, 46 completed the 12-week CR program and exercise tests. At baseline 69, 68, and 38% of the treadmill, step and cycle tests were successfully completed, respectively. At follow-up 67, 80, and 46% of the treadmill, step and cycle tests were successfully completed, respectively. No severe adverse events occurred. Significant improvements in V̇O_2peak were observed with CPET (3.6 ± 5.5 mL^.kg^–1.min^–1, p < 0.001) and the DASI (2.3 ± 4.2 mL^.kg^–1.min^–1, p < 0.001). Bland-Altman plots of the change in V̇O_2peak between CPET and the four V̇O_2peak estimation methods revealed the following: a proportional bias and heteroscedastic 95% limits of agreement (95% LoA) for the treadmill test, and for the cycle and step tests and DASI, mean bias’ and 95% LoA of 1.0 mL^.kg^–1.min^–1 (21.3, −19.3), 1.4 mL^.kg^–1.min^–1 (15.0, −12.3) and 1.0 mL^.kg^–1.min^–1 (13.8, −11.8), respectively.

Conclusion

Given the greater number of successful tests, no serious adverse events and acceptable mean bias, the step test appears to be a valid and safe method for assessing group-level mean changes in V̇O_2peak among patients in CR. The DASI also appears to be a valid and practical questionnaire. Wide limits of agreement, however, limit their use to predict individual-level changes.

Using rating of perceived exertion in assessing cardiorespiratory fitness in endometrial cancer survivors

For cancer survivors, who also often present with co-existing health conditions, exercise testing is often performed using submaximal protocols incorporating linear heart rate response for estimating the cardiorespiratory capacity and assessing exercise tolerance. However, use of beta-blocker medications, during sub-maximal protocols based on linear HR response can be problematic. Rating of perceived exertion (RPE), which takes into account an individual's overall perception of effort, can be used as a complementary tool that does not rely solely on the heart rate response to increased workload. We compared heart rate response (VO2HR) and self-rating of perceived exertion (VO2RPE) in a graded submaximal exercise test (GXT) in 93 endometrial cancer survivors. The results of the GXT were stratified according to whether participants were taking beta-blocker (BB) medications or not (non-BB). Among non-BB participants, there was no difference between the mean VO2HR and the mean VO2RPE estimates of cardiorespiratory capacity (mlO2//kg/min) (20.4 and 19.3, respectively; p = 0.166). Among BB participants, the mean VO2HR approached significant difference than the mean VO2RPE (21.7 mlO2//kg/min and 17.6 mlO2//kg/min, respectively; p = 0.087). Bland-Altman plots for both methods showed a proportional bias for the non-BB group; but not the BB group. Our results suggest that sub-maximal protocols based on Borg's Rating of Perceived exertion (RPE) produce differing results from sub-maximal protocols based on HR response when applied to clinical population taking BB medications. Using RPE instead of HR for participants on BB medications may be a better method for assessing the exercise tolerance for estimating the cardiorespiratory capacity in sub-maximal exercise testing.

Physiological Responses During the Lower Body Positive Pressure Supported Treadmill Test

Objective

To quantify changes in cardiopulmonary function using a lower body positive pressure supported (LBPPS) treadmill during the exercise tolerance test (ETT) in healthy subjects before applying the LBPPS treadmill in patients with gait problems.

Methods

We evaluated 30 healthy subjects who were able to walk independently. The ETT was performed using the Modified Bruce Protocol (stages 1–5) at four levels (0%, 40%, 60%, and 80%) of LBPPS. The time interval at each level of the LBPPS treadmill test was 20 minutes to recover to baseline status. We measured systolic blood pressure, diastolic blood pressure, peak heart rate (PHR), rating of perceived exertion (RPE), metabolic equivalents (METs), and oxygen consumption rate (VO₂) during each LBPPS condition.

Results

Systolic blood pressure increased as the LBPPS level was increased (40% to 80%). PHR, RPE, METs, and VO₂ were negatively associated with the LBPPS condition, although they were not always significant different among the LBPPS levels. The equation from a random effect linear regression model was as follows: VO₂ (mL/kg/min)=(2.75×stage)+(–0.14×LBPPS level)+11.9 (r²=0.69).

Conclusion

Detection of the changes in physiological parameters during a submaximal ETT using the LBPPS system may be helpful for applying the LBPPS treadmill in patients who cannot perform the ETT due to gait problems, even at submaximal intensity.

Economic evaluation of exercise-based cardiac rehabilitation in patients with a recent acute coronary syndrome

Health care decision-making requires evidence of the cost-effectiveness of medical therapies. We evaluated the cost-effectiveness of exercise-based cardiac rehabilitation (ECR) implemented according to guidelines. All the patients (n = 204) had experienced a recent acute coronary syndrome and were randomized to a 1-year ECR (n = 109) or usual care (UC) group (n = 95). The patients' health-related quality of life was followed using the 15D instrument and health care costs were collected from electronic health registries. The cost-effectiveness of ECR was estimated based on intervention and health care costs and quality-adjusted life years (QALYs) gained. The total average cost per patient was lower in ECR than in UC. The incremental cost was divided by the baseline-adjusted incremental QALYs (0.045), yielding an incremental cost-effectiveness ratio of -€24511/QALYs. A combined endpoint of mortality, recurrent coronary event, or hospitalization for a heart failure occurred for five patients in ECR and 16 patients in UC (HR 3.9, 95% CI 1.4-10.6, P = 0.004, relative risk reduction 73%, number needed to treat eight). ECR is a dominant treatment option and decreases the occurrence of adverse cardiac events. These results are useful for decision-making when planning optimal utilization of resources in Finnish health care.