1. Does Cardiac Rehabilitation (CR) Improve
Functional Capacity Of Patients?
An Evaluation Using The 6 Minute Walk Test (6MWT)
Natalie Wren | Kristina Dietz | Steve Meadows | University of Kent | School of Sport and Exercise Sciences
Introduction
Results
CR is recognised as part of a patient’s recovery & is embedded into clinical guidelines. CR is usually a comprehensive programme, including education, lifestyle change & exercise.
Exercise in CR has been shown to:
Improve mortality 20-30%: the higher the volume of exercise, the greater mortality reduction = higher survival rates (Myers et al., 2002).
Reduce morbidity 15-30%: the risk of other diseases being experienced are reduced (O'Connor et al., 1989).
Reduce secondary cardiac events.
Even a small MET improvement of 0.28 = 9% increase in survival (Kavanagh et al., 2002).
6MWT
10m distance, identified by two cones. The number of shuttles completed was recorded each minute along with RPE at the end of each minute. Total shuttles walked recorded.
METs
A MET is a unit used to estimate the amount of oxygen used by the body during physical activity. At rest, 1 MET = 3.5ml/kg/min. Walking at 2.5mph = 3.0 METs.
Graph 1: Patient Pacing in Pre & Post 6MWT
The results of the paired t-tests (n = 82) showed statistically significant differences for all functional outcome measures. On average from Pre to Post CR, total number of shuttles increased by 5.81 shuttles (SD = 4.66), walking speed increased by 0.36 mph (SD = 0.29) and estimated METs increased by 0.27 (SD = 0.22). All results were statistically significant with p-values <0.001.
Table 1: Participant Profile and Outcomes
Age
Total Number of Shuttles Walked
Walking Speed (mph)
METs
Participants %
Mean±SD
Min-Max
Pre
Post
Males = 58
70.7
64.38±9.94
40-83
42.43±7.04
48.70±8.87
2.75±0.81
3.16±1.00
3.09±0.62
3.41±0.76
Females = 24
29.3
65.46±10.69
47-86
40.58±9.21
45.29±8.80
2.54±0.58
2.83±0.55
2.93±0.44
3.16±0.42
Total = 82
64.70±10.11
40-86
41.89±7.72
47.70±8.93
2.62±0.48
2.98±0.56
2.99±0.37
3.27±0.43
Aims
Do patients attending CR improve functional capacity measured using the 6MWT
Evaluation of patient’s pacing over the 6MWT
Methods
Summary
Participants
82 Phase III patients with a range of cardiac conditions (MI, CABG, PCI).
6MWT Measurement
6MWT conducted in community settings pre & post CR.
Equipment: Cones x2, stopwatch, modified RPE Scale.
MET Calculations
ACSM metabolic calculations used to estimate MET expenditure and predicted VO2 (ACSM, 2014 p.173)
Example:
Predicted VO2 Calculation: (0.1 x 55) = 9
MET Value Calculation: 9 ÷ 3.5 = 2.57 METs
The results demonstrate a small, and possibly clinically significant, improvement in patients walking distance and speed and MET scores. This suggests that CR has an impact on the patients exercise capacity and identifies some, albeit small, physiological improvement. However, this improvement between the Pre and Post 6MWT’s could be due to a learning effect as there was no familiarisation test, due to resource limitations
References
American College of Sports Medicine. (2014) ACSM Guidelines for Exercise Testing Prescription, 9th edition. Baltimore: Lippincott Williams and Wilkins. Myers, J., Prakash, M., Froelicher, V., Partington, S., Atwood, J, E., (2002) Exercise capacity and mortality among men referred for exercise testing. The New England Journal of Medicine, 346, (11), Kavanagh, T., Mertens, D.J., Hamm, L.F., Beyene, J., Kennedy, J., Corey, P. and Shephard, R.J. (2002) ‘Prediction of long-term prognosis in 12,169 men referred for cardiac rehabilitation’, Circulation, 106, O'Connor, G, T., Buring, J, E., Yusuf, S., Goldhaber, S, Z., Olmstead, E, M., Paffenbarger Jr, R, S., Hennekens, C, H., (1989) An overview of randomized trials of rehabilitation with exercise after myocardial infarction. Circulation, 80, (2),