VALIDITY AND RELIABILITY OF THE INCREMENTAL SHUTTLE WALK TEST AND SIX-MINUTE WALK TEST IN CHRONIC HEART FAILURE Cowie, A.*, Thow, M.K., Granat, M., Mitchell, S.L. *PhD Student, Glasgow Caledonian University, Glasgow / Cardiac Rehabilitation Physiotherapist, NHS Ayrshire & Arran (aynsley.cowie@aaaht.scot.nhs.uk) TITLE OF PRESENTATION Mr John Smith Schools and Colleges Liaison
Background Valid - measures what it s supposed to measure Reliable - gives consistent results repeatedly PeakVO2 (peak oxygen uptake) from cardiopulmonary exercise test (CPET) = most accurate measure of exercise capacity (gold standard) CPET: incremental cycling / treadmill protocol to symptom-limited peak BUT time-consuming, costly, and often poorly tolerated (clinically inaccessible) Incremental Shuttle Walk Test (ISWT) and self-paced 6-minute Walk Test (6MWT) = popular clinical substitutes; simplistic, inexpensive, familiar
Background 6MWT (Butland et al, 1982) self-paced over known distance for 6 minutes (with rests as required) many trials in CHF* inconsistently confirming validity and reliability * = chronic heart failure ISWT (Singh et al, 1992) externally-paced, progressive walking speed (around cones) governed by audio signal less evidence to support use - very few trials in CHF Trials comparing tests in CHF: ISWT more valid Reliability confirmed though lack of consensus regards pre-test familiarisation / practice walk? 10m (Green et al, 2001; Morales et al, 1999; Pulz et al, 2008)
Aims To examine: Validity of the ISWT and 6MWT (in relation to symptom-limited treadmill CPET) Test-retest reliability of each walking test Whether familiarisation has any effect on walking test reliability
Sample Power calculation: n=22 (80% power) (Green et al, 2001) Recruited from CHF nurses, and cardiology clinics INCLUSION CRITERIA Left ventricular dysfunction Clinically stable for at least one month (ACPICR, 2006) Optimised cardiac medication doses EXCLUSION CRITERIA Contraindications to exercise testing (ACSM, 2006) Local NHS Ayrshire & Arran treadmill testing protocol (exclusions) adhered to
OUTCOMES: peakvo2 (ml.kg -1.min -1 ) walking test distance (m) Cosmed K4b 2 Methodology n=22 familiarised with either ISWT or 6MWT (randomly assigned) 1 x treadmill CPET, STEEP protocol (Northridge et al, 1990) 3 x ISWT and 3 x 6MWT (familiarised test first) Data from 1st walking test compared to data from CPET VALIDITY OF EACH WALKING TEST Data over 3 attempts of each walking test examined RELIABILITY OF EACH WALKING TEST Reliability data of those familiarised compared to those not EFFECT OF FAMILIARISATION ON RELIABILITY
Results CHARACTERISTICS VALUES n n=22 27 participants recruited initially n=22 completed study with no adverse events Mean age (years) 64 Age range (years) 51-76 Gender (males / females) 19 / 3 NYHA class: II / III 13 / 9 Aetiology of heart failure: - idiopathic 0 - ischaemic 14 - other 8 Baseline ECG: sinus rhythm / atrial fibrillation 17 / 5
PeakVO2 (ml.kg-1.min-1) Validity 25 CPET PeakVO2 Versus Walking Test PeakVO2 Mean peakvo2*: CPET - 16.99 ISWT - 13.43 20 6MWT - 14.39 (* = ml.kg-1.min-1) 15 10 CPET ISWT 6MWT Neither walking test stressed participants to the level of CPET
Validity CPET PeakVO2 Versus Walking Test Distance COMPARISON** r VALUE p VALUE 6MWT distance v. CPET pvo2 r = 0.62 p = 0.001 ISWT distance v. CPET pvo2 r = 0.48 p = 0.001 6MWT distance has stronger relationship with CPET peakvo2 - though both relationships significant (p<0.05) **regression correlation, closer to 1.0 = stronger relationship
Reliability & Familiarisation PeakVO2 Data Over 3 Attempts of Each Walking Test WALKING TEST ALL PARTICIPANTS ICC (p VALUE) THOSE FAMILIARISED 6MWT 0.74 (p=0.97) 0.58 (p=0.45) ISWT 0.84 (p=0.15) 0.86 (p=0.29) *Two-way ANOVA intra-class correlation co-efficient (closer to 1.0 = stronger relationship) ISWT showed better reliability - enhanced by familiarisation Reliability of 6MWT reduced with familiarisation All reliability analyses non-significant (p>0.05)
Conclusions Neither walking test stressed participants to the level of CPET 6MWT distance is a more valid representation of exercise capacity than ISWT distance ISWT demonstrated greater reliability - and reliability improved with familiarisation Familiarisation increased variation in 6MWT data, reducing its reliability As reliability is a pre-condition of validity, the ISWT may be the more valid test for clinical practice in CHF
References American College of Sports Medicine, 2006. Guidelines for exercise testing and prescription. 7 th Edition. Baltimore, Maryland: Lippincott Williams & Wilkins; Association of Chartered Physiotherapists in Cardiac Rehabilitation (2006) Standards for the exercise component of the phase III cardiac rehabilitation. London: ACPICR. Butland, R.J., Pang, J. & Gross, E.R. (1982) Two-, Six- and 12-minute Walking Tests in Respiratory Disease. BMJ, 284,1607-8. Green, D., Watts, K., Rankin, S., Wong, P. & O Driscoll, J., 2001. A Comparison of the Shuttle and 6-Minute Walking Tests with Peak Oxygen Consumption in Heart Failure. Journal of Science and Medicine in Sport, 4(3),292-300.
References Morales, F.J., Martinez, A., Mendez, M., Agarrado, A., Ortega, F., Fernandez Guerra, J. et al (1999) A Shuttle Walk Test for Assessment of Functional Capacity in Chronic Heart Failure. American Heart Journal, 138,291-8. Northridge, D., Grant, S., Ford, I., Christie, J., McLenachan, J., Connelly, D. et al. 1990. Novel Exercise Protocol Suitable for Use on a Treadmill or a Bicycle Ergometer. British Heart Journal, 64,313-316. Pulz C, Diniz RV, Tebexreni AS. Incremental shuttle and six-minute walking tests in the assessment of functional capacity in chronic heart failure. Canadian Journal of Cardiology 2008;24:131-5. Singh, S.J., Morgan, M.D.L., Scott, S., Walters, D., & Hardman, A.E., 1992. Development of a Shuttle Walking Test of Disability in Patients with Chronic Airways Obstruction. Thorax, 1019-24.