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Incremental shuttle walk test in the assessment of patients for heart transplantation
M E Lewis1, C Newall, J N Townend
1Heart and Lung Transplantation Unit, Department of Cardiothoracic Surgery, Queen Elizabeth Hospital, University Hospital NHS Trust, Birmingham B15 2TH, UK.
Objective:
To compare the incremental shuttle walk test (ISWT) with treadmill exercise testing (TT) derived measurement of peak oxygen consumption (peak VO(2)) in patients undergoing assessment for cardiac transplantation.
Design:
Prospective comparison. All investigations occurred during a single period of admission for transplant assessment.
Setting:
Single UK cardiothoracic transplantation unit.
Patients:
25 patients recruited (21 men). Mean age was 53 years.
Interventions:
Patients underwent two TT of peak VO(2) using the modified Naughton protocol and three (one practice) ISWT. Investigations were performed on consecutive days.
Main Outcome Measures:
Main outcome measures were repeatability of TT and ISWT assessments; relation between peak VO(2) and distance walked in the ISWT; and receiver operating characteristic (ROC) analysis to establish a distance walked in the ISWT that predicted which patients would have a peak VO(2) greater than 14 ml/min/kg.
Results:
Both the ISWT and the TT were highly reproducible. Following the first practice walk, mean (SD) ISWT distances were 400.0 (146) m (ISWT2) and 401.3 (129) m (ISWT3), r = 0.90, p < 0.0001. Mean peak VO(2) by TT was 15.2 (4.4) ml/kg/min (TT1) and 15.0 (4.4) ml/kg/min (TT2), r = 0.83, p < 0.0001. The results revealed a strong correlation between distance covered in the ISWT and peak VO(2) obtained during TT (r = 0.73, p = 0.0001). ROC analysis showed that a distance walked of 450 m allowed the selection of patients with a peak VO(2) of over 14 ml/min/kg.
Conclusions:
This work confirms the utility of the ISWT in the assessment of exercise capacity in patients with severe heart failure undergoing assessment for cardiac transplantation. ISWT may provide a widely applicable surrogate measure for peak VO(2) estimation in this population. Shuttle distance walked may therefore allow the convenient, serial assessment of patients with heart failure before referral for transplantation.