Original article
Determining the Minimal Clinically Important Difference for the Six-Minute Walk Test and the 200-Meter Fast-Walk Test During Cardiac Rehabilitation Program in Coronary Artery Disease Patients After Acute Coronary Syndrome

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Abstract

Gremeaux V, Troisgros O, Benaïm S, Hannequin A, Laurent Y, Casillas J-M, Benaïm C. Determining the minimal clinically important difference for the six-minute walk test and the 200-meter fast-walk test during cardiac rehabilitation program in coronary artery disease patients after acute coronary syndrome.

Objective

To estimate the minimal clinically important difference (MCID) for the 6-minute walk test (6MWT) and the 200-m fast-walk test (FWT) in patients with coronary artery disease (CAD) during a cardiac rehabilitation program.

Design

Prospective study using distribution- and anchor-based methods.

Setting

Outpatients from a cardiac rehabilitation unit.

Participants

Stable patients with CAD (N=81; 77 men; mean±SD age, 58.1±8.7y) enrolled 31±12.1 days after an acute coronary syndrome (ACS).

Interventions

Not applicable.

Main Outcome Measures

6MWT and 200-m FWT results before and after an 8-week cardiac rehabilitation program and at the 6th and 12th sessions. Patients and physiotherapists who supervised the training were asked to provide a global rating of perceived change in walking ability while blinded to changes in walk test performances.

Results

Mean change in 6MWT distance (6MWD) in patients who reported no change was −6.5m versus 23.3m in those who believed their performance had improved (P<.001). This result was consistent with the MCID determined by using the distribution method (23m). Considering a 25-m cutoff, positive and negative predictive values were 0.9 and .63, respectively. Conversely, there was no difference in 200-m FWT performance between these 2 groups (0.1 vs −1.4s, respectively). There was poor agreement with the physiotherapist's perceived change.

Conclusions

The MCID for 6MWD in patients with CAD after ACS was 25m. This result will help physicians interpret 6MWD change and help researchers estimate sample sizes in further studies using 6MWD as an endpoint.

Section snippets

Participants

Patients referred to the cardiac rehabilitation department of Dijon University Hospital after an ACS were invited to participate. Patients were eligible if they had been admitted to an ambulatory cardiac rehabilitation program after percutaneous transluminal coronary angioplasty or coronary stent placement after an ACS. Only patients admitted within 2 months after the ACS under optimal medical treatment according to the latest recommendations32 (ie, β-blockers, angiotensin-converting enzyme

Participants

Eighty-one patients were recruited, and all completed the rehabilitation program. Two patients did not complete the third evaluation (both had to stop training for 2 weeks for personal or family reasons). Demographic and anthropometric characteristics of the 81 included patients are listed in table 1.

Walk Test and Maximal Exercise Test Results

Overall, there were mean improvements of 73.2±56.5m in 6MWD (15.7%±12.2%) and 5±17.7 seconds in 200-m FWT time (−5.3%±10.8%) (fig 1). All walk tests were well tolerated both before and after

Discussion

We estimated MCID for the 6MWD at approximately 25m in patients with CAD who recently experienced an ACS and who had benefited from cardiac rehabilitation. This estimate was consistent regardless of the estimation method used (anchor or distribution based). Using the same method, we could not determine an MCID with satisfactory metrologic qualities for 200-m FWT time.

To our knowledge, this is the first study to evaluate the MCID for walk tests in patients with CAD. A previous study determined

Conclusions

Our study provides the first estimates of an MCID, approximately 25m, in performance at the 6MWT in a CAD population. This result supports the use of the 6MWT during cardiac rehabilitation programs in patients with CAD after ACS and will help practitioners and researchers interpret changes in 6MWD in this population.

Acknowledgments

We thank the rehabilitation team for participation in this study and Arnaud Dupeyron, MD, PhD, and Anthony Gelis, MD, MsC, for their unconditional 10-year support. The English was revised by Philip Bastable.

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