Usefulness of Serial Six-Minute Walk Distance in Ambulatory Heart Failure Patients

Introduction

Six-minute walk distance (6MWD) measurements can predict outcome after heart failure (HF) exacerbation. However, 6MWD may change during the ambulatory course. We examined repetitive 6MWD in ambulatory HF patients for variance, trends and correlation with clinical outcomes.

Methods

The 6MWD is performed routinely in our HF clinic. Patients who had ≥3 6MWD measurements between 12/2015-11/2017 were included.

Patients with the last recorded 6MWD≥400 meters were considered favorable and those walking unfavorable. These were compared by clinical characteristics and outcomes.

Results

175 patients with (median[IQR]) 6[4-10] clinic visits and 6[4-8] 6MWD measurements per patient were included. Mean age was 66.6±16 years, and 29.7% were female. Median difference in distance walk between consecutive measurements (Δ6MWD) was 5[-6-14.3] meters, with a standard deviation of 49.9[33.1-81.4] meters.

Favorable 6MWD was observed in 78 (44.6%) patients. There were 28(16%) patients that improved to ≥400m and 14(8%) that deteriorated to

Favorable patients walked further on their first test (427 vs. 259 meters; p<0.001), were significantly younger (mean age 59.9 vs. 71.9 years; p<0.0001), more were males (78.2% vs. 63.9%;p=0.04), less had hypertension or diabetes but more were smokers (51.3% vs. 37.1%; p=0.06) and had ischemic etiology (73.1% vs. 49.5%; p=0.002). Less were treated with furosemide (67.9% vs. 81.4%;p=0.039) without significant difference in other HF medications. In a multivariable model younger age, ischemic etiology, and 6MWD at first visit were independent predictors for favorable 6MWD.

Favorable patients had numerically less ER visits (5.1% vs. 12.4%; p=0.098) and hospitalizations (11.5% vs. 22.7%; p=0.041). Eight patients in the unfavorable group but none in the favorable group died (p=0.008).

Conclusions

Most HF patients maintain their ambulatory 6MWD, but 16% increase to >400m during follow-up. Patients walking>400m had favorable characteristics and better outcome. Repeating the 6MWD may be valuable to trace changing patient condition.