Abstract 2337: Role of Preoperative 6 Minute Walk Test in the Assessment and Prognosis of Patients with Severe Aortic Stenosis Undergoing Aortic Valve Replacement
Background: The 6 minute walk test (6MWT) is recommended to assess prognosis and the level of functional impairment in patients with chronic heart failure. We investigated the potential role of the 6MWT to assess the results of aortic valve replacement (AVR) in patients with severe aortic stenosis (AS).
Methods: Two hundred and ten patients with severe AS had a 6MWT and were enrolled in a randomized trial (ASSERT) comparing the effect of stentless (Freestyle) and stented (Mosaic) valves on left ventricular mass regression (previously published). Of these patients, 172 patients were randomized and followed up at 6 and 12 months (mean 392 ± 59 days, range 262 to 717 days), 36 patients were excluded at the time of the surgery but followed up during the hospital stay, and two patients had their surgery cancelled. The outcomes of this analysis were 6-minute walking distance and death or stroke after AVR.
Results: The mean distance walked at the preoperative 6MWT was 287 ± 124 m and the median was 297 m. The walked distance in the 6MWT improved significantly in both the stentless and the stented groups from baseline (299 ± 115 and 271 ± 130 m, respectively) to 6 months (351 ± 115 and 346 ± 128 m, respectively) (P< 0.001), and to 12 months (371 ± 119 m and 363 ±121 m, respectively) (p<0.001) but there were no significant differences between groups. Characteristics of patients who walked >300 m compared to patients >300 m respectively were: male (72% vs. 51%, p<0.001), height (170 vs. 165 cm, p<0.001), aortic valve area index (0.44 vs. 0.39 cm2/m2, p<0.033), BMI (26 vs. 28 kg/m2, p<0.001), NYHA class III-IV (33% vs. 55%, p<0.001), hypertension (35% vs. 56%, p<0.001), and chronic obstructive pulmonary disease (3% vs. 12%, p<0.009). The rate of death or stroke was 13.1% (n=14) in patients walking < than 300 m compared to 3.9% (n=4) in patients walking >300 m (p= 0.001). In a Cox proportional hazard model, walking >300 m at baseline (OR 0.15, 95% CI 0.04 – 0.58, p=0.006) was the only variable retained as an independent predictor of death or stroke at 12 months.
Conclusion: There was similar improvement of 6-minute walking distance after AVR with both valves. The information obtained from this simple sub-maximal exercise test may help to determine the risk of death or stroke after AVR.