Usefulness of the Six-Minute Walk Test After Continuous Axial Flow Left Ventricular Device Implantation to Predict Survival

Abstract

The goal of this study was to describe the predictors and significance of poor exercise tolerance after left ventricular assist device (LVAD) implantation. Despite LVAD therapy, some patients continue to exhibit exercise intolerance. The predictors and outcomes of these patients are unknown. A retrospective review of 65 LVAD recipients who performed 6-minute walk tests was conducted. Patients walking <300 m were considered to have poor exercise tolerance. Twenty patients exhibited poor exercise tolerance (221 ± 45 m), compared to 45 patients with better exercise tolerance (406 ± 76 m). Postoperatively, poor performers were not easily identified by functional symptoms alone, because 42% of these patients reported New York Heart Association functional class I or II symptoms. Preoperative New York Heart Association class, inotrope therapy, and intra-aortic balloon pump use were similar between the 2 groups. Multivariate analysis using all adequately powered (n >50) univariate predictors identified diabetes mellitus (odds ratio 10.493, p = 0.003) and elevated 1-month right atrial pressure (odds ratio 2.985 for every 5 mm Hg, p = 0.003) as significant predictors of poor performance (<300 m; area under the curve 0.85). The poorly performing group had increased mortality (p = 0.011), with 21% increased risk for overall mortality for every 10 m short of 300 m (fitted Cox model: hazard ratio 1.211, p = 0.0001). The distance walked in meters in a postoperative 6-minute walk test was the strongest predictor of late post-LVAD mortality (p = 0.0002). In conclusion, despite similar severity of heart failure preoperatively, some LVAD recipients may have persistent exercise intolerance postoperatively as assessed by the 6-minute walk test that is independently associated with subsequent reduced survival.