predictors of exercise capacity in heart failure

Background and Aim: Compromised exercise capacity is a major symptom in patients with heart failure (HF) and reduced left ventricular (LV) ejection fraction (EF). Six-minute walk test (6-MWT) is popular for the objective assessment of exercise capacity in these patients but is largely confined to major heart centres. The aim of this study was to prospectively examine functional parameters that predict 6-MWT in patients with HF and reduced LVEF. Methods: In 111 HF patients (mean age 60±12 years, 56% male), a 6-MWT and an echo-Doppler study were performed in the same day. In addition to conventional ventricular function measurements, global LV dyssynchrony was indirectly assessed by total isovolumic time - t-IVT [in s/min; calculated as: 60 – (total ejection time – total filling time)], and Tei index (t-IVT/ejection time). Also, LV and right ventricular function were assessed by mitral and tricuspid annular plane systolic excursion (MAPSE and TAPSE, respectively). Based on the 6-MWT distance, patients were divided into 2 groups: Group I: ≤300m and Group II: >300m. Results: The 6-MWT distance correlated with t-IVT and Tei index (r=-0.37, p<0.001, for both), lateral and septal e’ velocities (r=0.41, p<0.001, and r=0.46, p<0.001, respectively), E/e’ ratio (r=-0.37, p<0.001) and TAPSE (r=0.45, p<0.001), but not with the other clinical or echo parameters. Group I patients had longer t-IVT, lower E/e’ratio, TAPSE and lateral e’ (p<0.001 for all) compared with Group II. In multivariate analysis, TAPSE [0.076 (0.017-0.335), p=0.001], E/e’ [1.165 (1.017-1.334), p=0.027], t-IVT [1.178 (1.014-1.370), p=0.033] independently predicted poor 6-MWT performance (<300m). Sensitivity and specificity for TAPSE ≤1.9 cm were 66% and 77%, (AUC 0.78, p<0.001); E/e’ ≥10.7 were 66% and 62% (AUC 0.67, p=0.002) and t-IVT ≥13 s/min were 64% and 60% (AUC 0.68, p=0.002) in predicting poor 6-MWT. Combined TAPSE and E/e’ had a sensitivity of 68% but specificity of 92% in predicting 6-MWT. Respective values for combined TAPSE and t-IVT were 71% and 85%. Conclusion: In patients with HF, the limited exercise capacity assessed by 6-MWT, is multifactorial being related both to the severity of right ventricular systolic dysfunction as well as to raised LV filling pressures and global dyssynchrony.