Background: Quality of life is as important as survival in heart failure (HF) patients. Controversies exist with regards to echocardiographic determinants of exercise capacity in HF, particularly in patients with preserved ejection fraction (HFpEF). The aim of this study was to prospectively examine echocardiographic parameters that correlate and predict functional exercise capacity assessed by 6 min walk test (6-MWT) in patients with HFpEF.
Methods: In 111 HF patients (mean age 63 ± 10 years, 47% female), an echo-Doppler study and a 6-MWT were performed in the same day. Patients were divided into two groups based on the 6-MWT distance (Group I: ≤ 300 m and Group II: >300 m).
Results: Group I were older (p = 0.008), had higher prevalence of diabetes (p = 0.027), higher baseline heart rate (p = 0.004), larger left atrium - LA (p = 0.001), longer LV filling time - FT (p = 0.019), shorter isovolumic relaxation time (p = 0.037), shorter pulmonary artery acceleration time - PA acceleration time (p = 0.006), lower left atrial lateral wall myocardial velocity (a') (p = 0.018) and lower septal systolic myocardial velocity (s') (p = 0.023), compared with Group II. Patients with HF and reduced EF (HFrEF) had lower hemoglobin (p = 0.007), higher baseline heart rate (p = 0.005), higher NT-ProBNP (p = 0.001), larger LA (p = 0.004), lower septal s', e', a' waves, and septal mitral annular plane systolic excursion (MAPSE), shorter PA acceleration time (p < 0.001 for all), lower lateral MAPSE, higher E/A & E/e', and shorter LVFT (p = 0.001 for all), lower lateral e' (p = 0.009), s' (p = 0.006), right ventricular e' and LA emptying fraction (p = 0.012 for both), compared with HFpEF patients. In multivariate analysis, only LA diameter [2.676 (1.242-5.766), p = 0.012], and diabetes [0.274 (0.084-0.898), p = 0.033] independently predicted poor 6-MWT performance in the group as a whole. In HFrEF, age [1.073 (1.012-1.137), p = 0.018] and LA diameter [3.685 (1.348-10.071), p = 0.011], but in HFpEF, lateral s' [0.295 (0.099-0.882), p = 0.029], and hemoglobin level [0.497 (0.248-0.998), p = 0.049] independently predicted poor 6-MWT performance.
Conclusions: In HF patients determinants of exercise capacity differ according to severity of overall LV systolic function, with left atrial enlargement in HFrEF and longitudinal systolic shortening in HFpEF as the the main determinants.
Keywords: Doppler echocardiography; Exercise capacity; HFpEF; Heart failure; Six-minute walk test.