Background: Heart failure is a major and growing societal problem characterized by high mortality, frequent hospitalization, reduced quality of life and a complex therapeutic regimen. The six-minute walking test (6-MWT) may serve as a useful and reproducible test for assessing exercise capacity in heart failure patients and has been suggested as a simple, well-tolerated and inexpensive alternative to cardiopulmonary exercise testing (CPET). The CPET and 6-MWT are the most broadly used for assessing functional limitation in patients with heart failure. Echocardiography is well qualified to meet the growing need for noninvasive imaging in the expanding heart failure population.
Methods: This study included 132 consecutive patients (61 ± 10 years, 45% women) with stable heart failure. All patients underwent 6-MWT and Doppler echocardiographic examination on the same day. Clinical, biochemical and echocardiographic predictors were analyzed to assess predictors of exercise capacity. Patients were divided into two groups based on the 6-MWT distance. The first group comprised patients with limited exercise performance (≤ 300 m), and the second group, patients with good exercise performance (>300 m).
Results: In univariate analysis, patients' age [0.931 (0.895-0.968), P < 0.001], arterial hypertension [0.481 (0.239-0.967), P = 0.040], blood urea level [0.860 (0.759-0.975), P = 0.019], New York Heart Association (NYHA) class [0.441 (0.245-0.795), P = 0.006], early diastolic E wave [1.014 (1.000-1.029), P = 0.047], total isovolumic time (t-IVT) [0.868 (0.796-0.947), P = 0.001], Tei index [0.112 (0.028-0.450), P = 0.002], and E' of left-ventricular (LV) lateral wall [1.188 (1.099-1.400), P = 0.039] independently predicted poor 6-MWT performance (<300 m). In multivariate analysis, only patients' age [0.948 (0.902-0.996), P = 0.034], arterial hypertension [0.351 (0.133-0.922), P = 0.034], and t-IVT [0.828 (0.725-0.946), P = 0.005] independently predicted poor 6-MWT performance (<300 m).
Conclusion: In chronic stable heart failure patients, in addition to age, systemic hypertension as well as LV asynchrony, as reflected by prolonged t-IVT, are independent predictors of poor exercise capacity.