Survival Analysis / Echocardiography / Heart Failure / Humans / Female / Male / Body Mass Index / Middle Aged / Tumor necrosis factor-alpha / Prognosis / Sensitivity and Specificity / Exercise Test / Oxygen Consumption / Proportional Hazards Models / Predictive value of tests / Male / Body Mass Index / Middle Aged / Tumor necrosis factor-alpha / Prognosis / Sensitivity and Specificity / Exercise Test / Oxygen Consumption / Proportional Hazards Models / Predictive value of tests