The purpose of this study is to determine the relationship between levels of metabolites, such as lactate in the sweat of the skinm, and the severity of heart failure. We hope to determine whether the levels of lactate and other metabolites on the skin change as heart failure severity improves during a hospitalization. This information oculd also be used to develop ways to detect worsening heart failure severity using a sweat-based test. The study seeks to recruit patients admitted to Tufts Medical Center due to decompensated heart failure. There are 2 study visits which each require the collection of 15ml of fasted venous blood, a completed KCCQ, and holding a damped gauze between the palms for 2 minutes. The baseline study visit takes place within 72 hour of admission and the second study visit takes place within 3 and 60 days of the baseline visit when the patient meets criteria for clinical stability.