Methods of treating a subject having a cardiovascular disease, selecting a therapy for a subject having a cardiovascular disease, identifying a subject having a cardiovascular disease that will benefit or not benefit from exercise therapy, determining whether a subject having a cardiovascular disease should begin, continue, not begin, discontinue, or avoid exercise therapy, determining whether a subject having a cardiovascular disease should continue, discontinue, or avoid exercise therapy, reducing the risk of an adverse outcome (e.g., death) in a subject having a cardiovascular disease, and predicting the efficacy of exercise therapy in a subject having a cardiovascular disease. These methods include determining a level of soluble ST2 in a subject.