The study is designed to find out more about how mood and the nervous system affect the body's immune system. The investigators plan to study this in people who have been identified by their physician as being at-risk for the development of heart failure. There will be approximately 525 individuals participating in this study at UCSD and at the VASDHS. Individuals who will be asked to take part in this study will have a functional or structural heart problem apparent on an echocardiogram, or a previous heart attack, but no symptoms of heart failure. Some individuals will only complete one assessment (consisting of psychological questionnaires and interview, walk test, blood draw, and body measurements), whereas others deemed "high-risk" on the basis of a laboratory test, will be asked to complete that same assessment every 6 months for the duration of the study.

Inclusion Criteria:

1. Age range 18 years or older
2. ACC/AHA classification Stage B HF patients
3. Receiving optimal treatment according to their cardiologist and/or internists
4. An echocardiogram within the past 12 months
5. Ejection fraction: as described below in Initial Screening and Identification of Stage B Patients
6. Men and women of all ethnicities and races
7. Ability and physician clearance to perform mild exercise
8. With and without depressive symptoms and DSM-IV MDD
9. Ability to fully understand all elements of and sign the written informed consent before initiation of the study

Exclusion Criteria:

1. History of recent myocardial infarction (3 months)
2. Significant aortic or mitral stenosis, angina not adequately managed with nitrates
3. Coronary revascularization, mitral valve repair or any other cardiac surgery or implantation of a biventricular pacemaker within the past 2 months
4. Hypertension >180/110 mm Hg
5. Recent stroke or significant cerebral neurological impairment
6. Severe COPD, patients who require mechanical ventilation, with cardiogenic shock, volume depletion
7. Subjects with high suicide risk
8. Immune-related disorders including infectious diseases and autoimmune and inflammatory disorders
9. Morbid Obesity: BMI > 40 due to likelihood of inability to perform exercise
10. Women who are pregnant or nursing
11. Major mental illness as determined by referring provider

American College of Cardiology/American Heart Association (ACC/AHA) asymptomatic Stage B patients with B-Type natriuretic peptide (BNP) ≥ 65pg/ml