The purpose of clinical research is to look at the nature of disease and try to develop improved methods to diagnose and treat disease.The goal of this study is to evaluate the use of computed tomography (CT) scan of the heart in the diagnosis of disease in vein grafts after bypass surgery.

Patients who have bypass surgery with using vein grafts from their legs (saphenous veins) have a very high risk of developing blockages in the grafts. It has been shown in previous studies that the progression of disease in vein grafts is very quick and can result in chest pain, heart attacks or death. In the past, evaluation of the grafts was possible with heart catheterization only. The technique of CT scan is currently considered an effective way to look at vein grafts as well as the arteries around the heart to identify blockages.

Certain blood proteins have been associated with rapid progression of vein graft blockages. Our purpose is to not only to identify blockages at different stages after bypass surgery, but to investigate the causes of the rapid progression of the disease, including clinical history, risk factors and the blood proteins.

Inclusion Criteria:

1. Ability to provide informed consent.
2. Age equal to or greater than 18 years.
3. One(-/+60days), 3 (-/+60days), 5 (-/+60days), or 7 (-/+60days) years after coronary artery bypass graft surgery.

Exclusion Criteria:

1. Renal (kidney) insufficiency (creatinine greater than or equal to 1.6) or renal (kidney) failure requiring dialysis.
2. Atrial fibrillation (type of heart rhythm) or other markedly irregular rhythm.
3. Inability or refusal to provide informed consent.
4. Pregnancy or unknown pregnancy status.
5. Age less than 18 years.
6. Clinical instability as deemed by the attending physician, including cardiogenic shock, hypotension (low blood pressure-systolic blood pressure less than 90 mmHg), refractory hypertension (high blood pressure) (systolic blood pressure greater than 180 mmHg), sustained ventricular or atrial arrhythmia (types of heart rhythm) requiring intravenous medications.
7. Inability to tolerate beta-blockers, including those with chronic obstructive pulmonary disease (temporary narrowing of the tubes in the lungs) (or asthma requiring maintenance inhaled bronchodilators or steroids, complete heart block (chambers in the heart not beating in sync), second-degree atrioventricular block (chambers in the heart not beating in sync).
8. Known contrast dye allergy.

Referrals from physicians' office Patients' self-referral Age greater than 18 years old Both genders