In a cardiac catheterization procedure, your physician threads a thin tube called a catheter into your heart via a large vein in your groin, neck or arm. Surgical devices are then guided through the tube and used to diagnose heart problems or repair defects. The procedure can help in the diagnosis of coronary artery disease, heart valve problems and dysfunctional heart muscles. This is done by taking measures of the blood flow and pressure within the heart and via simultaneous imaging tests called coronary angiography. When blocked or narrowed coronary arteries are discovered, your cardiologist can address them through angioplasty and stenting during the cardiac catheterization. When necessary, he or she can also obtain a small sample of heart tissue for biopsy through the catheter. Patients are usually awake during cardiac catheterization and angioplasty, and can watch the entire procedure on a monitor.