Coronary Artery Disease

Cardiovascular disease is the leading cause of death in Western Europe and North America, accounting for about one third of all deaths. Coronary artery disease, which results in local narrowing (stenosis) and even occlusion of coronary arteries impairing the blood and oxygen supply to the heart, is the single most important causing factor. Traditional treatments for coronary artery disease include drug therapy, catheter-based treatments like balloon angioplasty with or without stent implantation, and coronary artery bypass surgery.

Drug therapy is non-invasive, and can alleviate some of the symptoms of heart disease. To date, however, it is not a cure for coronary artery disease, and is aimed primarily at patients with less severe disease.

Catheter based treatments (Percutaneous Coronary Interventions, PCI) are mostly based on inflatable balloon-tipped devices, which are inserted into the bloodstream through a small incision and which are then guided to the site to be treated using X-ray imaging. An expandable mesh-like metallic tube called a stent may be left in place permanently to improve long term patency (openness) by preserving the result of dilating the narrowed vessel by balloon inflation. Lacking the patient trauma associated with surgery, these treatments have become increasingly popular over the last fifteen years, rising to an estimated 645,000 procedures in the US alone in 2005. However, not all coronary artery narrowings and occlusions are suitable targets for this therapy. In addition, the possibility of restenosis, or recurrence of the local narrowing, is a distinct disadvantage as it may necessitate reintervention within six months in 10-35% of the cases. In recent years, stents coated with a drug to counteract restenosis have improved results, but may be associated with other risks like late stent thrombosis or late stent migration.

Coronary Artery Bypass Surgery (CABG) is characterized by the routing of one or more healthy blood vessels to locations downstream of the narrowed sites in coronary arteries. These bypass vessels can be either vein grafts harvested from the patient’s leg, or arteries from the arm or from the inside of the chest wall. The first two have two free ends that are connected upstream (proximal) to the aorta for their blood supply, and downstream (distal) to the target coronary artery. Arteries freed from the chest wall generally keep their own supply of blood as they are severed only on one end. Patients undergoing CABG typically receive 3 grafts, one from the chest wall that requires a distal connection or anastomosis, while the other two are connected to the aorta requiring a proximal and a distal anastomosis each. Conventional CABG surgery is invasive and traumatic to the patient, as it typically requires opening the chest by splitting the sternum, stopping the heart and connecting the blood circulation to a pump to establish cardiopulmonary bypass (CPB). This is necessary to provide the surgeon access to the heart and a motionless field to enable manually suturing the anastomoses. This is a delicate task that requires optical magnification, dexterity and many years of training owing to the small size of the vessels that typically measure 1.25-2.5 mm in diameter. Despite these difficulties, CABG is still the most effective treatment for extensive coronary artery disease, achieving the best long-term patient outcomes as measured by survival rate and need for reintervention. Especially arterial grafts have excellent long-term patency and durability. For this reason the left internal mammary artery (LIMA), harvested from the inside of the chest, is typically connected to the left anterior descending (LAD), the artery on the heart that is most critical to survival. The number of patients undergoing CABG in the USA was estimated to be 261,000 in 2005.

Coronary Artery Disease