substance builds up in the coronary artery, the main pathway carrying oxygen-rich blood to the heart. This can cause a blockage and/or a rupture, which can lead to a heart attack. Minimally invasive surgery As an alternative to open-heart surgery, which involves a five- to eight-inch incision in the chest wall, a surgeon may perform an endoscopic procedure by making very small incisions through which a camera and specialized tools are inserted. In robot-assisted heart surgery, a machine controlled by a cardiac surgeon is used to perform a procedure. The main advantage to this is the size of the incision required: three small port holes instead of an incision big enough for the surgeon's hands. The use of robotics in heart surgery continues to be evaluated, but early research has shown it to be a safe alternative to traditional techniques. Post-surgical procedures As with any surgical procedure, cardiac surgery requires postoperative precautions to avoid complications. Incision care is needed to avoid infection and minimize scarring. Swelling and loss of appetite are common. Recovery from open-heart surgery begins with about 48 hours in an intensive care unit, where heart rate, blood pressure, and oxygen levels are closely monitored. Chest tubes are inserted to drain blood around the heart and lungs. After discharge from the hospital, compression socks may be recommended in order to regulate blood flow. Risks The advancement of cardiac surgery and cardiopulmonary bypass techniques has greatly reduced the mortality rates of these procedures. For instance, repairs of congenital heart defects are currently estimated to have 4–6% mortality rates. A major concern with cardiac surgery is neurological damage. Stroke occurs in 2–3% of all people undergoing cardiac surgery, and the rate is higher in patients with other risk factors for stroke. A more subtle complication attributed to cardiopulmonary bypass is postperfusion syndrome, sometimes called "pumphead". The neurocognitive symptoms of postperfusion syndrome were initially thought to be permanent, but turned out to be transient, with no permanent neurological impairment. In order to assess the performance of surgical units and individual surgeons, a popular risk model has been created called the EuroSCORE. It takes a number of health factors from a patient and, using precalculated logistic regression coefficients, attempts to quantify the probability that they will survive to discharge. Within the United Kingdom, the EuroSCORE was used to give a breakdown of all cardiothoracic surgery centres and to indicate whether the units