Coronary artery disease involves blockages in the blood vessels of the heart that result in low blood flow to the heart muscle. Low blood flow can lead to a type of chest pain called angina or, if severe enough, to heart attack. Treatment for coronary artery disease includes medicines and more invasive treatments, such as bypass surgery or percutaneous coronary intervention (PCI). With PCI, doctors insert small balloons or tunnels (stents) attached to flexible tubes (catheters) into the large blood vessels in the patient's groin and thread them up into the heart. The stent and catheter are passed through the blocked vessels, a process that opens up the vessels. Information from high-quality studies shows that compared with medications, PCI reduces angina symptoms, but it does not reduce a person's chances of having or dying of a heart attack. However, some patients and doctors mistakenly believe that PCI does more than just reduce symptoms.