Restenosis

Restenosis is the recurrence of stenosis, a narrowing of a blood vessel, leading to restricted blood flow. Restenosis usually pertains to an artery or other large blood vessel that has become narrowed, received treatment to clear the blockage and subsequently become renarrowed. This is usually restenosis of an artery, or other blood vessel, or possibly a vessel within an organ. Restenosis is the recurrence of stenosis, a narrowing of a blood vessel, leading to restricted blood flow. Restenosis usually pertains to an artery or other large blood vessel that has become narrowed, received treatment to clear the blockage and subsequently become renarrowed. This is usually restenosis of an artery, or other blood vessel, or possibly a vessel within an organ. Restenosis is a common adverse event of endovascular procedures. Procedures frequently used to treat the vascular damage from atherosclerosis and related narrowing and renarrowing (restenosis) of blood vessels include vascular surgery, cardiac surgery, and angioplasty. When a stent is used and restenosis occurs, this is called in-stent restenosis or ISR. If it occurs following balloon angioplasty, this is called post-angioplasty restenosis or PARS. The diagnostic threshold for restenosis in both ISR or PARS is ≥50% stenosis. If restenosis occurs after a procedure, follow-up imaging is not the only way to initially detect compromised blood flow. Symptoms may also suggest or signal restenosis, but this should be confirmed by imaging. For instance, a coronary stent patient who develops restenosis may experience recurrent chest pain (angina) or suffer from a minor or major heart attack (myocardial infarction), though they may not report it. This is why it is important that a patient comply with follow-up screenings and the clinician follows through with a thorough clinical assessment. But it is also important to note that not all cases of restenosis lead to clinical symptoms, nor are they asymptomatic. Surgery to widen or unblock a blood vessel usually has a long-lasting beneficial effect for the patient. However, in some cases, the procedure itself can cause further narrowing of the vessel, or restenosis. Angioplasty, also called percutaneous transluminal coronary angioplasty (PTCA), is commonly used to treat blockages of the coronary or peripheral arteries (such as in the limbs). The balloon inserted into the narrowing ‘smashes’ the cholesterol plaques (atherosclerosis) against the artery walls, thus widening the size of the lumen and increasing blood flow. However the action damages the artery walls, and they respond by using physiological mechanisms to repair the damage. (See physiology below.) A stent is a mesh, tube-like structure often used in conjunction with angioplasty to permanently hold open an artery, allowing for unrestricted blood flow, or to support a weakness in the artery wall called an aneurysm. The artery can react to the stent, perceive it as a foreign body, and respond by mounting an immune system response which leads to further narrowing near or inside the stent. Damage to the blood vessel wall by angioplasty triggers physiological response that can be divided into two stages. The first stage that occurs immediately after tissue trauma, is thrombosis. A blood clot forms at the site of damage and further hinders blood flow. This is accompanied by an inflammatory immune response. The second stage tends to occur 3–6 months after surgery and is the result of proliferation of cells in the media, a smooth muscle wall in the vessel. This is also known as Neointimal Hyperplasia (NIHA). Vessel restenosis is typically detected by angiography, but can also be detected by duplex ultrasound and other imaging techniques.