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, and research is underway to determine if drug-coated balloons also improve restenosis outcomes.]] 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 re-narrowed. 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 vascular damage from atherosclerosis and related narrowing and re-narrowing (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 and 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 have 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.
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.
However late loss is only part of the terminology in describing the outcomes of vascular interventions. For instance, the implantation of a stent graft will first provide an acute gain in lumen diameter. In other words, there is an immediate gain in lumen size because the implanted stent opens up the vessel. However, over time, the body's inflammatory immune response (described below in the "Causes" section) reacts to the stent graft via smooth muscle proliferation, etc., which pushes the stent graft back, narrowing the vessel and losing at least a percentage of what was previously gained, or late loss.
The net gain of lumen diameter is the difference between acute gain and late loss and is a measure of stent-graft effectiveness.
There is some controversy over the accuracy of observing the lesion MLD itself, since many atherosclerotic lesions may create uneven "hills and valleys" within the lumen, making a true MLD difficult to obtain or estimate. Some research indicates calculating "area stenosis" is also a valid measure of actual vessel stenosis compared to diameter stenosis alone, but this requires additional analysis because a tracing of the lumen border must be performed. However, there are computer programs available to automatically perform this function. It may be helpful to obtain both percent diameter and area percent stenosis, especially since the two percentages may not always correlate with each other.
An occlusion, or the blocking of all blood flow through a vessel, is considered 100% percent diameter stenosis.
Drug-eluting stents, coated with pharmaceuticals that inhibit tissue growth and thus reduce the risk of restenosis from scar tissue and cell proliferation, are now widely used. These stents reduce the occurrence of restenosis, with clinical studies showing an incidence rate of 5% or lower.
If restenosis occurs within a stent (also known as in-stent stenosis), it may be treated with repeated angioplasty and insertion of another stent inside the original, often with a drug-eluting stent.
Over the past 5 years, ISR has been increasingly treated with a drug-coated balloon (DCB), which is a balloon coated with the same anti-cancer drugs that prevent restenosis, such as Paclitaxel. The balloon avoids the need for a double layer of metal which is used when an in-stent restenosis is treated with another stent within the original stent. Additionally, DCB treatment does not leave an implant in the body and is designed for faster drug delivery.
Alternative treatments include brachytherapy, or intracoronary radiation. The radiation kills cells and inhibits tissue growth (similar to a patient undergoing cancer therapy).
A 2010 study in India comparing coronary drug-eluting stents (DES) with coronary (BMS) reported that restenosis developed in 23.1% of DES patients vs 48.8% in BMS patients, and female sex was found to be a statistically significant risk factor for developing restenosis.
However, in newer-generation DES and BMS the restenosis rates are much lower. For example, the NORSTENT trial, presented in 2016, reports target-lesion revascularization rates of 5.3% and 10.3% for DES and BMS respectively.
The 2006 SIROCCO trial compared the sirolimus drug-eluting stent with a bare nitinol stent for atherosclerotic lesions of the subsartorial artery, reporting restenosis at 2 year follow-up was 22.9% and 21.1%, respectively.
A 2009 study compared bare nitinol stents with percutaneous transluminal angioplasty (PTA) in subsartorial artery disease. At 1 year follow-up, restenosis was reported in 34.4% of stented patients versus 61.1% of PTA patients.
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