Restenosis is a re-narrowing or blockage of an artery at the same site where treatment, such as a balloon angioplasty or stent procedure, has already taken place. Restenosis literally means the reoccurrence of stenosis. This is usually restenosis of an artery, or other blood vessel, but possibly any hollow organ that has been "unblocked". This term is
common in vascular surgery, cardiac surgery or interventional cardiology following angioplasty, all branches of medicine that frequently treat stenotic lesions.
Small tears develop in the artery wall when the balloon catheter is inflated, initiating an inflammatory cascade, a natural healing response. Platelets and white blood cells from the blood flow migrate into the injured intima (inner layer of the vessel) and form a small clot. Signals stimulate smooth muscle cells (cells from the wall of the artery) to migrate and divide, filling the wound. This process is enabled by the white blood cells releasing and activating tissue-digesting enzymes, forming a path for the smooth muscle cells to move. The combination of dividing and migrating cells go on to form an obstructing scar. As the amount of scar develops, blood flow is gradually reduced, leading to a heart attack. The failure rate of angioplasty ranges from approximately 25 percent to 40 percent.
Although stents (wire cages that prop open arteries) have become popular over the past decade by demonstrating a clear benefit in treating heart disease when compared to balloon angioplasty alone, they can still carry a failure rate of approximately 25 percent. In-stent restenosis is the result of a failed stent. An uncontrollable amount of scar has overgrown, burying the stent and compromising blood flow. Whether it is restenosis or in-stent restenosis, the end result is a narrowing of the artery that may eventually block the flow of blood to your heart. This can lead to further chest pain and may require further interventions or cardiac surgery.
Cardiologist have tried a number of approaches to decrease the risk of restenosis. Stenting is becoming more commonplace; after balloon angioplasty, a metal mesh is pressed against the wall of the artery that has been opened, decreasing the risk of restenosis. Other approaches include local radiotherapy and the use of immunosuppressive drugs, coated onto the stenting mesh. Analogues of rapamycin, such as tacrolimus (FK-506), sirolimus and more so everolimus, normally used as immunosuppressants but recently discovered to also inhibit the proliferation of vascular smooth muscle cells, have appeared to be quite effective in preventing restenosis in clinical trials.
Restenosis is generally treated with a second balloon angioplasty and/or stent implementation procedure. Sometimes there is no other option than to treat with coronary bypass surgery. Once a patient experiences restenosis, there is a 50 percent chance the patient will experience it again in the future. This recurrence generally occurs within six months of initial treatment and patients often return to their doctor every few months with debilitating symptoms. Physicians have had limited treatment options for these patients.