For optimal benefits, coronary angiography and PTCA should be performed as soon as possible. Most cardiologists recommend that the time interval between the patient’s arrival at the hospital and the deployment of the angioplasty balloon to open the artery should be less than 60-90 minutes.
For best results, the coronary angiogram and PTCA should be performed by an experienced cardiologist in a well-equipped cardiac catheterization laboratory. The cardiologist is considered experienced if he or she performs more than 75 such procedures a year.
The catheterization laboratory personnel are considered experienced if the facility performs more than 200 such procedures a year.
It also is important that there be a surgical team to perform immediate open-heart surgery (coronary artery bypass grafting) in the event that PTCA is unsuccessful in opening the blocked artery or if there is a serious complication of PTCA. For example, in a small number of patients, PTCA cannot be performed because of technical difficulties in passing the guide wire or the balloon across the narrowed arterial segment. Open-heart surgery also will be necessary if there is a serious complication such as coronary artery injury during PTCA or an abrupt closure of the coronary artery shortly after PTCA. These complications may occur in 1-2% of patients.
The most serious complication of PTCA is an abrupt closure of the coronary artery within the first few hours after PTCA. Abrupt coronary artery closure (that can lead to further heart damage) occurs in 5% of patients after simple balloon angioplasty (without stenting). Abrupt closure is due to a combination of tearing (dissection) of the inner lining of the artery, blood clotting at the site of the balloon, and constriction (spasm) or elastic recoil of the artery at the site where the balloon is inflated. Individuals at an increased risk for abrupt closure include women, patients with unstable angina, and patients having heart attacks.
The risk of abrupt closure of the coronary arteries can be reduced if:
- Aspirin is given during or after PTCA to prevent blood clotting. In fact, virtually all patients are maintained on aspirin indefinitely after PTCA to prevent arterial clots.
- Anticoagulants such as intravenous heparin are given during PTCA to further prevent blood clotting.
- Combinations of nitrates and calcium channel blockers are used to minimize Coronary artery spasm (see discussion that follows).
- Coronary artery stents are deployed to minimize coronary artery closure.
- The glycoprotein IIb/IIIa inhibitors are given.
Coronary artery stents
Coronary artery stents are small hollow cylinders that can be deployed over the angioplasty balloons and left within the coronary arteries to keep the arteries open. Stents help prevent abrupt closure of arteries shortly after PTCA . They also prevent restenosis (recurrent narrowing of the arteries) several months after PTCA.
Coronary stents decrease the risks of arterial dissections, elastic recoil, and artery spasm that can occur after PTCA and cause re-occlusion of the artery. Studies have shown that the incidence of abrupt coronary artery closure after PTCA has declined dramatically with the introduction of coronary stents.
Coronary stents also help to keep the coronary arteries open in the longer-term. After a successful PTCA, as many as 30-40% of patients will develop recurrent narrowing (restenosis) at the site of inflation of the balloon, usually within 6 months following PTCA. Restenosis may or may not be accompanied by symptoms such as angina. Thus, restenosis often is detected by Exercise stress tests performed 4 to 6 months after PTCA. The widespread use of coronary stents has reduced this incidence of restenosis by as much as 50%. The recent introduction of coated stents (stents that are coated with chemicals to further reduce restenosis) has reduced the incidence of restenosis to well under 10% and has been a major improvement in treatment.
Patients with coronary artery stents usually are maintained on full doses of daily aspirin. For the first 4-12 weeks after the placement of stents, patients are given an additional anti-platelet drug such as ticlopidine or clopidogrel because the metal surface of the stents may promote the formation of blood clots in the first several weeks after the stent is inserted.
Nitroglycerin is the most common nitrate used in the treatment of heart attacks. It can be given sublingually (under the tongue), as a spray, as a paste applied over skin, and intravenously. Intravenous nitroglycerine has a rapid onset of action and is commonly used in the initial (first 48 hours) treatment of heart attacks. Nitroglycerine is a vasodilator (blood vessel dilator), which opens arteries by relaxing the muscular wall of the artery. Nitroglycerine dilates coronary arteries as well as other blood vessels throughout the body. By dilating blood vessels, nitroglycerine lowers blood pressure, decreases the work that the heart must do, lowers the demand by the heart for oxygen, prevents Coronary artery spasm, improves blood flow to the heart muscle, and potentially minimizes the size of the heart attack. Nitroglycerine is especially helpful in patients with heart attacks who also have heart failure or high blood pressure.
The common side effects of nitrates are headaches and low blood pressure. Low blood pressure can cause weakness, dizziness, and, sometimes, even fainting. Nitrates should not be given in patients who have taken medicines for erectile dysfunction such as sildenafil (Viagra) and vardenafil (Levitra) in the preceding 24 hours, since severe low blood pressure may result. Nitrates should not be given in patients who have taken tadalafil (Cialis) in the preceding 36-48 hours because the effects of Cialis last longer than either sildenafil or vardenafil .
Diseases and Conditions Center
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