Percutaneous coronary intervention

Percutaneous coronary intervention (PCI), commonly known as coronary angioplasty or simply angioplasty, is a non-surgical procedure used to treat the stenotic (narrowed) coronary arteries of the heart found in coronary heart disease. These stenotic segments are due to the build up of cholesterol-laden plaques that form due to atherosclerosis. PCI is usually performed by an interventional cardiologist, though was developed and originally performed by interventional radiologists.

During PCI, a cardiologist feeds a deflated balloon or other device on a catheter from the inguinal femoral artery or radial artery up through blood vessels until they reach the site of blockage in the heart. X-ray imaging is used to guide the catheter threading. At the blockage, the balloon is inflated to open the artery, allowing blood to flow. A stent is often placed at the site of blockage to permanently open the artery.

Coronary artery bypass grafting (CABG), which bypasses stenotic arteries by grafting vessels from elsewhere in the body, is an alternative treatment. Most studies have found that CABG is better than PCI for reducing death and myocardial infarction. PCI has proven to be as effective and less costly than CABG in patients with medically refractory myocardial ischemia.

However, coronary revascularization by coronary artery bypass graft (CABG) is associated with an increased risk of stroke.

Medical uses
PCI does not have any benefit over taking appropriate medications for those with stable coronary artery disease. In those with unstable disease however it is beneficial.

Bare-metal stents (BMS) and drug-eluting stents (DES) result in an equivalent chance of death when used for primary angioplasty of ST elevation myocardial infarction. Cobalt-chromium stents which elutes everolimus appear to clot off less often than other types of stents including bare metal stents.

Adverse events
Coronary angioplasty is widely practiced and has a number of risks; however, major procedural complications are uncommon. Coronary angioplasty is usually performed by an interventional cardiologist, a medical doctor with special training in the treatment of the heart using invasive catheter-based procedures.

The patient is usually awake during angioplasty, and chest discomfort may be experienced during the procedure; the reporting of symptoms indicates the procedure is causing ischemia and the cardiologist may alter or abort part of the procedure. Bleeding from the insertion point in the groin or wrist is common, in part due to the use of anti-plateletclotting drugs. Some bruising is therefore to be expected, but occasionally a hematoma may form. This may delay hospital discharge as flow from the artery into the hematoma may continue (pseudoaneurysm) which requires surgical repair. Infection at the skin puncture site is rare and dissection (tearing) of the access blood vessel is uncommon. Allergic reaction to the contrast dye used is possible, but has been reduced with the newer agents. Deterioration of kidney function can occur in patients with pre-existing kidney disease, but kidney failure requiring dialysis is rare. Vascular access complications are less common and less serious when the procedure is performed via the radial artery.

The most serious risks are death, stroke, VF(non-sustained VT is common), myocardial infarction (heart attack) and aortic dissection. A heart attack during or shortly after the procedure occurs in 0.3% of cases; this may require emergency coronary artery bypass surgery. Heart muscle injury characterized by elevated levels of CK-MB, troponin I, and troponin T may occur in up to 30% of all PCI procedures. Elevated enzymes have been associated with later clinical outcomes such as higher risk of death, subsequent MI and need for repeat revascularization procedures. Angioplasty carried out shortly after a myocardial infarction has a risk of causing a stroke of 1 in 1000, which is less than the 1 in 100 risk encountered by those receiving thrombolytic drug therapy.

As with any procedure involving the heart, complications can sometimes, though rarely, cause death. Less than 2 percent of people die during angioplasty. Sometimes chest pain can occur during angioplasty because the balloon briefly blocks off the blood supply to the heart. The risk of complications is higher in:
 * People aged 75 and older
 * People who have kidney disease or diabetes
 * Women
 * People who have poor pumping function in their hearts
 * People who have extensive heart disease and blockages

Controversy
The value of angioplasty in rescuing someone having a heart attack (by immediately alleviating an obstruction) is clearly defined in multiple studies, but studies have failed to find reduction in hard endpoints for angioplasty vs. medical therapy in stable angina patients. The artery-opening procedure can temporarily alleviate chest pain, but does not contribute to longevity. The "vast majority of heart attacks do not originate with obstructions that narrow arteries".

Procedures
The term balloon angioplasty is commonly used to describe percutaneous coronary intervention, which describes the inflation of a balloon within the coronary artery to crush the plaque into the walls of the artery. While balloon angioplasty is still done as a part of nearly all percutaneous coronary interventions, it is rarely the only procedure performed.

Other procedures that are done during a percutaneous coronary intervention include:
 * Implantation of stents
 * Rotational or laser atherectomy
 * Brachytherapy (Use of radioactive source to inhibit restenosis.)

Sometimes a small mesh tube, or "stent", is introduced into the blood vessel or artery to prop it open using percutaneous methods. Angioplasty with stenting is a viable alternative to heart surgery for some forms of non-severe coronary artery disease. It has consistently been shown to reduce symptoms due to coronary artery disease and to reduce cardiac ischemia, but has not been shown in large trials to reduce mortality due to coronary artery disease, except in patients being treated for a heart attack acutely (also called primary angioplasty). In acute cases, there is a small but definite reduction of mortality with this form of treatment compared with medical therapy, which usually consists of the administration of thrombolytic ("clot busting") medication.

Technique
The angioplasty procedure usually consists of most of the following steps and is performed by physicians, physician assistants, nurse practitioners, nurses, radiological technologists and cardiac invasive specialist; all of whom have extensive and specialized training in these types of procedures.


 * 1) Access into the femoral artery in the leg (or, less commonly, into the radial artery or brachial artery in the arm) is created by a device called an "introducer needle". This procedure is often termed percutaneous access.
 * 2) Once access into the artery is gained, a "sheath introducer" is placed in the opening to keep the artery open and control bleeding.
 * 3) Through this sheath, a long, flexible, soft plastic tube called a "guiding catheter" is pushed. The tip of the guiding catheter is placed at the mouth of the coronary artery. The guiding catheter also allows for radiopaque dyes (usually iodine based) to be injected into the coronary artery, so that the disease state and location can be readily assessed using real time x-ray visualization.
 * 4) During the x-ray visualization, the cardiologist estimates the size of the coronary artery and selects the type of balloon catheter and coronary guidewire that will be used during the case. Heparin (a "blood thinner" or medicine used to prevent the formation of clots) is given to maintain blood flow.
 * 5) The coronary guidewire, which is an extremely thin wire with a radio-opaque flexible tip, is inserted through the guiding catheter and into the coronary artery. While visualizing again by real-time x-ray imaging, the cardiologist guides the wire through the coronary artery to the site of the stenosis or blockage.  The tip of the wire is then passed across the blockage.  The cardiologist controls the movement and direction of the guide wire by gently manipulating the end that sits outside the patient through twisting of the guidewire.
 * 6) While the guidewire is in place, it now acts as the pathway to the stenosis. The tip of the angioplasty or balloon catheter is hollow and is then inserted at the back of the guidewire—thus the guidewire is now inside of the angioplasty catheter.  The angioplasty catheter is gently pushed forward, until the deflated balloon is inside of the blockage.
 * 7) The balloon is then inflated, and it compresses the atheromatous plaque and stretches the artery wall to expand.
 * 8) If an expandable wire mesh tube (stent) was on the balloon, then the stent will be implanted (left behind) to support the new stretched open position of the artery from the inside.

Coronary stenting
Traditional ("bare metal") coronary stents provide a mechanical framework that holds the artery wall open, preventing stenosis, or narrowing, of coronary arteries. In normal patients in the usual case, stenting during PCI for an ST elevation myocardial infarction (STEMI) in a hemodynamically stable patient is not recommended because evidence does not show a likelihood of positive outcome for this and does show increased mortality and complications. Medical societies therefore recommend against stent placement into a noninfarct artery during PCI. Percutaneous transluminal coronary angioplasty (PTCA) with stenting, when indicated, has been shown to be superior to angioplasty alone in patient outcome by keeping arteries patent for a longer period of time.

Newer drug-eluting stents (DES) are traditional stents that are coated with drugs, which, when placed in the artery, release certain drugs over time. It has been shown that these types of stents help prevent restenosis of the artery through several different physiological mechanisms, which rely upon the suppression of tissue growth at the stent site and local modulation of the body's inflammatory and immune responses. Five drugs, Biolimus A9, Zotarolimus, sirolimus, everolimus and paclitaxel, have demonstrated safety and efficacy in this application in controlled clinical trials by stent device manufacturers. However, in 2006 three broad European trials seem to indicate that drug-eluting stents may be susceptible to an event known as "late stent thrombosis", where the blood-clotting inside the stent can occur one or more years post-stent. Late stent thrombosis occurs in 0.9% of patients, and is extremely dangerous and is fatal in about one-third of cases when the thrombosis occurs. New generation DES products, such as the BioMatrix stent marketed by Biosensors International since January 2008 in Europe, seek to eliminate this risk by using a biodegradable coating.

History
Coronary angioplasty, also known as percutaneous transluminal coronary angioplasty (PTCA), because it's done through the skin and through the lumen of the artery, was first developed in 1977 by Andreas Gruentzig. The first procedure took place Friday Sept 16, 1977 at Zurich, Switzerland. Adoption of the procedure accelerated subsequent to Gruentzig's move to Emory University in the United States. Gruentzig's first fellow at Emory was Merril Knudtson, who, by 1981, had already introduced it to Calgary, Alberta, Canada. By the mid-1980s, many leading medical centers throughout the world were adopting the procedure as a treatment for coronary artery disease (CAD).

Angioplasty is sometimes erroneously referred to as Dottering, after Interventional Radiologist, Dr Charles Theodore Dotter, who, together with Dr Melvin P. Judkins, first described angioplasty in 1964. As the range of procedures performed upon coronary artery lumens has widened, the name of the procedure has changed to percutaneous coronary intervention (PCI).