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To perform a percutaneous coronary intervention, the Doctor needs to be able to visualise the coronary arteries around the heart that are to be treated (called the coronary arteries). This is done by injecting a liquid (called contrast) into those arteries so that they can be seen on an x-ray camera. The liquid is injected through a long thin tube called a catheter.
Catheters can be inserted into the heart through two main pathways. The most common in the United Kingdom is to use the radial artery which is located in the wrist. Some patients require the procedure to be performed through the femoral artery – which is found at the top of leg, near the groin. Both arteries can be accessed under local anaesthesia which is given by an injection to the area.
Once the Doctor has gained access to the artery, a catheter is then guided under x-ray imaging until its tip reaches the mouth of the coronary artery. Each time a picture of the artery is needed, contrast is injected and the x-ray camera is run and the images are recorded. This is called a coronary angiogram.
The images shown below show a typical coronary angiogram of a patient with no blockages in their heart arteries. The vessels appear smooth and there is no blockages within the main vessels.
If a narrowing or blockage in the artery has been identified on the angiogram and it is suitable and appropriate to perform treatment, then a PCI procedure or ‘angioplasty’ can be performed. PCI stands for Percutaneous Coronary Intervention. PCI involves treatment of the heart artery and can be performed at the same time as the angiogram or, in some circumstances, the patient may be scheduled to return for a planned procedure.
The PCI procedure involves passing a very thin wire into the blocked artery. The wire is manipulated under x-ray control to cross the narrowing. This wire acts as a rail to deliver the balloons and stents needed to treat the artery. Initially a balloon is passed over the wire into the narrowed segment. Inflating the balloon squashes the blockage (made of fatty tissue and sometimes clot) out of the way and widens the artery. Frequently the walls of the artery recoil once the balloon is deflated. Therefore a stent (a small metal mesh in the shape of a tube) is usually implanted to keep the artery open. The stent is supplied crimped over a deflated balloon. As the delivery balloon inflates, the stent is expanded, pressing out against the arterial wall, holding it open. The balloon is then deflated and withdrawn, leaving the stent in place.
Once the artery has been treated, the wire is withdrawn, and the catheter removed. A pressure dressing is usually used to prevents bleeding from the puncture site at the wrist until it has clotted. If the femoral artery has been used, a special closure device may be deployed to stop major bleeding.
Following a PCI, most patients return home the next day, though some patients can be treated and discharged the same day. Patients admitted following a heart attack usually remain in hospital for longer (on average 3 days). Generally PCI is a very safe treatment but complications can occasionally occur either around the time of the procedure or weeks or months later.
Potential adverse events during hospital stay
PCI procedures are occasionally associated with adverse outcomes, and the most severe of these are called ‘Major Adverse Cardiac and Cerebrovascular Events’ (MACCE). These include events such as stroke, death, heart attack or the need for emergency coronary bypass surgery. While some of these adverse events may be complications of the PCI procedure itself, most are not, and instead are a result of the heart disease itself. A more detailed explanation is given the next section.
Potential complications after discharge
After PCI, the symptoms of angina are usually improved. There follows a period when the walls of the newly stretched arteries heal. Some patients can have a sense of tightness in the chest after a recent PCI procedure; this typically settles within a day.
The first stents were tubular wire meshes (“bare metal stents”) but some of these re-narrowed because of scar tissue developing inside the stent (“restenosis”). Research led to the development of stents with a plastic coating which contained special drugs to minimise the development of scar tissue (“drug eluting stents”). Although there was a slight concern that drug-eluting stents might be a little more prone to the developments of clots after implantation (“stent thrombosis”), improvements in stent technology and the routine use of two antiplatelet drugs (dual anti-platelet therapy) have led to improved outcomes. Now, drug-eluting stents are used as standard in the United Kingdom and the latest generation of these stents have been proven to be safe in very large studies involving tens of thousands of patients.
Drug-eluting stents require patients to take ‘blood thinning medicines’ for a period of time after the procedure. Your Doctor and Cardiology team will tell you how long to take these for. You must not stop them suddenly and only do so under the advice of your Cardiologist.
Currently there is a risk of less than 1 % per year of the treated vessel blocking abruptly due to clot formation. This is more likely to occur in those who have discontinued the blood thinning medicines earlier than planned. In patients who have previous stents who have sudden onset chest pain, particularly if associated with sweating, sickness and feeling breathless, then it is essential to seek emergency care immediately.
|List of abbreviations|
|ACS||Acute Coronary Syndrome|
|BCIS||British Cardiovascular Intervention Society|
|CABG||Coronary Artery Bypass Grafting|
|CHD||Coronary Heart Disease|
|MACCE||Major Adverse Cardiovascular and Cerebrovascular Event|
|NSTEMI||Non ST elevation Myocardial Infarction|
|PCI||Percutaneous Coronary Intervention|
|STEMI||ST elevation Myocardial Infarction|