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PCI or stent procedure - an explanation

To perform a percutaneous coronary intervention, the operator 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, which is inserted under local anaesthetic either through the femoral artery at the top of the leg, or the radial artery at the wrist. The 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. This is called a coronary angiogram.

Once the narrowing or blockage in the artery has been identified on the angiogram, the PCI procedure starts. A very thin wire is manipulated under x-ray control to cross the narrowing. This wire will 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 The balloon is then deflated and withdrawn, leaving the stent in place.

 

 

Once the artery has been treated, the wire is withdrawn, and the catheter removed.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.

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.

The first stents were tubular wire meshes (“bare metal stents”) but some of these re-narrowed because of scar tissue developing inside the stent. 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 technology and the routine use of two antiplatelet drugs (dual anti-platelet therapy) have led to improved outcomes.

 

Currently there is a risk of less than 1 % per year of the treated vessel blocking abruptly due to clot formation.

List of abbreviations
ACS Acute Coronary Syndrome
BCIS British Cardiovascular Intervention Society
CABG Coronary Artery Bypass Grafting
CHD Coronary Heart Disease
ECG Electrocardiogram
MACCE Major Adverse Cardiovascular and Cerebrovascular Event
NSTEMI Non ST elevation Myocardial Infarction
PCI Percutaneous Coronary Intervention
STEMI ST elevation Myocardial Infarction
UA Unstable Angina

Analysis of PCI operator outcomes

Individual operator outcomes from performing PCI