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Dr Diana R Holdright
MD, FRCP, FESC, FACC, MBBS, DA, BSc

Consultant Cardiologist

Dr Diana Holdright
 
 

Treatments - Coronary Angioplasty

Coronary angioplasty, also called percutaneous coronary intervention (PCI) or the balloon and stent procedure, is a treatment used to deal with tight narrowings in the coronary arteries that are affecting the blood supply to the heart. Coronary angioplasty was first undertaken in the 1970s, and since that time many remarkable technological advances have greatly increased the types of heart conditions that can be successfully treated with this technique. Originally used in stable, so called elective, situations to treat angina caused by a narrowing in one coronary artery, angioplasty is now a highly effective treatment for patients with a number of narrowings in one, two or all three coronary arteries, and not only in the stable elective situation but also in the emergency treatment of a heart attack, so called primary angioplasty. Indeed, the results are so good that primary angioplasty has become the treatment of choice for a heart attack, replacing thrombolysis, the clot buster medicine given as an injection into the vein, which had for many years been the standard treatment.

The technique bears some similarities to coronary angiography, in that it is also performed in the catheter laboratory with very similar equipment, but there are also fundamental differences, the most important being that angiography is an investigative tool, but angioplasty is a treatment. In preparation for the procedure the patient must not eat or drink for 4 to 6 hours beforehand; usual medication should be taken with a sip of water, but generally speaking water tablets (diuretics) are omitted on the day. Diabetics are given special advice, particularly those taking metformin or insulin, as are patients on warfarin. During the procedure itself, under local anaesthetic a fine flexible tube 2 to 3 mm in diameter is passed up the artery from the groin or wrist to the coronary artery using X-ray guidance. An extremely fine wire is passed along this tube, into and beyond the narrowing in the coronary artery. A very small deflated balloon is then passed over the wire and up to the site of the narrowing. There it is inflated, pushing the atheroma (furring up) into the vessel wall to relieve the obstruction to blood flow. This simple concept is surprisingly effective. However, if only a balloon is used, approximately one third of the narrowings recur, typically within the first four months of the procedure, which may well herald the return of anginal symptoms, known as restenosis.

In the 1980s coronary stents were developed to minimise the problem of restenosis. A bare metal stent is a precision-made tube of mesh, constructed from materials such as stainless steel or cobalt chromium, premounted on a deflated angioplasty balloon, such that when the balloon is inflated the stent expands to form a scaffold to keep the artery open. This enlarges the diameter of the vessel more than simple balloon angioplasty alone would achieve, and allows more blood to pass through, improving or relieving the symptoms of angina. The stent is typically a permanent device which remains in the artery when the deflated balloon is removed. Following stent insertion the likelihood of the narrowing recurring to the extent that angina returns is low, and significantly lower than with balloon angioplasty alone.

In recent years research has focused on reducing restenosis rates even further. Although the rates are much lower after stenting than after simple balloon angioplasty, there is still a possibility of restenosis. This led to the development of drug-eluting stents, which are impregnated with minute amounts of a drug that inhibits the process of restenosis. The results are very impressive, with restenosis rates in single figures, such that drug-eluting stents are now used preferentially over bare metal stents in most cases, especially in cases involving smaller arteries or longer narrowings, where restenosis rates with bare metal stents are typically higher.

After stent implantation the coronary artery forms a thin layer of cells over the stent struts. Until this is complete the metal struts have the potential to provoke clot or thrombus formation within the stent, which carries the risk of a heart attack. This is minimised by taking a combination of two blood thinners, aspirin and either clopidogrel or prasugrel, for a set period of time, following which most patients can reduce to aspirin alone. Dual antiplatelet therapy, with aspirin and clopidogrel or prasugrel, is given for a time period which is determined by the clinical scenario and the type of stent implanted; bare metal stents may only need this combination therapy for one month if implanted in an elective situation, while drug-eluting stents require the combination for one year and sometimes more, and most patients treated as emergency cases are given this treatment for up to one year. There are also occasions where a patient may be advised to remain on both drugs indefinitely.   

More recently bioabsorbable stents have been developed, which gradually dissolve over time, leaving behind only the healed natural artery. They have several potential advantages over metal stents; in particular they are less likely to cause clots and so the requirement for dual antiplatelet therapy will be reduced. This is currently an area provoking considerable interest and research.

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