Science commentary: Coronary angioplasty and stenting
Authors: Iqbal Malik, Abi Berger
Journal: BMJ (2002)

Two main interventions are available for opening up blocked coronary arteries: balloon angioplasty and open heart surgery. In percutaneous coronary angioplasty a wide lumen catheter is fed from the groin up to the aortic root and into the coronary arteries. A guide wire is passed through the catheter and across the stenosis in the coronary artery. The wire is used to guide a balloon (with a stent mounted on it if necessary) into the diseased section of the artery. The balloon is inflated, pushing the atheroma outwards and enlarging the lumen of the artery. A stent can be expanded to fit the artery. Once the stent is in place (confirmed by angiography), the wires and the catheter are removed.

Arterial restenosis remains a serious problem after percutaneous coronary angioplasty. It tends to occur within three months of the procedure and is due to proliferation of smooth muscle as a reaction to vessel injury. Restenosis used to occur in over 30% of patients after percutaneous coronary angioplasty, but with the use of stents and advances in stent design and improved techniques for implanting them the rates now lie between 10% and 20%.1,2 This is comparable to the 10% of vein grafts that are lost in the year after bypass grafting. The main risk factors for restenosis after percutaneous coronary angioplasty are diabetes, thrombus formation or inflammation in the coronary tree, and small vessel size.

Two recent trials found no difference between percutaneous coronary angioplasty plus stenting and bypass surgery for death or myocardial infarct in patients without diabetes within two years of the procedure. Angina does, however, recur more commonly after percutaneous coronary angioplasty and stenting than it does after bypass surgery.3,4 Despite this, percutaneous coronary angioplasty remains the more popular choice, and the number of procedures that are performed each year is increasing. Percutaneous coronary angioplasty usually requires just one or two days in hospital, and patients can expect to be back at work within a week. Surgery is much more invasive and requires lengthy rehabilitation.

No trials have looked specifically at people with diabetes, but subgroup analyses of existing trials indicate that angioplasty is not as successful as surgery for these patients.3,5 This reflects the higher acute risk of percutaneous coronary angioplasty in a diabetic patient and the higher restenosis rate. However, with the advent of the glycoprotein Iib-IIIa receptor blockers (given intravenously at the start of the procedure), new data indicate that the risks may match that of people with no diabetes.6,7 These agents reduce platelet aggregation, which in turn reduces the risk of clot formation. A multicentre trial presently under way in the United Kingdom compares percutaneous coronary angioplasty and stenting and the concomitant use of glycoprotein IIb-IIIa blockers with modern coronary artery bypass grafting. Preliminary results are expected within two years.

Stent development has enabled percutaneous coronary angioplasty to catch up with bypass graft surgery. Stent insertion using intravascular ultrasound guidance is the key to longer term success. In addition, localised radiotherapy at the time of stent implantation helps to reduce proliferation of smooth muscle. The newest stents (which are expensive and not yet in general use) are made of metal coated with a cytostatic agent such as sirolimus or paclitaxel.8,9 These agents are released slowly and locally to reduce proliferation of smooth muscle. Early trials with these newer stents suggest that less than 5% of people will have arterial restenosis.