Friday, January 20, 2012

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Percutaneous coronary intervention

PCI consists of balloon angioplasty followed by stenting.

Balloon angioplasty expands the coronary lumen by stretching and tearing the atherosclerotic plaque and vessel wall. The atherosclerotic plaque is also redistributed a little along its longitudinal axis. Elastic recoil of the stretched vessel wall generally leaves a 30 to 35 percent residual diameter stenosis. Although stand-alone balloon angioplasty is rarely used other than for very small (<2.25 mm) vessels, balloon angioplasty remains integral to PCI for predilating lesions before stent placement, deploying coronary stents, and further expanding stents after deployment.

Coronary stents are currently used in more than 90 percent of PCI procedures worldwide. Coronary stents lowers the incidence of vessel closure. Restenosis after coronary stent placement occurs in some patients due to excessive intimal hyperplasia within the stent.

While bare metal coronary stents reduce the incidence of angiographic and clinical restenosis compared to balloon angioplasty, angiographic restenosis (follow-up diameter stenosis >50 percent) still occurs in 20 to 30% of patients and clinical restenosis (recurrent angina due to restenosis in the treated segment) develops in 10 to 15 percent of patients in the first year after treatment. Restenosis with bare metal coronary stents occurs more often in patients with small vessels, long lesions, and in patients with diabetes mellitus. Use of drugs has not prevented restenosis after stent placement.

Drug-eluting stents, on the other hand, provide sustained local delivery of an anti-proliferative agent at the site of vessel wall injury. Trials have demonstrated the benefit of drug-eluting stents in patients with long (>20 mm length) and small (<2.5 mm) vessels.  This type of stent placement requires extended (up to 1 year) therapy with the combination of aspirin and clopidogrel to prevent stent thrombosis.


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