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Percutaneous coronary intervention (PCI) is a general concept covering procedures in the coronary arteries carried out via a catheter, eg, balloon angioplasty, for the purpose of widening a narrowed part of a vessel (stenosis). However, narrowing may later recur in a stenosis that has been widened (restenosis). Insertion of a thin, net-shaped, metal prosthesis (stent) has been shown to reduce the risk for restenosis by nearly half in comparison to balloon angioplasty alone. In comparing balloon angioplasty alone versus balloon angioplasty with stents, no differences have been found in the risks for mortality or myocardial infarction. During 2003, approximately 13 000 PCI procedures were performed in Sweden, whereof most involved the use of stents. A continuing problem is that symptoms may return due to tissue growing from the vascular wall in the stent (in-stent restenosis). Methods that involve coating the stent surface with drugs to prevent the growth of tissue in the stent (Drug Eluting Stents – DES) are currently being tested.
Seven randomized trials, covering 3 559 patients with narrowing in a single vessel, have compared treatment with drug eluting stents (DES) versus treatment with noncoated stents (Bare Metal Stents - BMS). Followup (up to one year) has shown that, on average, 4 percent of the patients treated with DES had undergone at least one repeat intervention in the stenosis. The corresponding percentage in the group treated with BMS varied among the studies, ranging from 11 percent to 21 percent. Some of the restenoses that led to repeat interventions were detected via the followup angiography specified by the protocol. Hence, it is unknown how many of these would have led to repeat intervention if the decision had been based solely on the recurrence of symptoms in the patient. Analysis of a registry of 958 consecutive patients from the Netherlands compared the results from routine treatment using DES and BMS respectively. When patients symptoms were used as the indication for re-intervention, the results showed that 3.7 percent of those receiving DES versus 10.9 percent of those receiving BMS had undergone at least one repeat intervention, eg, PCI or CABG (bypass surgery), within one year.
No comparisons between DES and BMS treatment groups have been reported with respect to symptoms, quality of life, or use of medication following intervention. In followup lasting up to one year, no difference was found in mortality or the occurrence of myocardial infarction between groups treated with DES or BMS, either in randomized trials or the registry. In the randomized trials, the risk for subacute thrombosis was less than 1 percent for both DES and BMS. Compared to BMS, the use of DES is thought to be associated with a higher rate of malapposition ie, on followup examination the entire surface area of the stent was not attached to the vessel wall. At 18-month followup, this was not found to result in any complications.
A drug eluting stent costs, on average, about 11 000 Swedish kronor (SEK) more than a stent that is not drug eluting. The additional cost to the Swedish health services of changing to DES, at the current volume of PCI, is estimated to be approximately 220 million SEK per year. Part of this cost would be offset by a decrease in the need for repeat procedures to treat restenosis. An analysis has shown cost savings of approximately 8 million SEK per year for every percentage point of decline in the need for repeat procedures. Nevertheless, the savings do not outweigh the additional cost of using DES. No studies were identified that investigated the cost effectiveness of changing to DES.
There is strong scientific evidence that DES treatment – in comparison to BMS – reduces the risk for restenosis in the stent (Evidence grade 1)*. Followup lasting up to one year has shown that fewer repeat interventions have been performed in patients treated with DES in comparison to patients treated with BMS (Evidence grade 1)*. The extent to which this has affected patients symptoms, well being, or the use of medication has not been reported. Followup lasting up to one year provides no support for differences in risks of myocardial infarction or death between DES and BMS. Likewise, there is no support for differences in side effects and complications between DES and BMS.
*Grading of the level of scientific evidence for conclusions. The grading scale includes four levels; Evidence grade 1 = strong scientific evidence, Evidence grade 2 = moderately strong scientific evidence, Evidence grade 3 = limited scientific evidence, Evidence grade 4 = insufficient scientific evidence.
This summary is based on a report prepared at SBU in collaboration with Assoc. Prof. Lars Grip, Sahlgrenska University Hospital, Göteborg and Assoc. Prof. Bengt Brorsson, SBU, Stockholm. It has been reviewed by Assoc. Prof. Per Tornvall, Karolinska Institute, Stockholm. The following manufacturers were given the opportunity to comment on this report: Boston Scientific Nordic AB and Johnson & Johnson.
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