In this issue of the Journal, Brott et al1 report a series of 13 patients who developed severe, life-threatening coronary artery spasms after implantation of a drug-eluting stent. Symptoms occurred either during or immediately after the procedure or within the first 4 weeks after stent implantation. In 1 patient, vasoconstriction was present in a follow-up angiogram at 1 year. Spasms resolved in most patients after administration of vasodilators, however, 2 patients did not respond to treatment and died. Another 2 patients required placement of an intra-aortic balloon pump for cardiogenic shock. This article compliments previous case reports of single or multivessel occlusive coronary artery spasms following Cypher™ and Taxus® stent implantation.2,3 Clinically relevant coronary artery spasms have previously been described in patients after high-dose intravascular beta-radiation.4 Coronary artery spasm following percutaneous coronary intervention (PCI) is a well-recognized phenomenon. Fischell et al reported coronary artery vasoconstrictive responses after balloon angioplasty in 1988, and attributed this phenomenon either to altered coronary artery autoregulation or local effects of platelet-derived vasoactive substances such as serotonin.5,6 However, vasomotor dysfunction after angioplasty usually disappears within the first days after the intervention, and does not lead to clinical symptoms. The mechanisms involved in clinically important vasomotor dysfunction after drug-eluting stent implantation or intracoronary radiotherapy remain elusive. Vasoconstriction may be due to enhanced platelet recruitment with release of vasoconstrictive mediators at the site of angioplasty and/or endothelial dysfunction. There is indication of endothelial dysfunction following Cypher and Taxus stent implantation.7–9 Endothelial dysfunction may be due to a direct toxic effect of the released drug, an acute or delayed hypersensitivity reaction (Kounis syndrome) to the drug or the polymer,10 or impaired or absent re-endothelialization after PCI barotrauma. Systemic and local hypersensitivity reactions after drug-eluting stent implantation have been recently reported by Nebeker.11 Four of the 17 patients died of stent thrombosis. The post-mortem examination of the first case presented by Brott et al1 revealed a few scattered mast cells within the adventitia of the left anterior descending artery, possibly pointing to a hypersensitivity reaction to the stent. Hypersensitivity reactions would fit well into the “periprocedural” occurrence of spasms. Incomplete or absent re-endothelialization of the drug-eluting stent could be another explanation for persistent endothelial dysfunction with vasoconstriction late after stent implantation. Recently published data on angioscopic examinations after sirolimus-eluting stent implantation have shown incomplete neointimal stent coverage in the majority of patients.12 In summary, Brott et al1 have nicely shown that vasomotor dysfunction after drug-eluting stent implantation proves to be of clinical relevance in a subset of patients. As the cause of vascular functional impairment remains undefined, we believe that further studies need to clarify this issue. A possible link between vasomotor dysfunction and late adverse events (i.e., late stent thrombosis or in-stent restenosis) must be sought.13
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