Complications / risks

Complications depend on the skills of the operator:

• overall mortality of 0.2%
• acute myocardial infarction in 3-5% of patients
• acute coronary occlusion in 1.4% of patients which requires an emergency CABG

Balloon dilatation and stent implantation injure the vessel wall. Healing occurs by migration and proliferation of smooth muscle cells and fibroblasts. Eventually the treated segment, including the stent struts, becomes covered by endothelium. Until the struts are endothelialised platelet aggregation leading to thrombotic occlusion of the stent is an ever present risk

• stent thrombosis occurs in around 1-2% of patients and, though most frequent during the first month, can occur several months or even years after the procedure (1)
  • usually presents with acute myocardial infarction and is accompanied by a high mortality
    • long-term clinical outcome after a first definite stent thrombosis is unfavorable, with a high mortality and recurrence rate
      • diabetes mellitus, left ventricular ejection fraction <45%, long total stent length, complex coronary lesions, TIMI (Thrombolysis In Myocardial Infarction) flow grade <3 after percutaneous coronary intervention, and implantation of an additional coronary stent during the emergent percutaneous coronary intervention for the stent thrombosis were associated with this unfavorable outcome (2)
• when healing is excessively proliferative the tissue encroaches on the lumen to cause restenosis; typically this develops within the first three to six months and is usually manifested by a return of angina
  • in contrast to stent thrombosis, restenosis rarely causes myocardial infarction
  • symptomatic restenosis occurs in between 4 and 20 percent of stents placed in native vessels, depending on factors that include the type, length and diameter of the stent; the number implanted, the coronary segment treated and the complexity of the lesion
  • diabetes and renal impairment are major risk factors for restenosis, and stents in old degenerated venous bypass grafts have a failure rate (restenosis or occlusion) of up to 50 percent

Reference:

• (1) British Heart Foundation Factfile (May 2008). Managing patients with coronary stents
• (2) van Werkum JW et al.Long-term clinical outcome after a first angiographically confirmed coronary stent thrombosis: an analysis of 431 cases. Circulation. 2009 Feb 17;119(6):828-34