Myocardial Infarction due to Percutaneous Coronary Intervention
The following are 10 points to remember about myocardial infarction (MI) due to percutaneous coronary intervention (PCI):
1. Periprocedural MI occurs in 5-30% of patients undergoing PCI. The wide variation in incidence of post-PCI MI is in part related to differences in local practice and diagnostic criteria.
2. Current guidelines endorse a class I recommendation for the measurement of cardiac biomarkers (the MB fraction of creatine kinase [CK-MB], cardiac troponin, or both) in patients who have signs or symptoms suggestive of MI during or after PCI, and for those undergoing complicated procedures.
3. The PCI guidelines give a class IIa recommendation for routine ascertainment of cardiac biomarkers 8-12 hours after PCI.
4. The PCI guidelines define a peri-PCI MI as a new CK-MB or troponin I or T rise greater than 5 times the upper limit of normal (ULN). The more recent universal definition of MI defines periprocedural MI as an elevation in cardiac biomarkers of >3 x ULN.
5. The major predictors of peri-PCI MI are lesion complexity (type C lesions, presence of thrombus, or lesions in a saphenous vein graft), procedural complexity (rotational atherectomy), or procedural complications (e.g., no flow or slow flow, side branch occlusion, etc).
6. While most angiographic complications are associated with peri-PCI MI, most patients with peri-PCI MI do not have an obvious underlying angiographic complication. Cardiac magnetic resonance imaging studies suggest that these infarcts may either be related to distal embolization or occlusion of small epicardial side branches.
7. Some studies suggest that any degree of post-PCI myonecrosis imparts an adverse mortality hazard with worse long-term outcome in those with greater elevation in CK-MB. Other studies suggest that this hazard is only seen in patients who have an elevation of CK-MB >5-8 x ULN, or in those who have a q wave infarction following PCI.
8. More recent studies suggest that preprocedural troponin elevation is a stronger predictor of long-term outcome, and postprocedural elevation does not appear to impart a similar risk of adverse events.
9. Compared with post-PCI MI, spontaneous MI is associated with a significantly worse long-term mortality hazard.
10. Implications for practice:
- Preprocedural troponin should be routinely obtained in all patients undergoing PCI, and those with elevated troponin should be considered for more aggressive antiplatelet therapies.
- Pre-PCI statin therapy may reduce the incidence of post-PCI MI, and this provides another reason to consider statins in all patients undergoing PCI.
- Emboli protection devices should be used if possible in patients undergoing PCI for saphenous vein graft lesions.
- Prolonging hospitalization by an extra day may be helpful in patients with a large degree of peri-PCI myonecrosis or new q wave infarct.
Keywords: Myocardial Infarction, Infarction, Atherectomy, Coronary, Biological Markers, Thrombosis, Saphenous Vein, Creatine Kinase, MB Form, Magnetic Resonance Imaging, Percutaneous Coronary Intervention
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