Currently both bare metal stents (BMS) and drug-eluting stents (DES) are used during percutaneous coronary intervention (PCI) for acute myocardial infarction (AMI). PCI has been demonstrated to reduce the rate of death or recurrent ischaemia when compared to medical therapy. To date trials comparing DES and BMS in acute MI have been limited by small size and follow up of 1 year or less; DES were shown to reduce the number of revascularisation procedures for restenosis but no significant differences were identified between DES and BMS at 1 year either in rate of death or subsequent myocardial infarction.
This study was based on an unselected population based cohort of 7217 patients undergoing PCI with stenting for AMI over an 18 month period in Massachusetts between 2003 and 2004. Propensity score matching was performed on 3 groups of patients:
• All patients with AMI
• All patients with AMI with ST elevation (STEMI)
• All patients with AMI without ST elevation (NSTEMI)
Patients receiving both DES and BMS were excluded form the analysis. The primary outcome was death from any cause within 2 years after the index procedure. Secondary outcomes included recurrent MI and repeat revascularisation.
4016 patients received DES and 3201 received BMS. The 2 year risk adjusted mortality rates were significantly lower for DES than for BMS in all patients with MI (10.7% vs 12.8%, p=0.02). Among patients with STEMI 8.5% vs11.6%, p=0.008) and among patients with NSTEMI (12.8% vs 15.6%, p=0.04). The 2 year risk adjusted rates of recurrent MI were reduced in patients with NSTEMI who were treated with DES and repeat revascularisation rates were significantly reduced with the use of DES compared to BMS for all groups.
The study has a number of limitations:
• No difference in the rates of clinical sequelae of stent thrombosis were observed but rates of stent thrombosis could not be directly calculated from this data set.
• The study was observational and despite the propensity score matching utilised, residual confounding cannot be excluded.
• Data on infarct size, which has been shown to be an important predictor of death in patients with AMI, was not available, nor were the quantitative angiographic findings. This is a potential limitation since DES were not available in the same range of vessel diameters as BMS and small vessel stenting is known to be associated with higher risks both at the time of the index procedure and during follow-up.
Conclusion? It appears safe, and may be more effective to use DES rather than BMS in AMI. Following NICE criteria on size and length may be the best way forwards.
- Mauri L, Silbaugh TS, Garg P etal. Drug Eluting or Bare Metal Stents for Acute Myocardial Infarction. N Engl J Med 2008;359:1330-42