Background: Thrombolytic therapy is well established as first-line treatment in patients with ST-segment elevation myocardial infarction (STEMI). However, primary percutaneous coronary intervention (PCI) has compared favorably with thrombolytic therapy and may be associated with better long-term mortality rates. Stenestrand and colleagues compared outcomes in patients receiving prehospital thrombolysis (PHT) or in-hospital thrombolysis (IHT) versus PCI.

The Study: Using comprehensive registry data, the authors of this prospective, observational, cohort study gathered outcomes data for patients with STEMI who were admitted to coronary care units in Sweden from 1999 to 2004. They calculated propensity scores to evaluate the likelihood of patients receiving PCI rather than the other options. Patient age was divided into tertiles, and additional adjustments were made for delays in time to treatment.

Results: Of the 39,192 patients, most (26,205, or 66.9 percent) received reperfusion therapy, with 7,084 (18.2 percent) receiving PCI; 3,078 (8.3 percent) receiving PHT; and 16,043 (41.3 percent) receiving IHT. Patients receiving PHT and PCI were mostly men, were younger, were more likely to smoke, had lower rates of heart failure, and had lower Killip scores. They were less likely to be taking diuretics and more likely to be taking aspirin, beta blockers, and statins. For various reasons, use of PCI in STEMI patients increased from 8.3 percent at the start of the study to 37.2 percent at the end of the study. Median delay times (time from symptom onset to intervention) were 167 minutes for IHT, 120 minutes for PHT, and 210 minutes for patients receiving PCI. PCI was performed after PHT or IHT in patients whose pain did not resolve with thrombolysis. In addition, nearly one half of patients with initial PHT and one third of those receiving initial IHT had PCI within two weeks of their STEMI event.

Hospital stays were shorter with PCI than with IHT and PHT, even after adjusting for baseline characteristics. After adjustment, in-hospital reinfarction rates and readmission rates for acute myocardial infarction within one year were lower for PCI than for PHT and IHT. Primary PCI also resulted in lower mortality than IHT at seven days, 30 days, and one year, and lower mortality than PHT at 30 days and one year.

Conclusion: In accordance with previous trials, PCI had favorable survival outcomes compared with PHT and IHT. Thrombolytic therapy is preferable only if PCI is delayed more than six to seven hours, and PHT or IHT appear to have equivalent survival outcomes with PCI only if they are administered within two hours of symptom onset.