BackgroundThere are very limited data investigating the influence of previous myocardial infarction (MI) on the clinical characteristics and in-hospital outcomes of recurrent acute MI(re-AMI) patients (pts). Method: The study population consisted of 12,925 consecutive AMI pts enrolled in the Korea Acute Myocardial Infarction Registry (KAMIR) study from November 2005 to April 2008. Among them, 1,227 (9.49%) pts presented with acute myocardial re-infarction (re-AMI group). We compared the clinical characteristics and in-hospital outcomes of re-AMI pts with those of first-onset AMI (first-AMI group, n=11,698). Results: The baseline characteristics were largely unfavorable in re-AMI group over first-AMI group. Pts in re-AMI group were older (64.95짹12.3 vs 63.3짹12.7, p=0.001), more male (74.1% vs 70.0%, p=0.003), NSTEMI (50.9% VS 37.9%, P<0.001), worse cardiac function (Killip III/IV, 21.1% vs 13.0%, p<0.001), and more prior revascularization history (p<0.001) than those of first-AMI group. Angiographic findings also demonstrated unfavorable characteristics in re-AMI group including more multi-vessel disease (p<0.001), smaller culprit vessel diameter (3.08짹0.43 vs 3.16짹0.43, p<0.001), less procedural success rate (p<0.001) and more CABG (p<0.001). Patients with re-AMI showed worse in-hospital outcomes including higher in-hospital mortality rate (6.4% vs 4.9%, p=0.018) and more complications (16.5% vs 13.4%, p=0.002) than those of first-AMI group. Conclusion: Patients with re-AMI presented with worse baseline clinical and procedural characteristics and these factors might have translated into worse in-hospital outcomes. Special caution and care should be exercised to the recurrent AMI pts who had history of previous MI.