Background: Prodromal angina pectoris (AP) has a cardioprotective effect by the mechanism of ischemic preconditioning, and the QRS score on the admission electrocardiogram (ECG) reflects myocardial damage at presentation. This study was undertaken to investigate the effect of prodromal AP on infarct progression after the onset of acute myocardial infarction (AMI).
Methods and results: The study group comprised 291 patients with a first ST-elevation AMI who underwent coronary angiography within 24 h of symptom onset. QRS score was calculated from the admission ECG. Patients were divided into 3 groups according to elapsed time from onset of AMI to angiography: early group (<2 h), intermediate group (2-6 h) and late group (6-24 h). Prodromal AP was defined as angina occurring 24 h before the onset of AMI. Patients with prodromal AP (n=101; 35%) had a significantly lower QRS score than those without (2.4+/-2.4 vs 3.2+/-3.0, P=0.02). In patients without prodromal AP, the QRS score linearly increased as elapsed time increased: 2.6+/-2.8, 3.0+/-3.0 and 5.5+/-2.9 in the early, intermediate and late groups, respectively. In patients with prodromal AP, the QRS score remained low until 6 h after onset and then increased: 2.0+/-1.8, 2.0+/-2.1, and 4.1+/-3.3, respectively.
Conclusions: The findings suggested that prodromal AP might delay infarct progression during the early hours after the onset of AMI and extend the window of time for reperfusion therapy.