Patients presenting with acute coronary syndromes (ACS) commonly have a responsible culprit coronary lesion. There is limited data on the natural history of this culprit lesion in the short term and whether there is a change in morphology of this lesion in the days following presentation. Furthermore, the effect of antithrombotic therapy on this process is unknown.

Sixty-eight patients presenting with ACS had their diagnostic study performed at our institution and had coronary angioplasty performed a few days later at a different hospital. Culprit lesion characteristics including minimum luminal diameter (MLD) and percentage diameter stenosis were determined on each occasion.

Acute myocardial infarction patients (n=14) had improved culprit lesion characteristics at angioplasty compared to baseline (diameter stenosis 78.9% versus 62.4%, p<0.01). Similarly, patients presenting with unstable angina (UA) or non-ST elevation myocardial infarction (non-STEMI) (n=54) had improved diameter stenosis (78.0% versus 72.7%, p<0.001). The change in MLD was greater in MI patients than UAP/non-STEMI patients (0.6mm versus 0.16mm, p<0.01).

Treatment of ACS patients with aspirin with anticoagulant therapy followed by delayed intervention results in angiographic improvement in lesion severity which may provide a more favourable environment in which to undertake percutaneous coronary intervention.