To use IVUS to assess (1) culprit plaque morphology and thrombus burden in patients with ST-elevation myocardial infarction; (2) the efficacy of thrombus removal with an aspiration catheter in 40 patients during primary PCI.

Primary PCI has become the preferred therapy for ST-elevation acute myocardial infarction. The TAPAS trial data suggests that widespread adoption of manual thrombus aspiration may improve clinical outcomes for patients undergoing primary PCI.

Little data exists on the degree to which thrombus is removed during thrombectomy and how much thrombus remains with the potential for distal embolisation during stent deployment. The mechanism of lumen enlargement after thrombus aspiration is also unknown. Since angiography only provides an outline image of the vascular lumen, such questions cannot be adequately addressed by this modality alone.

The aim of this study is to use IVUS to assess (1) culprit plaque morphology and thrombus burden in patients with ST-elevation myocardial infarction; (2) the efficacy of thrombus removal with an aspiration catheter during primary PCI.

Hypotheses In this study we will assess 40 patients with STEMI. Primary PCI will be performed according to our hospital standard working protocol with thrombus aspiration and balloon dilatation of the culprit lesion if necessary prior to stent deployment. IVUS imaging will be undertaken prior to, and following, passage of the aspirations catheter to assess (1) initial and (2) residual thrombus volume. A third and final IVUS imaging run will be performed after stenting of the culprit lesion. IVUS analysis will be performed off-line to assess the lumen enlargement and volume of residual thrombus at each stage. All studies will be undertaken with the approval of the local Clinical Research Ethics.

Aspirated material will be collected and analyzed. Clinical markers such as Troponin release and left ventricular function will be assessed.

Inclusion Criteria:

1. patients 18-75 years old with myocardial infarction with ST-segment elevation
2. symptoms of myocardial ischemia lasting more than 30 minutes
3. onset of symptoms within 12 hours of hospital presentation
4. ST-segment elevation of more than 0.1 mV in two or more leads on the ECG

Exclusion Criteria:

1. inability to obtain informed consent

2. use of fibrinolytic drug within 12 hours of presentation

3. comorbidity with anticipated life expectancy of < 6 months

4. cardiogenic shock on presentation

5. major bleeding diathesis

6. history of aspirin and clopidogrel intolerance

7. critical left main stem lesions

8. severe calcfic disease precluding safe passage of the imaging catheter

9. culprit lesion within saphenous vein grafts

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