Recent studies suggest important gender differences in the pathophysiology and prognosis of ST-segment elevation myocardial infarction (STEMI). This is the first prospective controlled study to assess gender differences in the mechanism of plaque rupture/erosion and thrombus formation in patients presenting with STEMI treated with primary angioplasty. Gender-related mechanisms of plaque rupture or erosion will be investigated using a combination of Quantitative Coronary Angiography, high resolution Optical Coherence Tomography of the culprit vessel and histopathologic analyses of thrombus aspirates of the infarct related lesion, performed by independent core laboratories, blinded to group (male or female) and clinical variables.

In OCTAVIA; enrollment in a 1:1 ratio according to gender group will be ensured by a computer-assisted matching algorithm for gender and age (< 50, 51-70, and > 70 years). Matching has the purpose to enable enrollment of an even number of male and female patients in balanced age groups. This type of dynamic algorithm is appropriate when the composition of the referral population is not known in advance.

OCTAVIA will assess gender differences in the mechanism of plaque rupture. The study will also evaluate the changes in the vascular territory remote from the infarct related lesion, the local vascular response to primary angioplasty interventions and the correlation with clinical outcomes over one year of follow-up. These data are important to support a gender based differential strategy and can have a substantial impact for the improvement of clinical practice in the treatment of women with STEMI.

The study sample of 140 patients is sized to address the hypothesis that the female population has a lower prevalence of plaque rupture (primary endpoint) at baseline OCT than the male population. Computations were conducted assuming a prevalence of rupture of 82% in males and 60% in female patients (22% lower).

Confirmatory power calculation was performed on the basis of stent Strut Coverage at 9 month follow-up (co primary endpoint). Stent-strut coverage and apposition have been linked to the risk of stent thrombosis. However, our understanding of DES healing in male and female patients with ST-segment elevation myocardial infarction is restricted to post-mortem data. The investigators assumed a per patient stent strut coverage (a continuous variable with right skewed distribution) with mean of 97.0% and standard deviation of 4.0% in men, versus mean of 95.0% and standard deviation of 4.0% in women, following Xience Prime implantation. Thus, aiming for a 5% 2-tailed superiority alpha, an 80% power, and assuming a 1:1 enrollment according to gender, a total of 64 patients per group should be enrolled. Anticipating a 10% dropout rate due to patients lost to follow-up and inadequate imaging (included major side branch sections), the total enrollment is set at 70 patients per group (total population of 140 subjects).

Inclusion Criteria:

• Acute Myocardial MI with ST segment Elevation, within 6 hours from symptoms onset
• Native coronary artery disease (no prior stent implant, no prior brachytherapy)
• Signed patient informed consent

Exclusion Criteria:

• Patients with left main disease
• infarct lesions in bypass grafts
• cardiogenic shock
• renal failure
• recent major bleeding
• allergy to aspirin or clopidogrel
• on anticoagulant therapy
• no suitable anatomy for OCT (extreme tortuousity, very distal culprit lesion, and large infarct vessel > 4 mm in diameter)