Characteristics of plaque disruption by intravascular ultrasound in women presenting with myocardial infarction without obstructive coronary artery disease.

Background: In a prospective study, we previously identified plaque disruption (PD: plaque rupture or ulceration) in 38% of women with myocardial infarction (MI) without angiographically obstructive coronary artery disease (CAD), using intravascular ultrasound (IVUS). Underlying plaque morphology has not been described in these patients and may provide insight into the mechanisms of MI without obstructive CAD.

Methods: Forty-two women with MI and <50% angiographic stenosis underwent IVUS (n = 114 vessels). Analyses were performed by a blinded core laboratory. Sixteen patients had PD (14 ruptures and 5 ulcerations in 18 vessels). Plaque area, % plaque burden, lumen area stenosis, eccentricity, and remodeling index were calculated for disrupted plaques and largest plaque by area in each vessel.

Results: Disrupted plaques had lower % plaque burden than the largest plaque in the same vessel (31.9% vs 49.8%, P = .005) and were rarely located at the site of largest plaque (1/19). Disrupted plaques were typically fibrous and were not more eccentric or remodeled than the largest plaque in the same vessel.

Conclusions: Plaque disruption was often identifiable on IVUS in women with MI without obstructive CAD. Plaque disruption in this patient population occurred in fibrous or fibrofatty plaques and, contrary to expectations based on prior studies of plaque vulnerability, did not typically occur in eccentric, outwardly remodeled, or soft plaque in these patients. Plaque disruption rarely occurred at the site of the largest plaque in the vessel. These findings suggest that the pathophysiology of PD in women with MI without angiographically obstructive CAD may be different from MI with obstructive disease and requires further investigation.