Acute medial dissection of the ascending aorta: evolution of reactive histologic changes.

BACKGROUND

The histologic reaction in the adventitia to aortic dissections may be relevant to dating the onset of symptoms and to providing insight into pathogenesis.

DESIGN

We prospectively studied 43 surgically excised acute ascending aortic dissections before false-lumen rupture, with emphasis on inflammatory reaction in the false-lumen wall in relation to duration of symptoms.

RESULTS

A total of 31 men and 13 women were included in the study. Duration of symptoms was <12 hours (n=9), 12 to 24 hours (n=12), 1 to 2 days (n=8), 2 to 7 days (n=11), and >1 week (n=3). Medial inflammation was predominantly lymphohistiocytic and was marked in 3 cases but limited to the region adjacent to the dissection plane, unlike aortitis. Adventitial neutrophils occurred before 12 hours, peaked between 12 and 24 hours, and were rare after 2 days. Eosinophils occurred after 1 day, peaked between 2 and 7 days, and were predominant between 2 and 4 days. Macrophages were present after 1 day and peaked between 2 and 7 days. Mesothelial reaction occurred only after 1 day. Apoptosis and mitotic figures involving stromal cells occurred after 12 hours and peaked between 1 and 2 days; mitotic figures persisted up to 7 days.

CONCLUSIONS

Adventitial inflammation is prominent soon after intimal injury in aortic dissections before rupture of the false lumen. The pattern of inflammation is distinct from aortitis and can be used to date early aortic dissections.