Prevalence of Aortic Intimal Defect in Surgically Treated Acute Type A Intramural Hematoma

Background. Controversies exist regarding the pathogenesis and adequate management of intramural hematoma (IMH) of the aorta that has been commonly defined as a dissection without intimal tear. Recent studies reported that intimal defects are found in some patients diagnosed as IMH. We aimed to investigate the prevalence of such cases in surgically treated patients. Methods. Preoperative and postoperative computed tomographic (CT) scan images were retrospectively reviewed for 37 patients who underwent surgery for Stanford type A acute IMH. Operative findings were also reviewed from the medical records. Results. In 18 patients (48.6%), intimal defects were suggested in preoperative computed tomography ( CT). During surgery, 27 patients (73.0%) had small intimal defects in the ascending aorta or arch, while 14 of them (51.9%) did not have preoperative CT findings suggestive of intimal defects. In 18 patients, the defects were located in the arch or distal ascending aorta, where they would not have been found if not inspected under total circulatory arrest. In all patients, the identified intimal defects were included in the aortic resection, or locally closed. Follow-up CT done at 4 months or longer after surgery showed that the IMH in the descending aorta disappeared or markedly improved in all patients. Conclusions. On the basis of our results, we think that a large proportion of IMH may have a similar pathogenic mechanism as classic dissection and the conventional definition of IMH should be changed. For type A lesions treated with surgery, we recommend thorough inspection of the ascending aorta and the arch under hypothermic circulatory arrest.