Background—The modern imaging techniques of transesophageal echocardiography, CT, and MRI are reported to have up to 100% sensitivity in detecting the classic class of aortic dissection; however, anecdotal reports of patient deaths from a missed diagnosis of subtle classes of variants are increasingly being noted.

Methods and Results—In a series of 181 consecutive patients who had ascending or aortic arch repairs, 9 patients (5%) had subtle aortic dissection not diagnosed preoperatively. All preoperative studies in patients with missed aortic dissection were reviewed in detail. All 9 patients (2 with Marfan syndrome, 1 with Takayasu’s disease) with undiagnosed aortic dissection had undergone ≥3 imaging techniques, with the finding of ascending aortic dilatation (4.7 to 9 cm) in all 9 and significant aortic valve regurgitation in 7. In 6 patients, an eccentric ascending aortic bulge was present but not diagnostic of aortic dissection on aortography. At operation, aortic dissection tears were limited in extent and involved the intima without extensive undermining of the intima or an intimal “flap.” Eight had composite valve grafts inserted, and all survived. Of the larger series of 181 patients, 98% (179 of 181) were 30-day survivors.

Conclusions—In patients with suspected aortic dissection not proven by modern noninvasive imaging techniques, further study should be performed, including multiple views of the ascending aorta by aortography. If patients have an ascending aneurysm, particularly if eccentric on aortography and associated with aortic valve regurgitation, an urgent surgical repair should be considered, with excellent results expected.