Dissecting aortic aneurysm involving a right-sided aortic arch.

In this case, the first reported instance of aortic dissection involving a right-sided arch, an anomalous fourth arch vessel, the left subclavian artery, arose from a congenital aortic diverticulum. This report emphasizes the need for precise anatomic definition with aortography to permit appropriate therapy when congenital anomalies of the aortic arch are complicated by dissecting hematoma.