Postmortem discovery of a rare five-vessel aortic arch with aberrant right subclavian artery and bilateral vertebral artery origin variants: embryological analysis and perioperative implications.

Complex aortic arch branching variants with multiple direct branches and variant vertebral artery origins are rare and typically incidental. We report a postmortem-confirmed case of a rare five-vessel aortic arch configuration identified in a 65-year-old man who underwent elective mitral and tricuspid valve repair for severe mitral regurgitation. The postoperative course was complicated by delayed neurological deterioration and fatal tonsillar herniation. Examination of the thoracic aorta revealed a five-branch aortic arch consisting of the right common carotid artery, left common carotid artery, left vertebral artery arising directly from the arch, left subclavian artery, and an aberrant right subclavian artery with a retroesophageal course. The right vertebral artery originated anomalously from the proximal right common carotid artery. This rare vascular configuration highlights the embryological complexity of multi-branch aortic arch variants and suggests potential implications for vertebrobasilar perfusion during cardiothoracic procedures. Recognition of such variants through careful preoperative imaging of the supra-aortic vessels may help reduce unforeseen perioperative risks.