Background <p>Acute type-A aortic dissection is a life-threatening condition requiring urgent intervention. Among its complications, coronary malperfusion is particularly fatal. Although rare, coronary artery stenosis after surgical repair is critical yet underrecognized.</p> Case presentation <p>A 77-year-old man underwent emergency aortic arch replacement for acute type-A aortic dissection. Intraoperative transesophageal echocardiography (TEE) initially showed no coronary involvement. However, ST-segment elevation and new hypokinesia appeared post-repair. TEE identified progressive left main coronary artery stenosis. Coronary angiography confirmed severe stenosis, leading to urgent coronary artery bypass grafting. The patient recovered well and was discharged on postoperative day 33.</p> Conclusions <p>This case highlights the importance of intraoperative TEE for early detection of coronary complications following acute type-A aortic dissection repair. Dissection can progress even after aortic replacement surgery and requires vigilance. Careful monitoring and prompt intervention are crucial to optimize the outcome of these rare but life-threatening events.</p>