Aorto-Right Atrial Fistula Caused by Subacute Type A Aortic Dissection Six Months After Double Valve Replacement: A Case Report and Literature Review

Abstract

Type A aortic dissection (TAAD) in Stanford classification after previous cardiac surgery is a rare but serious complication, with an incidence of 0.1%-0.2%. Previous sites of cannulation, cross-clamping, and anastomosis of vein grafts have been reported as potential entry points for aortic dissection. In some cases, the aortic dissection ruptures into a neighboring atrial chamber due to dense postoperative adhesions. In this report, we present a rare case of TAAD with an aorto-right atrial fistula after double valve replacement (DVR) and provide a literature review. A 76-year-old Japanese man presented with exertional dyspnea due to severe aortic regurgitation, moderate to severe mitral regurgitation, and paroxysmal atrial fibrillation. Preoperative plain computed tomography (CT) revealed ascending aorta and sinus of Valsalva diameters of 45 mm each. DVR and left atrial appendage (LAA) occlusion were performed. He was uneventfully discharged on postoperative day (POD) 21. Six months after the discharge, the patient complained of chest and back pain, orthopnea, and appetite loss. A family doctor firstly diagnosed him with muscle pain and belatedly realized that he suffered from acute heart failure and possible TAAD, leading to his referral to our hospital. Contrast-enhanced CT and echocardiography revealed an aorto-right atrial fistula caused by a subacute TAAD. Despite medical management, heart failure could not be controlled, necessitating emergency surgery. During the operation, the entry point of the TAAD was identified as a healthy aortic wall located just behind the previous aortotomy. An 8-mm fistula into the right atrium was observed from the false lumen. The fistula was closed with two 4-0 polypropylene felted mattress sutures only from the false lumen side and the ascending aorta was replaced with J-graft. Postoperative magnetic resonance imaging revealed a left pontine infarction, but all other postoperative examinations were unremarkable. The patient was transferred to another hospital on POD 43. Six months after the TAAD operation, he underwent 1-debranching thoracic endovascular aortic repair (TEVAR) for residual descending aortic dissection. He has been alive for five years since the TEVAR. Successful closure of the fistula and replacement of the ascending aorta were achieved in a patient with aorto-right atrial fistula caused by subacute TAAD after DVR and LAA occlusion. When preoperative imaging shows an ascending-aorta diameter ≥45 mm, it may be reasonable to discuss the concomitant replacement of aortic root, ascending aorta and partial /hemi arch, and the cannulation strategies, in line with American College of Cardiology and the American Heart Association (ACC/AHA) Class IIa guidance. Given the paucity of AAF cases after valve surgery, further multicenter series or registry data are needed to validate the optimal diameter threshold and cannulation approaches for preventing postoperative dissection.

Keywords: aortic atrial fistula; aorto-right atrial fistula; dissection rupture; double valve replacement; type a aortic dissection.

Figure 1. Preoperative findings of double valve replacement

A. Plain computed tomography revealed that the ascending aorta was 45 mm in diameter (orange arrow, axial view). B. The sinus of Valsalva was 45 mm in diameter (blue arrow, sagittal view).

Figure 2. Preoperative findings of type A aortic dissection

A: Chest radiography revealed cardiac and mediastinal enlargement. B: Contrast-enhanced CT showed that the dissected ascending aorta had enlarged to 60 mm in diameter (orange arrow). C: The reduced use of contrast agent made it difficult to identify the dissection entry point. D: The right atrium had enlarged to 96 mm (green arrow). E: Transthoracic echocardiography revealed a shunt flow (white arrow) from the false lumen of the ascending aorta (Ao) to right atrium (RA). The yellow arrowhead indicates the medial flap. RV is right ventricle.

Figure 3. Intraoperative findings

A: A 3-cm intimal tear (white arrow) was identified in the healthy aortic wall just behind the previous aortotomy, extending longitudinally from the sinotubular junction B: A fistula (yellow arrow) communicated between the false lumen (red arrow) of the ascending aorta and the right atrium. The blue arrow indicates true lumen. C: The outer layer of the fistula (yellow arrow) was robust. D: The fistula’s outer layer was closed using two 4-0 polypropylene felted sutures (purple arrows) from the false lumen side alone. E: We achieved successful closure of the fistula and central repair by replacement of the ascending aorta (black arrow).