Left atrial dissection is defined as a gap from the mitral or tricuspid annular area into the interatrial septum. It is most commonly occurs as a complication of mitral valve surgery. Herein, a patient is described who developed a left atrial dissection subsequent to multiple mitral valve procedures. The clinical presentation and surgical therapy for this condition is described with the aid of intraoperative photographic images. A brief discussion of this rare condition is also included, and the principles of surgical repair are elucidated. The Journal of Heart Valve Disease 2012;21: Left atrial dissection (LtAD) is defined as a gap from the mitral or tricuspid annular area into the interatrial septum or left atrial wall, creating a new chamber. Herein, the details of a patient are described who developed a large LtAD subsequent to multiple mitral valve procedures. Details of the approach to this difficult problem are provided, together with a brief review of the available and relevant literature. Case report A 77-year-old male was diagnosed with severe mitral regurgitation due to flail P3 of the posterior mitral leaflet, with mild annular calcification. The patient underwent mitral valve repair and coronary artery bypass grafting with a saphenous vein graft to the distal right coronary artery. After weaning from cardiopulmonary bypass (CPB), post-procedural transesophageal echocardiography (TEE) demonstrated severe mitral regurgitation that possibly was due to a stitch tear. The patient was reoperated on and a mitral valve replacement was performed using a 27 mm tissue valve. Both of the mitral leaflets were excised, and the annuloplasty ring was removed during this procedure. On postoperative day (POD) 3 the patient began to re-experience dyspnea at rest, and orthopnea. A repeat TEE suggested the presence of severe periprosthetic regurgitation around the anterior commissure, with a regurgitant volume of 52 ml as determined by the proximal isovelocity surface area method. A dissection flap was noted in the left atrium, demonstrating a true and a false lumen. The separation existed from the anterior part of the mitral annulus in a curvilinear manner towards the left lower pulmonary veins. The patient was transferred to the operating room, where an attempt was made to close the area of leakage with a large quantity of surgical glue and multiple pledgeted polypropylene sutures. He remained in a critical condition in the intensive care unit, and intra-aortic balloon pumping and TEE performed on POD 5 demonstrated a recurrence of the perivalvular regurgitation with a large LtAD. In order to define the exact anatomy of the LtAD, computed tomography (Fig. 1A) was performed that demonstrated an 8.8 × 7.5 × 5 cm chamber along the posteroinferior aspect of the left atrium. This was seen to compress the true left atrial cavity, narrowing the right-sided upper pulmonary veins and almost occluding the left inferior pulmonary veins. The defect in the periannular area (Fig. 1A, orange arrow), which was the neck of this dissection, could also be seen on the CT scan. A pre-procedural TEE (Fig. 1A-C) performed at the present authors’ institution had demonstrated a compressed true left atrial cavity with a normally functioning mitral bioprosthesis. The left lower pulmonary vein was almost obliterated, while a large periprosthetic defect was visualized that allowed a direct communication between the left ventricle and the LtAD, with an impressive oscillating flow (Fig. 1C, white arrow). Left Atrial Dissection after Mitral Valve Replacement can Mimic Periprosthetic Regurgitation Salil V. Deo 1 , Douglas A. Simonetto 2 , Salah E. Altarabsheh 1 , Sorin V. Pislaru 3 , Gregory W. Barsness 3 , Soon J. Park 1 Divisions of 1 Cardiovascular Surgery, 2 Internal Medicine and 3 Cardiovascular Diseases, Mayo Clinic, Rochester, USA Address for correspondence: Dr. Soon J. Park MD, Division of Cardiovascular Surgery, Mayo Clinic, 100 2 nd Street SW, Rochester 55905, Minnesota, USA e-mail: park.soon@mayo.edu © Copyright by ICR Publishers 2012