Unusual thrombus formation in the aorta after apicoaortic conduit for severe aortic stenosis

Abstract

Conventional valve replacement for aortic valve stenosis has significant operative risks in patients with dense, circumferential calcification of the ascending aorta. The apicoaortic conduit (AAC) is one of the alternative methods to eliminate the aortic manipulation. Several reports have demonstrated that a newly constructed double-outlet left ventricle maintains normally distributed blood flow throughout the systemic circulation without any deleterious physiologic effects. 1,2 However, we encountered the case of a patient who had unanticipated thrombus formation in the aortic arch that might have resulted from fractionation of the cardiac output and stagnation of the blood flow after construction of the AAC. Clinical Summary A 72-year-old woman with a history of diabetes mellitus and chronic renal insufficiency requiring hemodialysis experienced progressive dyspnea on exertion. Echocardiography demonstrated severe aortic stenosis caused by a calcified valve. Cardiac catheterization demonstrated a pressure gradient of 58 mm Hg across the aortic valve, a cardiac index of 3.5 L · min 1 ·m 2 , and 90% stenosis of the proximal right coronary artery. Computed tomography showed severe circumferential aortic calcification of the whole aorta, including the aortic root. To preclude the aortic valve procedure through a median sternotomy, we inserted the AAC through the left thoracotomy. The thoracic cavity was entered through the sixth intercostal space, and cardiopulmonary bypass was initiated with distal descending aortic cannulation and right femoral venous drainage. The patient was kept normothermic, and a 20-mm Hemashield graft (Meadox, Hemashield; Boston Scientific, Boston, Mass) was sewn to the descending aorta during side clamping. Continuous infusion of -blocker was started, and the heart rate was decreased to around 30 beats/min. In a head-down position, the left ventricular apex was enucleated with a 20-mm coring knife. The valved conduit incorporating a 23-mm stentless valve (Edwards Prima Plus; Stentless Bioprosthesis, Inc, Irvine, Calif) and a 20-mm Hemashield graft was anastomosed with the apical hole. The 2 parts of the conduit were then anastomosed. A saphenous vein graft placed from the coronary orifice of the stentless valve was grafted to the right coronary artery concomitantly. The postoperative course was uncomplicated, and the patient had improvement of symptoms. Computed tomography at 1 month after the operation demonstrated unobstructed conduit (Figure 1) and unexpected thrombus formation, possibly caused by stagnation of blood flow in the aortic arch (Figure 2). Administration of sodium warfarin was initiated immediately, and no thromboembolic events have been observed. Discussion Recent modifications of the technique and innovation of the technology has made it more feasible to accomplish the AAC for various complex lesions of the left ventricular outflow tract not easily amenable to other techniques. 3,4 In our case creation of an AAC combined with coronary revascularization was successfully performed with a pharmacologically controlled beating heart, which is a new and lessinvasive procedure even with the support of cardiopulmonary bypass. Furthermore, the use of a stentless bioprosthesis enabled us to obtain a larger valve orifice and to avoid anticoagulation. The patient was freed from heart failure symptoms, and postoperative computed to