Thrombotic Occlusion of an Aortic-Root Xenograft during Left Ventricular Assistance

Abstract

A 45-year-old man underwent repair of a congenital bicuspid aortic valve and complex aortic-root aneurysm with an aortic-root xenograft. A CentriMag® left ventricular assist device was implanted for cardiac support and was subsequently replaced with a HeartMate II® left ventricular assist device. A day later, the patient was returned to the operating room for control of bleeding, and thrombotic occlusion of the prosthetic aortic valve was detected. The patient underwent thrombus removal, oversewing of the prosthetic valve, and bypass of the left anterior descending coronary artery. This case emphasizes the hazard of bypassing a failed left ventricle with a cardiac assist device after aortic valve replacement, even with a bioprosthesis.

Postcardiotomy support with a left ventricular assist device (LVAD) after aortic valve and aortic root replacement presents a unique challenge. Even in the presence of a prosthetic aortic valve, aortic-root stasis can result in valve thrombosis. We describe the case of a patient who had thrombosis of an aortic-root xenograft during LVAD support after undergoing repair of a complex aortic aneurysm.

Case Report

A 45-year-old man was admitted to our hospital for repair of an aneurysm of the aortic root, ascending aorta, and proximal transverse aortic arch. He had a congenital bicuspid aortic valve, with severe valvular insufficiency. The aortic root and valve were replaced with a 25-mm Freestyle® porcine aortic-root xenograft (Medtronic, Inc.; Minneapolis, Minn). Flow in the dominant left main coronary artery was preserved by means of a hemi-Cabrol procedure.¹ Postoperatively, the patient could not be weaned from cardiopulmonary bypass, so a CentriMag® LVAD (Levitronix®, LLC, a subsidiary of Pharos, LLC; Waltham, Mass) was implanted for temporary support. One week later, the CentriMag pump was removed. However, because of further difficulties in weaning the patient from cardiopulmonary bypass, a HeartMate II® LVAD (Thoratec® Corporation; Pleasanton, Calif) was implanted with a graft-to-graft anastomosis to the ascending aorta for long-term support.

The next day, the patient was returned to the operating room for control of bleeding and chest closure. Transesophageal echocardiography showed thrombotic occlusion of the bioprosthetic aortic-root xenograft. Once cardiopulmonary bypass support was initiated, exposure of the aortic root disclosed a fully formed thrombotic occlusion of the aortic valve with a cast that anatomically duplicated the aortic valve cusp. After removing the thrombus (Fig. 1), we oversewed the leaflets of the prosthetic valve directly with Teflon-reinforced sutures (Fig. 2). The origin of the left main coronary artery was compromised, so we used a saphenous vein graft to bypass the artery.

Fig. 1 Photograph shows thrombus as a cast of the aortic valve with the coronary orifice.

Fig. 2 Intraoperative photograph shows the pledgeted 4-0 polypropylene sutures that were used to coapt the cusps and close the bioprosthetic aortic valve.

Postoperatively, the patient required hemodialysis 3 times weekly for acute renal failure. Three months after implantation of the HeartMate II, however, his renal function had fully recovered, and he no longer needed hemodialysis. His postoperative recovery was otherwise uneventful. After more than 2 years of HeartMate II support, he remained in New York Heart Association functional class I while awaiting cardiac transplantation as an outpatient.

Discussion

We have described the case of a patient who developed thrombosis of an aortic-root xenograft while being supported by an LVAD. The occlusion occurred despite intermittent opening of the aortic valve during the support period. This case emphasizes the hazard of bypassing a failed left ventricle with a cardiac assist device after aortic valve replacement—even if the valve is a bioprosthesis. In such cases, care must be taken to ensure that only partial left ventricular unloading occurs, allowing the aortic valve to open consistently and fully. If left ventricular function seems so impaired that this is impossible, it may be advisable to oversew or occlude the valve at the time of LVAD implantation.