EComment. Aortic thrombus after aortic valve bypass surgery

Abstract

Conventional aortic valve replacement (AVR) carries significant operative risks, especially in the elderly, high-risk patients with severe aortic valve stenosis including porcelain ascending aorta, complex left ventricular outflow tract obstruction, previous cardiac surgery (patent coronary grafts) or prior sternal infection, and previous radiation to the mediastinum. Transcatheter aortic valve implantation (TAVI) is an alternative therapeutic option in these complicated situations. Nevertheless, TAVI has some limitations in patients with severe aorto-iliac disease, small aortic annulus (<18 mm), and previous prosthetic valve. It is associated with an increased incidence of major stroke, an injury to atrioventricular conduction system, and major vascular complications. Due to a higher incidence of complications of TAVI, aortic valve bypass (AVB, apicoaortic conduit) surgery may be a therapeutic means of choice in high-risk patient populations with comorbidities. We read the article by Lund et al. [1] with great interest. The authors have shared with us their Danish experiences regarding AVB. They are to be commended for reminding us of another alternative in the armamentarium for the treatment of severe aortic stenosis. The authors clearly stated the benefits of AVB. However, there is mention of a few serious complications. We would like to add a short comment concerning the complications of AVB. AVB involves the use of a valved conduit to connect the left ventricular apex to the descending aorta, thereby providing an additional outlet for blood flow and relieving the left ventricular pressure overload. Despite these advantages, there are likely concerns about malperfusion, aortic stasis and the potential for complications concerning the conduit. The potential complications of AVB include bleeding, thromboembolic events, porcine valve deterioration, endocarditis, myocardial infarction, arrhythmias, pseudoaneurysm formation of left ventricular apex graft anastomosis, conduit dehiscence from left ventricular apex, ventricular septal defect as reported by the authors, and thrombus formation in the aorta. Aortic thrombus is a rare moribund complication of AVB and needs to be recognized. There have been some case reports of thrombus formation in the ascending aorta possibly caused by stagnation of native antegrade blood flow and fractionation of the cardiac output [2-5]. Parsa et al. [2] reported catastrophic complication of thrombus in the aortic root after AVB in a patient with severely left ventricular dysfunction, which required a left ventricular assist device. On the contrary, Takeda et al. [3] reported unusual thrombus formation in the aortic arch after AVB for severe aortic stenosis with good left ventricular ejection fraction. Kotani et al. [4], by postoperative cine MRI study, reported that 29% of the cardiac output occurred through the native aortic valve but antegrade flow had decreased to 6% of the cardiac output at one year after surgery. Takahashi et al. [5] described that thrombus formation may be due to flow competition after AVB, especially in cases with poor left ventricular function. Despite these undesired complications, we think that AVB still remains a safe and alternative option for a few high-risk complex patients in whom surgical AVR or TAVI is not feasible. Conflict of interest: none declared.