Valve Sparing Aortic Root Replacement

Introduction

The aortic root is the most proximal part of the aorta. It has a unique 3-dimensional configuration which also has a clover-like dilation of the sinuses of Valsalva. In this structure, the aortic valve forms a three-pronged crown. Each valve leaflet is attached to the aortic wall in a semilunar fashion, running from its basal attachment within the left ventricle to the distal attachment at the sinotubular junction. The imaginary circle which connects the lowest point on each semilunar attachment is called as the basal ring. The anterior half of the basal ring is muscular and posterior half is fibrous. The anterior half includes the base of the left and right coronary sinuses. The fibrous portion is considered weaker and easy to dilate. The semilunar attachment forms a somewhat hemodynamic (but not an anatomical) junction between the left ventricle and the aorta. The anatomical ventriculo-aortic junction is the circle lying just above the basal ring. The bundle of His lies immediately below the membranous ventricular septum. The diameter of the aorta at the ST junction is 81% of the diameter at the aortic sinuses and 97% at the basal ring.

The aortic root functions to channel blood but also supports the aortic valve leaflets. The clover-like dilation of sinuses of Valsalva is crucial for creating appropriate eddy currents in the supravalvular region. These eddies are important for initiating and coordinating aortic valve closure and promoting coronary artery blood flow.

Most aneurysms in the aortic root region are associated with degenerative changes in the elastic media of the aortic wall. However, in other regions of aorta, the major cause of aneurysms is usually atherosclerosis. This probably correlates with the higher concentration of elastic fibers in the media of the aortic root. The histological features of aortic root aneurysms are cystic medial degeneration, elastic fiber fragmentation and smooth muscle loss. Aortic root aneurysms can cause severe complications such as aortic rupture and dissection but also secondary aortic valve regurgitation. This occurs as a result of distorted 3D conformation of the aortic root and aortic valve complex. Aortic ectasia and aortic dissection are most common causes of mortality in patients with Marfan’s syndrome. Aneurysms associated with the bicuspid aortic valve are also a common pathology.

Most aneurysms in the aortic root region are associated with degenerative changes in the elastic media of the aortic wall.

Yacoub and colleagues and David and colleagues introduced a new technique called as valve-sparing aortic root replacement (VSRR). This method has the greatest advantage of eliminating the need for lifelong therapy with anticoagulant drugs. It also prevents potential risks related to prosthetic valves. Concomitant AR may also be caused due to disruption of the leaflets from their orientation as a result of enlargement of the aortic root. This type of AR could be repaired by restoring the original root geometry even without replacing the valves.

VSRR procedure

The VSRR procedure includes remodeling and reimplantation. Remodeling is also known as the Yacoub procedure. In this method, a scalloped graft is sutured to the sinus remnant situated around the attachment of the valve leaflets. Reimplantation is known as the David procedure which involves suturing of a cylindrical graft to the basal ring, and then suturing the sinus remnant to inside of the aortic graft. Coronary ostia are also re-implanted into the aortic prosthesis during both procedures in the same way as performed in the Bentall operation. One difference between the two procedures is the number of aortic suture lines. 2 rows are used in remodelling and 3 rows of sutures are used in reimplantation. Both VSRR techniques have achieved excellent early results, but they have pros and cons regarding aortic root physiology and aortic root support.

Remodeling is generally considered as a more rapid and technically less complicated procedure. The advantages of remodeling are that a billowed graft mimics the natural sinus of Valsalva. The absence of sub-annular sutures preserves some distensibility within the complex. These features allow more physiological leaflet motion or less cusp-closure stress. Therefore this technique is considered to enhance the long-term durability of the valve. One disadvantage of remodeling is that the absence of sub-annular sutures can create a risk of future postoperative annular dilation, resulting in recurrent AR. Another drawback is that two exposed aortic suture lines can result in a predisposition to severe bleeding.