**Aortic Valve Sparing Operations**

Bradley G. Leshnower and Edward P. Chen *Division of Cardiothoracic Surgery, Emory University School of Medicine* 

*USA* 

## **1. Introduction**

104 Aortic Valve Surgery

[24] Hanke T, Charitos EI, Stierle U, Robinson D, Gorski A, Sievers HH, Misfeld M. Factors

[25] Boodhwani M, de Kerchove L, Glineur D, Rubay J, Vanoverschelde JL, Noirhomme P,

[26] De Paulis R, De Matteis GM, Nardi P, Scaffa R, Bassano C, Chiariello, L. Analysis of

[27] Monti L, Mauri G, Balzarini L, Tarelli G, Brambilla G, Vitali E, Ornaghi D, Citterio E,

with cardiovascular magnetic resonance. Ann Thorac Surg 2011;91:92-96.

with a new aortic root conduit. Ann Thorac Surg 2002:53-57.

2009;137:314-319.

Thorac Cardiovasc Surg 2010;140:276-284.

associated with the development of aortic valve regurgitation over time after two different techniques of valve-sparing aortic root surgery. J Thorac Cardiovasc Surg

El Khoury G. Repair of regurgitant bicuspid aortic valves: A systematic approach. J

valve motion after the reimplantation type of valve-sparing procedure (david i)

Settepani F. Compliance of the valsalva graft's pseudosinuses at midterm follow-up

The treatment of aortic root and ascending aortic aneurysms often requires addressing concomitant aortic valve pathology. In the setting of aortic stenosis secondary to cusp degeneration, aortic valve replacement (AVR) is performed. However, when patients present with aortic insufficiency and normal cusp anatomy, a dilemma arises. Historically valve replacement has been performed; however, current options are all associated with their own specific issues. Implantation of a mechanical prosthesis commits the patient to lifelong anticoagulation and the concomitant risks of bleeding and thromboembolism. Use of a bioprosthetic valve eliminates the burden of anticoagulation, but these prostheses suffer from structural valve deterioration and commit the young patient to the potential need for a second or third operation. The optimal solution is to remove all diseased aorta while preserving and restoring the normal aortic cusps to their original geometry to allow for adequate coaptation and valve competency. The term "aortic valve-sparing operations" (AVS) was introduced by David in the 1990's to describe procedures which preserved, rather than replaced the aortic valve cusps during the treatment of aneurysms of the aortic root or ascending aorta with associated aortic insufficiency (1). These are technically demanding procedures which require in-depth knowledge and comprehension of aortic root anatomy and physiology. In this chapter we will review the anatomy and physiology of the aortic root and discuss the various AVS operations which have been used in the treatment of aortic root and ascending aortic aneurysms.

#### **2. Anatomy**

The aortic root is a complex structure composed of several components including the aortic annulus, valve cusps, sinus of Valsalva segments, and the sinotubular junction. The aortic annulus is defined by the attachment or hinge point of the cusp and has been described as scalloped or coronet shaped. It is attached to ventricular myocardium in 45% of its circumference and fibrous structures in the remaining 55%. The annulus rises from the nadir of one cusp and peaks at the commissure, the highest point of the annulus and the junction between two adjacent cusps. The area below the commissures is referred to as the subcommissural triangle.

Aortic Valve Sparing Operations 107

the STJ and the aortic valve commissures is realized when aneurysmal dilation of the STJ moves the commissures apart and results in loss of leaflet coaptation and aortic

The aortic root is a dynamic structure that expands and contracts throughout the cardiac cycle in a manner which maximizes blood flow through the aortic valve and minimizes stress on the aortic valve cusps. The components of the aortic root complex have a specific geometric relationship with each other to produce optimal hemodynamics. Pathologic alterations in any of the four components can change their interactions and result in valvular

AVS operations were designed for patients with aortic root or ascending aortic aneurysms and competent or regurgitant aortic valve function in the setting of normal cusps. Highly stenotic valves are rarely able to be preserved. The most common cause of aortic insufficiency in North America is annuloaortic ectasia. Young patients develop aortic root aneurysms beginning with dilatation of the sinus segments, followed by annular and STJ dilatation. Elderly patients can develop aortic insufficiency from ascending aortic aneurysms and subsequent dilatation of the STJ. In these patients, the aortic annulus and sinus segments are relatively normal. Marfan syndrome is the most common cause of aortic root aneurysms in young patients. Other connective tissue disorders such as ankylosing spondylitis, Ehlers-Danlos, osteogenesis imperfecta, rheumatoid arthritis, and lupus can cause aortic insufficiency. Aortic dissection is another common indication for an AVS operation. This dissection flap can extend into the aortic root and disconnect one of the aortic valve commissures from the aortic wall causing cusp prolapse and aortic insufficiency

Indications for surgical intervention upon aortic root and ascending aneurysms include the presence of symptoms, aortic size, rapid growth, and the degree of aortic insufficiency. Most patients with aortic aneurysms are asymptomatic. Symptomatic patients complain of chest pain, which is considered a sign of rapid growth, dissection or impending rupture(8). The guidelines for the treatment of asymptomatic patients are drawn from natural history studies which correlated serial aortic measurements and aortic complications (rupture or dissection). It has been demonstrated that the ascending aortic grows at a rate of 1mm/year, and by the time the diameter of ascending aneurysms reaches 6cm, patients have been

In the largest reported series from the Yale Aortic Institute comparing growth rates and complications, 50% of patients with ascending aortic aneurysms suffered aortic rupture or dissection at a median aortic diameter of 5.9 cm (10). Furthermore, there is a "hinge" point in the data which identifies a significant increase in the probability of rupture or dissection when an aneurysm reaches a size of 6.0cm. Therefore, elective repair of aortic root or ascending aneurysms in trileaflet valves is recommended at a diameter of ≥ 5.5cm or a growth rate of ≥0.5cm/year (8,10). Patients with genetic disorders such as bicuspid aortic valve, Marfan syndrome, Ehlers-Danlos, Turner syndrome, or a familial history of aneurysm

subjected to a lifetime 34% risk of rupture or dissection (9).

insufficiency.

dysfunction (4, 7).

(2).

**4. Indications** 

**3. Pathophysiology** 

The shape of the aortic cusps is semilunar. The base (hinge point) of the cusp is 1.5 times longer than the length of the free margin (Figure 1). The cusps have three component parts: the hinge point, the body and the coapting surface (free margin). The hinge point has the ability to bend repeatedly without weakening or fracturing due to stress. The body of the cusp has a limited degree of distensibility due to a sliding movement of the different layers that compose the valve. The coapting surface has a specific length which is important in ensuring valve competence under different loading conditions (3). Histopathology studies have revealed that the thick collagenous bundles which comprise the cusps are oriented in an optimal way to transmit stress to the aortic wall (4). Normal aortic valves have three cusps with three corresponding sinus of Valsalva segments. Bicuspid aortic valve is a heritable condition which occurs in 1-2% of the population. These patients have two functional cusps and three sinus segments.

Fig. 1. Geometric relationships of various components of the aortic root. The base of the aortic cusp is 1.5 times longer than its free margin (FM). The diameter of the aortic annulus (AA) is 10 to 15% larger than the diameter of the sinotubular junction (STJ) in children and young adults, but it tends to become equal with aging. Three semilunar cusps seal the aortic orifice. The height of the cusps must be longer than the radius of the aortic annulus. From David TE. Aortic Valve Repair and Aortic Valve-Sparing Operations. In: Cohn LH, ed. *Cardiac Surgery in the Adult.* New York, NY: McGraw Hill:935-948, 2008

Beginning at the aortic annulus, the aorta bulges outward to form three sinuses of Valsalva segments which end at the sinotubular junction (STJ). The shape of the sinus segment is thought to be important in creating vortices which have an effect on both valve opening and closing as well as coronary blood flow (4). In vitro finite element analysis has proven that the shape of the sinus segments plays a vital role in limiting the stress and strain on the cusps (5). The important relationship between the shape of the sinus and its physiologic function has led to the development of prosthetic aortic root grafts with pre-made bulging sinus segments, in attempt to recreate normal aortic root geometry (6).

The sinotubular junction (STJ) is a ridge which lies above the aortic valve commissures and marks the transition from the aortic root to the ascending aorta. The circumference of the sinotubular junction is 15-20% smaller than the aortic annulus in young people, but normalizes to approximately a 1:1 relationship in older age (2). The close relationship of

The shape of the aortic cusps is semilunar. The base (hinge point) of the cusp is 1.5 times longer than the length of the free margin (Figure 1). The cusps have three component parts: the hinge point, the body and the coapting surface (free margin). The hinge point has the ability to bend repeatedly without weakening or fracturing due to stress. The body of the cusp has a limited degree of distensibility due to a sliding movement of the different layers that compose the valve. The coapting surface has a specific length which is important in ensuring valve competence under different loading conditions (3). Histopathology studies have revealed that the thick collagenous bundles which comprise the cusps are oriented in an optimal way to transmit stress to the aortic wall (4). Normal aortic valves have three cusps with three corresponding sinus of Valsalva segments. Bicuspid aortic valve is a heritable condition which occurs in 1-2% of the population. These patients have two

STJ

AA

Fig. 1. Geometric relationships of various components of the aortic root. The base of the aortic cusp is 1.5 times longer than its free margin (FM). The diameter of the aortic annulus (AA) is 10 to 15% larger than the diameter of the sinotubular junction (STJ) in children and young adults, but it tends to become equal with aging. Three semilunar cusps seal the aortic orifice. The height of the cusps must be longer than the radius of the aortic annulus. From David TE. Aortic Valve Repair and Aortic Valve-Sparing Operations. In: Cohn LH, ed.

Beginning at the aortic annulus, the aorta bulges outward to form three sinuses of Valsalva segments which end at the sinotubular junction (STJ). The shape of the sinus segment is thought to be important in creating vortices which have an effect on both valve opening and closing as well as coronary blood flow (4). In vitro finite element analysis has proven that the shape of the sinus segments plays a vital role in limiting the stress and strain on the cusps (5). The important relationship between the shape of the sinus and its physiologic function has led to the development of prosthetic aortic root grafts with pre-made bulging

The sinotubular junction (STJ) is a ridge which lies above the aortic valve commissures and marks the transition from the aortic root to the ascending aorta. The circumference of the sinotubular junction is 15-20% smaller than the aortic annulus in young people, but normalizes to approximately a 1:1 relationship in older age (2). The close relationship of

*Cardiac Surgery in the Adult.* New York, NY: McGraw Hill:935-948, 2008

sinus segments, in attempt to recreate normal aortic root geometry (6).

functional cusps and three sinus segments.

FM

BASE

the STJ and the aortic valve commissures is realized when aneurysmal dilation of the STJ moves the commissures apart and results in loss of leaflet coaptation and aortic insufficiency.

The aortic root is a dynamic structure that expands and contracts throughout the cardiac cycle in a manner which maximizes blood flow through the aortic valve and minimizes stress on the aortic valve cusps. The components of the aortic root complex have a specific geometric relationship with each other to produce optimal hemodynamics. Pathologic alterations in any of the four components can change their interactions and result in valvular dysfunction (4, 7).
