Valve Repair in Aortic Insufficiency: A State-of-the-art Review

Abstract

Aortic valve insufficiency (AI) describes the pathology of blood leaking through the aortic valve to the left ventricle during diastole and is classified as mild, moderate or severe according to the volume of regurgitating blood. Intervention is required in severe AI when the patient is symptomatic or when the left ventricular function is impaired. Aortic valve replacement has been considered the gold standard for decades for these patients, but several repair techniques have recently emerged that offer exceptional stability and long-term outcomes. The appropriate method of repair is selected based on the mechanism of AI and each patient’s anatomic variations. This review aims to describe different pathologies of AI based on its anatomy, along with the different surgical techniques of aortic repair and their reported results.

1. INTRODUCTION

Aortic valve insufficiency (AI), also termed aortic valve regurgitation, indicates a valvular heart disease characterized by the valve’s leaflets' inappropriate coaptation. The valve’s inadequate closure is caused by issues associated with its integrity, such as dysfunction associated with either the aortic root, aortic valve leaflets, annulus or ascending aorta [1]. In AI, during ventricular diastole, blood that has already been ejected by the heart flows in the reverse direction from the aorta into the left ventricle. Consequently, this mechanism leads the left ventricle to be subjected to substantial stress due to volume overload [2].

The Framingham Heart Study began in 1948 with the objective of outlining the risk factors associated with coronary heart disease. The cohort that participated in the study consisted of 5,209 men and women of ages ranging from 28 to 62 years, with the prevalence of AI in the study cohort being 4.9% [2]. Furthermore, 0.5% of patients were detected with moderate to greater severity AI, the peak of cases was observed between the ages of forty to sixty, and it was observed that the severity and incidence increased with age. Gender wise, the Framingham Offspring Study detected that in the study population, 8.5% of women and 13% of men suffered from AI [2, 3]. Differences in the age and cause of manifestation of the disease have been detected between different geographical areas. In fact, younger patients with acute onset AI caused by infective endocarditis or rheumatic heart disease tend to be more prominent in developing countries, while in industrialized countries, it is more common to develop AI in older age, usually linked to senile degeneration and other pre-existing pathologies [1].

The development of symptoms associated with AI is usually gradual, occasionally requiring decades to manifest in the patient. AI symptomatology is characterized by angina pectoris, which usually worsens with physical exertion, orthopnea, dyspnea, paroxysmal nocturnal dyspnea, fatigue;, syncope and/or lightheadedness, palpitations [4]. Aortic valve pathologies were traditionally addressed with aortic valve replacement [5, 6]. However, during the last decades, the establishment of a systematic approach for aortic valve repair based on the AI classification and the development of valve-sparing repair techniques show encouraging long-term outcomes and have given the surgeons a variety of options [7-12].

This review aims to describe the different aortic valve repair techniques and their reported results. A review of the anatomy of the aortic valve and the pathology and classification of AI is also incorporated as these elements are crucial to understanding the basis of the different repair techniques.

2. AORTIC ROOT AND AORTIC VALVE ANATOMY

The left ventricle is joined with the ascending aorta via the aortic root [13]. The aortic root can be defined proximally by the aortic annulus and distally by the sinotubular junction (STJ) (Fig. 1) [14]. The aortic root acts as the outflow tract from the left ventricle, measuring about 2-3 cm in length [15] and consists of the following major components: (i) the aortic valve leaflets (cusps), (ii) the sinuses of Valsalva (aortic sinuses), (iii) the interleaflet triangles, (iv) the sinotubular junction, (v) the aortic annulus, and (vi) the ventriculoaortic junction (VAJ) [13, 16, 17] (Fig. 1).

Fig. (1).

Schematic representation of the aortic valve modified from Matsushima et al. [19]. The aortic valve, which is cylindrical in shape, has three leaflets with a 3D crown-like configuration. Each leaflet comprises two free margins, which are shared with the neighboring leaflets. The VAJ corresponds to the imaginary line that connects the lower third of the aortic cusps and goes through the interleaflet trigones’ bases. The lowest point of each semilunar insertion line is termed the leaflet nadir, with the virtual circumferential line connecting these nadirs being the VBR. Abbreviations: STJ: sinotubular junction; VAJ: ventriculoaortic junction; VBR: virtual basal ring.

2.1. Aortic Valve Leaflets (cusps)

The aortic valve is a cylindrical assembly that stems from the left ventricle and normally has three leaflets with a crown-like insertion line in 3-dimensional geometry [17-19] (Fig. 1). The mean length of this semilunar insertion line between two adjacent commissures was 51 ± 4.9 mm [20]. The leaflets are named right coronary (RC), left coronary (LC), and non-coronary (NC), based on which coronary artery stems from the respective sinus [18]. Each leaflet is a structure that comprises a semilunar line travelling from the aortic annulus to the STJ, the body of the leaflet, and two free margins with a thickened, central, and circular fibrous nodule named as the body of Arantius (Fig. 2) [21-23]. This nodule represents the coaptation site of the corresponding valve leaflets [21, 23]. According to a recent study, the mean free margin length that travels along the free margin between two adjacent commissures was 34.3 ± 3.1 mm [20]. It is important to mention that each leaflet’s rim is thicker than the body area and is named lunula; during diastole neighboring, lunulae overlap with each other enhancing valve support [23, 24].

Fig. (2).

Schematic representation of the anatomy of the aortic valve modified from Netter’s “Atlas of human anatomy”. The figure demonstrates an opened aortic valve showing the right, left and the non-coronary leaflets and their related detailed anatomy. Each leaflet has a semilunar line travelling from the aortic annulus to the STJ, the body of the leaflet, and two free margins with a thickened, central, and circular fibrous nodule (Body of Arantius). Because of the semilunar insertion attachment of the leaflets, three interleaflet triangles are formed as extensions of the left ventricular outflow tract and are found below the commissure in between the bases of two adjacent leaflets. The commissures, the leaflets’ nadir, and the lower third of the aortic cusps attain the level of the STJ, VBR, and VAJ, respectively. Abbreviatons: NC: non-coronary sinus; RC: right coronary sinus; LC: left coronary sinus; STJ: sinotubular junction; VAJ: ventriculoaortic junction; VBR: virtual basal ring.

The estimation of each aortic leaflet size is essential in planning a successful surgical repair approach, mainly in order to exclude excess or lack of leaflet tissue [17]. Typically, leaflet size corresponds to the aortic annulus and sinus size and according to a recent study, the mean leaflet size was calculated at 297 ± 41 mm² after specimen fixation in formalin [20, 24]. However, it is shown that there is a slight difference in the size of the three leaflets, with the NC leaflet being the largest [20, 24]. Since it is burdensome to determine the leaflet size in the operating room, an alternative parameter that helps achieve that is measuring the leaflet height [25]. For this purpose, it is critical to determine the effective and geometric leaflet height.

Effective height is defined as the distance from the ventriculoaortic junction to the central coaptation site (Fig. 3) [17]. Bierbach et al. found that aortic root size and patient size were associated with leaflets’ effective height; the mean effective height in adults with a mean body surface area of 1.87 ± 0.2 m² was 9.5 ± 1.4 mm [26]. These results were similar to the findings of a recent study which showed that the mean effective height was 8.5 ± 1.3 mm [20]. The geometric height is defined as the distance between the leaflet’s nadir and the center of the leaflet’s free margin (Fig. 3) [17]. In order to determine the geometric height, a study examined 329 patients who had aortic valve repair and showed that in a trifoliate aortic valve, the geometric height of RC, LC, and NC leaflets ranges between 12-25 mm, 12-25 mm, and 14-28 mm, respectively; the mean geometric height was 20 mm [25]. These results are in accordance with a recent study demonstrating that the mean geometric height was 18.9 ± 1.5 mm after analyzing 25 aortic root homografts [20].

Fig. (3).

Schematic representation of the effective and geometric height modified from De Kerchove et al. [20]. The effective height is defined as the orthogonal length between the aortic annulus and the middle of the free margin. The geometric height is the distance between the nadir and the middle of the free margin of the leaflet. Abbreviations: eH: effective height; gH: geometrical height; STJ: sinotubular junction; VBR: virtual basal ring.

2.2. Sinuses of Valsalva (Aortic Sinuses)

There are three enlarged segments of the aortic root wall above the aortic valve leaflets, which are called sinuses of Valsalva (Fig. 2). The parabolic hinge line of the leaflets serves as the proximal boundary of these sinuses, and the STJ serves as the distal boundary. The sinuses of Valsalva are named after the origin of the coronary arteries as left (LC), right (RC), and non-coronary (NC) sinus. The left and right coronary ostia can be found within the LC and RC, respectively [27]. The aortic sinuses consist mainly of elastic tissue, and in general terms, is thinner when compared to the proximal ascending aorta [28]. During systole, the trapped blood in the sinuses creates vortices that minimize the contact between the leaflets and the sinuses’ wall, and as a result there is stress reduction and damage prevention [27]. During diastole, the blood accumulates within the sinuses, ensuring smooth valve closure and supporting the coronary blood flow [27].

2.3. Interleaflet Triangles

The interleaflet triangles are found below the commissure in between the bases of two adjacent leaflets (Figs. 1 and 2) [18, 27]. Recent studies demonstrated that the mean distance between each interleaflet triangle’s base and its corresponding commissure (commissure height) was 20 mm [18, 20]. Even though the interleaflet triangles are anatomically part of the aortic root, they are considered hemodynamically as extensions of the left ventricular outflow tract (LVOT) [18, 29]. The triangle located between the LC and NC aortic valve sinuses (left trigone) is the largest of the three and is a part of the fibrous subaortic curtain as it extends and connects to the aortic leaflet of the mitral valve [30]. In the case of dissection of the left trigone, the transverse pericardial sinus is revealed [16, 27]. The second largest triangle is formed between the RC and NC aortic valve sinuses (right trigone) and it is in continuity with the ventricular fibrous membranous septum [27, 30]. In the case of dissection of the right trigone, there is an opening which boundaries the LVOT and the transverse sinus of the pericardium [16]. The right trigone, along with the fibrous membranous septum and the tendon of Todaro, forms the central fibrous body, which is the strongest part of the heart’s fibrous skeleton [30, 31]. The fact that the bundle of His goes through the central fibrous body makes this structure a critical landmark during aortic root surgical procedures [27, 30]. Damage to this structure can cause abnormalities in the atrioventricular conduction pathway requiring pacemaker implantation [32, 33]. The triangle between the LC and RC aortic valve sinuses connects to the muscular ventricular septum [34]. When this triangle is removed, a window is created going into the extracardiac space between the aortic root and the subpulmonary infundibulum, which forms the right ventricular outflow tract (RVOT) [27, 31].

2.4. Sinotubular Junction (STJ)

As it is mentioned earlier, the aortic valve leaflets have a crown-shaped semicircular line of insertion. The point where the apices of the semilunar insertion lines of two neighboring leaflets are met is defined as a commissure (Figs. 1 and 2). The straight line that connects two neighboring commissures is defined as commissure distance and has a mean length of 24.6 ± 2.7 mm [20].

The STJ is the imaginary circumferential line that joins the three commissures (Figs. 1 and 2) [17, 18, 27]. Anatomically, the STJ can be described as the superior border of the aortic sinuses and marks the transition from the aortic root to the ascending aorta [27]. It is important to note that the diameter of the STJ is typically 5 mm larger than the virtual basal ring [35]. A recent anatomical study showed that the mean diameter of the STJ was 26.6 ± 2.4 mm after analyzing 25 aortic root homografts [20]. It should be stressed that there are anatomical variations regarding the location of the coronary ostia with respect to the STJ. Although it is still debatable, coronary arteries stem at least 1 cm above the STJ are usually characterized as high take-off arteries and have been associated with sudden cardiac death, thus requiring specific attention during interventions [36].

2.5. Aortic Annulus

There is not just one definition in the literature regarding the aortic annulus. Cardiologists and radiologists who utilize echocardiography define the aortic annulus as the imaginary intraluminal line that connects the nadirs of the aortic valve’s leaflets in a circular way [27, 37]. Hence, they acknowledge the aortic annulus as the virtual basal ring (VBR) (Figs. 1 and 2). However, recent in vivo studies utilizing Computed Tomography (CT) scans showed that the VBR has an elliptical shape [35, 38, 39]. On the other hand, surgeons define the aortic annulus as the place where the three aortic leaflets are attached to the aortic wall [14, 40]. The surgical aortic annulus is considered to be a crown-shaped structure that extends from the VBR to the STJ [14, 37]. Also, the aortic annulus has been described by El Khoury et al. as a functional unit (functional aortic annulus; FAA) consisting of the STJ, the semicircular attachments of the three aortic leaflets, and the VBR [41].

It is important to mention that the aortic root thickness at the level of the VBR is 2.7 mm, 3.3 mm, and 2 mm at the point of the LC, RC, and NC leaflet, respectively. Also, the aortic root thickness at the base of the interleaflet triangles is 1.6 mm at the left trigone, 2.1 mm at the right trigone, and 3.3 mm at the LC-RC interleaflet trigone. The mean aortic root thickness at the level of the subvalvular plane was 2.5 mm [18].

2.6. Ventriculoaortic Junction (VAJ)

The VAJ is defined as the transition from the LVOT towards the aortic root and it is shaped by the virtual line, which connects the interleaflet trigones’ bases to the lower third of the aortic sinuses (Figs. 1 and 2) [16, 17, 37]. Anatomically, it is the place where the ventricular structures (i.e., muscular septum, aorto-mitral curtain, membranous septum) connect to the arterial system [37]. The mean VAJ diameter was found to be 24.2 ± 1.8 mm in a recent study by De Kerchove et al. [20].

3. PATHOLOGY OF AORTIC INSUFFICIENCY

AI is caused by inadequate coaptation of the aortic valve leaflets attributable to aberrations of the leaflets, aortic root, aortic annulus or ascending aorta, and it is classified as either acute or chronic. Acute AI is commonly caused by infective endocarditis, which usually results in anatomical changes of the leaflets, aortic cusp prolapse caused by ascending aorta laceration, and prosthetic valve dysfunction [42]. Furthermore, acute iatrogenic AI might occur in patients with percutaneous aortic balloon valvuloplasty [43]. The most common etiologies associated with chronic AI include rheumatic heart disease, which is predominantly common in developing countries. Several different pathophysiological processes resulting from rheumatic heart disease might cause AI, including retraction of the aortic valve cusps caused by fibrous infiltration leading to impaired systolic opening and diastolic closing of the valve. Additionally, rheumatic heart disease can cause the fusion of the valve’s commissures, leading to AI. Other common etiologies of chronic AI are myxomatous valve degeneration, infective endocarditis, valvular calcifications, congenital valve defects, such as bicuspid aortic valve, drug-induced valvulopathy, aortic root dilatation attributable to giant cell arteritis or syphilis, aortic annulus ectasia, aortitis, aortic dissection, and severe systemic hypertension [43, 44]. Furthermore, several medical conditions such as Marfan syndrome, Ehler-Danlos syndrome, osteogenesis imperfecta, rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, systemic lupus erythematosus, antiphospholipid syndrome, Behcet disease, Takayasu vasculitis, Crohn disease, and Whipple disease are seldomly responsible for the development of chronic AI [43, 44].

4. CLASSIFICATION OF AI

In this article, we will selectively focus on AI types I, II, and III. The proper classification of the insufficiency is of paramount importance since it will determine which surgical repair procedure will be applied by the surgeon. The classification of AI is based on the American Society of Echocardiography 2017 guidelines [45]. Type I AI is characterized by dilation of the aortic root or perforation of the cusps, while usually, the aortic leaflets maintain their normal functionality or there is slight cusp tethering. In type I, it is most often observed as a central jet. More specifically, AI type I is furtherly divided into four different categories: type Ia, Ib, Ic, Id. The prominent anatomic abnormality seen in type Ia insufficiency is the enlargement of the ascending aorta as well as of the sinotubular junction. Regarding type Ib, it presents with dilation of the sinotubular junction and of the sinuses of Valsalva. In type Ic, there is dilation of the aortic annulus, while in type Id, the aortic cusp is perforated. Moving on to type II aortic regurgitation, there is a significant aortic valve prolapse as a result of commissural disruption or excessive cusp tissue. The jet of type II AI is eccentric. Type III AI is marked by cusp restriction, which leads to the decreased motion of the leaflets due to either extensive fibrosis or calcifications. The regurgitation jet, in some cases, is central while, in others, eccentric [7, 17, 22, 46, 47].

For chronic AI cases, there is a different grading system as proposed by the American College of Cardiology (ACC) and the American Heart Association (AHA) [48]. Following these guidelines, chronic AR is subdivided into four categories: Stages A, B, C, and D. This grading system depends on various components such as the valve hemodynamics, valve anatomy, LV dilation, and the presence or absence of symptomatology. In more detail, stage A includes those who are at risk of AI and is identified by the disruption of the aortic valve. The valve hemodynamics are normal and no symptoms are present. Stage B comprises patients with progressive mild to moderate AI. Additionally, mild to moderate calcifications, rheumatic valve changes, and aortic sinuses dilation are observed. Apart from the left ventricular dilation, the LV volumes and the LV systolic function are maintained. There is no symptomatology present in the patient. In regard to stage C, it is characterized by severe AI, but like stages A and B, the patient does not experience any symptoms. The findings include aortic calcific changes, rheumatic valve changes, and dilation of the ascending aorta or aortic sinuses. LV dysfunction plays a significant role, and it is the parameter on which stage C is furtherly divided into stage C1 and stage C2. In stage C1, the LV ejection fraction is more than 50% with mild to moderate LV dilation, accompanied by an end-systolic dimension of less than 50 millimeters. Stage C2 is characterized by a LV ejection fracture of 55% or less and a severe LV dilation, accompanied by an end-systolic dimension bigger than 50 mm or an indexed LV end-systolic dimension above 25 mm/m². Lastly, stage D is defined by severe aortic regurgitation and by the presence of symptoms. The most common symptoms seen are angina, exertional dyspnea, as well as signs of heart failure. The rest of the features of stage D are similar to stage C [1, 48].

Clinically, AI can be classified as mild, moderate, and severe. This classification is based on quantitative factors, as seen in Table 1 [44, 49].

Table 1.

Classification of aortic valve insufficiency. The classification is based on the recommendations of the American Society of echocardiography.

-	Aortic Insufficiency
	Mild	Moderate		Severe
Vena contracta width (mm)	< 3	3 – 5.9		≥ 6
Aortic regurgitant width jet / LV outflow (%)	< 25	25 – 44	45 – 64	≥ 65
Volume of regurgitation (mL / beat)	< 30	30 – 44	45 – 59	≥ 60
Fraction of regurgitation (%)	< 30	30 – 39	40 – 49	≥ 50
Effective regurgitant orifice (mm2)	< 10	10 – 19	20 – 29	≥ 30

5. INDICATIONS FOR SURGERY

Surgical management of AI with either aortic valve replacement or repair has identical indications [22]. More specifically, surgical treatment is indicated in severe symptomatic chronic AI cases and severe asymptomatic chronic AI with left ventricular systolic dysfunction and a left ventricle ejection fraction lower than 50%. Surgery is also considered in severe asymptomatic AI with severe left ventricle dilation (LVESD index >25 mm/m² or LV end-systolic dimension >50 mm) but with normal left ventricular function (LVEF ≥50%). Furthermore, asymptomatic patients with severe AI, normal left ventricular function (LVEF ≥50%) at rest but with severe progressive dilation of the left ventricle (LV end-diastolic dimension >65 mm) can be candidates for aortic valve replacement or repair, given their risk of undergoing surgery is low [4, 22, 50].

6. SURGICAL REPAIR OF AI

In general, the surgical management of AI can be classified into two main categories: (i) remodeling of aortic annulus and aortic root repairs and (ii) valve repairs (Fig. 4) [5, 22]. Types Ia, Ib, and Ic AI are considered post-valvular tract repairs, whereas types Id, II, and III are considered valve repairs [22].

Fig. (4).

Classification of aortic insufficiency (AI) and suggested surgical approaches. Type I AI has normal leaflet motion and is associated with functional aortic annulus dilation or cusp perforation, type II is associated with cusp prolapse, and type III with cusp restricted motion. A standardized approach addresses all different pathologies identified: type Ia AI repair involves Asc graft and STJ remodeling; type Ib AI repair involves VSSR procedures; type Ic AI repair involves SCA; type Id AI repair requires the use of a pericardial patch; type II AI repair approach is based on leaflets’ condition; type III AI repair involves shaving excess fibrous tissue and removal of calcium deposits with/without patch). Care should be taken that the final effective height of the aortic valve cusps is 8-10mm at the end of the repair. Abbreviations: STJ: sinotubular junction; Asc: ascending aorta; SCA: subcommissural annuloplasty; VAJ: ventriculoaortic junction; VSRR: valve-sparing aortic root replacement. Modified from Prodromo et al. [22].

6.1. Remodeling of Aortic Annulus and Aortic Root Repairs

Type Ia AI repair involves the substitution of the ascending aorta with an aortic graft across or superior to the STJ, along with STJ’s remodeling using dacron graft sutures [51]. This approach aims to rectify the deficient valvular coaptation associated with STJ dilation [52] and restore normal hemodynamics [22]. If AI persists despite STJ’s remodeling, subcommissural annuloplasty (SCA) or implantation of a subcommissural ring should also be performed [22]. Nevertheless, studies showed that if the aortic annulus is dilated more than 28 mm then SCA should not be preferred since its outcomes fade away, and as a result, there is an increased chance of AI reappearance [53, 54].

Type Ib AI repair aims to correct the lack of valvular coaptation caused not only by the dilation of the STJ but also by the dilation of the VAJ [5, 22, 52]. This can be achieved either by performing valve-sparing reimplantation of the aortic root (David procedure) or by combining the remodeling of all three aortic sinuses (Yacoub procedure) along with SCA [22, 55]. David's technique includes positioning a dacron tube graft inside which the aortic valve is preserved by being firmly sewed to it [56]. Yacoub's technique aims to replace the aortic sinuses by utilizing a triple-tongued shaped graft; thus, the aortic sinuses and the STJ acquire their normal configuration [57]. Although the remodeling technique may compromise the stability of the annulus in the long-term [9], it maintains near normal aortic root hemodynamics and aortic valve leaflets’ movement, preserving the capability of the aortic root to expand [58]. On the other hand, even though the David technique addresses the annular base and STJ dilation, it does not preserve the aortic root hemodynamics [52]. Recent studies showed that when the diameter of the aortic annulus exceeds 25-28 mm, the reimplantation procedure is preferred to the remodeling procedure because the latter is considered a risk factor for AI recurrence [59-61]. Lansac et al. suggested a different approach that combines the advantages of Yacoub and David techniques by adding an external support ring to the level of the aortic annulus. By standardizing this procedure and adding the assessment of leaflet geometry by measuring the effective height (eH) intraoperatively to 8-10 mm, as described originally by Schäfers, they reported excellent results (CAVIAAR technique) [25, 58, 62, 63]. In a recent study it was demonstrated that CAVIAAR technique succeeded to stabilize the dimensions of the aortic annulus after 5 years of follow-up [64].

Tian et al.’s systematic review and meta-analysis utilized 606 patients who underwent the Yacoub procedure and 732 patients who underwent the David procedure from 13 medical centers in order to compare the outcomes of these surgical approaches [65]. The results showed that although the early mortality was similar for both techniques (0-6.9% for Yacoub and 0-6% for David), Yacoub approach was characterized by higher rates of AI recurrence in the follow-up period [65]. In accordance with these outcomes are the results of a recent study that showed that 15 to 20 years following the David procedure, only 4% of the patients needed reoperation [66]. On the other hand, Arabkhani et al. reviewed 31 articles and showed that when David and Yacoub procedures were compared to each other, they had similar survival and long-term outcomes, with early mortality and cumulative re-operation rate being 2% and 5%, respectively [67]. Lansac et al. demonstrated that CAVIAAR technique improves the outcomes of valve-sparing root replacement (VSRR) surgeries; reporting 99% freedom from aortic valve reoperation, 100% freedom from AI (grade 3 or greater) recurrence, and 96% freedom from crucial adverse post-operative events regarding the aortic valve [68].

Type Ic AI repair aims to address the dilation at the level of the VAJ by utilizing SCA, which provides firm support at the VAJ and decreases interleaflet triangles’ width [7]. If AI persists, then STJ annuloplasty should be performed [22].

6.2. Valve Repairs

Type Id AI repair aims to fix aortic leaflet perforation accompanied by FAA dilation without any lesions [5, 22]. The surgical approach to this type of AI is either direct local closure of the cusp fenestration or repair of the cusp perforation by utilizing a pericardial patch (autologous or bovine) [22]. Although the use of a patch as a technique compromises the outcome duration of the repair due to degeneration of the patch and disease progression of the valve, focal patch repair is expected to last longer [58]. Nowadays, research is focused on developing biological matrix scaffolds for aortic valve repair surgeries since it has been shown that xenopericardium and autologous pericardium have equivalent outcomes regarding patch degeneration after aortic valve repair [58].

Type II AI repair addresses cusp prolapse due to distention of free margins’ length [5, 22, 58]. When the leaflets are in a fine condition and there is a slight cusp prolapse, then a central cusp plication prolene suture is used in order to achieve normal eH and to bring the free margin length of all three leaflets to the same level [10, 22]. It is important to assess cusp mobility (i.e., check eH and leaflet coaptation) after the procedure since overcorrection may happen [58]. When leaflet free margin is brittle or symmetrical, leaflet prolapse is present and free margin resuspension is performed [10]. In this procedure, a running suture along the free margin is used in order to shorten and resuspend the leaflet, but it is not used regularly due to the possible association with overcorrection [10, 22, 58]. In the event that there is a larger prolapse, triangular resection is performed [5, 22]. In this technique, the excess leaflet portion is resected, and the resulting free margins are sutured with each other with or without the reinforcement of a pericardium patch [22].

Type III AI repair aims to correct leaflets’ restricted motion. This is achieved by shaving the redundant fibrous tissue, removing the calcium deposits off the leaflets, and adding a pericardium patch when leaflets' fenestrations are present.

It is important to note that above 30% of patients who need surgical intervention may have a combination of different types of AI [7] and based on each patient’s underlying aortic root’s anatomic variations and aortic valve’s pathology, a combination of surgical techniques is frequently required. Regarding isolated AI (i.e., there is no dilation of the aorta), Lansac et al. suggested a double annuloplasty procedure where one external ring is positioned at the STJ level (supravalvular), and a second external ring is placed at the base of the aortic annulus (subvalvular). In a comparative study, the double annuloplasty demonstrated longer lasting repair duration than the subvalvular annuloplasty and 97% freedom from reoperation in 7 years of follow-up; an outcome comparable to the results of the VSRR procedures [69]. Based on these results, Lansac and de Kerchove suggested that in cases of isolated AI repair, subvalvular annuloplasty should be preferred, and concurrent supravalvular annuloplasty or replacement of the ascending aorta should be performed when a low threshold is met [58].

Recently, a technique (HAART: hemispherical aortic annuloplasty reconstructive technology) was introduced that repairs and stabilizes the VAJ while preserving the native elliptical geometry of the aortic annulus [70]. HAART utilizes an internal ring that is designed based on the natural geometry of the aortic root during diastole with the help of computed tomography angiography images [70, 71]. So far, the largest study regarding HAART included 65 patients with AI of a trileaflet aortic valve and showed no in-hospital mortalities or complications related to the aortic valve. After a mean follow-up of 2 years, the survival rate was 95% and no mortality was attributed to a valve-related event, but 11% of the patients still required aortic valve replacement [70]. Several other recent studies showed similar results [72-75]. These results represent the initial experience with this technique and are promising as refinement with time and standardization may ameliorate outcomes even more. However, at this point, the relatively small number of patients reported and the lack of longer-term follow-up limit the ability to draw safe conclusions regarding HAART.

In Table 2, [60, 64, 66, 68, 69, 76] the characteristics and the long-term outcomes of the main surgical techniques that are utilized to correct AI are summarized. Although it is evident that the follow-up period is less for the CAVIAAR technique, it demonstrates an advantage in terms of freedom of reoperation and development of AI post-operatively when compared to David and Yacoub procedures. The main advantages and disadvantages of each surgical technique are displayed in Table 3.

Table 2.

Characteristics and long-term outcomes of David, Yacoub, and CAVIAAR surgical techniques.

Author, Year	Surgical Technique	No. of Patients	30-day Mortality (%)	Mean Follow-up (Months)	Freedom from Reoperation (%)	Freedom from AI (%)
David et al., 2010 [76]	David	228 (AI: 142)	1.8	78.4 ± 75.4	97.4	91
David et al., 2017 [66]	David	333 (AI: 144)	1.2†	123.6 ± 81.6	96.9	96.2
Lenoir et al., 2018 [64]	David	59 (AI: 26)	0	49.2 ± 42	98.4	86.4
David et al., 2010 [76]	Yacoub	61 (AI: 39)	1.6	120.6 ± 52.7	90.4	82.6
Schäfers et al., 2015 [60]	Yacoub	747 (AI: 640)	2	74.4 ± 52.8	91	N/A
Lansac et al., 2017 [68]	Yacoub	177 (AI: 79)	2.9	41.1 ± 36.4	89.5	77.4
Lenoir et al., 2018 [64]	Yacoub	83 (AI: 43)	0	43.2 ± 42	96.4	86.8
Lansac et al., 2016 [69]	CAVIAAR	232 (AI: 62)	1.8	40.1 ± 37.8	98.9	100
Lansac et al., 2017 [68]	CAVIAAR	177 (AI: 79)	2.9	41.1 ± 36.4	99	100

AI: aortic insufficiency.

^† Death within 90 days

* Median follow-up

Table 3.

Main advantages and disadvantages of surgical techniques used to repair aortic insufficiency. STJ: sinotubular junction; AV: aortic valve; VSRR: valve-sparing aortic root replacement.

Surgical Techniques	Advantages	Disadvantages
David	Stabilization of aortic annulus base & STJ	No preservation of aortic root’s hemodynamics
Yacoub	Preservation of aortic root’s normal hemodynamics & AV cusp movement	Aortic root stability compromise
CAVIAAR	Stabilization of aortic annulus base & STJ Preservation of aortic root’s normal hemodynamics & AV cusp movement	Not adequate long-term outcomes

CONCLUSION

Various procedures have been developed throughout the years in order to address AI. These techniques generally aim to repair or replace the aortic valve and adjust the structure of the aortic root and/or the ascending part of the aorta. As no perfect prosthesis exists, with the Achilles heel being valve degeneration for bioprostheses, and lifelong anticoagulation for mechanical valves, aortic valve repair techniques, when feasible, are preferred to aortic valve replacement. Indeed, aortic valve repair techniques not only offer the chance to stabilize the aortic root at the sub-/supravalvular level but also to remodel the native aortic valve. As follow-up increases for the different techniques, their advantages and disadvantages become more evident. The surgical technique depends on surgeons’ expertise and should be based on each patient’s anatomic variations and aortic valve pathology. Although the mid- and long-term outcomes after aortic valve repair are encouraging, the interpretation of these results is challenging due to variations among patient cohorts, the small number of patients, and the experience of the surgeons.

A standardized approach for each type of AI that considers the particular anatomy of each patient’s native valve and addresses all the different elements of the underlying AI pathology seems like the most reasonable path to take.

LIST OF ABBREVIATIONS

AI

Aortic Valve Insufficiency

STJ

Sinotubular Junction

LC

Left Coronary

RC

Right Coronary

NC

Non-Coronary

RVOT

Right Ventricular Outflow Tract

SCA

Subcommissural Annuloplasty

CONSENT FOR PUBLICATION

Not applicable.

FUNDING

None.

CONFLICT OF INTEREST

The authors declare no conflict of interest, financial or otherwise.