**4. Aortic valve replacement**

Before the emergence of surgical repair as an option to delay aortic valve replacement, the common management plan for most patients with isolated aortic stenosis was to perform balloon valvuloplasty until a replacement is needed. Isolated aortic valve replacement is generally associated with low mortality and morbidity especially if performed worsening the myocardial function [56]. However, the decision of which type of aortic valve replacement to choose is complex as it depends on many factors such as patient characteristics, medication compliance, access to care, etc. [57]. In younger patients, it is important to choose a valve replacement that is resistant to degeneration, infection, and has growth potential [56]. Whereas, in the older population, the priority lies in minimizing the need for anticoagulation due to potential thromboembolism complications [57, 58].

Tissue aortic valves can be either bioprosthetic with bovine or porcine valves, homografts, or allografts. They are generally preferred in older patients due to their low thromboembolism risk [57–59]. However, tissue valves are prone to a high risk of degeneration and structural failure which translates to high reoperation rates [56, 59–62],

#### *Advances in the Management of Congenital Malformations of the Aortic Valve DOI: http://dx.doi.org/10.5772/intechopen.105641*

hence their use needs to be carefully evaluated [58]. Additionally, they often come in sizes larger than 19 mm, lack growth potential, and are prone to patient-prosthesis mismatch (PPM) as the recipient grows. One of the few pediatric populations, where tissue replacement can be considered is teenage females who wish to be pregnant in the future due to lack of anticoagulation. However, if accompanying conditions such as atrial fibrillation, previous emboli, or an enlarged left atrium are present, the need for anticoagulation may still be warranted [56, 58, 62, 63]. Homografts may sometimes be available in smaller sizes suitable for younger children, and they are associated with excellent hemodynamics. They are also resistant to infection, which makes them preferred for patients with invasive endocarditis. However, the limitation of rapid valve deterioration leading to recurrent stenosis and regurgitation outweighs these benefits, hence its use is often discouraged [61].

The most attractive aspect of mechanical aortic valves is its superb durability. However, its biggest drawbacks are the need for anticoagulation which can significantly impact quality of life, and the lack of growth potential [58, 64, 65]. In older patients, this can lead to drug interactions and increased thromboembolic risks. In children, there can be possible compliance issues and difficulty with activity restraints, though children seem to have an overall lower risk of bleeding and thromboembolism [58]. Newer generation mechanical valves have been explored to prevent the need for warfarin and an INR goal >2.5, however, eliminating anticoagulation completely is still unattainable in mechanical valves [57]. In children with mechanical valves, the use of antiplatelet drugs instead of warfarin for anticoagulation can be considered [63]. Reoperations are uncommon in patients who have received mechanical valve replacements, and they are mainly due to PPM or subvalvular obstruction, both more prevalent in the younger recipients [58, 61, 64]. Overall, the freedom from reoperation for this subgroup is over 92% at 20 years in both adults and children [64].

The Ross procedure utilizes the patient's own pulmonary valve to replace the diseased aortic valve and a tissue valve for the pulmonary valve [59]. Though this procedure is more technically demanding than the other replacement methods, it produces better hemodynamics, fewer complications, and allows growth potential in the aortic valve [58, 59, 66]. Since the pulmonary autograft is relatively resistant to calcification or degeneration, trans-valvular gradients mostly remain unchanged from the immediate post-operative period. Additionally, having better post-replacement hemodynamics places less strain on the left ventricle, overall resulting in improved mortality [59].

The biggest disadvantage to this approach is that it results in a double valve disease where both valves will be at risk for reoperation and degeneration [60]. Some argue that most reoperations after a Ross procedure occur on the pulmonary conduit [60, 67], and this results in a higher total reoperation rate if both valves are considered, compared to mechanical replacement [60, 66, 68]. Many alternatives for the pulmonary valve have been investigated but none were superior to a homograft. The only exception was in young infants since homografts have poor durability [66].

The preferred age groups for the Ross procedure are older children and young adults, especially those with normal-sized aortic annulus due to procedure complexity [65, 66]. Infants less than age 1 generally have a high mortality rate of up to 20%, but this decreases as patient age increases and falls to almost 1% for children above 1 year old [58, 60, 69]. It is also important to note that patients who require the Ross procedure as an infant generally have critical stenosis with failed previous repair or balloon valvuloplasty which may have contributed to the high mortality [69]. Besides mortality, pulmonary valve reoperations were also reported to be higher in neonates and infants compared to older children [60, 69].

The most common complication of the Ross procedure is aortic root dilation causing regurgitation [58, 70]. Reoperation rates due to dilation can range from 8 to 30% within 10 years after surgery [66, 70]. Several methods to prevent dilation and improve durability have been explored. The most common strategy is to place external support, using either a Dacron (DuPont, Wilmington, DE) graft or a Gelweave (Vascutek Ltd., Renfrewshire, United Kingdom) sinus of Valsalva graft around the aortic root. Excellent results have been reported for this technique – freedom from dilatation for standard Ross at 3 years was 52%, and is 90% for supported Ross [58, 66, 68, 71, 72]. External stabilization using a strip of Daron at the STJ has also been explored and is considered a standard Ross procedure in some institutions for older children [66, 73]. Another common approach is to wrap the native aortic root around the pulmonary autograft for extra stabilization [70, 71]. However, this approach is limited by the size of the aortic root. In patients with bicuspid aortic valve and aortic insufficiency, their aortic roots are usually already dilated and hence will be unable to provide adequate support. On the other hand, patients with bicuspid aortic valves with aortic stenosis tend to have small aortic roots which are not feasible for this method of stabilization [73].

Despite promising results with different supported Ross procedures, these stabilization techniques should only be used for older children or young adults because it eliminates the growth potential which is a crucial benefit of the Ross procedure as a replacement option [14, 68, 71–73]. A new supported Ross technique with Konno annular enlargement using a subcoronary technique has been explored to extend the procedure to younger children. However, this procedure becomes extremely complicated, and long-term results are needed to prove its durability [72].

Between tissue and mechanical aortic valve replacements, mechanical replacements seem superior overall. Tissue valves do not require anticoagulation and can be available in smaller sizes; however, their high rate of valve degeneration and reintervention makes it a poor valve replacement option for young patients. On the other hand, mechanical valves have better durability and higher freedom from reoperation rates [64, 69]. Despite better long-term benefits, its impact on quality of life due to anticoagulation needs to be evaluated when considering this replacement option.

Both tissue replacement and the Ross procedure share similar immediate post-operative hemodynamic and are both resistant to infections. Furthermore, they are both available in small sizes and do not require anticoagulation. In terms of surgical technicality, tissue replacements are generally easier since it does not involve the pulmonary valve. However, tissue valves are associated with rapid valve deterioration, resulting in higher mortality and reoperation rates. Therefore, though it can be an option if resources are available, it is less preferred in the younger patients [59, 60, 69, 74].

Overall, there is no statistically significant difference in reoperation rates between mechanical replacement and the Ross procedure [65, 69]. However, surgeries involving the mechanical valve are less complicated since it does not involve the pulmonary valve or the aortic root procedures [64]. The Ross procedure may have superiority since it allows for growth potential and does not involve anticoagulation, resulting in more favorable cardiac and valve-related mortality [59, 60, 65, 69]. Nonetheless, it is difficult to compare these two approaches since the Ross procedure is usually performed on younger patients for congenital causes, whereas the mechanical replacement is favored in older patients with connective or rheumatic tissue pathologies, or preoperative aortic regurgitation [75].

#### *Advances in the Management of Congenital Malformations of the Aortic Valve DOI: http://dx.doi.org/10.5772/intechopen.105641*

Ultimately, all approaches to replacement have their own risk and benefits. To properly evaluate the best option, it is important to first consider the age of the patient, the need for growth potential, and the possible need for reoperations in the future. The second important point is then to assess for possible complications and comorbidities.

### **4.1 Repair vs. replacement**

The topic of whether aortic valve repair or replacement is the preferred approach to the management of aortic valve pathology is again controversial. Both aortic valve repair and replacement have produced similar results and shown their respective benefits and limitations [76]. Many institutions have started to express their preference to repair valves and delay replacement for as long as possible. Burrato and associates noted an increase in durability when the Ross procedure is done as a reoperation after valve repair and attributed this to the presence of postoperative scarring aiding in natural stabilization [77]. Similarly, favorable results were also reported by Popov et al. regarding mechanical valve replacement after previous repair [61].

There are subgroups of patients in whom repair has been shown to be a superior approach to replacement. Etnel et al. performed a meta-analysis and concluded that replacement is a suboptimal option in the pediatric population [60]. Generally, the repair is preferred in younger patients as it allows for growth potential, where most replacement options are unable to accommodate growth and will require multiple reoperations. Repair also avoids anticoagulation complications and activity restrictions [23, 78]. Danial et al. compared repair and the Ross procedure and concluded that both options were similar in terms of mortality and freedom from reintervention. However, aortic valve repair pulled ahead in terms of surgical morbidity and complications. They also noted that in patients who require immediate intervention, repair with a patch is the preferred option since it yields better short-term outcomes [64]. It is important to note that both young age and unicuspid valve morphology were identified as the greatest risk factors for poor outcomes in repairs [31]. Additionally, pediatric patients who present with an aortic valve deformity usually have complex pathology that requires multiple interventions. Hence, these risks and repair complexity should be weighed against the limitations of having a replacement [79]. It is possible that aortic valve repair should be considered for neonates and infants, whereas both aortic valve repair and the Ross procedure can be options for older children [78]. Ultimately, replacement may be unavoidable for patients who present with aortic valve disease at a young age.

Another population where a repair can be more favorable is in adults where replacement is contraindicated or those who are already undergoing other cardiac procedures at the same time [23, 27]. Regardless of the patient population, the surgeon's comfort level and experience in performing the aortic valve repair can also deter the decision as well [23, 80]. Another thought is to choose the management approach depending on whether the pathology is aortic stenosis, insufficiency, or mixed disease. Valve repair has shown satisfactory low reintervention rates for patients with aortic stenosis. However, the repair had a higher reintervention rate for patients with mixed disease or aortic insufficiency. This could however be institution dependent as repair outcomes depend largely on the surgeon's experience and expertise [81].

In conclusion, it is difficult to compare both modalities without bias as repair techniques are still evolving and there is still a lack of long-term data available.

Additionally, many complex repair techniques, especially for children, are only available at several specialized institution whereas aortic valve replacement techniques have been around for many decades and are known to be safe and successful among most surgeons [23]. Studies that focused solely on either repair or replacement usually consist of different patient populations with varying aortic valve pathology [29].

To increase the widespread practice of aortic valve repair techniques, there needs to be a standardized range of techniques to help guide surgeons through variations in valve deformities. More surgeons will need to be trained and familiarized with these techniques so that they will have the expertise to explore repair instead of relying on the reliable replacement option [23, 81]. An example algorithm was proposed by Danial and colleagues, where repair should be preferred if native cusps with good mobility can be achieved after shaving and/or debridement, there is at least one functional commissure, and a cusp-free margin that is composed of half native tissue. However, if the aortic annulus is less than two standard deviations, both repair and replacement can be done together with the Konno procedure [67, 81]. Another management pathway that was suggested for the pediatric population depended on peak systolic gradient or Doppler mean gradient [82].
