Mild
Moderate
Severe
Aortic valve area (cm2)
>1.5
1.0–1.5
<1.0
Mean pressure gradient (mmHg)
<20
20–39
>40
Indications for aortic valve replacement in aortic stenosis
Indication | Class of evidence |
|---|---|
Symptomatic patients with severe high-gradient AS | I |
Asymptomatic patients with severe AS and LVEF <50% | I |
Severe AS undergoing other cardiac surgery | I |
Symptomatic patients with low-flow/low-gradient severe AS with reduced LVEF with mean pressure gradient ≥40 mmHg or AVA ≤1.0 cm2 on dobutamine stress study | IIa |
Asymptomatic patients with − Very severe AS and low surgical risk − Severe AS and decreased exercise tolerance or exercise fall in BP | IIa |
Moderate AS undergoing other cardiac surgery | IIa |
Asymptomatic patients with severe AS, rapid disease progression and low surgical risk | IIb |
Aortic Regurgitation
AHA/ACC guidelines for the severity of aortic regurgitation
Mild | Moderate | Severe | |
|---|---|---|---|
Jet width (% LVOT diameter) | <25 | 25–64 | ≥65 |
Vena contracta (cm) | <0.3 | 0.3–0.6 | >0.6 |
Regurgitant volume (mL/beat) | <30 | 30–59 | ≥60 |
Regurgitant fraction (%) | <30 | 30–49 | ≥50 |
Effective regurgitant orifice area (cm2) | <0.10 | 0.10–0.29 | ≥0.3 |
AHA/ACC recommendations for aortic regurgitation surgical intervention
Recommendation | COR |
|---|---|
Symptomatically patients with severe AR regardless of LVEF | I |
Asymptomatic patients with chronic severe AR and LVEF < than 50% | I |
Severe AR undergoing other cardiac surgery | I |
Asymptomatic patients with severe AR with LVEF >50% and severe LV dilatation | IIa |
Moderate AR undergoing other cardiac surgery | IIa |
Asymptomatic patients with severe AR with LVEF >50% and with progressive severe LV dilatation and low surgical risk | IIb |
Patient Factors and Limitations
When considering an AVR, some patient factors and limitations may affect surgical planning and prosthesis choice. Specifically, the patient’s age, ability to tolerate long-term anticoagulation, and aortic root size are important factors for consideration. Each valve replacement option has a different expected durability. A younger patient may be better suited with a valve with a longer durability, to avoid the need for reoperation. However, if the patient’s life expectancy is shorter, valve durability may be less important when deciding on a valve prosthesis. In addition, some valve prostheses require life-long anticoagulation. Older patients or patients at higher risk of fall, patients at higher risk of bleeding, or patients who may desire future pregnancy may not be candidates for therapeutic anticoagulation. Alternatively, patients with an existing condition which already requires anticoagulation , such as atrial fibrillation or thrombotic disorders, may not need to consider anticoagulation when choosing a valve prosthesis . Lastly, aortic root size is an equally important determinant during aortic valve replacement. A small or heavily calcified aortic root may limit the size of the valve prosthesis which can be placed. Replacing the valve with too small a valve may place the patient at risk for an ongoing functional stenosis. Some valve prosthesis options have improved hemodynamics and flow compared to other valves of similar size, which may be important when faced with a small aortic root.
Options for Replacement
Mechanical Valve
St. Jude Medical (SJM) Regent™ mechanical heart valve. Reproduced with permission of St. Jude Medical, ©2017
Mechanical valves have some disadvantages as well. Perhaps the most prominent disadvantage is the need for anticoagulation. Anticoagulation-related hemorrhage is the most common valve-related event, and accounts for the highest mortality associated with valve-related events [7, 8, 11–15]. The target INR can vary based on patient risk factors, as well as valve choice. Thromboembolism is the second most common valve-related event, with rates ranging from 0.8% to 2.3% per patient year when anticoagulated, which is similar to that of bioprosthesis [8, 11–17]. Finally, the risk for prosthetic valve endocarditis must be considered as well. The incidence is similar between mechanical and biologic valves, with freedom from endocarditis with a mechanical valve around approximately 98% at 25 years [11, 15].
Overall, mechanical valves should be considered for younger patients, especially patients less than 60 years of age [11]. Any patients who require indefinite anticoagulation for other reasons should receive a mechanical valve [18]. Lastly, patients who would be considered high risk during any potential subsequent reoperations, such as patients with prior valve replacement or prior coronary bypass, should be considered for a mechanical valve [6, 19].
Bioprosthetic Valve
Bioprosthetic aortic valve implantation with St. Jude Trifecta™ aortic valve
St. Jude Medical (SJM) Trifecta™ aortic tissue valve. Reproduced with permission of St. Jude Medical, ©2017
Studies have shown higher reoperation rates in patients with bioprosthetic valves , as well as more structural valve deterioration (SVD) [20]. In most series, freedom from SVD falls rapidly after the 15 year follow-up [7, 20–22]. In addition, younger patients may be predisposed to premature bioprosthetic SVD [23, 24]. Stented bioprosthetic valves generally have lower effective orifice areas compared to that of mechanical valves, and may not be ideal in patients with small aortic roots. However, stentless biologic valves may have less residual gradients than stented valves [25]. Stentless valves are more complex to implant, requiring longer cross clamp times. Overall, bioprosthetic valves can be considered for older patients, specifically patients over 70 years old. A bioprosthesis is also a good option for patients with contraindications to anticoagulation, such as women of childbearing age who wish to become pregnant, patients with bleeding disorders, contraindication to anticoagulation, or patients who are noncompliant or refuse anticoagulation.
Homograft
Aortic root homografts (allografts) and porcine root xenografts are additional options for valve replacement. These options replace the aortic valve and the aortic root. They offer various advantages, including an excellent hemodynamic profile with low transvalvular gradients [26]. Homografts have a low risk of thromboembolism without the need for systemic anticoagulation. Furthermore, they offer potentially the lowest risk of prosthetic valve infection compared to other replacement options. However, these conduits carry the risk of structural deterioration which is inversely proportional to recipient age. In addition, older homograft donor age may contribute to higher rates of degeneration. The availability of homografts may also be limited, especially in larger sizes.
Overall, homografts and xenografts may be considered in various scenarios. The most common indication for a homograft is for the treatment of aortic valve endocarditis which has also affected the root [27, 28]. Compared to a valved conduit graft, a homograft or xenograft possesses minimal prosthetic material, which may be preferable in the setting of infection [29]. Another indication is use in a patient with a small aortic root. These conduits are stentless, which provides improved hemodynamics over other valve options. In addition, because the root is replaced, the risk of coronary obstruction by an oversized prosthesis is eliminated in these patients. Finally, because these conduits have a low risk of thromboembolism, they may be considered for patients who require valve and root replacement who cannot be anticoagulated [30].
Ross Procedure
The Ross procedure was first reported by Donald Ross in 1967 as an option for valve replacement in aortic valve disease. The procedure involves replacement of the diseased aortic valve with a pulmonary autograft and reconstruction of the right ventricular outflow tract (RVOT) with a homograft or xenograft. This procedure has proven long-term durability and the benefit of avoiding formal anticoagulation [31]. In 1987, Elkins and Stelzer began performing this operation in children leading to its adoption in the United States [32].
The main benefit of the Ross procedure is better hemodynamics across the replaced aortic valve when compared to a prosthetic valve. In the pediatric population, the Ross procedure remains a preferred choice for patients with left ventricular outflow tract (LVOT) obstruction. A significant benefit is that the valve can grow with the child, thereby avoiding multiple valve replacements. Additionally, long-term anticoagulation is not required and thrombosis occurs infrequently. The superior hemodynamics and freedom from anticoagulation makes the Ross procedure the ideal operation for active young patients with aortic valve disease.
Ideal patients for the Ross procedure are young adults with aortic valve disease and a normal-sized annulus [33]. Other patients to consider for the Ross procedure are women of childbearing age, high-level athletes, young patients with bleeding disorders or other factors preventing anticoagulation, and patients with greater than 20-year life expectancy who do not want full anticoagulation. With regard to age, some authors suggest the surgery should not be done in patients at the extremes of age. However, Schmidtke et al. reported on their experience with the Ross procedure in patients over the age of 60. They concluded that the procedure could be safely performed with excellent 7-year results in selected elderly patients up to the age of 70 [34]. After this age, the long-term benefits would be lost as the life expectancy is significantly reduced. Conversely, Willams et al. reported on their experience in infants less than 18 months of age and the results were also excellent [35]. These reports reinforce the applicability of the Ross procedure for patients regardless of age.
Contraindications to the Ross procedure include multi-vessel coronary artery disease, severely depressed left ventricular function, multiple valvular pathology, disease of the native pulmonary valve, connective tissue disease, and significant aortic root dilation.
One major criticism of the Ross procedure is that the operation converts a single valve pathology to a double-valve pathology (aortic and pulmonary), thereby increasing the incidence of reoperations on both the pulmonary autograft and the homograft [36, 37]. Reported incidences of reoperation range from 8 to 15% at 10 years [36]. The major indication for reoperation is dilation of the pulmonary autograft. However, revised surgical techniques at the index operation as well as better selection of surgical candidates can mitigate this complication.
The long-term outcomes of the Ross procedure are excellent. Compared to aortic valve replacement with either a mechanical or bioprosthetic valve, only patients who underwent the Ross procedure have shown survival which approached that of the general population [38]. The Ross procedure is a complex and technically demanding operation with a steep learning curve. Therefore, it should only be performed in highly specialized cardiac centers by experienced surgeons.
Valve Conduit
An additional option for AVR with aortic root or ascending aortic replacement is a valve conduit. The valve conduit typically consists of a mechanical valve which is annealed to a Dacron graft from the manufacturer. Alternatively, the surgeon may also create a valve conduit by suturing a bioprosthetic or mechanical valve to a graft. Valve conduits are considered the gold standard for aortic root replacement, but do carry the risk of prosthetic graft material and the potential for infection. Grafts are spared from degeneration and can last for a patient’s lifetime.
Aortic Root Enlargement
A small aortic root can be a potential limitation to aortic valve replacement. Patient prosthesis mismatch (PPM) can occur when a valve prosthesis effective orifice area is not sufficient for the patient’s body surface area, which can result in elevated gradients across the valve postoperatively. Several studies have shown that severe PPM has an adverse impact on survival. When faced with a small aortic root, a surgeon may consider aortic root enlargement in order to safely place a larger valve.
One option for aortic root enlargement involves incorporation of a bovine pericardial or Dacron patch to enlarge the diameter. There are three specific surgical techniques for aortic annular enlargement. In the Nicks procedure, the aortotomy is extended into the nadir of the non-coronary sinus and into the basal third of the anterior leaflet of the mitral valve. An autologous pericardial patch or a Dacron patch is fashioned in a teardrop shape to enlarge the annulus. The valve implantation sutures are then placed across the patch itself, as well as the remainder of the annulus. This procedure can allow the surgeon to place a valve up to two sizes larger than the native annulus [39]. Similarly, the Manougian procedure involves extending the aortotomy more posteriorly along the commissure of the non-coronary and left coronary cusps. This incision is carried through the aortic-mitral septum and onto the anterior leaflet of the mitral valve, while also opening the roof of the left atrium. A patch is then implanted along the mitral valve incision and the aortotomy, and the valve sutures may then be utilized to close the atriotomy [40]. The last and perhaps most radical option is the Konno-Rastan procedure , which involves making an enlarging incision to the left of the right coronary orifice, into the ventricular septum and along the free wall of the right ventricle [41]. A patch is utilized to repair the septum, as well as a second patch for the closure of the right ventriculotomy and annular enlargement. All root enlargement procedures may increase the operative risk with aortic valve replacement, and therefore should only be undertaken with caution.
Transcatheter Aortic Valve Replacement
Edwards SAPIEN 3™ transcatheter heart valve . Courtesy of Edwards Lifesciences LLC, Irvine, California
Edwards Commander™ delivery system for TAVR. Courtesy of Edwards Lifesciences LLC, Irvine, California
The PARTNER and CoreValve Pivotal Trials examined the utility of TAVR in the setting of inoperable, as well as high-risk, surgical patients. Overall, TAVR was associated with improved one and two-year mortality compared with medical management [42]. When TAVR was compared to surgery for high-risk patients, both the PARTNER and the CoreValve Trials found no difference in mortality at 30 days between the two groups. However, at 1 year, the CoreValve study noted a lower mortality with TAVR as compared to the surgical arm, while the PARTNER study found no difference [43, 44].
These trials have formed the basis of the current indications for TAVR . The AHA/ACC guidelines recommend surgical AVR for patients with low or intermediate surgical risk. Patients who have a prohibitive risk for surgery and a predicted post TAVR survival of greater than 12 months should be considered for TAVR. In addition, TAVR is a reasonable alternative to surgical AVR for patients who are high surgical risk [3]. It is likely that TAVR will be approved for use in low risk patients in the near future.
An additional PARTNER trial, the 2A trial , studied TAVR in intermediate-risk populations. There was no difference in disabling stroke, but the need for permanent pacemaker and the incidence of paravalvular leak was higher in the TAVR arm compared to the surgical arm. TAVR has since been approved by the US Food and Drug Administration for use in intermediate-risk populations. However, surgical AVR remains the gold standard for low- and intermediate-risk populations. For a more in depth review of TAVR, see Chap. 10.
Aortic Valve Repair
Aortic valve repair may be an option for selected patients who have aortic insufficiency or a normally functioning aortic valve associated with an aortic root or ascending aortic aneurysm. When considering a patient for aortic valve repair, the cause of the aortic insufficiency as well as the aortic cusp integrity are important determinants. Cusps with mobile and smooth-free margins may be good candidates for repair, while calcified, scarred, and fibrotic cusps may preclude an effective repair.
Overall, bicuspid aortic valve with prolapse is the most commonly performed aortic valve repair in adults [45, 46]. The prolapsing and elongated cusp can be plicated to shorten the free margin and improve coaptation. In addition, selected congenital disease and rheumatic disease may be repaired by cusp extension using autologous or bovine pericardium. Occasionally, a cusp perforation may be the sole cause of aortic insufficiency. Simple patch repair with pericardium can provide a durable repair in such circumstance. Finally, dilation of the sinotubular junction can increase the stress along the free margin of the cusps, which can ultimately lead to thinning and fenestrations. These fenestrations can be potentially repaired by running a suture along the free margin of the cusp. Careful evaluation of the valve is required for successful aortic valve repair [47].
Mitral Valve
Mitral valve disease including mitral regurgitation (MR) and mitral stenosis (MS) is caused by many different pathologies. Repair of the mitral valve is preferred to replacement in most cases of mitral regurgitation when appropriate.
Mitral Valve Repair
For patients with rheumatic, mixed, and degenerative mitral valve disease, mitral valve repair provides an improved quality of life with less morbidity and improved long-term survival when compared to mitral valve replacement [48]. Mitral repair is considered very durable, with many patients remaining free of reoperation up to 30 years from repair [49]. For this reason, repair should be performed whenever possible, specifically in the setting of mitral regurgitation (MR) . However, in contrast to MR, mitral stenosis (MS) is often not amenable to repair. Furthermore, some retrospective data suggests that for patients with MS, replacement may have a better outcome than commissurotomy or valvuloplasty [50].
Indications
The indications for mitral valve repair are broadening as techniques for mitral repair have improved and overall outcomes have improved. The AHA/ACC guidelines recommend mitral valve surgery for all patients both symptomatic and asymptomatic with severe, primary MR and an LVEF >30%. For patients with severe MR and an LVEF <30%, mitral valve repair can be considered. In addition, patients with moderate MR who are undergoing cardiac surgery for other indications can be considered for mitral valve repair.
For patients with secondary MR, mitral valve surgery is recommended if the MR is severe and the patient is undergoing coronary artery bypass or aortic valve replacement. Mitral valve repair can be considered for moderate secondary MR for patients undergoing other cardiac surgery. Lastly, mitral valve surgery can be considered for severely symptomatic patients with severe secondary MR with persistent symptoms despite optimal medical management of heart failure.
For all patients being considered for mitral valve surgery, adequate functional status before mitral valve surgery is preferred. Patients with symptoms of heart failure should be optimized as much as possible with diuresis preoperatively. Ventricular function is also important to consider when evaluating operative candidacy. For patients with severe MR, the left ventricular ejection fraction (LVEF) often decreases postoperatively, even for patients with a normal LVEF preoperatively [3].
Mitral Valve Repair Techniques
Various techniques have been developed for mitral valve repair. The choice regarding which technique to utilize is based on the pathology of valve dysfunction. In general, repair techniques are aimed at stabilizing the dilated or weakened annulus, as well as reducing the height of the prolapsing or flail leaflet to restore proper leaflet coaptation and prevent systolic anterior motion (SAM) .
Annuloplasty Rings
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