**7. Surgical–technical complications**

In spite of all implantation techniques of different stentless bioprostheses are demanding and require an aortic valve surgical experience, some situations can make trouble AVR intraoperatively or impair operative outcomes in the early postoperative period. Every surgeon must be aware of these troubles and keep in mind case specific technical solutions in the theater.

#### **7.1. Severe annular calcification**

ascending aortic replacement with a stentless bioprosthesis [47]. Last decade, ascending aortic replacement is the most preferred method for the treatment of porcelain aorta, but transfemoral [64] or transapical [65] AVI will replace the first choice of the treatment in this decade. These alternatives demonstrate significant advantages (especially very low incidence of neurological events, avoidance of cardiopulmonary bypass and circulatory arrest) in comparison to other

Many patients with moderate or severe calcific aortic stenosis have significant coronary disease, suggesting that the degenerative changes of the aortic valve leading to aortic stenosis may be part of a similar arteriosclerotic process. Coronary lesion can be also in different coronary arteries or massif calcification involves into coronary ostia. Combined surgical treatment is the main modality, but percutaneous coronary intervention is safer in patients undergoing transcatheter AVI, or in patients with high risk (high comorbidi‐ ties, reoperation, pericardial adhesion). Because hypercholesterolemia is related to in‐ creased risk of aortic valve calcification in patients with aortic stenosis, preventive treatment of hypercholesterolemia could play an important role to decrease or inhibit de‐

The best opportunity to improve the treatment of any hematologic disease or to prevent any complication aggravating by hematologic pathologies is avoidance from prosthetic foreign devices. Autologous tissue is the only biologic material preparing prosthetic valve, but that can be limited because of pericardial pathologies, inadequate surgical experience or technical problems. Mechanical valves have life-long durability with some possible hematologic complications such as thrombo-embolism, warfarin related hemorrhage, heparin induced thrombocytopenia, hemolysis. Prosthetic foreign material can also aggravate hematologic diseases. To decide which prosthesis can be the acceptable choice for AVR in patients with hematologic pathology is depend on patient's characteristics and patient-by-patient analysis is required. Biomaterials seem better than mechanical prostheses, and stentless aortic biopros‐ theses are the best alternatives because of absence of a rigid stent, biodynamic characteristics, larger EOA with lowest transvalvular obstruction, unnecessariness of anticoagulation, which might decrease hematologic complications. I prefer stentless xenografts for AVR in patients

Postoperative thrombocytopenia is a transient phenomenon, self–recovering after a few days without any treatment and without any observed recurrence in late follow-up. Microhemo‐ dynamic effects of the prosthesis structure or depending on the implantation technique and/or specific chemical preparations of biological prosthesis tissue could act as a trigger for the post-replacement thrombocytopenia. It seems to be possible that transient unspecific activation of platelets result in diffuse consumption and lower platelet levels. The reason for this phenomenon is unknown and the use of consistent monitoring is necessary to prevent severe falls in platelet count. It seems unrelated to the type of aortic bioprosthesis and I have

conventional techniques in the setting of severe aortic calcification.

**6.4. Concomitant severe coronary artery disease**

432 Calcific Aortic Valve Disease

velopment of aortic valve calcification [66].

**6.5. Concomitant hematologic disease**

with severe hematologic pathologies [67].

To replace the diseased aortic valve in patients with calcific aortic stenosis is a serious intervention because of extensive calcification. Debridement of all calcium deposits back to soft tissue improves seating of stentless prostheses in supra-annular position and provides better performance, and may be, protects devices early calcification. I always prefer deep debridement and decalcification of all around structures. If there is no any damage on the annulus, I implant a stentless valve with the single suture technique (supra-annular implan‐ tation); if not, I prefer the classic subcoronary technique and use pledgeted sutures in suban‐ nular position to repair defects. Calcification after stentless valve implantation is complicated if a stentless bioprosthesis is implanted in young patient: faster calcification in homografts has been reported compared with xenografts [71].

#### **7.2. Conduction disturbances**

Permanent of transient conduction defects are well-known complications of aortic valve surgery [72]. Higher degree atrioventricular blocks are often reversible and disappear before discharge from the hospital. Approximately 5% of patients undergone isolated AVR require permanent pacemaker implantation. Risk factors can be patient-specific: bicuspid aorta, annular calcification, hypertension, preexisting conduction disturbances, coronary artery disease. Surgeon-specific risk factors cause mostly mechanical injury of the atrioventricular conduction pathways during aortic valve surgery: annular decalcification, deep suture placement, suturing techniques, pressure on the conduction tissue. Atrioventricular block generally results from trauma to the atrioventricular node or His bundle in the region of membranous septum and right trigone beneath the non-coronary - right coronary cusps commissure. The continuous inflow suture line is the most common cause for atrioventricular block because this suture line is placed below each commissure in a horizontal plane based on the level of the nadir of the attachments of the native aortic valve leaflets to the native aortic valve annulus. Raising the continuous inflow suture line below non-coronary - right coronary commissure prevents such conduction complication. Interrupted inflow sutures are also safer than continuous technique. The best approach is the single suture line technique which does not need any inflow suture line.

#### **7.3. Coronary insufficiency**

Coronary flow complications are uncommon after stentless AVR, in spite of calcific aortic valve stenosis appears often with coronary ostia calcification with/without coronary artery disease. Myocardial ischemia developing after AVR can develop due to several reasons. Uniform adequate myocardial preservation during operation is the main preventive strategy. Coronary artery bypass grafting should be added aortic valve surgery if any coronary artery stenosis is proved angiographically before surgery. Technical or pathologic factors must also keep in mind. Extensive calcific involvement of coronary ostia or any calcific particle embolization can block antegrade coronary blood flow postoperatively. Endarterectomy or coronary artery bypass grafting should be performed if not any coronary lesion is proved. Decalcification of the aortic root may be well without any aggressive manipulation on coronary ostia, but rupture around coronary ostia can be fatal. Implantation techniques can damage coronary blood flow due to technical errors. Besides a learning curve for these more complex procedures, other factors that could potentially contribute to excess myocardial ischemia or bleeding causing coronary ostia complications. Technical problems can occur mostly during the aortic root replacement with stentless xenografts. This type of coronary insufficiency is uncommon and more often affects the right coronary artery [73]. Coronary buttons are prepared for suturing to xenografts, but they can be damaged because of extensive cutting, dissection, or aggressive decalcification of buttons. Severe tension on the button anastomoses can cause bleeding, rupture, kinking or obstruction. Preventive maneuvers are recognition of coronary orientation, routine xenograft rotation, adequate coronary button mobilization, oversizing xenograft. The subcoronary implantation is more secure procedure than the root replacement technique and technical complication causing coronary problems can occur very seldom if running sutures bite very close to the coronary ostia.

**7.5. Progressive sinotubular junction dilatation**

tendency to roll if oversized.

leading increase of leaflet stress and degeneration.

any leakage or stretching.

This late postoperative complication is observed in some stentless xenografts when they are implanted with the subcoronary technique. Currently, little is known of the diastolic properties of stentless valves that affect stress and strain on leaflets and, hence, their durability. Despite similar systolic performances, stentless prostheses behave differently during diastole. The commissures of the stentless bioprostheses have to follow the dimensional changes of the native aortic root not only in a cyclic mode but also the increase of the aortic diameter [76]. This change pulls apart the commissures leading to reduction of coaptation area of the cusps and late aortic insufficiency develops. Aortic regurgitation is often mild or moderate depend‐ ing on bioprosthesis type, especially in old generation, but re-operation rate is low. In a pressurized aortic root model, a series of in-vitro tests is conducted to determine how stentless valves behave in diastole, and how they adapt to different annulus-to-sinotubular junction (STJ) ratios [77]. Pericardial prostheses built to mimic a cylinder (ATS 3F and Sorin Solo) showed the greatest tolerance to STJ dilatation and a larger coaptation surface, but also a tendency to roll in on themselves in an italic S-shape if oversized. Valves built to mimic native aortic leaflets (porcine Prima Plus and Medtronic Freestyle) showed a reduced tolerance to STJ dilatation, resulting in regurgitation and a smaller coaptation surface, but also a reduced

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A significant difference of tolerance against aortic regurgitation with respect to dilatation of the sinotubular junction was found in an in vitro study: fresh porcine aortic root (higher) > fresh porcine pulmonary root > stentless porcine bioprosthesis (lower) [78]. This loss of adaptability may be related to the glutaraldehyde fixation leading stiffness and shrinkage of the bioprosthetic leaflets which leaves inadequate coaptation reserve. An increase of sinotub‐ ular junction diameter of more than 32% for the Toronto SPV and 43% for Medtronic Freestyle stentless valves results in a distinct loss of leaflet coaptation and causes aortic regurgitation.

New generation of pericardial stentless valves developed for subcoronary implantation have larger coaptation area than those old generation or porcine stentless valves, which may provide better adaptability to adverse changes in root dimensions [79]. With massif progressive stepwise dilatation at sinotubular junction level, the free edges of the leaflets are stretched wider and a triangle-shaped central coaptation defect will occur. For the 3F Aortic valve regurgitation started at approximately 156% of the labeled valve size and 145% for the Sorin Solo valve. The increased tolerance of pericardial bioprostheses may improve long-term valve performance, but durability of these valves may be affected by the redundant leaflet tissue

To overcome this disadvantage of stentless valves, a slight oversizing of the devices may result better valve competence and hemodynamic efficiency compared to size-for-size implantation. Sizing with a supra-annular seizer is helpful to find the largest stentless valve number which is minimum equal to the sinotubular junction diameter in patients with healthy aortic root. The single suture line technique is fixed prosthetic sinuses onto the native aortic wall to prevent

#### **7.4. Dehiscence**

Partial or severe dehiscence of aortic prosthetic valves is a serious, but very rare complication. Complete dehiscence occurs with sudden death and it is not seen during practice life. Demand on the severity of dehiscence, the clinic scenario can be variable. Limited dehiscence can be silent and stable, more serious dehiscence shows some signs and unstable. If the aortic root replacement technique is preferred dehiscence can be very small at the proximal or distal suture line which presents bleeding, hematoma or massif hemorrhage. Dehiscence observed after the subcoronary implantation technique is associated with aortic regurgitation, but using obliterating sutures prevent usually this complication. In the aortic root inclusion technique, the dead space between native and donor aortas might be prevented adequate fusion of the walls and healing of the anastomoses, which is observed mostly in non-coronary sinus [74]. Any symptomatic dehiscence investigated by echocardiography intra- or early postoperatively should be repaired and a reoperation should be performed immediately. In the absence of valve dysfunction, progressive dehiscence, or the development of thrombus a reoperation can be not necessary and conservative management will be safe during early- and long-term follow-up [75].

#### **7.5. Progressive sinotubular junction dilatation**

**7.3. Coronary insufficiency**

434 Calcific Aortic Valve Disease

bite very close to the coronary ostia.

**7.4. Dehiscence**

follow-up [75].

Coronary flow complications are uncommon after stentless AVR, in spite of calcific aortic valve stenosis appears often with coronary ostia calcification with/without coronary artery disease. Myocardial ischemia developing after AVR can develop due to several reasons. Uniform adequate myocardial preservation during operation is the main preventive strategy. Coronary artery bypass grafting should be added aortic valve surgery if any coronary artery stenosis is proved angiographically before surgery. Technical or pathologic factors must also keep in mind. Extensive calcific involvement of coronary ostia or any calcific particle embolization can block antegrade coronary blood flow postoperatively. Endarterectomy or coronary artery bypass grafting should be performed if not any coronary lesion is proved. Decalcification of the aortic root may be well without any aggressive manipulation on coronary ostia, but rupture around coronary ostia can be fatal. Implantation techniques can damage coronary blood flow due to technical errors. Besides a learning curve for these more complex procedures, other factors that could potentially contribute to excess myocardial ischemia or bleeding causing coronary ostia complications. Technical problems can occur mostly during the aortic root replacement with stentless xenografts. This type of coronary insufficiency is uncommon and more often affects the right coronary artery [73]. Coronary buttons are prepared for suturing to xenografts, but they can be damaged because of extensive cutting, dissection, or aggressive decalcification of buttons. Severe tension on the button anastomoses can cause bleeding, rupture, kinking or obstruction. Preventive maneuvers are recognition of coronary orientation, routine xenograft rotation, adequate coronary button mobilization, oversizing xenograft. The subcoronary implantation is more secure procedure than the root replacement technique and technical complication causing coronary problems can occur very seldom if running sutures

Partial or severe dehiscence of aortic prosthetic valves is a serious, but very rare complication. Complete dehiscence occurs with sudden death and it is not seen during practice life. Demand on the severity of dehiscence, the clinic scenario can be variable. Limited dehiscence can be silent and stable, more serious dehiscence shows some signs and unstable. If the aortic root replacement technique is preferred dehiscence can be very small at the proximal or distal suture line which presents bleeding, hematoma or massif hemorrhage. Dehiscence observed after the subcoronary implantation technique is associated with aortic regurgitation, but using obliterating sutures prevent usually this complication. In the aortic root inclusion technique, the dead space between native and donor aortas might be prevented adequate fusion of the walls and healing of the anastomoses, which is observed mostly in non-coronary sinus [74]. Any symptomatic dehiscence investigated by echocardiography intra- or early postoperatively should be repaired and a reoperation should be performed immediately. In the absence of valve dysfunction, progressive dehiscence, or the development of thrombus a reoperation can be not necessary and conservative management will be safe during early- and long-term This late postoperative complication is observed in some stentless xenografts when they are implanted with the subcoronary technique. Currently, little is known of the diastolic properties of stentless valves that affect stress and strain on leaflets and, hence, their durability. Despite similar systolic performances, stentless prostheses behave differently during diastole. The commissures of the stentless bioprostheses have to follow the dimensional changes of the native aortic root not only in a cyclic mode but also the increase of the aortic diameter [76]. This change pulls apart the commissures leading to reduction of coaptation area of the cusps and late aortic insufficiency develops. Aortic regurgitation is often mild or moderate depend‐ ing on bioprosthesis type, especially in old generation, but re-operation rate is low. In a pressurized aortic root model, a series of in-vitro tests is conducted to determine how stentless valves behave in diastole, and how they adapt to different annulus-to-sinotubular junction (STJ) ratios [77]. Pericardial prostheses built to mimic a cylinder (ATS 3F and Sorin Solo) showed the greatest tolerance to STJ dilatation and a larger coaptation surface, but also a tendency to roll in on themselves in an italic S-shape if oversized. Valves built to mimic native aortic leaflets (porcine Prima Plus and Medtronic Freestyle) showed a reduced tolerance to STJ dilatation, resulting in regurgitation and a smaller coaptation surface, but also a reduced tendency to roll if oversized.

A significant difference of tolerance against aortic regurgitation with respect to dilatation of the sinotubular junction was found in an in vitro study: fresh porcine aortic root (higher) > fresh porcine pulmonary root > stentless porcine bioprosthesis (lower) [78]. This loss of adaptability may be related to the glutaraldehyde fixation leading stiffness and shrinkage of the bioprosthetic leaflets which leaves inadequate coaptation reserve. An increase of sinotub‐ ular junction diameter of more than 32% for the Toronto SPV and 43% for Medtronic Freestyle stentless valves results in a distinct loss of leaflet coaptation and causes aortic regurgitation.

New generation of pericardial stentless valves developed for subcoronary implantation have larger coaptation area than those old generation or porcine stentless valves, which may provide better adaptability to adverse changes in root dimensions [79]. With massif progressive stepwise dilatation at sinotubular junction level, the free edges of the leaflets are stretched wider and a triangle-shaped central coaptation defect will occur. For the 3F Aortic valve regurgitation started at approximately 156% of the labeled valve size and 145% for the Sorin Solo valve. The increased tolerance of pericardial bioprostheses may improve long-term valve performance, but durability of these valves may be affected by the redundant leaflet tissue leading increase of leaflet stress and degeneration.

To overcome this disadvantage of stentless valves, a slight oversizing of the devices may result better valve competence and hemodynamic efficiency compared to size-for-size implantation. Sizing with a supra-annular seizer is helpful to find the largest stentless valve number which is minimum equal to the sinotubular junction diameter in patients with healthy aortic root. The single suture line technique is fixed prosthetic sinuses onto the native aortic wall to prevent any leakage or stretching.

#### **7.6. Reoperation of a stentless aortic bioprosthesis**

Stentless aortic valve reoperations may become more common as these bioprostheses reach the limits of their durability, which are a challenging procedure with an increased risk of death [80].The current generation of stentless valves have been implanted since the early 1990s and are therefore starting to reach the limits of their durability. Reoperation for stentless valves is a complex procedure, especially root inclusion or full-root replacement was preferred. The risk of trauma to the coronary ostia, aortic wall, aortic annulus, anterior mitral valve, and mem‐ branous septum can all occur when severe adhesions or calcification are present around the stentless valve. Reoperation after a stentless valve is more complex than after a stented tissue or mechanical valve if root replacement techniques is used in the first operation. However, reoperation of subcoronary implanted stentless bioprosthesis is easier than any stented prosthesis because cutting only the suture line is enough to remove the degenerated biopros‐ thesis. Valve-in-valve replacement with transfemoral [81] or transapical [82] AVI is a more conservative alternative strategy for re-replacement of degenerated xenograft in high risk patients.

when compared with stented valves (7.5% versus 3.3%; p = 0.026), but if stentless valves are used widely there is no significant difference in operative mortality between stentless and stented groups [87].Using autologous pericardium does not worse the early hospital outcome

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Several studies showed an improved mid-term (< 10 years) survival after stentless AVR compared to stented valves [88,89]. A meta-analysis shows that mortality at the first year is lower after stentless aortic bioprosthesis replacement than stented bioprosthesis, but not significant: 7.5% versus 8.9%; p = 0.73 [15]. Another meta analysis also confirm no significant difference for valve-related mortality between stentless and stented xenograft replacement in the first postoperative year [86]. Lehmann and associates [89] showed in a randomized trial that 8-year survival was 78.1% ± 3.8% stentless versus 66.7% ± 4.9% stented (p = 0.03). They concluded that there was no difference in survival when compared stentless patients with an

The long-term results (≥ 10 years) with stentless valves are excellent [90]. The overall 10- and 15-year survival rates of Freestyle bioprosthesis are 60.7% and 35%, respectively [91]. The 10 year actuarial survival (44.1% ± 4.3% in subcoronary, 47.3% ± 8.15 in full-root, and 45.4% ± 13.7% in root inclusion groups; p = 0.89) and freedom from valve-related death (94.5% ± 2.9% in subcoronary, 92.9% ± 5.8% in full-root, and 87.8% ± 12.5% in root inclusion groups; p = 0.17) are similar between implants techniques with the Freestyle stentless bioprosthesis [92]. Longer follow-up (> 15 years) of stentless valves is also necessary to compare the excellent results of stented valves to establish that stentless xenografts are significantly superior than stented

The rate of structural valve deterioration increases over time, especially after the initial 7 to 8 years after implantation. Structural degeneration increases long-term events and the rate of failure is < 1% at 10 years in patients older than 65 years [93]. Pericardial valves might be better than porcine valves, but all newer-generation bioprostheses are more durable. In spite of the rate of failure of any bioprosthesis decreases with the age of the patient at the time of implan‐ tation (< 10% at 10 years in patients older > 70 years), the number of implanted stentless xenografts has increased due to improved hemodynamic performance and long-term dura‐ bility during last decade. Theoretically, xenogenic stentless aortic valves have better durability than stented valves. But in real life, the freedom rate from structural valve deterioration is similar in stentless and stented bioprostheses (> 90% at 10 years). CryoLife O'Brien and St Jude Toronto SPV valves have worst durability compared the other stentless valves (Medtronic

When we focus on the implantation techniques, there are very rare papers in the literature. The overall freedom from reoperation with Freestyle stentless bioprosthesis is 91.0% and 75.0% at 10 and 15 years, whereas freedom from reoperation for structural valve deterioration was 95.9% and 82.3%, respectively. At 10 and 15 years, freedom from reoperation for structural valve deterioration is 94.0% and 62.6% for patients < 60 years of age and 96.3% and 88.4% for patients ≥ 60 years of age (p = 0.002) [90]. The actuarial freedom from reoperation (91.7% ± 3.5%

Freestyle, Edwards Prima, St Jude Biocor, Sorin Pericarbon and Solo, ATS 3f).

and early mortality is not seen [11].

age-matched German control population.

devices.

**8.2. Durability**
