**6. Special situations**

hemodynamic performance. There are two types of sutureless aortic bioprostheses in the

The Perceval S Aortic Bioprosthesis (Sorin Biomedia Cardio Srl, Sallugia, Italy) has been introduced for minithoracotomy incision [38]. After the device is introduced and parachuted down into aortic annulus and checking corrected position, a balloon dilatation of the inflow ring is performed in the Perceval S valve. If the device is in malpositioning the valve can be quickly removed using the 'χ movement' and repositioned [39]. Because there are only three number valves (21, 23, 25), paravalvular leakage can be observed in higher incidence (4.4% postoperatively and 4% during follow-up) which can be a result of either inadequate sizing or due to inappropriate decalcification of the annulus [40]. For an enlarged aorta with a ratio greater than 1.3, the predicted diameter according to body surface area represents a contrain‐ dication for this device. Early mortality (total 2.4%) and late death (total 2.5%) is acceptable

with lower transvalvular gradient (10.8 mmHg) at the first postoperative year [41].

year), lower paravalvular leakage (0.8%/year) [44].

The 3f Enable Aortic Bioprothesis (Model 6000; Medtronic Inc, Minneapolis, USA) is more different and the implantation is more easier: after insertion the device into aortic root in the corrected position, only pour warmer saline (> 30°) onto the device to fully deploy the Nitinol frame into its original shape [42]. If malpositioning occurs after complete de‐ ployment, rinsing with chilled saline makes the nitinol stent flexible and enhances reposi‐ tioning until the valve is correctly placed. Early clinical and hemodynamic performances of the 3f aortic bioprosthesis are similar to those of the regular stentless aortic valves, but both parameters could be inconsistent with the established stentless valves during midterm follow-up: unfavorable mean gradient especially with smaller number (≤ 23 mm), in‐ complete left ventricular regression, higher incidence of neurologic complications [43]. However, a multi-center study has shown better early and mid-term results: major para‐ valvular leakage 2.1%, neurologic events 0.7%, lower mean gradient (10.2 mmHg), lower valve-related early mortality rate (1.4%; total 3.6%); lower late mortality rate (1.5%; total 9.6%), excellent freedom from valve-related mortality at 1-year (96.5%; hazard ratio 1.6%/

The analysis of the current outcome of the use of sutureless aortic bioprostheses must take into consideration the preliminary nature of these devices and the relevant implantation learning curve. There are no comparative study analyzing the outcomes of sutureless and stentless bioprostheses, but it can be said that sutureless bioprostheses have better outcome (mortality, neurologic deficit, renal failure, bleeding) than conventional stentless valves in high-risk patients with aortic stenosis (such as older, female, left ventricular dysfunction, calcification in the ascending aorta, previously cardiac operation, pulmonary or renal disease? [45].

The approval of transcatheter aortic valve implantation (AVI) represents a fundamental change in the management of calcific aortic stenosis by offering an alternative to traditional surgical AVR in carefully selected patients. Patient-selection is very strict nowadays, and AVI is a reasonable alternative to surgical AVR in adults with severe symptomatic calcific aortic stenosis if they have suitable aortic and vascular anatomy for transcatheter AVI and a predicted

**5.7. Transcatheter (transfemoral or transapical) aortic valve implantation**

market.

428 Calcific Aortic Valve Disease

Calcific aortic stenosis is a long-term disease and usually associated with other cardiovascular pathologies. Before AVR, all these situations must be reassessmended and case-specific operation procedure and its alternatives must be planned. If we do not think preoperatively that any specific situation needs an intervention intra-operatively, spontaneously home-made resolutions can be also very helpful in the theater when we decide to correct this pathology.

#### **6.1. Proximal ascending aorta aneurysm**

Severe aortic stenosis is usually combined with proximal ascending aorta aneurysm causing by turbulent flow. The gold standard treatment is composite aortic valve and root replacement. Several surgical teams have devised strategies to construct their homemade composite conduits intra-operatively. It can be a mechanical valved conduit with excellent long-term results [47]. If any contra-indication for anticoagulation therapy, a composite bioprosthetic valved conduit will be the best alternative. Because severe calcific aortic stenosis is often an elderly disease, improved durability of bioprostheses stimulates also their use in the setting of ascending aorta replacement if proximal ascending aorta requires replacement in this population. The concept of composite bioprosthetic valved conduits has also been taken up by the industry and these conduits are already commercially available in different sizes. There are several technical options to allow replacement of the aortic root and ascending aorta using either stented or stentless bioprosthesis [48]. There are basically two alternatives to built a composite graft with a stentless bioprosthesis: the subcoronary technique and the full-root technique.

The subcoronary implantation technique requires a tubular graft and double suture lines for device implantation is necessary. A stentless valve is placed inside a Dacron tube graft leaving a proximal free margin (3-5 mm) and the proximal suture line of the stentless bioprosthesis is fixed to the graft with a running mattress suture [49]. The free end of the tube graft is then sutured to the native annulus with pledgeted interrupted mattress sutures, and following this, the upper circumference of the stentless valve is reimplanted within the tube graft using a second running mattress suture. To avoid the potential drawbacks of a straight cylindrical tube an aortic graft with pseudo-sinuses can be used [50] or David-V procedure using a stentless bioprosthesis can be applied to build new sinuses [51]. I implant firstly tubular synthetic graft using pledgeted interrupted mattress sutures subannularly, and then a stentless valve is implanted using the single suture line technique as described above. The ready-to-use composite biological valved graft is also available in practice currently [The BioValsalva composite grafts (Sulzer Vascutek, Renfrewshire, Scotland, UK)] [52].

ostia, or prolonged operation times. The full-root replacement technique is technically more demanding, but it prevents residual gradient postoperatively, and if one number larger conduit is selected the possible largest orifice area will be gained. Subcoronary techniques with/without intact non-coronary sinus can be also used in these patients with excellent hemodynamics in smaller valve sizes and appropriate device can be implanted safely and

Stentless Bioprostheses for Aortic Valve Replacement in Calcific Aortic Stenosis

http://dx.doi.org/10.5772/55373

431

Another alternative technique is aortic annulus enlargement to prevent patient-prosthesis mismatch and a two-size-larger prosthesis could be inserted. The most commonly used technique is enlargement of the aortic annulus with a biologic or synthetic patch which can be performed in different approach [60]. A modification of the Manouguian technique has been introduced for aortic annulus enlargement without using a patch [61]. A tubular aortic bioprosthesis of one or two sizes larger than the size of the native annulus is prepared for modified subcoronary implantation technique and non-coronary sinus wall be kept intact. The prosthesis is sutured directly on the enlarged annulus after the aortic incision is extended through the commissure, and the aorta is closed directly with the mural wall of the tubular

The scope of porcelain aorta ranges from isolated plaques to the circumferential calcification of the ascending aorta. Typically, a heavily calcified ascending aorta with calcific aortic stenosis involves aortic annulus, aortic valve, aortic root and ascending aorta (± distal aortic segments). This scenario is associated with higher operative mortality and morbidity than isolated severe calcific aortic stenosis. A more recent study have been demonstrated a link between arterio‐ sclerotic changes in aortic valve and ascending aorta [62]. This study compared healthy patients with severe aortic stenosis patients shows that the prevalence of aortic root calcifica‐ tion (26% versus 54%; p = 0.008) and of atheroma in the ascending aorta (7% versus 24%; p < 0.001) are higher in aortic valve disease patients and patients coexisting coronary artery disease have more extensive arteriosclerotic changes in the thoracic aorta compared with those with

The operative management of severe calcific aortic stenosis with porcelain aorta can be difficult and complex because of difficulty of clamping the ascending aorta, aortotomy, supra-annular sutures, or aortic root replacement, and the risk of calcific embolization of major branches (coronary, carotid, or other arteries), aortic dissection. Digital palpation with a lowered systemic blood pressure or epiaortic sonographic evaluation can be used to confirm that there is a softer spot in the aortic arch for cannulation intra-operatively. If there is no any healthy site on the distal ascending aorta or aortic arch for regular arterial cannulation (34%), alterna‐ tive arterial cannulation should be performed through innominate (8%), axillary (24%) or femoral (34%) artery [63]. There are several alternatives to perform AVR: standard replace‐ ment, endarterectomy for calcified porcelain aorta, no touch technique under circulatory arrest (no cross-clamp, no endarterectomy, no ascending aorta replacement), total replacement of the ascending aorta replacement (with/without circulatory arrest), apico-aortic valved conduit, transcatheter AVI. I prefer standard AVR if it is possible, if not I perform David-V total

easily [59].

xenograft.

**6.3. Porcelain aorta**

aortic stenosis alone and control subjects.

The full-root technique is preferred in order to reduce distortion risk leading valve regurgita‐ tion or deterioration, but the commercially available stentless porcine aortic root devices are usually too short to replace the host ascending aorta. There are also four alternatives to suture a stentless conduit directly to the distal ascending aorta with extended tubular devices: extended version of stentless porcine aortic root bioprosthesis, direct anastomosis after extensive mobilization of the host aorta, interposition of a Dacron tube graft, and total xenopericardial valved conduit. The availability of extended root xenograft is extremely limited, but this approach can achieve an anastomosis between xenograft and the distal ascending aorta [53]. Primary end-to-end anastomosis might prevent the need for graft interposition, but extensive mobilization of the aortic arch and its branches can be dangerous and some tension might be left at the distal anastomosis with a risk of late dehiscence and false aneurysm development [54]. The most practical technique appears to be the insertion of a Dacron tube graft between the xenograft root and the native distal ascending aorta [55]. There is a new bioprosthetic conduit, constructed using individual non-coronary porcine cusps, which are fitted on a scalloped shaped tubular bovine pericardium [56]. The 15 cm long pericardial cuff is long enough to facilitate the anastomosis between the conduit and the remaining distal aorta. If mid- or long-term results will confirm excellent results, this option will be an attractive alternative to the others techniques.

#### **6.2. Small aortic annulus**

Aortic valve replacement with a small stented prosthetic valve is technically straightforward and frequently performed, but it may result in patient-prosthesis mismatch and a high residual outflow gradient, which is significant risk factor for early mortality [57]. Patient-prosthesis mismatch is associated with an increase in all-cause and cardiac-related mortality over longterm follow-up, and current efforts to prevent prosthesis-patient mismatch should receive more emphasis and a widespread acceptance to improve long-term survival after AVR [58]. When the aortic annulus diameter is less than 20 mm, a relatively high transvalvular velocity has to be expected after valve replacement. In these cases, a stentless bioprosthesis with/ without aortic root enlargement would provide better hemodynamic results than stented valves.

For severe small aortic root with small aortic annulus, a xenograft root replacement can be the first alternative and this technique avoids the aortic annulus enlargement, but it can be problematic because of reimplantation of the coronary arteries, calcified aorta and/or coronary ostia, or prolonged operation times. The full-root replacement technique is technically more demanding, but it prevents residual gradient postoperatively, and if one number larger conduit is selected the possible largest orifice area will be gained. Subcoronary techniques with/without intact non-coronary sinus can be also used in these patients with excellent hemodynamics in smaller valve sizes and appropriate device can be implanted safely and easily [59].

Another alternative technique is aortic annulus enlargement to prevent patient-prosthesis mismatch and a two-size-larger prosthesis could be inserted. The most commonly used technique is enlargement of the aortic annulus with a biologic or synthetic patch which can be performed in different approach [60]. A modification of the Manouguian technique has been introduced for aortic annulus enlargement without using a patch [61]. A tubular aortic bioprosthesis of one or two sizes larger than the size of the native annulus is prepared for modified subcoronary implantation technique and non-coronary sinus wall be kept intact. The prosthesis is sutured directly on the enlarged annulus after the aortic incision is extended through the commissure, and the aorta is closed directly with the mural wall of the tubular xenograft.

#### **6.3. Porcelain aorta**

sutured to the native annulus with pledgeted interrupted mattress sutures, and following this, the upper circumference of the stentless valve is reimplanted within the tube graft using a second running mattress suture. To avoid the potential drawbacks of a straight cylindrical tube an aortic graft with pseudo-sinuses can be used [50] or David-V procedure using a stentless bioprosthesis can be applied to build new sinuses [51]. I implant firstly tubular synthetic graft using pledgeted interrupted mattress sutures subannularly, and then a stentless valve is implanted using the single suture line technique as described above. The ready-to-use composite biological valved graft is also available in practice currently [The BioValsalva

The full-root technique is preferred in order to reduce distortion risk leading valve regurgita‐ tion or deterioration, but the commercially available stentless porcine aortic root devices are usually too short to replace the host ascending aorta. There are also four alternatives to suture a stentless conduit directly to the distal ascending aorta with extended tubular devices: extended version of stentless porcine aortic root bioprosthesis, direct anastomosis after extensive mobilization of the host aorta, interposition of a Dacron tube graft, and total xenopericardial valved conduit. The availability of extended root xenograft is extremely limited, but this approach can achieve an anastomosis between xenograft and the distal ascending aorta [53]. Primary end-to-end anastomosis might prevent the need for graft interposition, but extensive mobilization of the aortic arch and its branches can be dangerous and some tension might be left at the distal anastomosis with a risk of late dehiscence and false aneurysm development [54]. The most practical technique appears to be the insertion of a Dacron tube graft between the xenograft root and the native distal ascending aorta [55]. There is a new bioprosthetic conduit, constructed using individual non-coronary porcine cusps, which are fitted on a scalloped shaped tubular bovine pericardium [56]. The 15 cm long pericardial cuff is long enough to facilitate the anastomosis between the conduit and the remaining distal aorta. If mid- or long-term results will confirm excellent results, this option

Aortic valve replacement with a small stented prosthetic valve is technically straightforward and frequently performed, but it may result in patient-prosthesis mismatch and a high residual outflow gradient, which is significant risk factor for early mortality [57]. Patient-prosthesis mismatch is associated with an increase in all-cause and cardiac-related mortality over longterm follow-up, and current efforts to prevent prosthesis-patient mismatch should receive more emphasis and a widespread acceptance to improve long-term survival after AVR [58]. When the aortic annulus diameter is less than 20 mm, a relatively high transvalvular velocity has to be expected after valve replacement. In these cases, a stentless bioprosthesis with/ without aortic root enlargement would provide better hemodynamic results than stented

For severe small aortic root with small aortic annulus, a xenograft root replacement can be the first alternative and this technique avoids the aortic annulus enlargement, but it can be problematic because of reimplantation of the coronary arteries, calcified aorta and/or coronary

composite grafts (Sulzer Vascutek, Renfrewshire, Scotland, UK)] [52].

will be an attractive alternative to the others techniques.

**6.2. Small aortic annulus**

430 Calcific Aortic Valve Disease

valves.

The scope of porcelain aorta ranges from isolated plaques to the circumferential calcification of the ascending aorta. Typically, a heavily calcified ascending aorta with calcific aortic stenosis involves aortic annulus, aortic valve, aortic root and ascending aorta (± distal aortic segments). This scenario is associated with higher operative mortality and morbidity than isolated severe calcific aortic stenosis. A more recent study have been demonstrated a link between arterio‐ sclerotic changes in aortic valve and ascending aorta [62]. This study compared healthy patients with severe aortic stenosis patients shows that the prevalence of aortic root calcifica‐ tion (26% versus 54%; p = 0.008) and of atheroma in the ascending aorta (7% versus 24%; p < 0.001) are higher in aortic valve disease patients and patients coexisting coronary artery disease have more extensive arteriosclerotic changes in the thoracic aorta compared with those with aortic stenosis alone and control subjects.

The operative management of severe calcific aortic stenosis with porcelain aorta can be difficult and complex because of difficulty of clamping the ascending aorta, aortotomy, supra-annular sutures, or aortic root replacement, and the risk of calcific embolization of major branches (coronary, carotid, or other arteries), aortic dissection. Digital palpation with a lowered systemic blood pressure or epiaortic sonographic evaluation can be used to confirm that there is a softer spot in the aortic arch for cannulation intra-operatively. If there is no any healthy site on the distal ascending aorta or aortic arch for regular arterial cannulation (34%), alterna‐ tive arterial cannulation should be performed through innominate (8%), axillary (24%) or femoral (34%) artery [63]. There are several alternatives to perform AVR: standard replace‐ ment, endarterectomy for calcified porcelain aorta, no touch technique under circulatory arrest (no cross-clamp, no endarterectomy, no ascending aorta replacement), total replacement of the ascending aorta replacement (with/without circulatory arrest), apico-aortic valved conduit, transcatheter AVI. I prefer standard AVR if it is possible, if not I perform David-V total 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 conventional techniques in the setting of severe aortic calcification.

not observed this phenomenon only in stentless pericardial valves, but also in different bioprostheses [68]. However, thrombocytopenia after implantation of the stentless pericardial xenografts can develop more common and becomes dangerous for the patient [69,70].

Stentless Bioprostheses for Aortic Valve Replacement in Calcific Aortic Stenosis

http://dx.doi.org/10.5772/55373

433

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.

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

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

**7. Surgical–technical complications**

been reported compared with xenografts [71].

**7.1. Severe annular calcification**

**7.2. Conduction disturbances**

not need any inflow suture line.

#### **6.4. Concomitant severe coronary artery disease**

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‐ velopment of aortic valve calcification [66].

#### **6.5. Concomitant hematologic disease**

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 with severe hematologic pathologies [67].

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 not observed this phenomenon only in stentless pericardial valves, but also in different bioprostheses [68]. However, thrombocytopenia after implantation of the stentless pericardial xenografts can develop more common and becomes dangerous for the patient [69,70].
