**Which Valve to Who: Prosthetic Valve Selection for Aortic Valve Surgery**

Bilal Kaan İnan, Mustafa Saçar, Gökhan Önem and Ahmet Baltalarli *Kasmpaşa Military Hospital, İstanbul, Pamukkale University, Denizli, Turkey* 

## **1. Introduction**

Harken et al. had performed the first aortic valve replacement in subcoronary position in 1960 (Harken, 1960). The "caged ball" valve used in this operation pioneered to the prosthetic valves and in the last 50 years many valve types were begun to be used. The early and long term results of the patients undergone aortic valve surgery do not depend not only the patient-related factors and the type of the surgery. The selected prosthetic valve is one of the most important factor affecting survival. According to the analysis of the multicenter randomized trials made by Hammermeister et al. involving the recent 15 years, more than one third of the deaths among the patients undergone aortic valve surgery were found to be related to the prosthetic valve (Hammermeister, 2000). The expectance from an ideal prosthetic valve is to correct the present valve pathology, to possess normal functions, to normalize patient's life standards or at least to improve it obviously, and to preserve this status during the patient's lifelong. Additionally, the implantation of the ideal prosthetic valve should be easy, the prosthetic valve should be replaced with low mortality and morbidity, should not cause a damage to the cardiovascular system, the hospitalization period should be short, the valve should be inexpensive (Rahimtoola, 2010). In spite of the whole developments in the prosthetic valve technology, the ideal prosthetic valve is not found yet, that's why the task of the surgeon is to select the prosthetic valve not depending on the nature of the disease but should be individualized to each patient.

Nowadays, the replacement alternatives for aortic valve replacement are mechanical valves, biological xenograft valves, homograft valves, autograft valves and valves implanted transapically or percutaneously which usage has increased in the recent years. Because of various advantages and disadvantages, these alternatives are prefered to each other. However, for the most appropriate valve choice, each patient should be evaluated individually. Additionally, improvements in the drug technology and risk preventing measures, due to the deceleration in the development of cardiovascular diseases, the age of the operated patients and the surviving period following the operation is increasing gradually. Cardiovascular diseases become the most important factor determining the life quality and surviving ratio in the elderly population. The main purpose of the aortic valve replacement is the improvement of life quality by prolonging the patient's life (Kolh, 2007;

Which Valve to Who: Prosthetic Valve Selection for Aortic Valve Surgery 37

Additionally, some factors provide making a decision on the valve selection regardless of the patient's age. In case of previous thromboembolism history, chronic atrial fibrillation, low ejection fraction, previously implanted valve type and intracardiac thrombus, the selection of the valve is made regardless of the patient's age. The replacement of mechanical prosthetic valves is not appropriate in the patients with low sociocultural level, exposed to frequent traumas due to occupational reasons, predisposed to bleeding, unwilling to use or is contraindicated to use anticoagulants. Biological valve options are good alternatives in these patients. In patients with small ventricle, when mitral valve replacement and aortic valve replacement are needed to be done together, and the usage of mechanical prosthesis is not appropriate due to their high profile, biological valves have to be selected for replacement. These prosthetic valves are similar according to the perioperative mortality and immediate and long term survival (Silberman, 2008). These similar results have been shown not only for the elderly patients but also for middle aged patients (Carrier, 2001; Khan, 2001). But, during the biological valve replacement cardiopulmonary bypass time and ischemic time are longer than in those with mechanical valve replacement (Silberman, 2008) and especially stentless biologic valve implantation is more difficult in technical aspect. Thus, surgical experience and how the patients will be affected from the longer operation time are the other factors should be considered. The fact that stentless biological valves have hemodynamic advantages (Silberman, 2001), possibility of a replacement of larger sized prosthesis (Del Rizzo, 1994), better durability (Bach, 2005) and long term survival ratios (Albertucci, 1994; Westaby, 2000) in comparison with the stented biological valves, provides their preference in the young patients. The advantages of Ross procedure with respect to postoperative survival, life quality and reoperation requirement in adult patients undergone homograft and autograft aortic root replacement will provide it becoming widespread

Transcatheter aortic valve implantation (TAVI) recently developed and commonly used in some centers as a good alternative technique for the patients in whom the aortic valve replacement is with high risk (Cribier, 2006; Webb, 2007; Walther, 2007, Rode's-Cabau, 2010). In these patients, surgeon has to choose optimal valve and obtain the largest prosthetic valve area. TAVI has excellent hemodynamic performance. In the patients who had myocardial dysfunction, apoptosis of the cardiomyocites triggered by the ischemia, oxidative stress and inflammatory injury during the open heart surgery, could retard the postoperative recovery and improvement of myocardial functions (Anselmi, 2004, Vahasilta, 2005). In these risky patients, TAVI could protect the myocardial functions and LVEF can be

It was offered to choose mechanical valves in patients having chronic renal disease because of earlier degeneration by rapid calcification of biological valves. But, in ACC/AHA guideline updated in 2006, there is no recommendation for the choice of prosthetic valve type for these patients. Probably, this revision depends on new studies claimed similar results for both mechanical and biological prosthetic valve types for the patients on dialysis (Lucke, 1997; Kaplon, 2000; Herzog, 2002; Brinkman, 2002; Bonow, 2006). After these results, the criteria for the choice of valve type in the patients on dialysis shifted as those in patients without on dialysis. With holding intact parathormon, calcium, and phosphor levels at optimal levels, not only early degeneration of biological valves can be prevented but also the survival the patients on dialysis can be increased (Kazama, 2007; Kimata, 2007; Nakai, 2008). Degeneration of new generation biological valves has decreased in dialysis patients as in

those non-dialysis patients with the technological improvements (Brinkman, 2002).

(Hammermeister, 2000; Stassano, 2009; El-Hamamsy, 2010).

increased after the intervention (Webb, 2007; Bauer, 2004; Clavel, 2009).

Thourani, 2008). For that reason, by selecting the most appropriate valve for each patient, complications due to the valve can be decreased. Because the rate of the complications of the selected valve are affected by the age and comorbidities of the patients.

Traditionally, the most important criteria for the valve selection is the patient's age, but with the improvements in the production of prosthetic valves and fixation methods, different criteria began to come into prominence. Perforations due to the stress or dystrophic calcifications are hold to be responsible of the structural degeneration of the biological valves (Jameison, 1995). It was shown that the new generation bioprotheses are more durable and needed less reoperation in a long period (Silberman, 2008; Potter, 2005; Valfre, 2006). In addition, improvements achieved in the anticoagulant agents. The superiority of the biological valves would be limited by the technology providing patient's self-monitoring of international normalized ratio (INR) (Siebenhofer, 2004) and the development of new anticoagulant agents (Salam, 2004). These developments and innovations will be effective in the revision of the criteria in the selection of valve.

Generally, biological valves are preferred in the patients older than the age of 70 years. Besides the lower thromboembolic and hemorragic complications incidence at that age, durability of biological valves is enough for the survival of patients following aortic valve replacement (Cosgrove, 1995; Langley, 1999; Masters, 2004). Additionally, the usage of chronic anticoagulation therapy for the biological valves is not necessary as is in the mechanical valves. Generally, the mechanical valves which are more durable than the biological valves are chosen in the patients younger than the age of 60 years, because of their expected longer survival. At that age an early calcification due to the increase of the collagen degeneration and increased calcium turnover was seen in the biological valves (Gross, 1998). However, the selection of prosthetic valve is more difficult between the age 60 and 70 years. The selection of the valve can be easier by paying attention to co-morbidities. Biological valves are preferred in the patients with coronary heart disease because of the decrease in their expected survival. Additionally, generating less turbulence flow by biological valves increases the coronary by-pass graft flow (Hassanein, 2007). When a comparison is made between the biological valves, stentless biological valves are seen more advantageous in terms of coronary flow reserves. Stentless biological valves are an appropriate choice in the patients with left ventricular dysfunction in terms of postoperative recovery (Bakhtiary, 2006).

In some patients, the decision of the valve selection is unrelated to the age. Young female patients planning to become pregnant is a special patient group. In these patients, with the avoidance of an anticoagulation therapy during the pregnancy via biological valve replacement (De Santo, 2005), in experienced centers Ross procedure is offered as an alternative therapy (Bonow, 2008). Additionally, it is suggested that not only the mechanical prosthetic valves or anticoagulant agent usage, but at the same time the acceleration of the structural degeneration of biological valves is an important issue needed to be avoided during the pregnancy (Jamieson, 1988).

The pulmonary autograft procedure in patient with aortic valve disease is an alternative to the prosthetic valves and the aortic allograft. This technique was introduced in 1967 by Donald Ross (Ross, 1967). The benefits of the Ross procedure are the superior durability of the pulmonary autograft when compared to biological valves in the aortic position, the growth potential of the autograft, and avoidance of prolonged anticoagulation (Akhyari, 2009). Hence, this procedure is primarily used in young or growing patients.

Thourani, 2008). For that reason, by selecting the most appropriate valve for each patient, complications due to the valve can be decreased. Because the rate of the complications of the

Traditionally, the most important criteria for the valve selection is the patient's age, but with the improvements in the production of prosthetic valves and fixation methods, different criteria began to come into prominence. Perforations due to the stress or dystrophic calcifications are hold to be responsible of the structural degeneration of the biological valves (Jameison, 1995). It was shown that the new generation bioprotheses are more durable and needed less reoperation in a long period (Silberman, 2008; Potter, 2005; Valfre, 2006). In addition, improvements achieved in the anticoagulant agents. The superiority of the biological valves would be limited by the technology providing patient's self-monitoring of international normalized ratio (INR) (Siebenhofer, 2004) and the development of new anticoagulant agents (Salam, 2004). These developments and innovations will be effective in

Generally, biological valves are preferred in the patients older than the age of 70 years. Besides the lower thromboembolic and hemorragic complications incidence at that age, durability of biological valves is enough for the survival of patients following aortic valve replacement (Cosgrove, 1995; Langley, 1999; Masters, 2004). Additionally, the usage of chronic anticoagulation therapy for the biological valves is not necessary as is in the mechanical valves. Generally, the mechanical valves which are more durable than the biological valves are chosen in the patients younger than the age of 60 years, because of their expected longer survival. At that age an early calcification due to the increase of the collagen degeneration and increased calcium turnover was seen in the biological valves (Gross, 1998). However, the selection of prosthetic valve is more difficult between the age 60 and 70 years. The selection of the valve can be easier by paying attention to co-morbidities. Biological valves are preferred in the patients with coronary heart disease because of the decrease in their expected survival. Additionally, generating less turbulence flow by biological valves increases the coronary by-pass graft flow (Hassanein, 2007). When a comparison is made between the biological valves, stentless biological valves are seen more advantageous in terms of coronary flow reserves. Stentless biological valves are an appropriate choice in the patients with left ventricular dysfunction in terms of postoperative recovery (Bakhtiary,

In some patients, the decision of the valve selection is unrelated to the age. Young female patients planning to become pregnant is a special patient group. In these patients, with the avoidance of an anticoagulation therapy during the pregnancy via biological valve replacement (De Santo, 2005), in experienced centers Ross procedure is offered as an alternative therapy (Bonow, 2008). Additionally, it is suggested that not only the mechanical prosthetic valves or anticoagulant agent usage, but at the same time the acceleration of the structural degeneration of biological valves is an important issue needed to be avoided

The pulmonary autograft procedure in patient with aortic valve disease is an alternative to the prosthetic valves and the aortic allograft. This technique was introduced in 1967 by Donald Ross (Ross, 1967). The benefits of the Ross procedure are the superior durability of the pulmonary autograft when compared to biological valves in the aortic position, the growth potential of the autograft, and avoidance of prolonged anticoagulation (Akhyari,

2009). Hence, this procedure is primarily used in young or growing patients.

selected valve are affected by the age and comorbidities of the patients.

the revision of the criteria in the selection of valve.

during the pregnancy (Jamieson, 1988).

2006).

Additionally, some factors provide making a decision on the valve selection regardless of the patient's age. In case of previous thromboembolism history, chronic atrial fibrillation, low ejection fraction, previously implanted valve type and intracardiac thrombus, the selection of the valve is made regardless of the patient's age. The replacement of mechanical prosthetic valves is not appropriate in the patients with low sociocultural level, exposed to frequent traumas due to occupational reasons, predisposed to bleeding, unwilling to use or is contraindicated to use anticoagulants. Biological valve options are good alternatives in these patients. In patients with small ventricle, when mitral valve replacement and aortic valve replacement are needed to be done together, and the usage of mechanical prosthesis is not appropriate due to their high profile, biological valves have to be selected for replacement.

These prosthetic valves are similar according to the perioperative mortality and immediate and long term survival (Silberman, 2008). These similar results have been shown not only for the elderly patients but also for middle aged patients (Carrier, 2001; Khan, 2001). But, during the biological valve replacement cardiopulmonary bypass time and ischemic time are longer than in those with mechanical valve replacement (Silberman, 2008) and especially stentless biologic valve implantation is more difficult in technical aspect. Thus, surgical experience and how the patients will be affected from the longer operation time are the other factors should be considered. The fact that stentless biological valves have hemodynamic advantages (Silberman, 2001), possibility of a replacement of larger sized prosthesis (Del Rizzo, 1994), better durability (Bach, 2005) and long term survival ratios (Albertucci, 1994; Westaby, 2000) in comparison with the stented biological valves, provides their preference in the young patients. The advantages of Ross procedure with respect to postoperative survival, life quality and reoperation requirement in adult patients undergone homograft and autograft aortic root replacement will provide it becoming widespread (Hammermeister, 2000; Stassano, 2009; El-Hamamsy, 2010).

Transcatheter aortic valve implantation (TAVI) recently developed and commonly used in some centers as a good alternative technique for the patients in whom the aortic valve replacement is with high risk (Cribier, 2006; Webb, 2007; Walther, 2007, Rode's-Cabau, 2010). In these patients, surgeon has to choose optimal valve and obtain the largest prosthetic valve area. TAVI has excellent hemodynamic performance. In the patients who had myocardial dysfunction, apoptosis of the cardiomyocites triggered by the ischemia, oxidative stress and inflammatory injury during the open heart surgery, could retard the postoperative recovery and improvement of myocardial functions (Anselmi, 2004, Vahasilta, 2005). In these risky patients, TAVI could protect the myocardial functions and LVEF can be increased after the intervention (Webb, 2007; Bauer, 2004; Clavel, 2009).

It was offered to choose mechanical valves in patients having chronic renal disease because of earlier degeneration by rapid calcification of biological valves. But, in ACC/AHA guideline updated in 2006, there is no recommendation for the choice of prosthetic valve type for these patients. Probably, this revision depends on new studies claimed similar results for both mechanical and biological prosthetic valve types for the patients on dialysis (Lucke, 1997; Kaplon, 2000; Herzog, 2002; Brinkman, 2002; Bonow, 2006). After these results, the criteria for the choice of valve type in the patients on dialysis shifted as those in patients without on dialysis. With holding intact parathormon, calcium, and phosphor levels at optimal levels, not only early degeneration of biological valves can be prevented but also the survival the patients on dialysis can be increased (Kazama, 2007; Kimata, 2007; Nakai, 2008). Degeneration of new generation biological valves has decreased in dialysis patients as in those non-dialysis patients with the technological improvements (Brinkman, 2002).

Which Valve to Who: Prosthetic Valve Selection for Aortic Valve Surgery 39

term results have significantly improved due to technical optimization, better myocardial protection and postoperative management. In studies, the term elderly is often used to describe different population. Some researchers define elderly population as older than 70 years (Tseng, 1997), whereas others define elderly as being older than 65 years (Florath, 2005). Structural failure of bioprostheses are strongly related to the patient's age at valve insertion (Akins, 1998). Bioprostheses have a significantly higher rate of reoperation. Freedom from reoperation for bioprostheses is >95% at 5 years, >90% at 10 years, but <70% at 15 years. However freedom from reoperation for mechanical valves is >95% at 5 years and >90% at 15 years (Desai, 2008). Many cardiac surgeons opt patient age 70 years or older as a routine age for insertion of bioprostheses. Several studies have compared stentless and stented aortic valve bioprosthesis. Stentless aortic bioprostheses were shown to be hemodynamically superior to stented aortic bioprostheses (Borger, 2005; Walther 1999). Stentless aortic bioprostheses provide a larger effective orifice area and lower transvalvular gradients postoperatively because of the absence of a sewing ring and stent. However the implantation of the stentless valve is more difficult and is generally associated with longer myocardial ischemic time and may therefore have a higher perioperative complication rates (Borger, 2005). Choice of mechanical aortic prostheses in elderly patients is often due to different factors, including the use of anticoagulation for other diseases, less need of reoperation and preference of the patient or surgeon. In patients younger than 60 years of age, mechanical prosthesis is recommended because of prosthesis durability (Emery, 2005; Carrier, 2001). In the age between 60 and 70 years, other individual factors have to be taken

Transcatheter aortic valve implantation has become a clinical reality, applied to high-risk patients who are elderly or not operative candidates. TAVI has been developed as an endovascular alternative to surgical aortic valve replacement. This technique is performed with transfemoral or transapical routes. Successful implantation rate has been found

Homografts and autologous pulmonary valves are good alternatives for infants and childhood patients. In this method advantages like the growing ability, perfect durability, avoidance of prolonged anticoagulation, excellent hemodynamic performance, low transvalvar pressure gradient, large effective orifice area of pulmonary autologous valve are shown (Alsoufi, 2009; Gatzoulis, 1999). Complications like neoaortic failure seen in the postoperative period has decreased following the improvements in the implantation techniques of autologous pulmonary valves (David, 2000; Takkenberg, 2006), and pulmonary allograft stenosis has decreased due to appropriate usage of anti-inflammatory agents (Carr-White, 2001; Raanani, 2000). For that reason while the usage of aortic route replacement and Ross procedure are getting widespread, on the other hand it is suggested that in case of usage of pulmonary autograft the operation is complex and while during the repair of one valve pathology, two valves are jeopardized (Alexiou, 2000). It is suggested that in the childhood, metallic valves are good alternatives to Ross procedure because of their quite easier implantation, their perfect durability and hemodynamic performance (Alexiou, 2000). In the literature, late period thromboembolism and hemorrhagic complications following mechanical valve replacement in the childhood are reported in a quite low rates (Ibrahim, 1994; Champsaur, 1997; Mazzitelli, 1998; Lupinetti, 1997). The most important disadvantage of the mechanical valves in the childhood is the requirement of replacement of them with bigger size later. However, in a great majority of the childhood patients adult sized mechanical valve replacement is possible with aortoplasty technique

between 85% and 100% (Al-Attar, 2009; Johansson, 2011).

into account.

Because of the high mortality ratio after aortic valve replacement, measures should be taken for the prevention of infective endocarditis. Although, infective endocarditis risk after mechanical and biological valve replacement is similar in both prosthetic valve types, in case of a need for aortic valve replacement in a patient with infective endocarditis, allografts have advantages with respect to resistance to active endocarditis. But it is difficult to obtain allografts at any time and the valve durability depends on donor age, time after explantation from donor, and host immunologic response (Yacoup, 1995; Takkenberg 2002).

There are few prospective, randomized studies comparing the valve types used in aortic valve replacement. Besides, the valve types compared in these studies are limited. Large studies comparing all the prosthetic valves the autografts, mechanic valves, xenograft tissue valves will be helpful for the optimal prosthetic valve choice.

Because, the increase of durability for new generation biological valves and the decrease of the elective operations risk by the improvements of surgical techniques, the biological valves will be used widespread in the younger patients (Silberman, 2008; Bonow, 2006). We have to present this option to patients. Thus, the patients could join the decision process for the choice of the prosthetic valve type. Additionally, the patient's should learn the frequency of coagulation monitorization, the possibility for disturbed mechanical valve sound, hemorrhagic complications by using mechanical valve and reoperation caused by the structural degeneration for the biological valves.

In the patients planning to undergo aortic valve replacement, not only the patient's age but also patient's life expectancy, coagulopathy, life-style, occupation, comorbidities, anticoagulant therapy contraindication, surgeon's experience should be reviewed for the choice of the most appropriate prosthetic valve type for each person (Silberman, 2008 ). In this way, the best survival and improved life quality can be offered to the patient.

The factors should be kept in mind which will be given in details below:

	- Chronic atrial fibrillation
	- Chronic renal failure
	- Malignancies
	- Small aortic annulus
	- Other valve diseases
	- Aortic dilatation

## **2. Patient's age**

Biologic or mechanical aortic valve prostheses have been widely used in patients with aortic valve disease. The choice of prostheses remains controversial due to the higher rate of structural dysfunction with bioprosthesis and due to the risk of thromboembolism or hemorrhage releated to the anticoagulation treatment of a mechanical prosthesis. The elderly population is increasing due to increase in the human life span. Thus cardiac surgery is increasing in the elderly. In elderly patients with aortic valve replacement, early and long-

Because of the high mortality ratio after aortic valve replacement, measures should be taken for the prevention of infective endocarditis. Although, infective endocarditis risk after mechanical and biological valve replacement is similar in both prosthetic valve types, in case of a need for aortic valve replacement in a patient with infective endocarditis, allografts have advantages with respect to resistance to active endocarditis. But it is difficult to obtain allografts at any time and the valve durability depends on donor age, time after explantation

There are few prospective, randomized studies comparing the valve types used in aortic valve replacement. Besides, the valve types compared in these studies are limited. Large studies comparing all the prosthetic valves the autografts, mechanic valves, xenograft tissue

Because, the increase of durability for new generation biological valves and the decrease of the elective operations risk by the improvements of surgical techniques, the biological valves will be used widespread in the younger patients (Silberman, 2008; Bonow, 2006). We have to present this option to patients. Thus, the patients could join the decision process for the choice of the prosthetic valve type. Additionally, the patient's should learn the frequency of coagulation monitorization, the possibility for disturbed mechanical valve sound, hemorrhagic complications by using mechanical valve and reoperation caused by the

In the patients planning to undergo aortic valve replacement, not only the patient's age but also patient's life expectancy, coagulopathy, life-style, occupation, comorbidities, anticoagulant therapy contraindication, surgeon's experience should be reviewed for the choice of the most appropriate prosthetic valve type for each person (Silberman, 2008 ). In this way, the

Biologic or mechanical aortic valve prostheses have been widely used in patients with aortic valve disease. The choice of prostheses remains controversial due to the higher rate of structural dysfunction with bioprosthesis and due to the risk of thromboembolism or hemorrhage releated to the anticoagulation treatment of a mechanical prosthesis. The elderly population is increasing due to increase in the human life span. Thus cardiac surgery is increasing in the elderly. In elderly patients with aortic valve replacement, early and long-

from donor, and host immunologic response (Yacoup, 1995; Takkenberg 2002).

valves will be helpful for the optimal prosthetic valve choice.

best survival and improved life quality can be offered to the patient. The factors should be kept in mind which will be given in details below:

structural degeneration for the biological valves.

• Chronic atrial fibrillation • Chronic renal failure

• Malignancies • Small aortic annulus • Other valve diseases • Aortic dilatation • Active infective endocarditis

• Patient's age • Comorbidities

• Young women • Pregnancy

**2. Patient's age** 

• Redo valve surgery

term results have significantly improved due to technical optimization, better myocardial protection and postoperative management. In studies, the term elderly is often used to describe different population. Some researchers define elderly population as older than 70 years (Tseng, 1997), whereas others define elderly as being older than 65 years (Florath, 2005). Structural failure of bioprostheses are strongly related to the patient's age at valve insertion (Akins, 1998). Bioprostheses have a significantly higher rate of reoperation. Freedom from reoperation for bioprostheses is >95% at 5 years, >90% at 10 years, but <70% at 15 years. However freedom from reoperation for mechanical valves is >95% at 5 years and >90% at 15 years (Desai, 2008). Many cardiac surgeons opt patient age 70 years or older as a routine age for insertion of bioprostheses. Several studies have compared stentless and stented aortic valve bioprosthesis. Stentless aortic bioprostheses were shown to be hemodynamically superior to stented aortic bioprostheses (Borger, 2005; Walther 1999). Stentless aortic bioprostheses provide a larger effective orifice area and lower transvalvular gradients postoperatively because of the absence of a sewing ring and stent. However the implantation of the stentless valve is more difficult and is generally associated with longer myocardial ischemic time and may therefore have a higher perioperative complication rates (Borger, 2005). Choice of mechanical aortic prostheses in elderly patients is often due to different factors, including the use of anticoagulation for other diseases, less need of reoperation and preference of the patient or surgeon. In patients younger than 60 years of age, mechanical prosthesis is recommended because of prosthesis durability (Emery, 2005; Carrier, 2001). In the age between 60 and 70 years, other individual factors have to be taken into account.

Transcatheter aortic valve implantation has become a clinical reality, applied to high-risk patients who are elderly or not operative candidates. TAVI has been developed as an endovascular alternative to surgical aortic valve replacement. This technique is performed with transfemoral or transapical routes. Successful implantation rate has been found between 85% and 100% (Al-Attar, 2009; Johansson, 2011).

Homografts and autologous pulmonary valves are good alternatives for infants and childhood patients. In this method advantages like the growing ability, perfect durability, avoidance of prolonged anticoagulation, excellent hemodynamic performance, low transvalvar pressure gradient, large effective orifice area of pulmonary autologous valve are shown (Alsoufi, 2009; Gatzoulis, 1999). Complications like neoaortic failure seen in the postoperative period has decreased following the improvements in the implantation techniques of autologous pulmonary valves (David, 2000; Takkenberg, 2006), and pulmonary allograft stenosis has decreased due to appropriate usage of anti-inflammatory agents (Carr-White, 2001; Raanani, 2000). For that reason while the usage of aortic route replacement and Ross procedure are getting widespread, on the other hand it is suggested that in case of usage of pulmonary autograft the operation is complex and while during the repair of one valve pathology, two valves are jeopardized (Alexiou, 2000). It is suggested that in the childhood, metallic valves are good alternatives to Ross procedure because of their quite easier implantation, their perfect durability and hemodynamic performance (Alexiou, 2000). In the literature, late period thromboembolism and hemorrhagic complications following mechanical valve replacement in the childhood are reported in a quite low rates (Ibrahim, 1994; Champsaur, 1997; Mazzitelli, 1998; Lupinetti, 1997). The most important disadvantage of the mechanical valves in the childhood is the requirement of replacement of them with bigger size later. However, in a great majority of the childhood patients adult sized mechanical valve replacement is possible with aortoplasty technique

Which Valve to Who: Prosthetic Valve Selection for Aortic Valve Surgery 41

2004). Life expectancy of the patient who has malignancy has to be considered on decision for choice of prosthetic aortic valve. Biological aortic valve may be a good choice if life expectancy is about five years or less in patients with malignancy (Rahimtoola, 2010). Aortic valve replacement is an effective therapy for patients with aortic valve pathologies, however, transvalvular gradient is almost always higher than the physiologic gradients of the aortic valve. This gradient is related to the valve size and body surface area. Severe patient-prosthesis mismatch have been found to be associated with increased early and late mortality (Rao, 2000). Aortic root enlargement procedures are an option in patients with small aortic root. However, these techniques have been found to be associated with prolonged myocardial ischemia and perioperative bleeding which is frequently seen in the elderly patients (Kunihara, 2006). Stentless biologic aortic valves or homografts seem like good choice for patients with small aortic root size at risk for patients-prosthesis mismatch (Bonow 2008). Subcoronary implantation of stentless bioprostheses has been associated with residual transvalvular gradients (Milano, 2001). Kunihara and colleagues showed that full aortic root replacement using a stentless aortic bioprostheses may be advantageous in patients with small aortic root (Kunihara, 2006). Transcatheter aortic valve implantation may be an alternative to prevent patient-prosthesis mismatch in high-risk patients (Jilaihawi, 2010). Moderate patient-prosthesis mismatch is generally well tolerated in elderly patients who have small aortic root (Takaseya, 2007). However, the effect of patientprosthesis mismatch is more important in younger patients. New generation mechanical aortic valve which design to increase orifice area by modifying the outside geometry of the orifice housing may be an option in younger patients with small aortic root (Bach, 2002). Additionally, mechanical aortic valves which can be implanted supraannular position may be preferable in younger patients with small aortic root (Roedler, 2008). Pulmonic valve autotransplantation may be preferred to prevent patient-prosthesis mismatch and allow growth of the autograft in children (Bonow 2008). Root enlargement techniques should be considered in younger patients when a severe patient-prosthesis mismatch can not be

Whether bioprosthesis or mechanical valve in simultaneous aortic and mitral valve surgery will be associated with a better result remains under debate. There is no specific recommendation for surgical strategy of multiple valve disease in ACC/AHA practice guideline (Bonow, 2008). Caus and colleagues reported that the rate of reoperative mortality was significantly higher in patients >65 years who had double valve replacement (Caus, 1999). Hence, some surgeons recommend mechanical valves for the majority of patients in double valve replacement (Urban, 2011). However, a cohort study of 1057 patients showed that biologic valves have the best in-hospital and long-term survival in patient ≥70 years

Composite graft replacement of the aortic root is a favored technique in dilatation of the ascending aorta associated with aortic valve pathologies. It is more complex than isolated aortic valve replacement. Replacement of the aortic valve and the ascending aorta with a conduit consisting of a mechanical valve and a dacron tube is generally preferred procedure. This technique has been described by Bentall and Debono in 1968 (Bentall H, 1968) and it has led to increased life expectancy for patients with Marfan syndrome. In spite of initial mortality risk is higher, long term survival has been found similar to aortic valve replacement in patients with composite mechanical valve-graft conduit aortic root replacement (Kalkat, 2007). Homografts and conduits consisting of a stented or stentless xenograft valve may be the choice especially in elderly or in patients with endocarditis.

undergoing concomitant aortic and mitral valve replacement (Leavitt, 2009).

avoided with these models of prostheses.

(Nicks, 1970). Thus, it is suggested that in this age group mechanical prosthetic valves are good alternatives of biological ones. Another alternative to Ross procedure are allografts. Allograft aortic valves do not vary in the early and late period due to hemodynamic respect (Lupinetti, 2003).
