**3. Comorbidities**

Atrial fibrillation is the most common arrhythmia in patients undergoing aortic valve surgery (Ngaage, 2006). Many studies show that atrial fibrillation is a risk factor for decreased long-term survival (Vidaillet, 2002; Stewart, 2002). Loss of synchronous atrioventricular contraction results in ventricular dysfunction or congestive heart failure. The Framingham Study shows that stasis of blood flow in the left atrium, three- to five fold increases risk of stroke in a patient with atrial fibrillation (Wolf, 1991). Currently, acetylsalicylic acid and warfarin are approved antithrombotic agents for stroke prevention in patients with atrial fibrillation. However randomized trials are shown that antiplatelet agents are less effective than anticoagulant agents (Hart, 1999). It seems that first choice is mechanical aortic valve because of the need anticoagulant therapy in patients with chronic atrial fibrillation undergoing aortic valve surgery. Nevertheless an old patient more than 60 to 65 years who has atrial fibrillation may be preferable to insert a biologic aortic valve due to an increased risk of bleeding with anticoagulant therapy (Rahimtoola, 2003). If bleeding obliges discontinuing anticoagulant therapy, then this is a risk of thrombosis in patient with mechanical aortic valve.

Patients with chronic renal failure have a poor long-term survival secondary to their underlying renal disease. Four-year survival of patients on hemodialysis or peritoneal dialysis, regardless of whether they undergo valve replacement, is approximately 40% (Brinkman, 2002). Chronic renal failure is also a significant risk factor for increased morbidity and mortality in patients undergoing cardiac surgery (Kogan, 2008). Chronic uremia, hypertension, hyperlipidemia and increased calcium phosphate product associated with secondary hyperparathyroidism predispose to cardiac valvular abnormalities in patients with chronic renal failure. Early studies on biologic valve implantation in these patients show accelerated calcification of bioprosthetic valves (Lamberti, 1978; Monson, 1980). Therefore, mechanical valves were recommended by the ACC/AHA in patient with chronic renal failure and the guideline considered the use of biologic valves potentially harmful. (Bonow, 1998). However, current studies demonstrated that no significant survival difference between mechanical and bilologic valves (Brinkman, 2002; Thourani, 2011). Furthermore, several studies recommend biological valve instead of mechanical valve in patients on chronic dialysis (Lucke, 1997). Chronic renal failure is a known major risk factor for bleeding in patients with anticoagulant therapy (Lanefeld, 1989). These patients have also a increased risk of endocarditis due to frequent vascular access and impaired immunity (Chan, 2006). The type of aortic valve chosen for these patients should be individualized to the age of the patient and expected long-term survival. Older and patients with relative short life expectancy should be considered as candidates for biological aortic valve.

Malignant tumors is another comorbidity in patients undergoing aortic valve replacement. Currently there is no specific study investigating effects of the type of aortic valve prostheses on survival in these patients. However analyses revealed that the presence of a malignant tumor was an independent risk factor on survival after cardiac surgery (Mistiaen,

(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

Atrial fibrillation is the most common arrhythmia in patients undergoing aortic valve surgery (Ngaage, 2006). Many studies show that atrial fibrillation is a risk factor for decreased long-term survival (Vidaillet, 2002; Stewart, 2002). Loss of synchronous atrioventricular contraction results in ventricular dysfunction or congestive heart failure. The Framingham Study shows that stasis of blood flow in the left atrium, three- to five fold increases risk of stroke in a patient with atrial fibrillation (Wolf, 1991). Currently, acetylsalicylic acid and warfarin are approved antithrombotic agents for stroke prevention in patients with atrial fibrillation. However randomized trials are shown that antiplatelet agents are less effective than anticoagulant agents (Hart, 1999). It seems that first choice is mechanical aortic valve because of the need anticoagulant therapy in patients with chronic atrial fibrillation undergoing aortic valve surgery. Nevertheless an old patient more than 60 to 65 years who has atrial fibrillation may be preferable to insert a biologic aortic valve due to an increased risk of bleeding with anticoagulant therapy (Rahimtoola, 2003). If bleeding obliges discontinuing anticoagulant therapy, then this is a risk of thrombosis in patient with

Patients with chronic renal failure have a poor long-term survival secondary to their underlying renal disease. Four-year survival of patients on hemodialysis or peritoneal dialysis, regardless of whether they undergo valve replacement, is approximately 40% (Brinkman, 2002). Chronic renal failure is also a significant risk factor for increased morbidity and mortality in patients undergoing cardiac surgery (Kogan, 2008). Chronic uremia, hypertension, hyperlipidemia and increased calcium phosphate product associated with secondary hyperparathyroidism predispose to cardiac valvular abnormalities in patients with chronic renal failure. Early studies on biologic valve implantation in these patients show accelerated calcification of bioprosthetic valves (Lamberti, 1978; Monson, 1980). Therefore, mechanical valves were recommended by the ACC/AHA in patient with chronic renal failure and the guideline considered the use of biologic valves potentially harmful. (Bonow, 1998). However, current studies demonstrated that no significant survival difference between mechanical and bilologic valves (Brinkman, 2002; Thourani, 2011). Furthermore, several studies recommend biological valve instead of mechanical valve in patients on chronic dialysis (Lucke, 1997). Chronic renal failure is a known major risk factor for bleeding in patients with anticoagulant therapy (Lanefeld, 1989). These patients have also a increased risk of endocarditis due to frequent vascular access and impaired immunity (Chan, 2006). The type of aortic valve chosen for these patients should be individualized to the age of the patient and expected long-term survival. Older and patients with relative short life expectancy should be considered as candidates for biological aortic

Malignant tumors is another comorbidity in patients undergoing aortic valve replacement. Currently there is no specific study investigating effects of the type of aortic valve prostheses on survival in these patients. However analyses revealed that the presence of a malignant tumor was an independent risk factor on survival after cardiac surgery (Mistiaen,

(Lupinetti, 2003).

**3. Comorbidities** 

mechanical aortic valve.

valve.

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 avoided with these models of prostheses.

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

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.

Which Valve to Who: Prosthetic Valve Selection for Aortic Valve Surgery 43

seen after the treatment (Elkayam2005; Roudaut 2003). As the data about this topic is limited the complication rates seen in nonpregnant patients can be taken into consideration. A surgical treatment during pregnancy can be required in patients without benefits despite medical treatments and percutaneous approaches. Although the maternal mortality is below 3% for pregnant patients undergoing CPB with aortic valve replacement, fetal loss reaches 20% (Pomini 1996). Some strategies like avoiding hypotermia, providing enough perfusion pressure are recommended in order to decrease these adverse effects of CPB. Besides that, because of the effects of cardioplegia usage like hemodilution and hyperkalemia, recently some valve operation in beating heart also are reported (Tehrani 2004). The choice of valve type for valve replacement in pregnancy is similar to the choice criteria in young women patients. In a similar way it is difficult to make a decision about the valve choice because of the degeneration risk of the biological valves in young women and the requirement of anticoagulation for the mechanical valves, the fact that the trombosis of the mechanical valves during pregnancy can be a cause of mortality, and the limited data about how the homografts are influenced during pregnancy. However, the participation of the patient in the decision process has to be provided by discussing with the pregnant patient and informating her for all of the possible complications and frequencies. During the decision besides the current pregnancy, the expectation of a new pregnacy in future is also important (Elkayam2005). On the contrary to the results of the previous studies, recent studies have demonstrated that pregnancy does not cause a deterioration or calcification in biological valves (Reimold 2003).

Especially in the developing countries valve diseases requiring a surical intervention is seen frequently in young age group due to the fact that rheumatic valve diseases are not very uncommon. Although the valve repairement is the most ideal treatment method in young age group, in case of a serious impaired structure of the valve a repairement is not always possible. In that situation valve replacement is needed. A prothesis choice is still a controverisal issue in young patients needing prosthetic valve replacement (Solymar 1991; Trimn 2007). The reason is that all of the chosed prosthetic valves have their own advantages and disadvantages. That's why the decision has to be made according to the most suitable valve alternative for the patients' characteristics. The patient has to be informed about the advantages and disadvantages of the valve types in terms of possible complications. Thereafter, the patient has to be involved in the decision process. Young women have a different situation among the patients undergoing valve surgery because of the pregnancy possibility. The fact that the bioprothesis used in young age can be exposed to early degeneration because of the rapid body metabolism or the requirement of anticoagulants in patients with preference of mechanical prosthetic valves are situations which have to be evaluated seperately. As the valve lesion present before pregnancy will become more pronounced with the pregnancy, patients can undergo a comfortable period during the pregnancy with the intervention to the valve lesion in that period. In these approaches, along with the medical treatment support, when required, balloon-plasty is the first preference. By postponding of the sugical interventions during the pregnancy, maternal and fatal risk due to the surgery is tried to be prevented. Yet if there is no benefit although the applied medical treatment and percutaneous intervention, valve repairment or valve replacement is applied surgically. The main difficulty in that stage is the choice of the valve

**6. Prosthetic valve choice in young women** 

type which will be used.

Other option is pulmonary autograft for aortic root replacement. In the study of Akhyari and colleagues, pulmonary autograft had no advantages over composite grafts regarding mid-term morbidity and mortality in aortic position (Akhyari, 2009).
