The patient is placed in the supine position under general anesthesia. The chest, abdomen, perineum, and lower extremities are prepped and draped in sterile fashion. Standard median sternotomy and exposure of the heart are performed. The orientation of the aortic root is visualized more easily if only the right side of the pericardium is tacked upward. This rotates the heart counterclockwise and allows the apex of the heart to sink into the left chest, thus improving the exposure of the aortic root. Arterial and venous cannulation is undertaken, and appropriate connections are made to the pump oxygenator. If the patient has no significant aortic insufficiency, an antegrade cardioplegia tack is placed, and in all cases a retrograde cardioplegia cannula also is placed. When everything is in readiness for the initiation of cardiopulmonary bypass, careful dissection is undertaken to separate as much of the aortic root from the pulmonary artery and right ventricular outflow tract as possible. Care must be taken in dissecting anteriorly to avoid injury to the right coronary artery. A careful dissection at this point can result in significant exposure of the aortic root and therefore decrease the amount of time needed to perform the aortic root replacement when the aorta is cross-clamped. After confirmation of an activated clotting time (ACT) longer than 400 s, cardiopulmonary bypass is performed and the aorta is cross-clamped. Whenever possible, the heart should be arrested with antegrade cardioplegia to promote better and faster distribution of the cardioplegia. A switch to retrograde cold blood cardioplegia may be considered especially in the presence of significant aortic regurgitation. The authors give intermittent shots of 250 mL every 20 min during the cross-clamp period. This is supplemented with a cold saline-infused cooling jacket placed around the left ventricle. A right superior pulmonary vein vent is placed to keep the heart decompressed.
The ascending aorta is transected approximately 3 to 4 cm above the right coronary ostium. The aortic valve is inspected at this point, and if the situation is appropriate for valve preservation, the valve is not excised. If the valve is diseased so that its successful preservation is not possible, it is excised and debridement of the annulus is carried out if necessary. At this point, both the left and the right coronary buttons are dissected free, taking care not to mobilize them significantly. Significant mobilization may result in disorientation and kinking of the button after anastomosis to the Dacron graft. Specific techniques and choices for aortic root replacement are discussed below.
Systemic rewarming is begun at an appropriate point in the implantation procedure to avoid imposing extra time waiting for the patient to reach normothermia before separation from cardiopulmonary bypass. After root replacement, the vent is removed, and it is useful to give the final shot of cardioplegia antegrade to inspect for significant bleeding points that can be repaired before removal of the cross-clamp and also as an initial test of valve competence. The cross-clamp is removed with the patient placed in the Trendelenburg position and with an ascending aortic vent on. Ventricular and atrial pacing wires are placed, and mechanical ventilation is resumed. De-airing maneuvers such as lung hyperinflation, side-to-side shaking of the chest, and manual agitation of the heart are performed with the heart partially ejecting. Transesophageal echocardiography is very helpful in the assessment of de-airing and also in the interrogation of the valve for correct leaflet function. The patient is weaned from bypass at a systemic temperature of 36.5 to 37°C with good ventilation parameters. Protamine is given slowly, and the patient is decannulated. Meticulous hemostasis is obtained, a midline mediastinal drain (36F thoracostomy tube) is placed, and the patient is closed in the standard fashion.
Aortic Root Replacement: Choices and Results
The current gold standard for aortic root replacement is the composite valve-graft replacement. Typically this consists of a mechanical valve that is annealed to a double-velour woven Dacron graft at the factory. The most commonly used version is the St. Jude composite valve-graft, although other brands are available. The operation consists of removal of the aortic root in its entirety except for the coronary ostia that are left surrounded by a small circular rim of native aorta. The aortic valve also is excised. After appropriate sizing, pledgeted horizontal mattress nonabsorbable sutures are placed across the annulus in everting fashion (i.e., from aorta to ventricle) and are placed across the sewing ring of the composite valve-graft. The composite valve-graft is seated, and the sutures are tied and cut. For an extra measure of hemostasis, it is useful to suture the remaining rim of the aortic root directly to the sewing ring of the composite valve-graft in running fashion with 3-0 polypropylene sutures. Small holes are made just above the valve in the graft with ophthalmic cautery to allow suture implantation of the right and left coronary buttons. The authors use a small amount of albumin–glutaraldehyde biological glue to seal the interstices of these suture lines to aid in achieving hemostasis, but with the understanding that this step is not a substitute for meticulous surgical technique. A distal anastomosis of the Dacron graft to the ascending aorta then is performed (Fig. 33-4). In the operation originally described by Bentall and Debono in 1968,2 the aortic root was not excised and the coronary ostia were sewn side to side to the Dacron graft. Subsequently, Kouchoukos and coworkers excised the native aorta, leaving the coronary ostia surrounded by a small circular rim of native aorta (“Carrel buttons”) for direct end-to-side reimplantation.3 This constitutes the standard operation performed today. It is therefore not academically appropriate to refer to the latter procedure simply as a Bentall operation; instead, it is a modification of that operation.
Insertion of a composite graft with the button technique. The aorta is opened vertically (A), and the coronary ostia are mobilized sufficiently (B) before the valve is seated (C). The coronary buttons are sewn to the graft (D) to complete the repair. (Reproduced with permission from Svensson LG, Crawford ES. Aortic dissection and aortic aneurysm surgery: Clinical observations, experimental investigations, and statistical analyses: Part III. Curr Probl Surg 1993;30:1–72. Copyright Elsevier.)
Younger individuals may opt for a replacement of a composite graft containing a mechanical valve, accepting the potential complications associated with warfarin administration. In older patients (i.e., those above 65–70 years of age) a composite graft consisting of a stented bioprosthetic valve sewn to the Dacron graft by the surgeon at the time of operation may be used. Although these valves are not commercially available, the surgeon can select the appropriate bioprosthetic valve by sizing the annulus after the native valve is excised and then suture it to an appropriately selected Dacron graft. The operation then proceeds as for a composite mechanical valve graft.
During redo aortic root replacements, the tissues around the aortic root, especially posteriorly, can be very difficult to dissect; therefore, mobilization of the coronary artery may be difficult or dangerous. The Cabrol technique18 of coronary reimplantation involves the placement of 8- or 10-mm tube grafts to each coronary ostium with a side-to-side connection to the main aortic graft (Fig. 33-5). This procedure can be complicated by kinking of the right or left limb of the side graft if it is not oriented correctly in addition to the long-term risk of right coronary artery occlusion. An alternative approach involves direct reimplantation of the right coronary button (which almost always can be mobilized sufficiently) and reimplantation of the left coronary artery with an interposition graft between the aortic graft and the left coronary ostium.
Composite valve-graft insertion with the Cabrol technique. The tube graft to the left main ostium is brought behind the composite graft, and the composite graft is sutured to the aortic arch or to the graft that has been used for arch replacement. Finally, the coronary interposition graft is sutured to the right coronary artery ostium and the anastomosis (side-to-side) is completed. (Reproduced with permission from Svensson LG, Crawford ES. Aortic dissection and aortic aneurysm surgery: Clinical observations, experimental investigations, and statistical analyses: Part III. Curr Probl Surg 1993;30:1–72. Copyright Elsevier.)
The results of composite valve-graft aortic root replacement operations are generally very good but are dependent on the indication for operation. Gott and associates reviewed the extensive experience at Johns Hopkins with aortic root replacement in Marfan syndrome patients over a 24-year period.19 Two hundred thirty-five Marfan patients underwent elective aortic root replacement with no 30-day mortality. The actuarial freedom from thromboembolism, endocarditis, and reoperation on the residual aorta 20 years postoperatively was 93 percent, 90 percent, and 74 percent, respectively. Lai and associates reviewed the Stanford experience with composite valve-graft (CVG) replacement for acute type A aortic dissection.20 Thirty-day, 1-year, and 6-year survival estimates of 86 ± 8, 81 ± 9, and 65 ± 16 percent were seen with composite valve-graft replacement, with a 6-year freedom from reoperation of 100 percent. Ehrlich and coworkers21 reported on 84 patients older than 65 years of age (median age was 74 years with a range of 66 to 89 years) who underwent CVG aortic root replacement over an 11-year period. Hospital mortality was 8.3 percent (7 of 84), with 16 late deaths (19 percent) noted during a median follow-up of 3.2 years (range 0 to 10 years). The authors concluded that composite valve-graft replacement in elderly patients results in low operative mortality, has excellent long-term survival, and averts fatal aneurysm rupture even in that higher-risk population.
The Composite Valve-Graft Versus Separate Valve-Graft Controversy
In many cases an acceptable alternative to full CVG aortic root replacement is ascending aortic replacement starting at the sinotubular junction in association with separate aortic valve replacement [separate valve-graft (SVG)], leaving an intervening segment of the patient’s own aortic root from which the coronary ostia originate. The SVG procedure is less technically demanding and is useful when the sinotubular junction is not effaced and the aortic root is not dilated. It is useful in elderly patients in whom a shorter cross-clamp time may limit morbidity, especially those with acute type A without significant annuloaortic ectasia. A relatively common problem is significant ascending aortic dilatation associated with aortic valve replacement for a bicuspid aortic valve. It is well known that patients with bicuspid aortic valves are predisposed to the development of ascending and root aneurysm. The cause is multifactorial and includes hemodynamic factors and heredity.22
McCready and associates23 observed an approximately 15 percent incidence of significant root dilatation an average of 6.5 years after the SVG procedure. Houel and coworkers24 found mortality rates of 7.7 percent with CVG versus 11 percent with SVG (p = not significant). Actuarial survival at 10 years postoperatively in these groups was 77.7 ± 5.6 versus 75.8 ± 6.9 percent (p = not significant). However, freedom from late complications of the ascending aorta was significantly different (97.3 ± 1.9 percent CVG versus 68.3 ± 9.0 percent SVG at 10 years postoperatively). The SVG technique was identified as a risk factor for late complications of the ascending aorta by multivariate analysis (p = 0.01; odds ratio 9). In light of these data, an aggressive approach to CVG replacement in this population is recommended in patients with acceptable risk.25 When the sinotubular junction and aortic root are intact so that SVG is considered appropriate, the procedure first described by Wheat and associates4 may be useful to maximize exclusion of as much native aortic root tissue as possible without incurring the extra technical challenge of a full CVG implantation. The decision to pursue CVG replacement to exclude all potentially diseased aortic root tissue should be tempered by an increased operative mortality rate compared with an isolated aortic valve replacement. The SVG technique may provide a reasonable compromise between these two procedural extremes, especially if concomitant procedures must be performed in the same setting; however, there is a risk of aneurysmal dilatation of the intervening aorta over time.
Stentless Valve as an Alternative for Aortic Root Replacement
The Freestyle aortic root bioprosthesis (Medtronic, Inc., Minneapolis, MN) is a stentless porcine aortic root prepared with low-pressure and zero-pressure fixation processes and α-aminooleic acid leaflet anticalcification treatment, with the aim of optimizing both hemodynamics and bioprosthesis durability. The device can be implanted as a subcoronary or modified subcoronary valve replacement, as a complete aortic root replacement (total root), or as a root inclusion. Initial implantations in human subjects began in 1992, and the device has been approved for clinical use in the United States since 1997. The implantation technique of this prosthesis is similar to that for CVG replacement described above. Bach and colleagues26 reported the 8-year results of a multicenter cohort of 700 patients (of whom 93 percent were over 60 years of age) followed prospectively who received various configurations of this prosthesis. A total root replacement was performed in 162 of those patients, with actuarial freedom from valve-related death of 92.3 percent, freedom from structural deterioration of 100 percent, and freedom from moderate or more aortic regurgitation of 98.7 percent. Oral anticoagulation is not required postoperatively.
Homograft Aortic Root Replacement
Aortic root replacement can be performed with a cryopreserved homograft aortic root. This operation is more technically demanding because of the less rigid nature of the tissue used. The operative technique is similar to the techniques described above except that many authors advocate a continuous running suture for the implantation of the left ventricular outflow tract side to the annulus. In addition, this proximal suture line must be planar; that is, it should not follow the scallops of the aortic annulus but should run somewhat under the commissures. This operation is particularly well suited for patients in the age range of 40 to 60 years (e.g., those with congenital bicuspid aortic valve pathology) who require aortic root replacement but do not wish to take oral anticoagulants. In addition, homograft root replacement is the operation of choice for extensive native and PVE. The analysis by McGiffin and associates27 showed that the use of homografts in patients under 40 years of age was associated with an unacceptably high incidence of valve failure over a 15-year period. They demonstrated improved freedom from recurrent endocarditis when allograft tissue was used for aortic valve replacement compared with the use of prosthetic valve material. Grinda and colleagues28 evaluated the short- and long-term results of cryopreserved aortic viable homograft (CAVH) in the treatment of active aortic endocarditis. One hundred four patients underwent CAVH replacement for active aortic valve endocarditis; 73 percent of those operations involved the native aortic valve, and 27 percent involved a prosthetic aortic valve. CAVHs were inserted using the aortic root replacement technique in 89 percent of those patients. Actuarial survival at 10 years was 83 percent, with 93 percent of the patients free from cardiac death. At 10 years, the actuarial rate for freedom from reoperation was 76 percent and that for freedom from recurrent endocarditis was 93 percent. No thromboembolic complications were observed.
The Ross procedure consists of removal of the native aortic valve and root with preservation of the coronary buttons, followed by excision of the patient’s own pulmonary valve encased in the pulmonary artery distally and a small rim of right ventricular outflow tract muscle proximal to the annulus. It is mandatory to rule out any abnormalities in the pulmonary valve (fenestrations) and significant mismatch in the size of the aortic root and right ventricular outflow tract before proceeding with the autograft explants. Close attention needs to be paid to any anomalous coronary artery crossing the right ventricular outflow tract and preserving the first septal branch of LAD as one proceeds with excision of the autograft. The pulmonary valve, after excision, is translocated to the aortic position as a root replacement, with sewing of the right ventricular muscle to the aortic annulus in a planar fashion, reimplantation of the coronary ostia, and a distal anastomosis between the pulmonary arterial end of the autograft and the ascending aorta. The right ventricle–pulmonary artery side then is reconstructed with a valved pulmonary homograft (Fig. 33-6). This procedure should be performed by surgeons who are extremely competent at aortic root operations. Although the procedure is very demanding technically, the results are outstanding, with 80 percent freedom from reoperation at 20 years,29 with the failures roughly evenly distributed between the autograft and allograft sides. Recent reports have shown early dilatation of the autograft with neoaortic valve insufficiency (Fig. 33-7).30 Histologic analysis shows evidence of medial degeneration in both the aorta (Fig. 33-8) and the pulmonary artery of patients with bicuspid compared with tricuspid aortic valves.31 This is not surprising since embryologically the aorta and the pulmonary artery develop from a common truncus. Over time, gradual dilatation of the neosinuses of Valsalva is observed. This may be addressed by incorporation of aortic root stabilization adjuncts during the time of initial surgery.32 In light of these data and given its technically demanding nature, many surgeons have tempered their enthusiasm for the Ross procedure and reserve it for young patients especially children who need a biologically viable root to achieve optimal growth.
Insertion of a pulmonary autograft into the aortic position (Ross procedure). The pulmonary autograft is seated in the aortic annulus with interrupted simple sutures (A). Attention is paid to ensure that the valve is properly seated, as the pulmonary valve does not have the differences in valve cusp edge lengths that the aortic valve has. The homograft is sutured into position in the native pulmonary outflow tract to complete the procedure (B). (Reproduced with permission from Svensson LG, Crawford ES. Aortic dissection and aortic aneurysm surgery: Clinical observations, experimental investigations, and statistical analyses: Part III. Curr Probl Surg 1993;30:1–72. Copyright Elsevier.)
Magnetic resonance image of the neoaortic root demonstrating dilatation of the pulmonary autograft and an abrupt transition to normal diameter at the distal suture line, as shown by the arrow. (Reproduced with permission from Sundt TM, Moon MR, Xu H. Reoperation for dilatation of the pulmonary autograft after the Ross Procedure. J Thorac Cardio Surg 2001;122(6):1249–1252. Copyright Elsevier.)
A. Histologic features of aortic section from a patient with normal trileaflet aortic valve. There are no intimal changes. B. Histologic features of the ascending aorta from a 33-year-old patient with bicuspid aortic valve disease. Note the significant medial destruction and the accumulation of mucoid material (arrow). There is a marked fragmentation of elastic tissue. (Reproduced with permission from de Sa M, Moshkovitz Y, Butany T, David TE. Histological abnormalities of the ascending aorta and pulmonary trunk in patients with bicuspid aortic valve disease. J Thorac Cardiovasc Surg 1999;118(4):588–594. Copyright Elsevier.)
Valve-Sparing Aortic Root Replacement
Approximately 30 percent of patients who require aortic root replacement have a normal aortic valve that leaks because of sinotubular junction effacement and/or aortic annular dilatation secondary to degenerative causes or connective tissue diseases such as Marfan syndrome. Rather than excising the aortic valve and replacing the root with prosthetic valve material, an operation that encloses the native valve within normal aortic root geometry should restore competency. In 1979, Sir Magdi Yacoub introduced an aortic valve-sparing root replacement (“remodeling,” David-II) procedure consisting of excision of all the native aortic tissue except for a small rim around the valve leaflets.5 An appropriately sized Dacron graft then is fashioned into three scallops at one end and sutured to the residual aortic tissue, followed by coronary reimplantation (Fig. 33-9).
Operative technique of the remodeling (Yacoub) valve-sparing aortic root replacement. (Reproduced with permission from Yacoub MH, Gehle P, Chandrasekaran V. Late results of a valve-preserving operation in patients with aneurysms of the ascending aorta and root. J Thorac Cardiovasc Surg 1998:115(5);1080–1089. Copyright Elsevier.)
In approximately 1988, Dr. Tirone David introduced the valve-sparing “reimplantation” (David-I) procedure,6 in which sutures placed proximal to the aortic valve annulus are sewn to the Dacron graft. In this way, when the graft is seated, the valve sits entirely inside the graft and is attached to it from the inside with a second suture line after coronary reimplantation. The appropriate graft size is selected by measuring the average aortic valve leaflet height in millimeters, multiplying this value by 4/3, and adding 4 to 6 mm to this number to account for the thickness of the left ventricular outflow tract under the aortic annulus.12
The Yacoub remodeling procedure does not protect the aortic annulus and leaves it susceptible to dilatation and hence valvar insufficiency over time. David addressed this problem by placing a Teflon felt buttress under the fibrous portion of the annulus (David-III) but abandoned that modification in favor of the reimplantation procedure. If reoperation is required because of valvar incompetence after the remodeling procedure, a full aortic root replacement is necessary because of the persistence of unprotected native aortic root tissue. In contrast, with the David reimplantation procedure, the entire aortic root and annulus are enclosed in graft material, preventing dilatation over time. If reoperation is required, the graft can be opened, the native valve can be excised, and a stented or stentless valve of choice may be sutured directly into the graft, obviating the need for a much more difficult root re-replacement.
With the original David operation, isolated case reports described native valve failure with fibrotic, retracted aortic leaflets seen at reoperation, perhaps consistent with repeated trauma to the leaflets secondary to the lack of “neosinuses” produced with the Yacoub procedure.33 The David procedure has undergone two iterations to address this issue. The first (David-IV) involved the selection of a graft 4 to 6 mm larger in diameter than the calculation dictates and plication of the neosinotubular junction down to the correct size. With the current (David-V) modification, the Dacron graft used for the aortic root replacement is oversized by 6 to 8 mm in diameter and then pleated at the annular and new sinotubular junction.34 The graft will billow outward when it is subjected to arterial pressure, thus creating neosinuses. At Hopkins (Fig. 33-10), we use a modified David I reimplantation procedure using the Valsalva graft, which has prefashioned pseudosinuses.35 Our procedure differs from the original David I reimplantation technique in that only three subannular sutures are placed. The subannular sutures serve only to anchor the base of the graft below the annulus, holding the entire aortic valve complex within the graft and are not hemostatic. We believe that use of the Valsalva graft in a reimplantation procedure provides both annular stabilization and preservation of sinuses. The size of the graft is based on optimal sinotubular junction sizing using valve sizers, determined intraoperatively after transection of aorta. A graft that is 2 to 3 mm larger is chosen as the graft will sit outside the aortic valve complex. Most patients in our experience35 have had optimal sinotubular junction diameters of 28 to 30 mm and end up receiving a 30- to 32-mm graft. We have not found that measurement of leaflet dimension and formulas for graft selection are useful. The Valsalva graft is available in sizes 24 to 34 mm, which can accommodate majority of aortic roots encountered in clinical practice. Although patients with annular diameters greater than 34 mm may undergo valve sparing root surgery, in our experience, these patients typically have thin, stretched out abnormal leaflets and often have severe valvular regurgitation. Surgeon experience and patient selection are important factors for good outcomes after VSRR. Modified Bentall operation still remains the procedure of choice in patients with severe regurgitation, leaflet asymmetry, and fenestrations and those having bicuspid valves with significant thickening or prolapsed.
Reimplantation (David-I) valve-sparing aortic root replacement- the Hopkins modification. A. Stay sutures are placed above each coronary artery, and the sinuses are excised, leaving a 4- to 5-mm sinus remnant attached to the annulus. The coronary arteries are widely mobilized; the dissection remains close to the annulus rather than the coronary to avoid “button-holing” the undersurface of the coronary artery. The area of fibrous continuity between the aorta and pulmonary artery should be separated down to a level flush with the nadir of the right sinus annulus. Some dissection of right ventricular muscle from the aorta at the anterior (right-noncoronary) commissure is sometimes necessary, but one should avoid overzealous use of the cautery here, as our only case of permanent heart block necessitating a permanent pacemaker resulted from a thermal or electrical injury to the AV node during this dissection. In our technique, pledgetted mattress sutures of 2-0 Tevdek are placed about 2 mm below the nadir of the annulus in each of the three sinuses; only two subannular sutures are used if a bicuspid valve is present. The mattress suture should not be too wide, as it may distort the base of the leaflet. If the surgeon prefers, additional subannular sutures can be placed but our experience suggests they are rarely necessary, as the bottom suture line is to secure the graft below the valve and not for hemostasis. Additional subannular sutures can be placed after the graft is lowered and the initial subannular sutures are tied. This will allow the additional subannular sutures to follow the natural curve of the annulus and be accurately placed through the graft, rather than be placed in a single plane, which is difficult to achieve near the left–right commissure, and places the conduction system at risk anteriorly. B. The horizontal mattress subannular sutures are passed from inside out through the bottom collar of the graft. The commissural stay sutures are retrieved through the graft, which is then lowered and the three subannular sutures are tied. Using pledgetted 4-0 Prolene sutures, we fix the top of the commissures, just above the valve leaflets, to the STJ of the graft. This height is appropriate for the majority of patients. This usually creates some tension on the commissures, but one should resist the temptation to locate the commissure lower, which will result in leaflet prolapse. The Prolene sutures are tied outside the graft, and the stay sutures are removed. C. The internal suture line approximating the annulus and sinus remnant to the inside of the graft is the next step. We begin in the left coronary sinus, using a continuous 4-0 Prolene and an RB-1 needle. Whenever possible, one should direct the needle away from the valve to minimize the chance of leaflet injury. As this is the hemostatic suture line, it should be completed meticulously and in unhurried fashion. Folds of the graft are sites of potential internal leak and bleeding and can be avoid by pulling on the aortic tag at the top of the commissure, straightening the course of the annulus and graft to facilitate sewing. We prefer to perform the internal sutures line in the order of left sinus, noncoronary sinus, and finally, the right sinus. (Reproduced with permission from Cameron DE, Vricella LA. Valve-sparing aortic root replacement with the Valsalva graft. Op Tech Thorac Cardiovasc Surg 2009;14:297–308. Copyright Elsevier.)
The results of the David operation have been excellent, with 100 percent freedom from reoperation in Dr. David’s hands.36 Similar excellent results have been reported by other investigators.35 Patients benefit from the long-term durability associated with preservation of their own valves, and anticoagulation is not required postoperatively.35,36
Postoperative Care and Surgical Results
Immediate postoperative care should focus on control of hypertension (for which intravenous sodium nitroprusside is used most commonly) and maintenance of adequate filling pressures (central venous pressure 10–15 mm Hg, pulmonary capillary wedge pressures in the range of 15–18 mm Hg). Dual-chamber pacing is required in a small proportion of patients who leave the operating room in conduction block. Often this resolves within 24 to 48 h. If conduction block persists longer than 4 to 5 days, permanent pacemaker insertion should be considered. In patients with no conduction disturbances, pacemaker wires can be removed on the third or fourth postoperative day. The patient should be placed on telemetry for the duration of the hospital stay, however. The mediastinal tube is removed for outputs less than 150 mL per 24 h.
Patients with mechanical valves are started on oral warfarin on the second postoperative day. The use of daily aspirin coupled with a target International Normalized Ratio (INR) of 2.0 to 2.5 provides satisfactory anticoagulation and minimizes long-term bleeding and thrombotic events. Patients with bioprosthetic valves can be managed with aspirin alone, with no warfarin required.
The 30-day (early) mortality for aortic root replacement varies from 0 to 10 percent.25,35 This number is approximately doubled with redo operations. Reoperation for mediastinal hemorrhage should be required in less than 10 percent of cases. Complete heart block requiring pacemaker insertion occurs in about 1 to 2 percent in most series. Stroke occurs in approximately 1 to 4 percent of these patients. There is no practical pharmacologic strategy for the prevention of postoperative atrial fibrillation, which occurs up to one-third of the time (in patients with no previous history). Careful correction of electrolytes and chemical cardioversion with intravenous and oral amiodarone are preferred and are successful 90 to 95 percent of the time. Patients should be maintained on oral amiodarone for approximately 1 month, by which time the threat of recurrent atrial fibrillation should be resolved. In patients who require warfarin, the use of amiodarone makes it very difficult to manage the INR, and consideration should be given to alternative antiarrhythmics such as sotalol and procainamide. Patients with persistent atrial fibrillation despite attempts at chemical and electrical cardioversion should be maintained on oral warfarin until the arrhythmia resolves.