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Byrne JG, Phillips BJ, Cohn LH. Reoperative Valve Surgery.
In: Cohn LH, Edmunds LH Jr, eds. Cardiac Surgery in the Adult. New York: McGraw-Hill, 2003:10471056.

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Chapter 42

Reoperative Valve Surgery

John G. Byrne/ Bradley J. Phillips/ Lawrence H. Cohn

MECHANICAL VS. BIOLOGICAL VALVES
REOPERATIVE AORTIC VALVE SURGERY
????Historical Points
????Approaches and Techniques
????????THE STANDARD: RESTERNOTOMY
????????MINIMALLY INVASIVE REOPERATIVE AORTIC VALVE REPLACEMENT
????????REPLACEMENT OF HOMOGRAFTS AND ALLOGRAFTS
REOPERATIVE MITRAL AND TRICUSPID VALVE SURGERY
????Historical Points
????Approaches and Techniques
????????RESTERNOTOMY
????????RIGHT THORACOTOMY
CONCLUSION
REFERENCES

?? INTRODUCTION
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The number of patients undergoing reoperation for valvular heart disease is increasing and will continue to increase as the general population ages.1 These reoperations most commonly involve progression of native valve disease after nonvalve surgery and structural deterioration of a bioprosthesis. In fact, structural failure of a biological valve should be considered as part of their natural evolution and fully appreciated by both the surgeon and patient prior to implantation.2 Reoperations are technically more difficult than primary operations because of adhesions around the heart and the common association of pulmonary hypertension with valve dysfunction. Also, replacement operations are often performed in functionally compromised patients who tolerate complications poorly or have little reserve. In the past, reoperative valve surgery has been associated with a considerably higher operative mortality than primary valve surgery, particularly in patients who have had multiple prior replacements.3 However, in the modern era there has been some improvement in both morbidity and mortality.4,5

Reductions in operative risk and postoperative morbidity after reoperative valve surgery have been made in the past few years by advances in myocardial protection, as well as the proper use of deep hypothermic cardiac arrest.6 Utilization of peripheral cannulation techniques to institute cardiopulmonary bypass has become a relatively standard practice.79 Early institution of partial cardiopulmonary bypass is thought to prevent injury to the hypertensive right ventricle or patent coronary artery bypass grafts during reoperative sternotomy. This technique decreases myocardial distension, thereby reducing oxygen consumption.3

Successful replacement of the diseased cardiac valve usually results in gratifying symptomatic and hemodynamic improvement. Maintenance of this improved state, however, depends on acceptable prosthetic valve function. Improvements in valve design have lessened, but not eliminated, the incidence of primary bioprosthetic valve failure.1012 Thus, the risk of re-replacement for bioprosthetic failure remains a factor to be considered in the selection of valve type.13


?? MECHANICAL VS. BIOLOGICAL VALVES
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Mechanical valvular prostheses have the distinct advantage of longevity but carry a risk of anticoagulant-related bleeding as well as thromboembolic events (TE), which are dependent on valve design, structural materials, and host-related interactions.14 While endocarditis, dehiscence, perivalvular leak, and pannus formation are common to both biological and mechanical valves, acute prosthetic thrombosis is mostly a complication of mechanical valves.15,16 Mechanical prostheses are usually selected in younger recipients because of their proven durability over time, yet thrombogenecity remains a persistent risk that requires lifelong anticoagulation. In a 12-year comparison of Bj?rk-Shiley versus porcine valves, Bloomfield et al documented severe bleeding complications of 18.6% versus 7.1%, respectively.17 These rates, however, must be balanced with the known risk of tissue valve failure and expected risks of further intervention.

In evaluating reoperations for bioprosthetic failure, Husebye et al reviewed their 20-year experience.13 Operative mortality for the first reoperation (n = 530 patients) was 5.9% for the aortic position and 19.6% for the mitral position. Overall operative mortality was 14% (n = 69 patients) and 7% (n = 14 patients) for the second and third reoperations, respectively. In the aortic position, operative mortality was 2.4% for NYHA I patients, 1.6% for NYHA II, 6.3% for NYHA III, and 20.8% for NYHA IV. The mortality for elective mitral valve reoperation was 1.4%; urgent procedures, 8%; and emergency procedures, 37.5%. Based on this, the authors recommended that reoperation should be undertaken when valve dysfunction is first noted.13

Jones et al also reviewed their experience with first heart valve reoperations involving 671 patients between 1969 and 1998.4 Their overall operative mortality for first-time heart valve reoperation was 8.6%, which is similar to the results published by Lytle18 (10.9%), Cohn3 (10.1%), Akins19 (7.3%), Pansini2 (9.6%), and Tyers20 (11.0%). In their series, mortality increased from 3.0% for reoperation on a failed repair or reoperation at a new valve site to 10.6% for prosthetic valve dysfunction or periprosthetic leak; mortality increased to 29.4% for associated endocarditis or valve thrombosis. Concomitant coronary artery bypass grafting was associated with a mortality of 15.4% compared to 8.2% when it was not required. Among 336 patients requiring re-replacement of prosthetic valves, mortality was 26.1% for re-replacement of a mechanical valve compared with 8.6% for re-replacement of a tissue valve. The authors found through multivariate analysis that significant predictors of mortality were year of reoperation, age, indication, concomitant coronary artery bypass grafting, and the replacement of a mechanical valve rather than a tissue valve.4

Structural degeneration of a bioprosthesis is the leading cause and the most frequent indication for reoperation in patients with tissue valves.21,22 The most appropriate valve substitute for the individual patient is still a source of much controversy. This choice should be adapted to each individual patient depending on age, life expectancy, valve size, and cardiac as well as noncardiac comorbidities.23 Some studies comparing the long-term outcome between biological and mechanical aortic valve prostheses have yielded similar results in regards to overall valve-related complications.22,2427 However, most recent large studies have documented that anticoagulant-related bleeding with mechanical valves must be balanced against life expectation and the risk of biological valve re-replacement.2831 Bioprosthetic valves are known to undergo a time-dependent process of structural deterioration that results in dysfunction and requires re-replacement in 12 to 15 years.24 Furthermore, encouraged by the availability of stentless valves and homografts, more surgeons are placing an aortic bioprosthesis in progressively younger age groups.23,3235 In addition, many patients do not accept the risks of an anticoagulant-related hemorrhage, which are 0.5% per patient-year for a major event and 2% to 4% per patient-year for a minor event.14


?? REOPERATIVE AORTIC VALVE SURGERY
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Historical Points

Historically, aortic valve surgery usually involved the placement of a mechanical valve. In the past, there were only a few generally accepted indications to use a bioprosthesis for primary, isolated aortic valve replacement: (1) the presence of well-established contraindications to continuous anticoagulation; (2) the inability to adequately monitor prothrombin levels; and (3) patients whose survival was limited and more dependent on issues unrelated to their valve dysfunction.22,23 However, in recent years the use of biological valves in the aortic position has become more common.29,30

Reoperations are technically demanding and many patients present in a poor functional state that increases the reoperative mortality rate of a failing aortic bioprosthesis, in some series up to 19%.17,36,37 However, elective re-replacement of malfunctioning aortic bioprostheses can be performed with results similar to the primary operation.23,38 The presence of concomitant coronary artery disease and pulmonary hypertension have been shown to be independent risk factors.23 These patients need careful surveillance once the probability of bioprosthetic dysfunction begins increasing 6 to 10 years after implantation.12 In regards to valve surveillance and timing of reoperation, the following variables are clinically relevant to managing patients with an aortic bioprosthesis: a history of endocarditis prior to the first operation; perioperative infectious complications; coronary artery disease acquired after the first operation; an increase in pulmonary artery pressure; and a decrease in left ventricular function during the interval.23 Proper timing of the reoperation is important, because duration of clinical signs with a dysfunctional aortic bioprosthesis may be misleading. The need for an emergency reoperation of a biological valve, itself, is the most important factor in contributing to poor patient outcome yielding a consistently high early mortality rate of 25% to 44%.39

Approaches and Techniques

THE STANDARD: RESTERNOTOMY

The evolution of cardiac surgery through the last few decades has led to the popularization of various surgical approaches. Thoracotomy was once used extensively to gain access to mediastinal structures. Then, median sternotomy became the standard approach. However, in reoperative cases, repeating the sternotomy carries definite risks. Prior to proceeding with a resternotomy, the relationship between anterior mediastinal structures and the posterior aspect of the sternum, as visualized on chest radiograph or computed tomography (CT), must be assessed carefully.40 Preparations for emergency femorofemoral cardiopulmonary bypass should be completed prior to beginning the resternotomy. Sternal wires from the previous operation should be carefully undone, but left in place as a safeguard during sternal division. An oscillating (not reciprocating) bone saw can be used to divide the anterior sternal table. Most authors recommend dividing the posterior table using a combination of scissors and lateral retraction.4042 Following this, other mediastinal structures should be carefully dissected using rake retraction. The pericardial dissection plane can be developed by starting at the cardiophrenic angle and then slowly advanced cephalad and laterally on the surface of the right heart. Cephalad dissection should start with innominate vein identification and then carried down the superior vena cava, noting location of the right phrenic nerve. Repairing small ventricular or atrial lacerations should not be attempted before releasing the tension of the surrounding adhesions. Repair of great vessel injuries is best done under CPB.40 Active hemorrhage during a second sternotomy is usually due to adherence of the heart or great vessels to the posterior sternum. Whether this could be prevented by interposition of pericardium or other mediastinal tissue at time of the first operation is debatable.42 The incidence of resternotomy hemorrhage is between 2% and 6% per patient reoperation.4345

In a report of 552 patients who had undergone reoperative prosthetic valve surgery, 23 (4%) had complications related directly to sternal opening.13 Of these, 5 patients had entry into the right atrium, 7 patients had lacerated right ventricles, 9 patients had injuries to the aorta, and there were 2 patients in whom a previously placed coronary graft was divided. Nineteen of the 23 complications occurred during a first-time reoperation. Overall, there were 2 operative deaths related to resternotomy. The first death involved division of a previously placed coronary graft during reentry. The second death was due to laceration of the aorta with subsequent exsanguination.13

Macanus et al reviewed their experience with 100 patients undergoing repeat median sternotomy.44 Eighty-one patients had one repeat sternotomy while the others had undergone multiple sternotomies. All had a previous valve procedure in the past and were reoperated upon for progressive rheumatic valvular disease or for complications related to the prosthesis. Complications included operative hemorrhage in 8 patients, postoperative hemorrhage in 2, seroma in 4, and dehiscence, wound infection, and hematoma in 1 patient each. There was one operative death directly related to resternotomy hemorrhage.44

When major hemorrhage does occur upon sternal entry, attempts at resternotomy should be abandoned. The patient should be immediately heparinized while obtaining femoral arterial and venous cannulation. Blood lost from the resternotomy should be aspirated with cardiotomy suction and returned to the pump-oxygenator. Once bypass has been established, core cooling can commence, flow rates are reduced, and the sternal division completed, followed by direct repair of the underlying injury.42 Accepting the risk of this scenario, we routinely expose peripheral cannulation sites prior to beginning a resternotomy.

MINIMALLY INVASIVE REOPERATIVE AORTIC VALVE REPLACEMENT

"Minimally invasive" valve procedures have gradually become more accepted as new technologies and instrumentation develop.46 Reoperative procedures pose an area in which minimally invasive procedures may be of direct benefit.47,48 Our surgical approach for reoperative AVR is shown in Figure 42-1.46 In all patients, peripheral cannulation sites are exposed and dissected prior to beginning the partial upper resternotomy. An external defibrillator is placed on the patient prior to draping for subsequent defibrillation, as necessary. A transesophageal echo (TEE) probe is used in every patient. An "inverted T"49 partial upper resternotomy is carried out to the 3rd or 4th intercostal space depending on the estimated position of the aortic valve as documented by TEE. The oscillating saw is used to divide the anterior sternal table while the straight Mayo scissors, under direct visualization, divide the posterior sternal table. The chest wall incision is then extended laterally into the intercostal spaces on both sides. In the setting of a patent LIMA-LAD graft, or other anterior CAB grafts, patients are placed on cardiopulmonary bypass (CPB) prior to partial resternotomy. Mediastinal dissection is limited to the ascending aorta for clamping and aortotomy. The right atrium (RA) is dissected only if it is cannulated. Although intrathoracic cannulation is preferred, we frequently use peripheral cannulation to avoid clutter in the chest. Retrograde cardioplegia, if necessary, is delivered via a transjugular coronary sinus catheter. Vacuum assistance for venous drainage is used in the majority of cases. On CPB, all patients are systemically cooled to 20?C to 25?C. Patients with patent LIMA-LAD grafts are routinely cooled to 20?C. If collateral flow from the patent LIMA-LAD graft flows out of the left main ostium on CPB and obscures the operative field, pump flows are turned down temporarily to allow visualization. Venting is accomplished by placing a pediatric vent through the aortic annulus.



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FIGURE 42-1 Partial upper resternotomy for reoperative AVR. The previous sternotomy incision is exposed to the 3rd or 4th intercostal space, depending on the position of the aortic valve as documented by transesophageal echocardiography. After dissection of the ascending aorta, paying particular attention to the position of CAB grafts and their proximal anastomoses, cannulation is carried out. In this illustration, the ascending aorta and innominate vein are cannulated. Frequently, however, other cannulation sites are required due to space limitations in the chest. The ascending aorta is cross-clamped and the aortic valve re-replacement is conducted in the standard fashion. (Reproduced with permission from Byrne J, Karavas A, Adams D, et al: Partial upper re-sternotomy for aortic valve replacement or re-replacement after previous cardiac surgery. Eur J Cardiothorac Surg 2000; 18:282.)

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The aortic valve surgery is then performed based on patient indications. While closing the aortotomy, intracardiac air is removed by insufflating the lungs and decreasing flows on CPB. Patients are also tilted from side to side to help with de-airing, and the ascending aortic vent is left open until separation from CPB. Temporary epicardial pacing wires are placed on the anterior surface of the right ventricle before the aortic cross-clamp is removed. Two 32F right-angled submammary chest tubes are then placed through the right pleural space, one angled medially into the mediastinum and one angled posterior into the pleural space. Decannulation and closure is then performed in the standard manner.

Reoperative procedures are challenging due to diffuse mediastinal and pericardial adhesions. A large incision that increases the operative field has also been associated with a higher risk of injury to cardiac structures, CAB grafts, and greater bleeding with subsequent transfusion requirements.5053 A smaller incision, on the other hand, will reduce the area of pericardiolysis, thus limiting these effects. The remaining intact lower sternum will preserve integrity of the caudal chest wall, thereby enhancing sternal stability and promoting an earlier extubation.46,54

With our increasing experience in minimally invasive reoperative AVR, we have refined our technique as an alternative to conventional full resternotomy.46 In doing so, we have ascertained certain technical details of the partial upper resternotomy approach (Table 42-1). By following these guidelines, we have yet to convert any patient to a full resternotomy. Lateral chest x-ray and/or TEE is helpful in locating the level of the aortic valve and determining the proximity of the aorta to the posterior aspect of the sternum.49 If necessary, additional information can be obtained with CT scanning or magnetic resonance imaging (MRI). Also, extension of the sternal incision laterally on both sides through the intercostal spaces helps to later reapproximate the sternum. We have tried to limit mediastinal and pericardial dissection primarily to the aorta, believing that this is the principal reason for decreased bleeding and transfusion requirements postoperatively.46,48,55,56 The right ventricle, which is often attached to the sternum, does not need to be dissected. Also, injuries to patent but atherosclerotic vein grafts can be reduced with this "no-touch technique."57


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TABLE 42-1 Thirteen technical details for successful aortic valve replacement after previous cardiac surgery by use of partial upper resternotomy

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Arterial and venous cannulation sites can vary considerably, reflecting the individual choice of the operating surgeon and the sufficiency of intrathoracic space. Possible cannulation sites, other than standard ones, include the axillary artery, innominate vein, and percutaneous femoral vein.58,59 The use of innominate vein or percutaneous femoral vein cannulation and the use of the retrograde cardioplegia coronary sinus catheter have been extremely helpful in minimizing the dissection of the right atrium. At present, we consider this approach to be our standard for isolated, elective reoperative aortic valve surgery.46

REPLACEMENT OF HOMOGRAFTS AND ALLOGRAFTS

Aortic valve replacement with a homograft or autograft has been used increasingly because of their excellent freedom from thromboembolism, resistance to infection, and superior hemodynamic performance.32 Although in younger patients durability is superior to that of stented xenografts,35,60 many patients will subsequently require aortic valve re-replacement for structural degeneration of the homograft or autograft valve.61

The requirement for a second aortic valve operation for patients with previous homograft or autograft is expected to increase, as popularity and availability of these valves increase. Recently, Hasnet et al documented the results of 144 patients who underwent a second aortic homograft replacement, with a hospital mortality rate of 3.5%.61 However, since this is a relatively rare operation at most centers, we believe that a simplified approach may be optimal. Our approach to this rare problem has been to perform aortic valve re-replacement using a mechanical valve or stented xenograft, while reserving a second homograft for specific indications such as endocarditis, associated root pathology, or a very young patient with contraindications to a mechanical valve.

It is expected that approximately one third of patients less than 40 years of age will require aortic valve re-replacement within 12 years after homograft. This is primarily due to structural valve degeneration. Thus, the issue of homograft or autograft durability is particularly pertinent for this subgroup of younger patients who are expected to live beyond 15 years from time of operation.60

Hospital mortality of homograft re-replacement varies widely across many centers, and ranges between 2.5% and 50%.34,62,63 Variations in sample size, valve selection, surgical techniques, and patient factors, as well as the experience of the surgeons, may account for these wide differences. Currently, there is no consensus as to the optimal surgical method of primary homograft AVR. The technique of primary homograft operation may have relevance at reoperation because calcification or aneurysmal dilation of the homograft may pose surgical challenges at reoperation. Sundt and others34,62,63 have documented the feasibility of aortic valve re-replacement after full root replacement with a homograft. In our own series of 18 patients, full root, mini-root, and subcoronary techniques were all amenable to valve re-replacement.32


?? REOPERATIVE MITRAL AND TRICUSPID VALVE SURGERY
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Historical Points

Fundamental to a flawless surgical procedure is excellent and consistent exposure of the mitral valve.64 Historically, the mitral valve has been exposed through a variety of surgical approaches, including median sternotomy, right thoracotomy, left thoracotomy, and transverse sternotomy.65 The median sternotomy and right thoracotomy will be discussed in detail below; however, a brief description of the other approaches is warranted.

The left thoracotomy has been used in recent years to gain access to the mitral valve. This incision is made through the fourth intercostal space and the left pleural cavity is entered in the standard fashion.65 However, this approach provides limited access to the other cardiac chambers as well as poor visibility of the mitral valve apparatus, which is anatomically directed towards the right. This left-sided approach is typically reserved for cases in which reoperative sternotomy or right thoracotomy is considered unacceptable. A bilateral anterior thoracotomy (i.e., transverse sternotomy) carried out through the fourth intercostal space has also been described.66 Rarely used today, this incision transects the sternum transversely requiring ligation of both internal mammary arteries. Regardless of the actual approach, once CPB has been established and the heart exposed, there are several incisions that can be employed to view the underlying mitral valve. The standard left atriotomy begins with blunt dissection of the interatrial groove, allowing the right atrium to be retracted medially and anteriorly. The right superior pulmonary vein at its junction with the left atrium is then exposed and the left atrium is opened at the midpoint between the right superior pulmonary vein insertion and the interatrial groove. This incision is extended longitudinally both superiorly and inferiorly to give enough exposure of the mitral valve. Care must be taken to avoid inadvertent injury to the posterior wall of the left atrium and, when closing, one must avoid including the posterior wall of the right pulmonary vein.

The right atrial transseptal approach has become more popular in recent years especially in reoperative valve surgery. After opening the RA, the interatrial septum is incised starting at the fossa ovalis and directed vertically upward for a few centimeters (Fig. 42-2). This technique is especially helpful in reoperative surgery, since it minimizes the amount of dissection required. Superior, biatrial atriotomy, left ventriculotomy, and aortotomy have all been well described11,53,64,65,67,68 as approaches to the mitral valve; each one has varying advantages and disadvantages.



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FIGURE 42-2 Sondergaard's groove approach. (A) The left atrium enlarges to the right, increasing visualization from the right thoracotomy approach. (B) The interatrial groove (Sondergaard's groove) is dissected approximately 1 cm deep, down to the left atrial wall. The purse-string suture is placed in the nondissected area. This prevents tearing of the dissected left atrial wall when the suture is tied down. (C) Sagittal view shows location of the mitral valve in relation to the atriotomy. (Reproduced with permission from Hanh D, Pezzella T: Closed mitral commissurotomy utilizing right thoracotomy approach. Asian Cardiovasc Thorac Ann 2000; 8:192.)

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Approaches and Techniques

RESTERNOTOMY

Resternotomy is still the most common approach in reoperative mitral valve surgery. In many cases, this incision provides full and adequate exposure. This is especially true when concomitant procedures are necessary. However, reoperative median sternotomy has known risks, including injury to or embolism from prior grafts, sternal dehiscence, excessive hemorrhage, and inadvertent cardiac injury.69 Patients with valvular heart disease may be especially prone to these complications because atrial dilatation can result in significant cardiomegaly, atrial thinning, and adherence of the heart to the posterior sternum. As we have previously discussed, patients undergoing prosthetic valve reoperation have a 4% incidence of complications directly related to sternal reentry, which can cause intraoperative death.13,18 Resternotomy has also been noted to be particularly hazardous in the presence of patent internal mammary grafts. Injury to a patent LIMA graft has an associated mortality rate approaching 50%.42,69 Furthermore, manipulation of patent but diseased saphenous vein grafts can result in embolization into the native coronary circulation with resulting morbidity and mortality.70,71 In the setting of reoperative surgery, the initial resternotomy is likely to be the most dangerous part of the operation.72 In this situation, we have tried to employ techniques that avoid resternotomy.

RIGHT THORACOTOMY

The right anterolateral thoracotomy approach was one of the first surgical approaches to the mitral valve, and it has become a safe alternative to resternotomy for mitral valve replacement (Fig. 42-3).6,42,73,75 This approach provides excellent exposure of the valves (mitral and tricuspid) with minimal need for dissection within the pericardium. In our recent experience with this approach,72,76,77 all patients had double-lumen endotracheal tubes placed and operations were performed in the right lateral thoracotomy position. We routinely prepared and draped the right groin to allow femoral cannulation, if necessary. Preoperative and intraoperative Doppler transesophageal echocardiography was performed in all patients, as well as standard intraoperative cardiac monitoring and thermodilution Swan-Ganz catheterization. A right thoracotomy was made and the chest entered through the bed of the fifth rib. Adhesions of the right lung to the chest wall or pericardium were divided by electrocautery. The pericardium was entered anterior to the phrenic nerve. Arterial cannulation was performed via the ascending aorta with the use of a flexible aortic cannula. Bicaval venous cannulation was carried out with a 28F (DLP) cannula in the superior vena cava and a 32F (USCI) flexible cannula in the inferior vena cava. Patients were then cooled to 25?C. Fibrillatory arrest occurred spontaneously in the majority of patients. Aortic cross-clamping was usually not required. The mitral valve was then approached through the left atrium by dissection of the intra-atrial groove or through the atrial septum (Fig. 42-4). As the valve procedure was completed, we began rewarming (Fig. 42-5).



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FIGURE 42-3 Right anterolateral thoracotomy. Right anterolateral thoracotomy through the 4th intercostal space and standard left atriotomy. (Reproduced with permission from Balasundaram SG, Duran C: Surgical approaches to the mitral valve. J Card Surg 1990; 5:163.)

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FIGURE 42-4 Atrial incision through the fossa ovalis. When the right atrium is incised, an incision is made in the atrial septum through the fossa ovalis. Retraction sutures, on both the right atrium and the atrial septum, of 2-0 silk, are then used to elevate the septum and to keep the left atrium open. The mitral valve will then be exposed (inset). (Reproduced with permission from Byrne JG, Mitchell ME, Adams DH, et al: Minimally invasive direct access mitral valve surgery. Semin Thorac Cardiovasc Surg 1999; 11:212.)

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FIGURE 42-5 Closure. In the transeptal approach, the atrial septum is approximated with running 4-0 Prolene sutures and is left open until the aortic cross-clamp is removed and the air is evacuated. The left ventricle should be filled with fluid before removal of the cross-clamp to help dislodgment of intraventricular air. Once the cross-clamp has been removed, air is evacuated vigorously from the left atrium through the septum or the left atrium itself, and the sutures are tied. The right atrium is then closed with running 4-0 Prolene sutures in two layers. Transesophageal echocardiogram has been very important in helping to monitor the clearing of air from the intracardiac structures. We consider it mandatory in the minimally invasive technique in which access to the entire cardiac structure is limited. (Reproduced with permission from Byrne JG, Mitchell ME, Adams DH, et al: Minimally invasive direct access mitral valve surgery. Semin Thorac Cardiovasc Surg 1999; 11:212.)

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The left ventricular vent was positioned across the valve while an air needle, on suction in the ascending aorta, was used to remove any ejected air. The patient was then placed in the Trendelenburg position and de-airing accomplished under two-dimensional transesophageal echocardiography guidance. When core temperatures reached 36?C, the patient was weaned from cardiopulmonary bypass. Temporary atrial and ventricular pacing wires were placed and exteriorized through the chest wall. Closure was then routine. At the conclusion of the procedure, patients were returned to the supine position and reintubated with a single-lumen endotracheal tube for postoperative ventilation.

The use of a small right anterior thoracotomy, femorofemoral bypass, and deep hypothermia has increased since our initial report in 1989.78 Reduced blood use, and decreased risk of LIMA or cardiac structural injury during sternal reentry, makes it a desirable approach for almost all complicated mitral reoperations. Deep hypothermia (approximately 20?C) and low-flow femorofemoral bypass perfusion, without the necessity of aortic cross-clamping, provides adequate myocardial protection.79 Cardiopulmonary bypass times, blood loss, blood product usage, and LIMA injury rates have been lower in reoperative patients undergoing right thoracotomy than in those with resternotomy.69,73,79,80

Certain issues must be considered before the right thoracotomy approach can be utilized. Patients who require simultaneous coronary artery bypass grafting will generally require a median sternotomy, although isolated right-sided grafting may be performed. Simultaneous replacement of the aortic valve is difficult from a thoracotomy approach and should generally be performed through a resternotomy. Significant aortic insufficiency can make effective perfusion on CPB difficult because, after opening the left atrium, blood will be returned to the pump oxygenator via cardiotomy suction. Unless the ascending aorta is clamped, effective end-organ perfusion will not be achieved. Also, in the setting of aortic insufficiency (AI), exposure of the mitral valve may be difficult and require core cooling to allow low flow rates. Left ventricular distension and injury can also occur with fibrillatory arrest. Patients with greater than minimal aortic insufficiency should either be excluded from a right thoracotomy approach or expected to require aortic cross-clamping either with traditional clamping or balloon occlusion. Significant right pleural disease, especially scarring in the right hemithorax, has previously been a relative contraindication to a right thoracotomy, although our series includes two patients with a previous right thoracotomy who did not represent an overwhelming challenge.69

Vleissus reported on 22 patients who underwent a minimally invasive right thoracotomy approach to the atrioventricular valves.81 The procedures performed included mitral valve repair (n = 12), mitral valve replacement (n = 5), prosthetic mitral valve re-replacement (n = 4), repair of perivalvular leak (n = 3), tricuspid valve repair (n = 5), and closure of an atrial septal defect (n = 7). Mean bypass time was 109 minutes with a mean fibrillatory time of 62 minutes. Operative mortality in this group was 0% and none of the patients experienced a wound complication. At follow-up, all patients thought their recovery from this approach was more rapid and less painful than their original sternotomy.81

Holman et al reported their experience in 84 patients undergoing reoperative mitral valve surgery via right thoracotomy.82 Myocardial management included ventricular fibrillation in 10 patients, beating heart in 58 patients, and hypothermic blood cardioplegia in 16 patients. The mean duration of cardiopulmonary bypass was 63 ? 56 minutes. There were no perioperative strokes and the operative risk for patients who received cardioplegic arrest was significantly greater than in the other two groups (p = .007). The authors concluded that procedures on the beating or fibrillating heart were feasible in most patients and are at least as safe as surgery using cardioplegic arrest.82


?? CONCLUSION
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The most common indication for valve re-replacement is structural valve degeneration of porcine bioprostheses.3 After 8 to 10 years of follow-up, biological valves begin to structurally deteriorate, especially in young patients and in the mitral position. Accelerated follow-up intervals should be the rule in these patients to avoid missing early degeneration. When patients have been allowed to fall into NYHA class IV, reoperative mortality has been directly affected.


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