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Minimally invasive valve surgery
Cardiovascular Pathology 13 (2004) 176 – 181
Minimally invasive valve surgery What the pathologist should know Tomislav Mihaljevic *, Daniel Unic, John G. Byrne, Lawrence H. Cohn Division of Cardiac Surgery, Brigham and Women’s Hospital, 75 Francis Street Boston, MA 02115, USA Received 20 October 2003; received in revised form 22 December 2003; accepted 22 December 2003
Abstract Minimally invasive approaches in cardiac surgery have emerged as an alternative to standard techniques particularly in patients udergoing valvular surgery. Their established benefits for the patients are likely to cause their widespread use in the future. The purpose of this is to provide an overview of modern minimally invasive approaches in valvular surgery with an emphasis on aspects of the surgery relevant for cardiovascular pathologists. D 2004 Elsevier Inc. All rights reserved. Keywords: Minimally invasive valve operations; Approaches for valvular surgery
1. Introduction Minimally invasive approaches in cardiac surgery have emerged as a new and interesting alternative to a variety of established, standard operations for the cardiac surgery in the adult. These techniques allow reduction of surgical trauma, pain, length of hospitalization, and overall cost of treatment [1]. The development of the less invasive surgical approaches was enabled through development and adoption of new technologies. Technological advances were made in several areas pertinent to cardiac surgery and could be generally divided in the advances related to the primary procedure (new valve repair techniques, robotic surgical systems, improvements of cardiopulmonary bypass technology, etc.) and those related to the improved diagnostics and intraoperative monitoring (transesophageal echocardiography, epiaortic scanning). Less invasive operations have been described in coronary revascularization and valvular and aortic surgery. Although coronary surgery still represents the most commonly performed operation in cardiac surgery, minimally invasive approaches in coronary revascularization have been mostly restricted to the isolated single-vessel (left anterior descending artery) revascularization. The most important limiting factor in adaptation of minimally invasive techniques in coronary surgery is related to the inability to adequately * Corresponding author. Tel.: +1-617-732-7678; fax: +1-617-732-6559. E-mail address: [email protected] (T. Mihaljevic). 1054-8807/04/$ – see front matter D 2004 Elsevier Inc. All rights reserved. doi:10.1016/S1054-8807(03)00154-6
visualize all coronary arteries through a single small incision. Furthermore, the performance of coronary anastomosis through via minimally invasive approach is technically very demanding regardless of recent technologic advances [2]. In contrast to minimally invasive incisions in coronary surgery, minimally invasive valvular surgery has been accepted as an equally valuable surgical approach for patients with isolated valvular disease. Excellent surgical exposure of individual valves (aortic, mitral, and tricuspid) can be accomplished through a single small incision allowing valve repairs or replacements of equal quality as those performed through standard incisions. New techniques of valve repairs and preservation (predominantly mitral and tricuspid valves) have been incorporated in minimally invasive approaches. The introduction of new and less invasive approaches has also resulted in the potential for development of complications, which differ from complications observed in patients who were operated using standard approaches. The purpose of this article is to provide a review of current techniques in modern minimally invasive valve surgery with particular emphasis on aspects of surgery, which could be relevant for cardiovascular pathologist.
2. Minimally invasive aortic valve surgery Calcific aortic stenosis represents the most common indication for aortic valve replacement in adult population.
T. Mihaljevic et al. / Cardiovascular Pathology 13 (2004) 176–181
Typically, these are elderly patients in their seventh or eighth decade of life with multiple comorbidities. Advanced age and associated medical problems put these patients in higher risk category for surgical treatment. On the other hand, aortic valve replacement is the only therapeutic option, since there is no alternative effective medical or interventional therapy for severe symptomatic aortic stenosis. The obvious need to minimize surgical trauma in such frail patients has resulted in the development of minimally invasive approaches for aortic valve replacement. 2.1. Surgical technique The 6- to 8-cm incision is made beginning halfway between the sternal notch and the angle of Louis. Partial upper sternotomy is performed from the sternal notch to the fourth intercostal space, extending into the space to the right, forming a reversed L shape. The extension of the sternotomy into the intercostal space often results in the violation of the right pleural space. Alternatively, the incision can be extended into both intercostal spaces. The main disadvantage of the extended (inverse T) incision is the potential of injury to the left internal thoracic artery, which prevents its potential use for coronary artery bypass in the future [3]. Right anterior thoracotomy through the third intercostal space [4] represents alternative to upper sternotomy, but is associated with division of the right internal mammary artery and partial transection of the right pectoral muscle, which results in increased postoperative discomfort. Both incisions allow excellent exposure of the aortic valve. Cardiopulmonary bypass is than established by cannulation of the distal ascending aorta and right atrium. Venous
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cannulation can be performed using a small (20F) venous cannula, which can be placed percutaneously in the femoral vein and advanced into the right atrium. Vacuum-assisted venous drainage represents a major technologic improvement of extracorporeal bypass circuits, which allows adequate venous drainage through small-diameter cannulas. Percutaneous placement of venous cannulas eliminates the need for cannulation of the right atrium and improves visualization in the operative field. The potential morbidity associated with venous cannulation is related to the local injury to the femoral vein or injury to the inferior vena cava and its tributaries during advancement of the cannula into the right atrium. The risk of such injuries can be minimized by guide-wire-assisted cannula placement under transesophageal echo guidance. Once the cardiopulmonary bypass is initiated and aorta cross-clamped, the aortic valve is exposed through the oblique aortotomy, which extends into the noncoronary cusp. The choice of aortic valve prosthesis and the technique of aortic valve replacement are identical to those used in standard ‘‘open’’ operations. Upon the completion of the valve replacement, the aortotomy is closed with running polypropylene suture (Fig. 1). Potential disadvantages of the partial sternotomy are the inadequate visualization of the ventricles, and inability to evacuate air from the ventricles at the end of the operation. These limitations can be overcome by the use of transesophageal echocardiography, which accurately estimates the amount of air within the heart. The intracardiac air can be than safely evacuated through the vent placed in ascending aorta, without causing peripheral air emboli. The use of carbon dioxide in the operative field allows fast absorption of intracardiac gas bubbles. The combination of both tech-
Fig. 1. Minimally invasive aortic valve operation: sternal incision.
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niques has kept the rate of perioperative neurologic complications comparable to those of standard procedures [5]. The above-described approaches have been successfully applied to other types of aortic surgery like aortic root replacement, replacement of the ascending aorta, and redo aortic valve replacement [6]. At our institution, every patient with isolated aortic valve disease is considered for minimally invasive aortic valve replacement. The obvious contraindication for minimally invasive aortic valve replacement is the presence of significant coronary artery disease. Morbid obesity presents relative contraindication for less invasive aortic valve surgery due to the difficulties in adequate exposure in such patients.
3. Minimally invasive mitral valve surgery Techniques for minimally invasive mitral valve surgery have undergone considerable refinement over the past decade and have approached the goal of reducing surgical trauma while maintaining the efficacy of the standard ‘‘open’’ procedure.
Myxomatous mitral valve disease with resultant mitral regurgitation presents the most common indication for isolated mitral valve surgery in the United States. Rheumatic mitral valve disease and endocarditis represent other, less common indications for isolated mitral valve repair or replacement. Typical patient with myxomatous mitral valve prolapse, in contrast to the patient with aortic stenosis, is an active individual in the fifth or sixth decade of life. These patients are highly interested in minimally invasive surgical techniques that would allow them faster return to daily activities [1]. A better understanding of mitral valve anatomy, function, and physiology has stimulated the development of many surgical techniques o treat the mitral regurgitation. Mitral valve repair now represents the standard of care for majority of patients with mitral valve prolapse and associated mitral regurgitation. 3.1. Surgical approaches Minimally invasive approaches for isolated mitral valve surgery include partial lower sternotomy, right parasternal approach, and limited right lateral thoracotomy.
Fig. 2. Minimally invasive mitral valve operation through partial lower sternotomy: (A) sternal incision and (B) transeptal approach.
T. Mihaljevic et al. / Cardiovascular Pathology 13 (2004) 176–181
Fig. 3. Parasternal approach for minimally invasive mitral valve operation: thoracotomy incision and incision for femoral cannulation.
3.1.1. Partial lower sternotomy Partial lower sternotomy (‘‘mini-sternotomy’’) is performed through a small 6- to 8-cm incision overlying distal aspect of the sternum. The sternotomy extends from the sterno-xiphoid junction upward to the second intercostal space and extends into the right interspace (Fig. 2). Care is taken to prevent injury to right internal mammary artery. Minimally invasive approach requires modification of the cannulation techniques for cardiopulmonary bypass. The ascending aorta is cannulated through the incision using a small cannula. In cases where small incision does not allow adequate aortic exposure, peripheral arterial cannulation via femoral artery represents a suitable alternative. Venous cannulation is usually accomplished by direct cannulation of the superior vena cava through the sternotomy. Inferior vena cava is cannulated with a small percutaneous transfemoral cannula advanced over the guide-wire and under guidance of the transesophageal echocardiography [3] (Fig. 2). Vacuum-assisted venous drainage allows adequate venous drainage despite small cannula size. The potential complications related to the peripheral cannulation include retrogade aortic dissection due to the inappropriate placement of the cannula in femoral artery. Injury to the aortic wall intima can serve as the entry point of the retrograde dissection once the cardiopulmonary bypass is instituted and retrograde arterial blood flow initiated. Early detection of this complication by TEE is of a paramount importance for adequate treatment. Peripheral venous cannulation with the advancement of the long, small-diameter cannula via femoral vein into the right atrium can potentially result in the tear inferior vena cava or its tributaries. This complication can be avoided by the placement of the venous cannula under TEE guidance. Incidence of serious complications related to the peripheral cannulation is well below 0.1% in our experience. After establishing cardiopulmonary bypass, the aorta is cross-clamped and the heart is arrested with cardioplegic solution. Mitral valve exposure can be accomplished through the right atrium with subsequent incision in the interatrial
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septum (transeptal approach) or directly through the left atrium (direct approach). The blood flow to the right atrium has to be interrupted with the use of caval tourniquets if transeptal approach is being used. Excellent mitral valve exposure can be achieved through oblique atriotomy and incision through the interatrial septum. This approach introduces risks of injury to the conduction system and a small risk of iatrogenic postoperative atrial septal defect in cases of incomplete closure of the incision in the interatrial septum. Right atriotomy causes scar formation in the atrial tissue, which can serve as a basis for the formation of postoperative atrial arrhythmias. These complications led to the more widespread use of the direct approach through the left atriotomy, which is currently our standard approach. 3.1.2. Parasternal approach Parasternal approach is accomplished through the 5- to 7cm-long incision over the third and fourth costal cartilages (Fig. 3). A small portion of both is then resected. This allows an appropriate approach of the right atrium. Mitral valve exposure is accomplished using the transeptal approach. The parasternal approach was abandoned due to the marginal exposure of the atrial structures and a high incidence of postoperative lung herniation through the chest wall defect [7]. 3.1.3. Limited right lateral thoracotomy and robotically assisted mitral valve repair Excellent exposure of the mitral valve can be achieved through a small right lateral thoracotomy. A small 6-cm incision is made in the fourth intercostal space, and the pericardium is opened anterior to the right phrenic nerve. This approach allows exposure of the right and left atrium, as well as ascending aorta and the superior vena cava.
Fig. 4. Robotic surgery.
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Lateral placement of the incision allows direct view of the mitral valve through the left atriotomy with the minimal retraction of the atrial structures. One disadvantage of this approach is the relatively long distance from the incision to the mitral valve. This necessitates the use of special long thoracoscopic instruments or robotic surgical systems. Robotic surgical systems allow precise handling of especially designed instruments in a small space. Surgeon controls the movement of the instruments from the console, which is remote from the patients [8] (Fig. 4). The threedimensional view of the operative field is provided by a high-resolution camera and image-processing unit, which are integrated in the surgeon’s console. Mitral valve repair is accomplished through the small lateral thoracotomy and two small separate incisions for insertion of robotic instrument arms. 3.1.4. Technique of mitral valve replacement and repair Regardless of the approach used, the actual mitral valve replacement or repair is performed in the same manner. Mitral valve replacement is becoming a rare operation
reserved for patients in whom mitral valve repair cannot be safely accomplished (patients with rheumatic mitral valve disease, severe endocarditis with extensive valve destruction, or rare cases of severe bileaflet myxomatous valve disease). Mitral valve repair represents the preferred surgical technique for the treatment of myxomatous and ischemic mitral valve disease. Most techniques in mitral valve repair involve annuloplasty, which reduces the diameter of dilated mitral annulus. The reduction in the size of the mitral annulus can be accomplished by insertion of partial or complete annuloplasty rings. The resolution of normal annular diameter results in improved valve coaptation and competency [9]. Redundant portions of myxomatous valve can be resected and reconstructed by performing a ‘‘sliding’’ valvuloplasty. Annuloplasty and partial resection of prolapsed portions of mitral valve leaflets represent two major steps in mitral valve repair for most patients with myxomatous valve disease and posterior leaflet prolapse [10] (Fig. 5). In less frequent cases of anterior leaflet prolapse, the competence of the mitral valve apparatus can be achieved through annulo-
Fig. 5. Mitral valve repair: quadrangular resection, posterior leaflet sliding plasty, and ring annuloplasty.
T. Mihaljevic et al. / Cardiovascular Pathology 13 (2004) 176–181
plasty and a variety of reconstructive procedures of the anterior leaflet. Triangular resection of redundant portions of anterior leaflet can be used to restore leaflet geometry. Alternatively, chordal transfer from the posterior leaflet can be used to prevent prolapse of the anterior leaflet. In cases with ruptured chordae, these can be reconstructed using Gore-Tex sutures. An elegant and versatile repair technique introduced by Alfieri consists in suturing edges of prolapsed leaflet portions to one another, creating a ‘‘double-orifice’’ mitral valve. This technique has been used mostly in myxomatous valve repairs, although its use has been described in a variety of other pathologic processes involving mitral valve (ischemic regurgitation, endocarditis). This technique can be used alone or in conjunction with annuloplasty [11].
4. Tricuspid valve repair Surgical approaches in minimally invasive tricuspid valve repair are similar to those previously described for mitral valve. Minimally invasive tricuspid valve repair is usually performed in conjunction with mitral valve repair, since indications for the isolated tricuspid valve repair are rare. Repair techniques include suture annuloplasty, ring annuloplasty, and bicuspidation of the tricuspid valve. DeVega suture annuloplasty is most frequently used in repair of moderate tricuspid valve incompetence. The suture is passed as a semicircular stitch in the tricuspid annulus from the anteroseptal to the posterior commissure. The other arm of the same suture is passed parallel to the first arm (partial purse-string suture). Both ends of the suture are then tied over the pledget at the posterior commissure to decrease the tricuspid orifice and restore valve competency [12]. Other feasible and simple method consists of exclusion of the posterior leaflet and ‘‘bicuspidation’’ of the tricuspid valve. This is accomplished with the pledgeted suture that approximates anteroposterior and posteroseptal commissure. With this maneuver, the competency is restored by exclusion of the posterior leaflet [13]. Formal tricuspid annuloplasty with partial annuloplasty rings (Carpentier, Cosgrove) is usually reserved for severe forms of tricuspid valve regurgitation. Partial rings are inserted into the annulus using interrupted mattress sutures starting from the anteroseptal commissure and extending to the posteroseptal commissure, avoiding injury to the conduction system. The use of the annuloplasty rings ensures durable repair [14].
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5. Conclusion Minimally invasive valve surgery represents an established alternative to the standard ‘‘open’’-valve surgery. Less invasive approaches result in reduction of operative trauma and therefore faster recovery of the patient, without compromising the quality of the valve surgery. Further technologic advances in robotic technology, and intraoperative echocardiography will further improve treatment of valvular heart disease.
References [1] Cohn LH, Adams DH, Couper GS, Bichell DP, Rosborough DM, Sears SP, Aranki SF. Minimally invasive cardiac valve surgery improves patient satisfaction while reducing cost of cardiac valve replacement and repair. Ann Surg 1997;26(4):421 – 8. [2] Stanbridge RD, Hadjinikolaou LK. Technical adjuncts in beating heart surgery comparison of MIDCAB to off-pump sternotomy: a meta-analysis. Eur J Cardiothorac Surg 1999;16(Suppl 2):S24 – 33. [3] Cohn LH. Operative incisions for minimally invasive cardiac surgery. Oper Tech Card Thorac Surg 2000;5(3):146 – 55. [4] Cosgrove DM, Sabik JF, Navia JL. Minimally invasive valve operations. Ann Thorac Surg 1998;1535 – 8. [5] Bonacchi M, Prifti E, Giunti G, Frati G, Sani G. Does ministernotomy improve postoperative outcome in aortic valve operation? A prospective randomized study. Ann Thorac Surg 2002;73(2):460 – 5 (February). [6] Byrne JG, Karavas AN, Cohn LH, Adams DH. Minimal access aortic root, valve and complex ascending aortic surgery. Curr Cardiol Rep 2000;2(6):549 – 57. [7] Byrne JG, Mitchell ME, Adams DH, Couper GS, Aranki SF, Cohn LH. Minimally invasive direct access mitral valve surgery. Semin Thorac Cardiovasc Surg 1999;3:212 – 22. [8] Nifong LW, Chu VF, Bailey BM, Maziarz DM, Sorrell VL, Holbert D, Chitwood WR. Robotic mitral valve repair: experience with the da Vinci system. Ann Thorac Surg 2003;75:438 – 43. [9] Carpentier A. Cardiac valve surgery—the ‘‘French correction’’. J Thorac Cardiovasc Surg 1983;86:323 – 37. [10] Jebara VA, Mihaileanu S, Acar C, et al. Left ventricular outflow tract obstruction after mitral valve repair: results of the sliding leaflet technique. Circulation 1993;88(5, Pt 2):1130 – 4. [11] Maisano F, Schreuder JJ, Oppizi M, Fiorani B, Fino C, Alfieri O. The double-orifice technique as a standardized approach to treat mitral regurgitation due to severe myxomatous disease: surgical technique. Eur J Cardio-Thorac Surg 2000;17:201 – 5. [12] De Vega NG. La anuloplastia selective, regulable y permanente. Una tecnica original para el tratamiento de la insufficiencia tricuspide. Rev Esp Cardiol 1972;25:555 – 6. [13] Kay JH, Maselli-Campagna G, Tsuji HK. Surgical treatment of tricuspid insuffiency. Ann Surg 1965;162:53 – 8. [14] McCarthy JF, Cosgrove DM. Tricuspid valve repair with the Cosgrove – Edwards annuloplasty system. Ann Thorac Surg 1997;64: 267 – 8.
Minimally invasive valve surgery What the pathologist should know Tomislav Mihaljevic *, Daniel Unic, John G. Byrne, Lawrence H. Cohn Division of Cardiac Surgery, Brigham and Women’s Hospital, 75 Francis Street Boston, MA 02115, USA Received 20 October 2003; received in revised form 22 December 2003; accepted 22 December 2003
Abstract Minimally invasive approaches in cardiac surgery have emerged as an alternative to standard techniques particularly in patients udergoing valvular surgery. Their established benefits for the patients are likely to cause their widespread use in the future. The purpose of this is to provide an overview of modern minimally invasive approaches in valvular surgery with an emphasis on aspects of the surgery relevant for cardiovascular pathologists. D 2004 Elsevier Inc. All rights reserved. Keywords: Minimally invasive valve operations; Approaches for valvular surgery
1. Introduction Minimally invasive approaches in cardiac surgery have emerged as a new and interesting alternative to a variety of established, standard operations for the cardiac surgery in the adult. These techniques allow reduction of surgical trauma, pain, length of hospitalization, and overall cost of treatment [1]. The development of the less invasive surgical approaches was enabled through development and adoption of new technologies. Technological advances were made in several areas pertinent to cardiac surgery and could be generally divided in the advances related to the primary procedure (new valve repair techniques, robotic surgical systems, improvements of cardiopulmonary bypass technology, etc.) and those related to the improved diagnostics and intraoperative monitoring (transesophageal echocardiography, epiaortic scanning). Less invasive operations have been described in coronary revascularization and valvular and aortic surgery. Although coronary surgery still represents the most commonly performed operation in cardiac surgery, minimally invasive approaches in coronary revascularization have been mostly restricted to the isolated single-vessel (left anterior descending artery) revascularization. The most important limiting factor in adaptation of minimally invasive techniques in coronary surgery is related to the inability to adequately * Corresponding author. Tel.: +1-617-732-7678; fax: +1-617-732-6559. E-mail address: [email protected] (T. Mihaljevic). 1054-8807/04/$ – see front matter D 2004 Elsevier Inc. All rights reserved. doi:10.1016/S1054-8807(03)00154-6
visualize all coronary arteries through a single small incision. Furthermore, the performance of coronary anastomosis through via minimally invasive approach is technically very demanding regardless of recent technologic advances [2]. In contrast to minimally invasive incisions in coronary surgery, minimally invasive valvular surgery has been accepted as an equally valuable surgical approach for patients with isolated valvular disease. Excellent surgical exposure of individual valves (aortic, mitral, and tricuspid) can be accomplished through a single small incision allowing valve repairs or replacements of equal quality as those performed through standard incisions. New techniques of valve repairs and preservation (predominantly mitral and tricuspid valves) have been incorporated in minimally invasive approaches. The introduction of new and less invasive approaches has also resulted in the potential for development of complications, which differ from complications observed in patients who were operated using standard approaches. The purpose of this article is to provide a review of current techniques in modern minimally invasive valve surgery with particular emphasis on aspects of surgery, which could be relevant for cardiovascular pathologist.
2. Minimally invasive aortic valve surgery Calcific aortic stenosis represents the most common indication for aortic valve replacement in adult population.
T. Mihaljevic et al. / Cardiovascular Pathology 13 (2004) 176–181
Typically, these are elderly patients in their seventh or eighth decade of life with multiple comorbidities. Advanced age and associated medical problems put these patients in higher risk category for surgical treatment. On the other hand, aortic valve replacement is the only therapeutic option, since there is no alternative effective medical or interventional therapy for severe symptomatic aortic stenosis. The obvious need to minimize surgical trauma in such frail patients has resulted in the development of minimally invasive approaches for aortic valve replacement. 2.1. Surgical technique The 6- to 8-cm incision is made beginning halfway between the sternal notch and the angle of Louis. Partial upper sternotomy is performed from the sternal notch to the fourth intercostal space, extending into the space to the right, forming a reversed L shape. The extension of the sternotomy into the intercostal space often results in the violation of the right pleural space. Alternatively, the incision can be extended into both intercostal spaces. The main disadvantage of the extended (inverse T) incision is the potential of injury to the left internal thoracic artery, which prevents its potential use for coronary artery bypass in the future [3]. Right anterior thoracotomy through the third intercostal space [4] represents alternative to upper sternotomy, but is associated with division of the right internal mammary artery and partial transection of the right pectoral muscle, which results in increased postoperative discomfort. Both incisions allow excellent exposure of the aortic valve. Cardiopulmonary bypass is than established by cannulation of the distal ascending aorta and right atrium. Venous
177
cannulation can be performed using a small (20F) venous cannula, which can be placed percutaneously in the femoral vein and advanced into the right atrium. Vacuum-assisted venous drainage represents a major technologic improvement of extracorporeal bypass circuits, which allows adequate venous drainage through small-diameter cannulas. Percutaneous placement of venous cannulas eliminates the need for cannulation of the right atrium and improves visualization in the operative field. The potential morbidity associated with venous cannulation is related to the local injury to the femoral vein or injury to the inferior vena cava and its tributaries during advancement of the cannula into the right atrium. The risk of such injuries can be minimized by guide-wire-assisted cannula placement under transesophageal echo guidance. Once the cardiopulmonary bypass is initiated and aorta cross-clamped, the aortic valve is exposed through the oblique aortotomy, which extends into the noncoronary cusp. The choice of aortic valve prosthesis and the technique of aortic valve replacement are identical to those used in standard ‘‘open’’ operations. Upon the completion of the valve replacement, the aortotomy is closed with running polypropylene suture (Fig. 1). Potential disadvantages of the partial sternotomy are the inadequate visualization of the ventricles, and inability to evacuate air from the ventricles at the end of the operation. These limitations can be overcome by the use of transesophageal echocardiography, which accurately estimates the amount of air within the heart. The intracardiac air can be than safely evacuated through the vent placed in ascending aorta, without causing peripheral air emboli. The use of carbon dioxide in the operative field allows fast absorption of intracardiac gas bubbles. The combination of both tech-
Fig. 1. Minimally invasive aortic valve operation: sternal incision.
178
T. Mihaljevic et al. / Cardiovascular Pathology 13 (2004) 176–181
niques has kept the rate of perioperative neurologic complications comparable to those of standard procedures [5]. The above-described approaches have been successfully applied to other types of aortic surgery like aortic root replacement, replacement of the ascending aorta, and redo aortic valve replacement [6]. At our institution, every patient with isolated aortic valve disease is considered for minimally invasive aortic valve replacement. The obvious contraindication for minimally invasive aortic valve replacement is the presence of significant coronary artery disease. Morbid obesity presents relative contraindication for less invasive aortic valve surgery due to the difficulties in adequate exposure in such patients.
3. Minimally invasive mitral valve surgery Techniques for minimally invasive mitral valve surgery have undergone considerable refinement over the past decade and have approached the goal of reducing surgical trauma while maintaining the efficacy of the standard ‘‘open’’ procedure.
Myxomatous mitral valve disease with resultant mitral regurgitation presents the most common indication for isolated mitral valve surgery in the United States. Rheumatic mitral valve disease and endocarditis represent other, less common indications for isolated mitral valve repair or replacement. Typical patient with myxomatous mitral valve prolapse, in contrast to the patient with aortic stenosis, is an active individual in the fifth or sixth decade of life. These patients are highly interested in minimally invasive surgical techniques that would allow them faster return to daily activities [1]. A better understanding of mitral valve anatomy, function, and physiology has stimulated the development of many surgical techniques o treat the mitral regurgitation. Mitral valve repair now represents the standard of care for majority of patients with mitral valve prolapse and associated mitral regurgitation. 3.1. Surgical approaches Minimally invasive approaches for isolated mitral valve surgery include partial lower sternotomy, right parasternal approach, and limited right lateral thoracotomy.
Fig. 2. Minimally invasive mitral valve operation through partial lower sternotomy: (A) sternal incision and (B) transeptal approach.
T. Mihaljevic et al. / Cardiovascular Pathology 13 (2004) 176–181
Fig. 3. Parasternal approach for minimally invasive mitral valve operation: thoracotomy incision and incision for femoral cannulation.
3.1.1. Partial lower sternotomy Partial lower sternotomy (‘‘mini-sternotomy’’) is performed through a small 6- to 8-cm incision overlying distal aspect of the sternum. The sternotomy extends from the sterno-xiphoid junction upward to the second intercostal space and extends into the right interspace (Fig. 2). Care is taken to prevent injury to right internal mammary artery. Minimally invasive approach requires modification of the cannulation techniques for cardiopulmonary bypass. The ascending aorta is cannulated through the incision using a small cannula. In cases where small incision does not allow adequate aortic exposure, peripheral arterial cannulation via femoral artery represents a suitable alternative. Venous cannulation is usually accomplished by direct cannulation of the superior vena cava through the sternotomy. Inferior vena cava is cannulated with a small percutaneous transfemoral cannula advanced over the guide-wire and under guidance of the transesophageal echocardiography [3] (Fig. 2). Vacuum-assisted venous drainage allows adequate venous drainage despite small cannula size. The potential complications related to the peripheral cannulation include retrogade aortic dissection due to the inappropriate placement of the cannula in femoral artery. Injury to the aortic wall intima can serve as the entry point of the retrograde dissection once the cardiopulmonary bypass is instituted and retrograde arterial blood flow initiated. Early detection of this complication by TEE is of a paramount importance for adequate treatment. Peripheral venous cannulation with the advancement of the long, small-diameter cannula via femoral vein into the right atrium can potentially result in the tear inferior vena cava or its tributaries. This complication can be avoided by the placement of the venous cannula under TEE guidance. Incidence of serious complications related to the peripheral cannulation is well below 0.1% in our experience. After establishing cardiopulmonary bypass, the aorta is cross-clamped and the heart is arrested with cardioplegic solution. Mitral valve exposure can be accomplished through the right atrium with subsequent incision in the interatrial
179
septum (transeptal approach) or directly through the left atrium (direct approach). The blood flow to the right atrium has to be interrupted with the use of caval tourniquets if transeptal approach is being used. Excellent mitral valve exposure can be achieved through oblique atriotomy and incision through the interatrial septum. This approach introduces risks of injury to the conduction system and a small risk of iatrogenic postoperative atrial septal defect in cases of incomplete closure of the incision in the interatrial septum. Right atriotomy causes scar formation in the atrial tissue, which can serve as a basis for the formation of postoperative atrial arrhythmias. These complications led to the more widespread use of the direct approach through the left atriotomy, which is currently our standard approach. 3.1.2. Parasternal approach Parasternal approach is accomplished through the 5- to 7cm-long incision over the third and fourth costal cartilages (Fig. 3). A small portion of both is then resected. This allows an appropriate approach of the right atrium. Mitral valve exposure is accomplished using the transeptal approach. The parasternal approach was abandoned due to the marginal exposure of the atrial structures and a high incidence of postoperative lung herniation through the chest wall defect [7]. 3.1.3. Limited right lateral thoracotomy and robotically assisted mitral valve repair Excellent exposure of the mitral valve can be achieved through a small right lateral thoracotomy. A small 6-cm incision is made in the fourth intercostal space, and the pericardium is opened anterior to the right phrenic nerve. This approach allows exposure of the right and left atrium, as well as ascending aorta and the superior vena cava.
Fig. 4. Robotic surgery.
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T. Mihaljevic et al. / Cardiovascular Pathology 13 (2004) 176–181
Lateral placement of the incision allows direct view of the mitral valve through the left atriotomy with the minimal retraction of the atrial structures. One disadvantage of this approach is the relatively long distance from the incision to the mitral valve. This necessitates the use of special long thoracoscopic instruments or robotic surgical systems. Robotic surgical systems allow precise handling of especially designed instruments in a small space. Surgeon controls the movement of the instruments from the console, which is remote from the patients [8] (Fig. 4). The threedimensional view of the operative field is provided by a high-resolution camera and image-processing unit, which are integrated in the surgeon’s console. Mitral valve repair is accomplished through the small lateral thoracotomy and two small separate incisions for insertion of robotic instrument arms. 3.1.4. Technique of mitral valve replacement and repair Regardless of the approach used, the actual mitral valve replacement or repair is performed in the same manner. Mitral valve replacement is becoming a rare operation
reserved for patients in whom mitral valve repair cannot be safely accomplished (patients with rheumatic mitral valve disease, severe endocarditis with extensive valve destruction, or rare cases of severe bileaflet myxomatous valve disease). Mitral valve repair represents the preferred surgical technique for the treatment of myxomatous and ischemic mitral valve disease. Most techniques in mitral valve repair involve annuloplasty, which reduces the diameter of dilated mitral annulus. The reduction in the size of the mitral annulus can be accomplished by insertion of partial or complete annuloplasty rings. The resolution of normal annular diameter results in improved valve coaptation and competency [9]. Redundant portions of myxomatous valve can be resected and reconstructed by performing a ‘‘sliding’’ valvuloplasty. Annuloplasty and partial resection of prolapsed portions of mitral valve leaflets represent two major steps in mitral valve repair for most patients with myxomatous valve disease and posterior leaflet prolapse [10] (Fig. 5). In less frequent cases of anterior leaflet prolapse, the competence of the mitral valve apparatus can be achieved through annulo-
Fig. 5. Mitral valve repair: quadrangular resection, posterior leaflet sliding plasty, and ring annuloplasty.
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plasty and a variety of reconstructive procedures of the anterior leaflet. Triangular resection of redundant portions of anterior leaflet can be used to restore leaflet geometry. Alternatively, chordal transfer from the posterior leaflet can be used to prevent prolapse of the anterior leaflet. In cases with ruptured chordae, these can be reconstructed using Gore-Tex sutures. An elegant and versatile repair technique introduced by Alfieri consists in suturing edges of prolapsed leaflet portions to one another, creating a ‘‘double-orifice’’ mitral valve. This technique has been used mostly in myxomatous valve repairs, although its use has been described in a variety of other pathologic processes involving mitral valve (ischemic regurgitation, endocarditis). This technique can be used alone or in conjunction with annuloplasty [11].
4. Tricuspid valve repair Surgical approaches in minimally invasive tricuspid valve repair are similar to those previously described for mitral valve. Minimally invasive tricuspid valve repair is usually performed in conjunction with mitral valve repair, since indications for the isolated tricuspid valve repair are rare. Repair techniques include suture annuloplasty, ring annuloplasty, and bicuspidation of the tricuspid valve. DeVega suture annuloplasty is most frequently used in repair of moderate tricuspid valve incompetence. The suture is passed as a semicircular stitch in the tricuspid annulus from the anteroseptal to the posterior commissure. The other arm of the same suture is passed parallel to the first arm (partial purse-string suture). Both ends of the suture are then tied over the pledget at the posterior commissure to decrease the tricuspid orifice and restore valve competency [12]. Other feasible and simple method consists of exclusion of the posterior leaflet and ‘‘bicuspidation’’ of the tricuspid valve. This is accomplished with the pledgeted suture that approximates anteroposterior and posteroseptal commissure. With this maneuver, the competency is restored by exclusion of the posterior leaflet [13]. Formal tricuspid annuloplasty with partial annuloplasty rings (Carpentier, Cosgrove) is usually reserved for severe forms of tricuspid valve regurgitation. Partial rings are inserted into the annulus using interrupted mattress sutures starting from the anteroseptal commissure and extending to the posteroseptal commissure, avoiding injury to the conduction system. The use of the annuloplasty rings ensures durable repair [14].
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5. Conclusion Minimally invasive valve surgery represents an established alternative to the standard ‘‘open’’-valve surgery. Less invasive approaches result in reduction of operative trauma and therefore faster recovery of the patient, without compromising the quality of the valve surgery. Further technologic advances in robotic technology, and intraoperative echocardiography will further improve treatment of valvular heart disease.
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