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Ann Thorac Surg 1998;65:307
© 1998 The Society of Thoracic Surgeons
Division of Cardiothoracic Surgery, Department of Surgery, New York University Medical Center, New York, New York, USA
Dr Spencer, New York University Medical Center, 530 First Ave, Suite 9V, New York, NY 10016.
Presented at the Forty-third Annual Meeting of the Southern Thoracic Surgical Association, Cancun, Mexico, Nov 7–9, 1996.
Abstract
Experiences with 1,000 patients undergoing mitral valve reconstruction at New York University over the past 18 years are summarized. A continuing follow-up (98% complete) demonstrated that 88% of patients are free from recurrent insufficiency 10 years after the operation. Reconstruction is feasible in nearly 90% of patients with mitral valve prolapse, with an operative mortality near 2%. Accordingly, operation is now recommended at an early stage with the first sign of left ventricular systolic dysfunction, while the patient is still in sinus rhythm. Most operations have been done with the Carpentier techniques of segmental resection with annuloplasty and insertion of a Carpentier ring. Recently, two other repair techniques and a minimally invasive operative approach have been evaluated. A triangular resection of a prolapsing anterior leaflet has been done in more than 100 patients with excellent results. Also, a posterior "folding plasty" has been employed in more than 40 patients with a large redundant posterior leaflet, minimizing the need for annular plication. A minimally invasive approach to the mitral valve has now been employed in 130 patients over the past year, using a right mini-thoracotomy and the Port-Access (Heartport, Inc, Menlo Park, CA) approach. This technique employs catheters introduced through femoral vessels to institute cardiopulmonary bypass and cardioplegic arrest. The operative approach and techniques for mitral valve reconstructive operations continue to evolve, with excellent results and improved patient benefits.
I (F.C.S.) want to express my appreciation to your President, Dr William Alford, and your organization for the honor of being your guest speaker for your 43rd Annual Meeting. Your President sent me some historical data describing the origin of your organization. I especially want to compliment Dr Harvey Seiler, who is in the audience today, for his foresight and perseverance in launching this organization more than four decades ago. The idea was strictly his own. Like many new ideas, it required a lot of hard work and persistence to make his dream develop into this vigorous organization, which now represents the majority of thoracic surgeons in the southern United States.
Today, I want to discuss both cumulative experiences and developing techniques of mitral valve reconstruction for mitral insufficiency. Reconstruction for mitral insufficiency has been a subject of major investigation in our Department of Surgery at New York University (NYU) for the past 18 years [1] [2] [3] [4]. Our initial experiences began near 1979 after a visit to Paris by Dr Stephen B. Colvin of our faculty to observe the techniques developed by Dr Alain Carpentier at the Hôpital de Broussais.
Initially, the techniques used were entirely those that Carpentier had developed over the preceding decade in Paris [5]. Similar results had been duplicated in rheumatic patients by Duran and associates in Spain [6], supporting the feasibility of wider use of valve repair.
Our initial experiences were cautious ones [1] to determine the feasibility of reconstruction of degenerative valves, for Carpentier’s work had been principally with young patients with rheumatic disease, these patients often having greater tensile strength from dense scar formation. The NYU program was developed principally by Dr Colvin, who personally performed the majority of operations during the first 4 to 5 years. After sufficient experience had been acquired, the technique was adopted by other members of our cardiac surgical faculty. The evolving techniques were reported in detail by Galloway and associates in 1988 [4].
Major questions initially included the applicability of these techniques to different types of mitral insufficiency, the long-term durability of valve repair, and the possible advantages of valve repair over prosthetic valve replacement, particularly in terms of freedom from late valve-related complications such as thromboembolism, anticoagulant-related hemorrhage, and endocarditis. The original Carpentier techniques occasionally resulted in two relatively rare but significant complications: (1) obstruction of the left ventricular tract by systolic anterior motion of the anterior leaflet of the mitral valve [7] [8] and (2) myocardial infarction caused by injury of the circumflex coronary artery during plication of the annulus of the mural leaflet, especially in patients with a dominant circumflex coronary.
Basic Data
More than 1,000 mitral valve reconstructions have been performed between 1979 and 1997. The average age of the patients was approximately 59 ± 16 years. About 50% of the cases resulted from degenerative mitral disease, manifested as prolapse, often with ruptured chordae. Other causes were rheumatic fever, ischemia, endocarditis, and congenital defects (Table 1A):
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Before operation, by the New York Heart Association classification, 48.7% of patients were in class III, 25.6% in class IV, 23.0% in class II, and 2.2% in class I.
Concomitant procedures were done in about 40% of patients, such as aortic valve replacement, tricuspid valve repair, or coronary artery bypass.
Operative Indications
The most common indications for operation were symptomatic severe mitral insufficiency, with enlargement of the left ventricular end-systolic and end-diastolic dimensions on echocardiography. Most patients had an enlarged left atrium with intermittent or permanent atrial fibrillation, and dyspnea on exertion.
Initially, more seriously ill patients were operated on; so in the overall NYU series, about 75% were in class III or class IV. In recent years, however, as experience increased, operation has been more frequently recommended in patients with a paucity of symptoms when echocardiography demonstrates severe insufficiency and early left ventricular systolic dysfunction. Operating at this early stage while patients remain in a sinus rhythm has the great advantage of permanently avoiding anticoagulants. A significant advantage of reconstruction over valve replacement is freedom from anticoagulants; this is lost if permanent atrial fibrillation has already evolved. Most importantly, long-term normal ventricular function is maintained when operation is performed early, improving survival.
Methods
Preoperative Evaluation
Echocardiography is clearly the most valuable diagnostic technique, as it demonstrates both the magnitude of the regurgitation and abnormalities in the anterior or posterior leaflets. Mitral valve repair for insufficiency resulting from rupture of chordae of the posterior leaflet is one of the simplest forms of repair, whereas a more complex repair is required with billowing of both the anterior and posterior leaflets, with elongated or ruptured chordae and diffuse insufficiency.
Cardiac catheterization is done to detect associated coronary artery disease in select patients, primarily those with symptoms suggestive of ischemia or prior infarction, and for most patients more than 55 years of age.
No fixed contraindication to repair has been found. Neither age, pulmonary hypertension, nor coronary disease has been found to be a strong contraindication. A decision regarding repair is usually based on different associated conditions in individual patients. Dense annular calcification is the most common technical concern, but it can be treated in many patients by selective removal of calcium [9].
Operative Techniques via Standard Sternotomy
Cardioplegia
Cold blood cardioplegia has been routinely employed; initially about 15 to 20 mL/kg is infused. This is now frequently done using a retrograde technique, infusing through the coronary sinus, as this technique minimizes air trapping in the coronary arteries. Topical hypothermia is also used, wrapping the heart with a cold pad for insulation. Cardioplegia is reinjected every 20 to 30 minutes in appropriate amounts, keeping the myocardial temperature, measured with a needle thermistor, less than 15°C. If cooling of the right ventricle is inadequate, supplemental periodic infusions of cold blood into the aortic root to perfuse the right coronary may be used.
Left Atrial Incision
Most operations have been performed through the standard left atriotomy incision, made posterior to the interatrial groove. In a few patients the atrial septum has been widely exposed by separating the right and left atrium in the so-called groove of Sondergaard, using the techniques described by Larbalestier and associates [10]. This permits placement of the atrial incision at a more anterior level and provides better exposure.
The standard left atriotomy gives excellent exposure with a large left atrium, but with a small left atrium exposure is often unsatisfactory. Several different types of left atrial incisions have been described for this type of problem. The superior biatrial transseptal approach through the right atrium, atrial septum, and the top of the left atrium, described by Smith [11] (Fig 1Fig 2Fig 3), gives excellent exposure and has been used frequently in recent years in patients in whom difficult exposure is anticipated. The only uncertainty with this approach is the hazard of loss of sinus rhythm, as the sinus node artery is divided. Exposure of the valve is uniformly excellent, however.
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Most of our experiences initially were with the standard rigid annuloplasty ring, but in recent years the flexible Carpentier-Edwards Physio Ring (Baxter) or the flexible Seguin ring (St. Jude Medical, St. Paul, MN) has been used with increasing frequency. The flexibility of these rings is an attractive feature. In patients with severe annular dilatation the standard rigid ring is still preferred, however, as this gives better stabilization of the annulus.
Recent Modifications
In the past 2 to 3 years there have been two important modifications in operative technique, and in the past 2 years there has been a major conceptual change in the overall operative approach.
Two innovative technical changes introduced at NYU by Colvin and associates [12] [13] were (1) the use of triangular segmental excision as the primary treatment for anterior leaflet prolapse [12] and (2) the use of a leaflet folding plasty technique instead of rectangular resection for the treatment of posterior leaflet prolapse [13].
A ground-breaking conceptual change was the introduction of the "minimally invasive" techniques for mitral valve surgery, made possible by the development of peripheral perfusion and balloon occlusion of the aorta for cardioplegia delivery, using a closed chest cardioplegia delivery system [14] [15] [16] (Port-Access Endovascular Cardiopulmonary System; Heartport, Inc, Menlo Park, CA).
Triangular Segmental Excision of Prolapsing Aortic Leaflet
Historically, repair of a prolapsing anterior leaflet was more difficult and hazardous than repair of a prolapsing posterior leaflet. With the posterior leaflet, a large amount of the prolapsing diseased tissue can be removed, after which plication of the annulus reapproximates the incised valve edges, which can then be sutured without tension. Surprisingly, large segments of the posterior leaflet can be excised, as much as 4 to 5 cm in some patients with marked left atrial enlargement, representing more than 50% of the annulus.
A similar technique cannot be used for repair of prolapsing anterior leaflet, because of the fixed nature of the fibrous trigones. Carpentier initially reported excising small triangular segments of the aortic leaflet, as much as 15%, but stated in his report in 1983 [5] that the technique had been unreliable and recommended that it no longer be used. His experience at that time had been principally with rheumatic valves.
The conventional approach for repair of an anterior leaflet pathology has been either (1) shortening of the elongated chordae or (2) transposition of chordae attached to a corresponding segment of posterior leaflet. These techniques gave good initial results, but several reports have described recurrent mitral insufficiency, especially caused by rupture of shortened chordae. For this reason, Colvin’s group [12] explored the concept of primary triangular excision of a prolapsing anterior leaflet, which our group has now progressively adopted as the most frequently used treatment for anterior leaflet prolapse. Excellent results have been obtained to date in more than 100 patients.
The basic guidelines are to perform a narrow triangular excision, resembling an isosceles triangle, usually excising no more than 1.5 cm of prolapsing anterior leaflet tissue (Fig 4Fig 5Fig 6). The excision is carried to healthy, stout chordae on each side, which are used as support for the reconstructed leaflet. In some cases with significant billowing in several zones, a double anterior leaflet triangular excision has been done. Results with the triangular resection technique have been so reliable that the previously used chordal shortening or chordal transposition techniques are now rarely used at our institution.
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As shown in Fig 7Fig 8Fig 9, after a rectangular excision of 2 to 3 cm of prolapsing leaflet, the annulus of the excised leaflet is not plicated. Instead, the margins of the two remaining leaflets are each sutured to the mitral annulus, which does not narrow the annulus as much as with standard repair, and which lowers the site of coaptation between the anterior and posterior leaflets. After the incised margins of posterior leaflet have been sutured to the annulus, the edges of the leaflet are approximated with sutures (see Fig 9). This technique has the advantage of requiring minimal plication of the annulus and is especially attractive with a dominant circumflex circulation, because extensive annular plication in such patients may kink a large circumflex coronary artery and produce myocardial infarction.
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Minimally Invasive Mitral Valve Repair
"Minimally invasive" mitral surgery, performed through a small anterior mini-thoracotomy incision or "port" using cardiopulmonary bypass and cardioplegic arrest introduced through the groin (Port-Access; Heartport, Inc), was successfully perfected by surgeons at Stanford and NYU in 1996, and has now been applied in more than 130 patients at our institution. These results were reported by Galloway and associates at the 1997 meeting of the American Heart Association [16]. The feasibility of a truly minimally invasive operative approach to the mitral valve represents a significant conceptual breakthrough in valvular heart surgery.
The Port-Access operation is performed through a short (5 to 7 cm) right anterior mini-thoracotomy, rather than through a conventional sternotomy, without dividing the sternum or resecting a rib. After femoral arterial and venous perfusion are established, a balloon Endoaortic Clamp (Heartport, Inc) is passed from the femoral cannula into the ascending aorta and the heart is arrested by the delivery of cardioplegia either into the aortic root or the coronary sinus using a specially designed catheter. The intracardiac repair is accomplished using specially designed instruments, because of the limitations in exposure with the short incision. After completion of the intracardiac procedure and closure of the cardiotomy incisions, the balloon Endoaortic Clamp is released and air is aspirated through the proximal catheter in the ascending aorta. Extensive experimental studies established the feasibility and safety of this method [14] [15] before a phase I trial was initiated by NYU and Stanford in 1996.
In the first year of its use the Port-Access method was used in more than 130 mitral valve operations at NYU, achieving excellent results when used for either repair or replacement. The operative mortality has been 1.1% for isolated mitral operations, without any signs of significant air embolism [16]. The data, therefore, suggest that repair or replacement may be done with equal efficacy as with the sternotomy approach [16].
Of importance, patients undergoing "minimally invasive" mitral valve operations appear to have shorter overall recovery times of only 2 to 3 weeks with less pain and an improved cosmetic result when compared with patients requiring a sternotomy. This decrease in morbidity is impressive, as patients are often discharged from the hospital within 2 to 4 days after operation and return to full activity within 3 weeks. If future data confirm this excellent initial experience, it would seem that much of the morbidity from valve operations may have been from the sternotomy incision and chest retraction. Certainly, the introduction of minimally invasive mitral valve surgery has irrevocably changed the options for surgically treating mitral valve disease, and these techniques offer great promise for numerous patient benefits. Minimally invasive mitral valve surgery will almost certainly be used with increasing frequency in the future.
Results
Postoperative Care
After operation, anticoagulant therapy with warfarin is given for 2 to 3 months to minimize the risk of embolism from annuloplasty ring. The atrial appendage is obliterated in patients with atrial fibrillation. In patients remaining in a sinus rhythm, warfarin administration is stopped after 3 months and an antiplatelet agent, usually aspirin, is given for at least 1 year. In patients remaining in atrial fibrillation, low-dose anticoagulation with warfarin is continued, aiming for an international normalized ratio of 2.
Correction of the mitral insufficiency is confirmed by echocardiography both intraoperatively and before discharge from the hospital. Thereafter, patients are evaluated yearly by echocardiography. Prophylactic antibiotics are given with any invasive procedures that might cause a bacteremia, such as complicated dental procedures or endoscopy. This is similar to the guidelines used after insertion of a prosthetic valve.
Operative Mortality
The operative mortality at NYU for isolated mitral valve repair has been 2% over 18 years, and 5% for combined mitral procedures. Similar results have now been achieved with the minimally invasive Port-Access approach.
Repair Versus Replacement
Throughout the past decade we have applied a selective approach to each patient operated on, deciding on valve repair versus replacement in relation to both the pathologic abnormalities in the mitral valve and the presence of additional cardiac pathology. Over the past 3 years, about 40% to 50% of all patients undergoing mitral valve operations at NYU have had reconstruction performed; in the other patients prosthetic replacement with a mechanical or tissue prosthesis was performed (Table 1).
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Conclusion
Data from NYU in more than 1,000 patients undergoing valve repair over 18 years clearly indicate that mitral valve reconstruction can be performed in the vast majority of patients with mitral insufficiency from degenerative disease. Long-term results have been excellent in this group. Late results have been less satisfactory in older patients with extensive rheumatic disease, as the inflammatory process involves the entire substance of the leaflets, usually progressing to extensive fibrosis, contraction, and calcification. Repair in the young rheumatic population has been quite successful, however. In patients with mitral insufficiency caused by endocarditis, extensive defects have been repaired by using a combination of different techniques with excellent success.
In ischemic patients the data are less clear, because the pathology varies widely and the insufficiency may result from an isolated infarction with involvement of a chorda or from grossly impaired contraction of the ventricular wall and annular dilatation. In such patients repair is highly successful for the appropriate pathology, such as annular dilatation [17], but the long-term prognosis is often determined by the degree of coronary disease and the underlying ventricular function. In many patients with severe acute insufficiency caused by recent infarction, valve replacement may be the more predictable option.
Mitral valve reconstruction is especially attractive compared with replacement in patients in the early stages of their disease. Generally, this involves patients with severe insufficiency and early systolic dysfunction who still have a sinus rhythm. A successful operation in such patients, many of whom have few symptoms, has the advantages of maintaining normal long-term left ventricular function while avoiding the need for anticoagulation. Hence, because the success of repair is very predictable in these patients, early operation is now recommended based on echocardiographic findings, such as progressive diastolic volume overload and early systolic dysfunction. Operation should also be strongly considered once the left atrial size exceeds 4.5 cm, especially if the patient is experiencing intermittent atrial fibrillation.
Most recently, mitral valve surgery has entered the minimally invasive era. The early results described above with minimally invasive valve repair are exciting and offer great promise. Hopefully, these approaches will give the same excellent long-term results, but with less early morbidity and cosmetic deformity than surgeons are currently achieving with more standard methods. It is exciting to the senior author that the techniques for the treatment of valvular heart disease continue to evolve. In my opinion, the future of valvular heart surgery never looked brighter.
References
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