Advances in Cardiac Surgery: Valve Repair
AbstractValvular heart disease is the fifth most common cardiovascular disorder; the first four are hypertension, coronary artery disease, congestive heart failure, and stroke.1 Valvular heart disease may develop acutely, but more commonly it is a chronic process, evolving over many years. Severe valvular heart disease eventually leads to heart failure and dysrhythmias unless the course of the disease is interrupted.2 Valvular heart disease affects persons of all ages who have valvular dysfunction due to congenital or acquired causes. Most valve repairs for congenital valvular disorders are performed immediately after birth or during childhood. Common causes of acquired valvular heart disease include degenerative heart disease, rheumatic heart disease, and infective endocarditis. Less common causes include trauma, lupus erythematosus, tumors, syphilis, cancer, and arthritic disease.Significant advances have been made in the past several decades in the early assessment and management of valvular heart disease. Innovations in diagnostic tools, pharmacological developments, and improved invasive and surgical techniques have contributed to these advances. Cardiac catheterization, color flow Doppler imaging, trans-esophageal echocardiography, and cardiac magnetic resonance imaging have revolutionized the diagnostic approach.3 Pharmacological agents such as diuretics, nitrates, digitalis, anticoagulants, calcium channel blockers, phosphodiesterase inhibitors, antidysrhythmics, and antibiotics have improved the medical management of valvular heart disease. Balloon valvuloplasty provides patients with mitral stenosis and aortic stenosis an invasive yet non-surgical option for treatment of valve disease. Balloon valvuloplasty has been used successfully to treat mitral stenosis in patients without heavily calcified valves and has been used as a temporizing procedure in patients for whom surgery is a risk.3,4Great strides have been made in the surgical treatment of heart valve disease. In the 1950s, surgery was used to repair damaged heart valves. In the early 1960s, the first valve replacement surgery with a prosthetic valve was performed.5 Valve replacement became the preferred surgical technique, because prosthetic valves were easy to insert and reliable.6 Complications associated with valve replacement include wear of the prosthetic valve, thromboembolism, hemorrhage due to use of anticoagulants, and prosthetic valve endocarditis. According to Frankel and Brest,3 after valve replacement surgery, the disease process that involved the native valve is replaced by another disease process, one that involves the prosthetic valve. Therefore, surgeons turned with renewed interest to repair and reconstruction of cardiac valves. Valve repair eliminates or at least minimizes many of the problems associated with valve replacement.The focus of this article is repair of cardiac valves for adults with acquired valvular disorders. The prevalence of cardiac valve disease and valve dysfunction is reviewed, and the most common techniques for repair of the mitral and aortic valves are described. Outcomes after valve repair are discussed, and specific priorities in patients’ care are emphasized.Although less information is available on the epidemiology of valvular heart disease than on that of atherosclerotic disease, both diseases are common and are associated with appreciable morbidity and mortality.7 A steady decrease has occurred in the incidence of rheumatic heart disease, the most common single cause of valvular heart disease.8 However, rheumatic fever continues to be prevalent, especially in developing countries, in the tropical areas of the world, and in isolated pockets of developed countries.9 In the late 19th century, reports of acute rheumatic fever worldwide were numerous. In the United States, hospitals in Philadelphia, New York, and Boston reported thousands of cases of rheumatic fever; however, in the early 1900s, incidence reports in the United States were sparse and were not duplicated to note trends.10 The best records are available from Denmark, where the annual incidence of the disease, which was 200 per 100000 in 1862, had decreased to 50 per 100000 by 1940 and to 11 per 100000 by 1962.8 Likewise, a steady decrease has occurred in the incidence of rheumatic heart disease in the United States. In 1950, approximately 15000 persons in the United States died of rheumatic fever or rheumatic heart disease.1 From 1987 to 1997 the death rate for rheumatic heart disease decreased by 33.2%.1 Although the prevalence of rheumatic heart disease is decreasing, it is estimated that currently 1.8 million persons in the United States have the disease and that approximately 35000 patients are hospitalized annually because of rheumatic heart disease.1Although the overall incidence of rheumatic heart disease is declining, no significant changes have occurred in the prevalence of valvular heart disease.1,11 Two factors that influence this lack of change are the improvement in assessment of valvular disorders and the increased number of elderly persons. Advances in diagnostic tests have made diagnosis of valvular dysfunction more precise, leading to a greater number of recognized cases.12,13 The aging of the population, especially in developed countries, has increased the prevalence of degenerative valve disease.14The mitral valve lies between the left atrium and the left ventricle. The valve consists of 2 leaflets: a large anterior (aortic) leaflet and a small posterior (mural) leaflet. The leaflets join at 2 commissures (the lateral and medial) and are supported by a subvalvular mechanism. The subvalvular mechanism consists of the papillary muscles and the chordae tendineae (Figure 1). The mitral valve leaflets arise directly from the mitral annulus, with the anterior leaflet attaching to one third of the annulus and the posterior leaflet attaching to approximately two thirds of the annulus. The chordae tendineae originate from the fibrous tips of the papillary muscles and connect into the free edges and the undersurfaces of the mitral leaflets. Primary chordae are attached to the leaflet edges, and secondary chordae are attached to the undersurface of the leaflet. Additional tertiary chordae arise from the posterior left ventricular wall and attach to the undersurface of the posterior leaflet.16 The chordae divide and subdivide into more than 100 chordae that support the 2 mitral valve leaflets.17 The chordae tendineae and the papillary muscles prevent the prolapse of the leaflets into the left atrium during systole and contribute to the competency of the mitral valve.18The aortic valve consists of 3 cusps or leaflets: the left cusp, the right cusp, and the noncoronary cusp (Figure 2). The aortic valve lies between the left ventricle and the ascending aorta. The aortic valve does not have a subvalvular mechanism. The aortic cusps open as blood is propelled into the aorta and close when the pressure in the aorta is greater than the pressure in the left ventricle.Valvular disorders most often affect the valves on the left side of the heart, the mitral and aortic valves. The mitral and aortic valves are constantly exposed to high pressures and mechanical stress that can lead to cardiac valve damage. When a valve is open, blood flows from one chamber through the valve to the next. A pressure gradient does not exist between the 2 chambers or between the structures (chamber or vessel) above and below the valve. However, as valvular dysfunction develops and progresses, pressure gradients between the 2 structures develop.Valvular dysfunction is a gradual process; the valve or valves affected become stenotic or insufficient. A stenotic valve does not open entirely, resulting in a decreased amount of forward blood flow. An insufficient or regurgitant valve does not close completely, so some blood flows backward instead of forward.The 3 most common types of acquired valve disorders are degenerative disease, rheumatic disease, and infective endocarditis. Degenerative disease occurs as a gradual destruction of the valve due to constant wear and tear. The degeneration occurs slowly and is characterized by increased thickening, stiffening, and calcification of the leaflets.19 Valve calcification develops as a person ages. Calcification of the valve occurs as collagen fibers become thick and disoriented, the amount of mucopolysaccharides decreases, and progressive accumulation of fatty tissue occurs.20 The development of calcium infiltration reduces mobility of the valve leaflets, increases tension on the chordae, elevates the leaflets, and facilitates chordal elongation or rupture.20 Rheumatic disease begins with fusion of the valve leaflets at the commissures. Then the area of fusion enlarges, leading to fibrosis and constriction of the chordae tendineae and thickening and calcification of the leaflets.21 Infectious endocarditis directly damages valve tissue.Valvular heart disease is usually a chronic, progressive disease. Cardiac compensatory mechanisms often maintain a state of equilibrium for years before valvular function deteriorates to the point at which signs and symptoms are evident and more definitive therapy is needed.22 The natural history of valvular heart disease has been dramatically altered during the past 30 years by medical and surgical management.Surgical methods for improving the function of diseased cardiac valves include valve reconstruction and valve replacement with mechanical prostheses, biological prostheses, or homograft valves.23 Although valve reconstruction can be performed to improve the function of insufficient or stenotic valves, most surgeries are performed because of valve insufficiency.Replacement of the mitral valve is indicated for patients with severe valve calcification, marked subvalvular stenosis, or mitral stenosis accompanied by marked mitral regurgitation.24 Replacement of the native aortic valve with a prosthetic valve is used for patients with severely damaged valves. Valve replacement also is used when valve repair is unsuccessful.The type of valve surgery is usually established at the time of the operation. Preoperative prediction of the operation that can be performed is based on the location and type of valvular disease and the skill and experience of the surgeon.25Patients with cardiac valve disease are monitored closely by a cardiologist to determine the best time for valve surgery. Data obtained with transesophageal echocardiography are used to decide the best time for cardiac surgery and the type of repair needed.25 The data aide in determining the location and severity of leaflet prolapse; leaflet mobility and restriction; the point of leaflet coaptation; presence and severity of annular calcification; chordal fusion; and site, direction, and size of regurgitant blood flow.26 Cardiac valve surgery is commonly performed as soon as signs and symptoms of valvular dysfunction begin to occur. Ideally, surgery is performed before the development of left ventricular dysfunction or atrial enlargement that may lead to atrial dysrhythmias.Traditionally, cardiac valve surgery involved a median sternotomy incision, cardiopulmonary bypass, and cannulation of the right atrium and the aorta. Recently, valve surgery has been performed by using minimally invasive approaches.Minimally invasive surgery is performed by using instruments designed to provide intracardiac retraction and to allow the surgeon to work through small thoracotomy incisions or ports.27 Percutaneous cardiopulmonary bypass, an intra-aortic balloon catheter for aortic occlusion, and instillation of a cardioplegic solution are used.28 Video-assisted techniques may be used.29–32 The early results of minimally invasive cardiac repair surgeries have been promising.27,30,33–35The term valvuloplasty is used to describe both valve repair and valve reconstruction. Although valve repair and reconstruction can be used to treat aortic valve disease, they are more commonly used to treat mitral valve dysfunctions. The mitral valve is more complex than the aortic valve both anatomically and functionally.36Open mitral commissurotomy is used when the mitral valve is stenotic because of fused commissures. The fused commissures are incised from the annulus to the center of the mitral valve (Figure 3). The goals of open mitral commissurotomy are to improve leaflet mobility and to increase the size of the valve orifice. The procedure is most effective when the valve leaflets are thin and pliable. The length of the commissurotomy must be precise. If the incision extends too far toward the annulus, an annuloplasty may become necessary.18Open mitral commissurotomy is used early in the disease process. Indications for use of open mitral commissurotomy rather than mitral valve replacement include a loud opening snap on auscultation, good leaflet mobility on ventriculograms and echocardiograms, and no evidence of valvular calcification on radiographs.21 Surgery is recommended for patients when cardiac catheterization reveals that the mitral valve area is less than 1.5 cm2.21Surgery for mitral insufficiency is recommended on the basis of the patient’s signs and symptoms and the results of cardiac catheterization and echocardiography. An annuloplasty involves reconstruction of an insufficient mitral valve and is used to repair a deformed or dilated mitral valve annulus. The valve annulus is composed of a fibromuscular ring.Two surgical techniques may be used if the mitral valve annulus is enlarged. Figure 4 depicts the first technique, in which the valve annulus is sutured to reduce the size of the enlarged annulus. The sutures are placed at both commissures, incorporating only the posterior annulus.18 In the second technique, a prosthetic annuloplasty ring is inserted (Figure 5). The annuloplasty ring is sewn to the mitral valve annulus to reshape the annulus.Annuloplasty rings can be pre-shaped (rigid or semirigid) or flexible. The size and shape of the mitral valve annulus change during and systole because of the and of the of the mitral annuloplasty rings were rings were to annular associated with chronic atrial and ventricular mitral valve repair by tension on valvular leaflet by the mitral and prevent annular more annuloplasty rings are that a annuloplasty ring improved valvular A more annuloplasty ring the patient’s mitral valve annulus because the valve annulus can during and become during of the mitral valve annulus, calcium is the annulus is and valve repair is as valve calcification may mitral valve insufficiency can also be to dysfunction of the subvalvular mechanism. chordae or chordae contribute to prolapse of the anterior or posterior valve leaflets, resulting in mitral the chordae tendineae support the valve leaflets and prevent the leaflets from into the left atrium during If the chordae are or some of are they provide the valve resulting in prolapse of the leaflets into the left atrium during the mitral valve leaflets mitral insufficiency the posterior valve leaflet is chordae tendineae function of valve leaflets. The chordae tendineae are and attached to the mitral valve leaflet or to the papillary Figure depicts a used to chordae tendineae in which the chordae tendineae are and sutured to the valve leaflet. chordae tendineae can also be and the papillary or and sutured to the of a papillary (Figure chordae of the anterior leaflet may be replaced by chordae from the posterior chordae can also be replaced by chordae made of natural or such as procedure is to as chordal replacement (Figure of chordae tendineae is used to or fused chordae tendineae are chordae are in an to the chordae and improve support of the valve leaflets. If several chordae tendineae a is performed by a of fibrous tissue (Figure and degenerative changes in the leaflet with elongation or of the chordae can in mitral in the posterior or anterior leaflets. of a valve leaflet may a of the leaflet (Figure A prosthetic annuloplasty ring is usually to provide support to the valve annulus after valve leaflet leaflet reconstruction may be to repair damaged leaflets. of the mitral valve valvular However, and destruction of leaflets or chordae are with valve The leaflets may be with of or New chordae tendineae are from reported of a posterior leaflet chordae and papillary to repair a posterior mitral valve muscles may become or during of The damaged papillary muscles can be of mitral valve repair and reconstruction is at the of surgery. solution was into the left ventricle to valve commonly transesophageal echocardiography is used in the at the of the surgery to the of the valve If problems are repair or reconstruction is or the valve may to be of the aortic valve is not as developed as is repair of the mitral valve. of a stenotic or insufficient aortic valve is more than repair of the mitral valve because the mechanism is more aortic commissurotomy may be used on stenotic or fused aortic valves. The commissures are incised in an to open the stenotic of the valve cusps may contribute to aortic are from the aortic valve. aortic valve became of severely stenotic aortic valves was performed at some aortic valve were aortic valve repairs were because of the high prevalence of and after valve The of mitral valve repair and the of the surgical have renewed interest in aortic valve for treatment of aortic may be more than repair for treatment of aortic is due to cusp retraction fibrosis or and or is due to of the aortic retraction is by or the cusp with or A of a aortic valve cusp is in an to aortic are used to repair in the aortic valve Valve may decrease or the amount of by of the aortic valve annulus. valve aortic tissue is to the of the aortic valve leaflets contribute to aortic developed a to the edges of valve leaflets to improve or aortic with mitral valve repair of the aortic valve is The of the repair is at the of surgery by using transesophageal mitral commissurotomy is performed to improve valve function in a stenotic mitral valve with commissurotomy for patients with New and heart reported that of patients with New heart failure had years after The for commissurotomy and valve replacement are to and to valve reconstruction another surgical option for patients acute mitral insufficiency due to reported that were for patients valve repair than for patients mitral valve replacement to cardiac valve repair surgery were in Most of the involved patients who had mitral valve repair and 2). valve repair has been used to treat patients with mitral mitral stenosis, and mitral valve disease mitral stenosis and mitral have been reported for patients who had mitral valve repair for treatment of mitral valve dysfunction by degenerative valve disease, rheumatic valve disease, and endocarditis. A of types of valve repair surgeries have been annuloplasty with and without prosthetic leaflet leaflet chordal chordal chordal and papillary valve repair and mitral valve replacement have been 1). the is after mitral valve repair than after mitral valve patients who had mitral valve at to years were the or than the for patients who had mitral valve from were also for both of to for valve repair and to for valve for patients who had mitral valve repair were to and 2). who had mitral valve repair and no cardiac surgical had of or have been reported for patients who had mitral valve to years after mitral valve repair surgery, from were from to valve repair surgery can be performed with and valve repair has been used successfully to stenosis and early aortic valve performed mechanical of the aortic valve on and years after surgery, the from were and Although may stenosis, the prevalence of late and the prevalence of have the use of this the aortic valves of patients who had aortic The rate was and the from rate was and that surgery for aortic valve repair is not yet an because of the for was by who that patients on for aortic and mitral valve repair had a rate of and a from rate of data to be after aortic valve this the early and of aortic valve repairs are with valve valve repair is usually recommended in the disease process. The of this treatment is that the is usually the valve dysfunction is less and left ventricular function may be If surgery is performed for mitral valve repair or an surgical is However, often cardiac valve repair surgery is performed with cardiac surgical or aortic valve surgery and coronary artery surgery. management to the type of cardiac surgery of and and and early of are of patients after cardiac valve repair is to care of patients after cardiac valve In the assessment of the patient’s is The goals of management are to and reduce with valvular disease often have increased cardiac Although the cardiac valve is the heart time to to the improved Preoperative artery pressures are a for usually in the if replacement is on the basis of right atrial and artery agents may be in the to cardiac agents may be to improve cardiac and may be to decrease and in for cardiac dysrhythmias is in the commonly after valve surgery, because the mitral and aortic valves close to the or heart may because of or to the may and at dysrhythmias are a common after cardiac surgery and with increased after cardiac valve is usually is and to prevent atrial therapy is after cardiac valve Although is usually not after cardiac valve therapy is commonly after cardiac valve is of cardiac valve surgery, after the and are for 2 and for patients in patients cardiac valve surgery specific to cardiac valve repair the of for the management of patients with valvular heart a to of treatment with and and of the when the has an of to therapy may be recommended for patients after valve therapy is for patients who have a history of atrial left atrial or a mechanical patients therapy is assessment and of of the is the be at to the as by the the of and with patients and the patients’ before patients are from the are have and are to large of and and fatty which increase the of of the many with increased of the can reduce the of and that may with because both the of endocarditis is a and of cardiac valve is recommended for patients with acquired valvular who have valve repair must antibiotics before surgery, and invasive to the of cardiac valve who has had an of rheumatic fever is at high for of acute rheumatic with a history of rheumatic fever antibiotics as the of rheumatic patients are by cardiac surgeon the first of surgery. The for on patient’s therapy of therapy is patients usually have with a cardiologist at least the number of cardiac valve repairs most more patients with coronary artery disease and valve dysfunction have coronary artery surgery and valve In an increased number of patients have one valve and another valve number of patients also have of an cardiac valve. The may to to or the repair may be but the valve may repair of developed valvular Although the prevalence of cardiac valves is have been invasive are currently used for valve New to minimally invasive valve repair be used for patients who have valve repair in the is that surgical of cardiac to change cardiac surgery. mitral valve surgery is The the for valve repair with surgery. of the mitral valve is performed the surgeon at a surgical instruments used to the surgery. The are by and to the of the the thoracotomy From the where the surgeon or can with the has been used successfully in repair of valve leaflets and chordae and of annuloplasty valve that mitral valve repair surgery can be successfully performed with this advances in tissue of tissue from the posterior leaflet of the valve has been used to repair mitral valve valve leaflets are and may be used in the has been in patients cardiac valve so many of and at are increase in the number of valve repairs If a valve can be an to the valve is The native valve is and the of chronic and prosthetic valve failure are the repair may not a it may surgery for valve replacement and the associated with prosthetic valve data for mitral valve repair are Additional data for aortic valve repair are According to and valve when be to in both mitral and aortic aortic valve repair has not yet the of for of an of this also for in the development of for this
https://doi.org/10.4037/ccn2003.23.2.72