CHAPTER 10: Mitral Valve Repair
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History of Mitral Valve Repair
The first successful mitral valvotomies were performed in the 1920s by Cutler and Levine in Boston (1) and Souttar in England (2). Subsequent attempts by both groups were disappointing, likely in part owing to the lack of such basic resources as blood transfusion, antibiotics, and safe anesthesia. After 25 years had elapsed, Charles P. Bailey, Dwight Harken, and Russell Brock had each devised successful methods of closed mitral valvotomy. Despite the development of safe cardiopulmonary bypass techniques, pioneered by Gibbon at Thomas Jefferson and refined by Kirklin at the Mayo Clinic, continued success with closed approaches delayed the widespread acceptance of "open heart" approaches to mitral commissurotomy until the 1970s.
Early attempts were made to repair regurgitant mitral valves (MVs) with ingenious closed approaches, such as circumferential annular sutures. With the advent of reasonably safe cardiopulmonary bypass, Lillehei and colleagues (3) first carried out direct repair in 1957. In 1961, Starr and Edwards (4) reported the first successful MV replacement, and after this, enthusiasm for mitral repair waned. In Europe, Carpentier, Duran, and others developed effective and reproducible methods to repair regurgitant MVs and were ultimately able to demonstrate the superiority of these methods over mitral replacement, stimulating renewed interest in mitral repair worldwide.
Indications for Mitral Valve Repair and Timing of Intervention
Historically, MV replacement was delayed until nearly intractable heart failure and often marked deterioration of left ventricular (LV) function developed. This strategy was based on the morbidity and mortality of the operation in addition to further loss of LV function postoperatively as a consequence of detachment of the chordal apparatus from the papillary muscles. The advantages of mitral repair over mitral replacement include the preservation of LV function through preservation of the chordal attachments, low rates of thromboembolism, the lack of a requirement for anticoagulants (beyond aspirin), and excellent durability. Given the excellent long-term results of modern mitral repair techniques, the threshold for surgical intervention has been appreciably lowered. The American College of Cardiology/American Heart Association Task Force on Practice Guidelines in Valvular Heart Disease recommends that patients with functional class II symptoms or higher and severe mitral regurgitation (MR) and asymptomatic patients with severe MR and echocardiographic evidence of LV dysfunction (LV end-systolic dimension 45 mm, ejection fraction 0.60) undergo repair. When a successful repair is probable, the weight of evidence favors surgical intervention in asymptomatic patients with severe MR and normal LV function (5).
Similarly, the indications for the surgical repair of mitral stenosis (MS) have evolved to include patients in functional class III or higher with a valve area of 1.5 cm2 or less. In patients who have favorable anatomy, catheter-based balloon mitral valvuloplasty is a competing recommendation (5).
Results of Mitral Valve Repair
With the development of standardized techniques for MV reconstruction, Deloche et al. (6) demonstrated that MV repair was feasible in 95% of patients with degenerative valve disease, 70% with rheumatic valve disease, and 75% with ischemic valve disease. The long-term results after MV repair were excellent, with very low rates of thromboembolism, reoperation, and valve-related mortality. Echocardiographic follow-up analysis revealed no or mild MR in 92% of patients. Gillinov et al. (7) analyzed 1,072 patients undergoing mitral repair for degenerative disease at the Cleveland Clinic. Although this study corroborated the excellent long-term results of Deloche et al. (92.9% freedom from reoperation at 10 years), the results varied when analyzed by anatomic subgroup (Fig. 10.1). Optimal results (97% freedom from reoperation at 10 years) were observed in patients with isolated posterior leaflet prolapse for which the surgical repair included posterior resection and ring annuloplasty. An isolated anterior leaflet repair, chordal-shortening techniques, posterior leaflet resection without annuloplasty, and annuloplasty alone all significantly decreased durability (7) (Fig. 10.2). In addition, residual MR of grade 2+ or higher at the termination of the procedure was shown to decrease the durability of repair (8).
FIG. 10.1. Pathologic anatomy of degenerative mitral valve disease (n = 1,072). Dilated annulus, 16% slice; elongated chordae, 24% slice; anterior and posterior chordal rupture, 5% slice; anterior chordal rupture, 6% slice; posterior chordal rupture, 49% slice. (From Gillinov AM, Cosgrove DM, Blackstone EH, et al. Durability of mitral valve repair for degenerative disease. J Thorac Cardiovasc Surg 1998;116:734743, with permission.)
Patients with rheumatic disease had significantly worse repair results (76% freedom from reoperation at 15 years) (6). Yau et al. (9) demonstrated improved risk-adjusted, long-term survival in patients with rheumatic disease undergoing mitral repair in comparison with mitral replacement.
ASSESSMENT OF THE PATIENT FOR MITRAL VALVE REPAIR
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Preoperative Clinical Assessment
The cardiology referral for MV repair is based on clinical signs and symptoms and on echocardiographic and cardiac catheterization findings. Preoperative transthoracic echocardiographic (TTE) imaging often provides satisfactory information regarding the degree of MR or MS, annular size, involvement of anterior or posterior leaflets, chordal and papillary muscle structural integrity, and overall LV size and LV systolic function. In the absence of satisfactory TTE images, transesophageal echocardiography (TEE) provides improved visualization of MV pathology.
Intraoperative Transesophageal Echocardiographic Evaluation
A detailed intraoperative TEE evaluation of the mitral apparatus is critical for planning surgery, assessing results, and predicting the long-term durability of the MV repair (7,10). A comprehensive and systematic approach to evaluating the mitral anatomy is described in Chapter 8. There are currently no widely accepted criteria for establishing which patients should undergo MV repair. The feasibility of repair depends on the anatomic lesions of the valve and the skill of the surgeon. A complete evaluation of the heart and great vessels by intraoperative TEE is critical because incidental findings (severe atherosclerotic aortic disease, undiagnosed aortic insufficiency, regional wall motion abnormalities suggestive of ischemia, left atrial [LA] thrombus, intracardiac masses) often significantly affect surgical planning.
Functional classification of mitral regurgitation.
Carpentier (11) introduced a functional rather than a pathologic model of the regurgitant MV in which the focus is on the opening and closing motions of the leaflets.
Type I: normal leaflet motion:
Leaflet motion in MR can be normal (type I), in which case the MR is caused by annular dilation that leads to failed coaptation or leaflet perforation (e.g., from endocarditis) (Fig. 10.3A,B).
Perforated anterior leaflet of the mitral valve
Arrowhead demonstrates a perforation in the anterior leaflet of the mitral valve.
Color Doppler of perforated anterior leaflet of the mitral valve
Color flow Doppler imaging demonstrates an eccentric posterior directed jet originating from the perforation in the anterior leaflet of the mitral valve.
FIG. 10.3. Carpentier classification of leaflet motion. A: Type I, normal leaflet motion, depicted here with annular dilation and central mitral regurgitant (MR) jet. B: Type I, normal leaflet motion with leaflet perforation. Note normal degree of coaptation between anterior and posterior leaflets. C: Type II, flail of posterior leaflet, depicted here secondary to ruptured marginal chordae. The MR jet is directed anteriorly. D: Type II, flail of anterior leaflet, depicted here secondary to ruptured marginal chordae. The MR jet is directed posteriorly. E: Type III, restricted leaflet motion. The posterior leaflet is depicted here as tethered, causing a "relative prolapse" of the anterior leaflet. The MR jet is directed posteriorly. F: Types I and III, restricted leaflet motion, depicted here in a dilated failing heart. Annular dilation (type I) and leaflet restriction secondary to downward displacement of the papillary muscle heads (type III) commonly coexist in this condition.
Type II: excessive leaflet motion:
When leaflet motion is excessive (type II), prolapse of the leaflet edge in systole beyond the plane of the annulus results in an eccentric regurgitant jet directed away from the prolapsing leaflet (Fig. 10.3C,D). Common causes of prolapse are chordal rupture or elongation, papillary muscle rupture, and papillary muscle elongation/dysfunction. It should be noted that papillary muscle dysfunction related to ischemic heart disease is associated with adjacent segmental wall motion abnormalities.
Chordal rupture with leaflet prolapse
ME four chamber view demonstrating a prolapsing segment of the anterior leaflet secondary to chordal rupture.
Eccentric mitral regurgitation
Color Doppler evaluation of the same patient as above demonstrating a very eccentric posterior directed jet of mitral regurgitation originating from the flailed anterior leaflet segment.
Type III: restricted leaflet motion:
Restrictive leaflet motion may involve both inadequate opening in diastole (MS) secondary to commissural fusion (rheumatic disease) and inadequate closure in systole (MR) secondary to chordal thickening/fusion (rheumatic disease) or LV dilation. Inadequate closure keeps the valve edge below the plane of the annulus, resulting in a relative prolapse of the adjacent normal leaflet above the line of coaptation (Fig. 10.3E). The resultant regurgitant jet is directed toward the restricted leaflet. Various lesions can coexist, and the goal of repair is to address the component lesions systematically (Fig. 10.3F).
The Carpentier nomenclature designates the posterior leaflet segments as P1, P2, and P3. P1 is adjacent to the anterolateral commissure, P2 is the middle scallop, and P3 is adjacent to the posteromedial commissure. The anterior leaflet has less clearly defined segments designated as A1, A2, and A3, corresponding to the adjacent posterior leaflet segments. The TEE short-axis view of the LV with some anteflexion provides the "fish mouth" view of the MV, in which the A3 and P3 segments are at the top of the screen and the A1 and P1 segments are at the bottom (anterior leaflet to the left) (Fig. 10.4A). In the surgeon's view, A3 and P3 are to the right, and A1 and P1 are to the left (anterior leaflet superior) (Fig. 10.4B). A simple way of demonstrating the surgical view is to tilt one's head to the left while viewing the echo image, thereby visualizing P1, P2, and P3 from left to right inferiorly and A1, A2, and A3 from left to right superiorly. At least three nomenclature systems are commonly used by surgical teams in repair of the MV (see Chapter 8). Concordance in the use of nomenclature by the surgical team is important to avoid confusion and misdiagnosis.
Carpentier classification system of the mitral valve
A TG basal SAX view demonstrating the Carpentier classification system for the mitral valve.
FIG. 10.4. Mitral valve leaflet segments. A: Echocardiographic short-axis or "fish mouth" view. B: Surgeon's view through open left atrium from the patient's right side. The echocardiographic view is rotated 90 degrees counterclockwise relative to the surgeon.
Reporting the transesophageal echocardiographic findings before mitral repair.
The report of the findings before mitral repair must include the degree of MR or MS, the specific location of prolapsing or flail leaflet segments, areas of tethering and restriction, and areas of normal leaflet function. Leaflets should also be assessed for perforations, calcifications, excessive length, thickened appearance, and mobility. Annular calcification (most common posteriorly) should be noted. The subvalvular apparatus is assessed for chordal thickening, and for papillary muscle and ventricular wall function. Robust secondary chordae, which may be suitable for transposition to prolapsed leaflets, can often be identified by TEE. Because the goal of the intraoperative TEE examination before repair is to evaluate the function of the MV, it is critical to evaluate the valve in a hemodynamic state comparable to that of the awake, ambulatory patient. The use of inotropes or vasopressors may be necessary to achieve this end. The secondary effects of the valvular disease, including LA enlargement with or without thrombus, and the size and function of the left and right ventricles should be discussed with the surgeon.
Assessing the risk for systolic anterior motion.
Systolic anterior motion (SAM) of the MV with resultant left ventricular outflow tract obstruction (LVOTO) develops in more than 16% of patients following MV repair (1214). A complete TEE examination after repair will identify this complication. However, intraoperative TEE analysis of the mitral apparatus before bypass can identify the patients in whom this complication is likely to develop. The data allow the surgeon to perform a "sliding leaflet" procedure or modifications of this repair technique and thereby significantly reduce the occurrence of SAM (1416).
The mechanism of SAM/LVOTO is multifactorial, the major cause being excess mitral leaflet tissue (as in the "floppy mitral valve" of myxomatous disease). Anteriorly displaced papillary muscles, a nondilated LV, and a narrow mitral-aortic angle have also been proposed as contributing factors (14). The incidence of SAM/LVOTO after MV repair has been shown to increase in patients with a more anterior position of the leaflet coaptation point. This may be the consequence of a relatively large posterior leaflet, shifting coaptation closer to the base of the anterior leaflet and causing both anterior displacement of the coaptation line and an increase in the amount of slack leaflet tissue in the outflow tract. An elongated anterior leaflet may cause a similar increase in the amount of slack leaflet available to obstruct LV outflow.
Maslow et al. (13) investigated various pre-repair TEE variables to determine the most useful measurements with which to assess the preoperative risk for SAM/LVOTO. These included the anterior leaflet (AL) and posterior leaflet (PL) lengths, used to determine the AL/PL ratio, and the distance from the coaptation point to the septum (C-sept) (Fig 10.5). The incidence of post-repair SAM/LVOTO was greater in patients with an AL/PL ratio below 1.0 than in patients with an AL/PL ratio above 3.0. SAM/LVOTO was more likely to develop in patients with a C-sept of 2.5 cm or less than in patients with a C-sept of 3.0 cm or more (13). The identification of patients at high risk for SAM/LVOTO affects the pharmacologic management of hemodynamics after bypass, which is aimed at reducing this complication (discussed later), and alters the surgical techniques described above.
FIG. 10.5. Schematic demonstrating the transesophageal echocardiographic measurements used before repair to assess the risk for systolic anterior motion. AL, anterior leaflet length; PL, posterior leaflet length; C sept, distance from the coaptation point to the septum; LVID, left ventricular internal diameter in systole. (Adapted from Maslow AD, Regan MM, Haering JM, et al. Echocardiographic predictors of left ventricular outflow tract obstruction and systolic anterior motion of the mitral valve after mitral valve reconstruction for myxomatous valve disease. J Am Coll Cardiol 1999;34:20962104.)
Direct surgical inspection of the mitral apparatus.
Before the use of intraoperative TEE became widespread, pre-repair valve analysis depended entirely on direct surgical inspection with the heart and mitral apparatus in the "tensed" state. This was accomplished by exposing the valve during ventricular fibrillation, either before application of the aortic cross-clamp or after cross-clamping with infusion of cold blood in the aortic root at physiologic pressure to reduce the risk for air embolization (17). In the current era, the surgeon plans most of the operation based on the intraoperative TEE findings, so that it is not necessary to evaluate the valve before the administration of cardioplegia. Although in the empty, flaccid heart nearly all leaflet edges can be shown to prolapse above the annular plane, direct inspection after cardioplegia remains a vital step in confirming the location of pathology and the suitability of the various valve structures for the planned repair (18). Leaflet prolapse or restriction is identified by the application of nerve hooks to the leaflet edge and comparison with "normal" leaflet segments, usually the P1 segment. Direct inspection allows the identification of ruptured or elongated chordae and of robust secondary chordae that can be transposed to prolapsing segments. Inspection of the papillary muscles determines the suitability of chordal-shortening approaches or the placement of artificial chords. Leaflet perforations and annular calcification are identified.
In MS, the degree of commissural fusion, leaflet calcification, and subchordal disease and the suitability of commissurotomy are determined by visual inspection.
SURGICAL REPAIR OF MITRAL REGURGITATION
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Exposing the Mitral Valve
Good exposure of the MV is a prerequisite to adequate repair. Incision in the interatrial groove with bicaval cannulation is a widely used approach, with exposure improved by dissecting the left and right atria to allow a more medial incision (19). A transseptal approach with bicaval cannulation via a right atriotomy, with or without extension into the roof of the LA, also provides excellent exposure. If exposure is still difficult, the placement of annuloplasty ring sutures and the application of tension will "deliver" the valve into the surgical field. Left-sided pericardial traction sutures should be relaxed. Meticulous attention to myocardial protection, either by intermittent antegrade or a combination of antegrade and retrograde cardioplegia, is an absolute necessity to allow for the safe clamp time necessary to perform a complex repair. TEE can assist in the successful placement of a coronary sinus catheter, particularly in redo surgery in which the palpation of posterior structures is limited.
This section is intended to give the echocardiographer an appreciation of the common surgical procedures used in MV repair. A better understanding of the common repair techniques can guide the post-repair TEE evaluation.
Repair of leaflet prolapse
Isolated P2 prolapse:
When resection and ring annuloplasty are performed, a prolapsed P2 segment is the most reliably repaired regurgitant lesion (7) (Fig. 10.6). Briefly, the P2 segment is resected from scallop to scallop in a quadrangular fashion. Intact chordae are detached from the papillary muscles (a robust, intact chord may be preserved to repair another prolapsing segment). The annulus is plicated with a horizontal mattress suture, and direct approximation of the leaflet edges is undertaken.
Posterior mitral valve leaflet prolapse
Midesophageal 4 chamber view in a patient with posterior mitral valve leaflet prolapse (arrow)
Color Doppler of moderate mitral insufficiency
Color Doppler of patient above demonstrating moderate mitral insufficiency with a predominately anteriorly directed jet.
FIG. 10.6. Transesophageal four-chamber view of the mitral valve depicting prolapse/flail of the P2 segment of the posterior leaflet. See Anatomical View in Appendix.
In the case of excessive leaflet length or other factors predisposing to SAM, or in all cases (author preference), a sliding plasty can be carried out (Fig. 10.7). In sliding leaflet plasty, after P2 resection, the P1 and P3 segments are partially detached from their hinge line, starting at the P2-facing edge. Horizontal mattress sutures are then placed through the annulus to reduce the gap left by the resection of P2. The leaflets are reattached to the annulus and their edges reapproximated. After leaflet repair, a ring annuloplasty is performed, with the ring sized to the anterior leaflet area and intercommissural distance.
FIG. 10.7. Carpentier technique for preventing systolic anterior motionthe sliding leaflet technique. A: In cases of excess tissue of the mural leaflet, the quadrangular resection is completed by two triangular resections of the posterior leaflet remnants to correct excess leaflet tissue. B: Remnants are translated medially to close the gap. C,D: Repair is completed, and the ring is inserted to reinforce the repair. (From Jebara VA, Mihaileanu S, Acar C, et al. Left ventricular outflow tract obstruction after mitral valve repair: results of the sliding leaflet technique. Circulation 1992;88:3034, with permission.)
Isolated anterior leaflet prolapse:
Resection is not a reliable approach for the larger anterior leaflet, except for repair of a very small, focal prolapsing area by triangular resection (11). The prolapsing anterior leaflet (Fig. 10.8) can be repaired by means of chordal transfer, artificial chordal replacement, or chordal-shortening techniques. Chordal transfer involves transferring robust chords either from a secondary position on the anterior leaflet or from an adjacent posterior leaflet edge (the latter requiring a quadrangular resection, as described earlier). Artifical chords (Gore-Tex) can be placed from the papillary muscle head to the leaflet edge. A major challenge is adjusting the length of the chords, often by judging adjacent, nonprolapsing leaflet segments. Nevertheless, excellent long-term results have been demonstrated with chordal replacement (8). Finally, elongated chords can be shortened. The trenching technique, in which elongated chords are buried in a trench cut in the papillary muscle and sutured in place, was previously popular, but long-term durability was unsatisfactory (7,20). Papillary muscle shortening, especially for billowing valves in which multiple chords are elongated, has become popular. The method is efficient because multiple chords are shortened at once; however, exposure can be challenging, and long-term results are not yet available.
FIG. 10.8. Transesophageal four-chamber view of the mitral valve depicting prolapsing A2 segment of the anterior leaflet. See Anatomical View in Appendix.
In cases of prolapse of both the anterior and posterior leaflets (Fig. 10.9), a systematic approach combining quadrangular resection with chordal transposition, shortening, or replacement is required. If there is dominant posterior prolapse with a myxomatous, prolapsing anterior leaflet, isolated quadrangular resection with ring annuloplasty can be satisfactory (21).
FIG. 10.9. Transesophageal five-chamber view of the mitral valve depicting bileaflet prolapse.
Papillary muscle rupture:
Rupture of a papillary muscle complicating an acute myocardial infarction can affect the entire papillary muscle (one third of cases), resulting in bileaflet flail, or only one head (two third of cases), resulting in flail of either the anterior or posterior leaflets. The posteromedial papillary muscle is most often affected (75% of cases) because the coronary circulation to the inferior wall is not redundant. A single ruptured papillary head can be reimplanted in adjacent endocardium. In cases with extensive necrosis of the papillary muscle and adjacent myocardium, an MV replacement with preservation of the remaining intact chords should be carried out (22).
Repair of ischemic mitral regurgitation:
Patients with ischemic MR are a diverse group in regard to acuteness of presentation, LV function, and causes of MR (papillary muscle dysfunction, segmental LV wall dysfunction, leaflet restriction, annular dilation, chordal rupture, papillary muscle rupture). A variety of procedures have been used to manage these problems, including the leaflet/chordal repair techniques described earlier, ring and suture annuloplasty for annular dilation/leaflet restriction, and valve replacement with or without chordal preservation. Although mitral repair is demonstrably superior to replacement for nonischemic MR, the issue remains unresolved for ischemic MR because of the heterogeneity of this patient population. For example, Duarte and colleagues (23) reported very good 10-year survival in patients with 3+ MR treated with coronary artery bypass grafting (CABG) alone. Rankin et al. (24) and Akins et al. (25) demonstrated improved results when the regurgitant MV was repaired rather than replaced, whereas Cohn et al. (26) reported better survival with replacement (with chordal preservation) than with repair. Of note, in the analysis of Cohn et al., repair of functional MR (secondary to annular dilatation or leaflet restriction) resulted in a 5-year survival of 43%, whereas replacement in this group resulted in a 5-year survival of 92%.
In summary, the issue of replacement versus repair remains uncertain in patients with mild-moderate ischemic MR undergoing CABG. In patients with severe MR, either mitral repair or mitral replacement with chordal preservation can yield acceptable results.
Mitral ring annuloplasty in cardiomyopathy.
One of the most exciting developments has been mitral ring annuloplasty for patients with congestive heart failure (CHF) and moderate to severe MR. Functional MR in CHF is caused by failed leaflet coaptation resulting from a combination of annular enlargement and ventricular dilation, the latter leading to leaflet restriction (27,28). Mitral ring annuloplasty in patients with New York Heart Association class IV CHF and MR results in a 2-year survival of 70% (29). Hence, mitral ring annuloplasty offers another therapeutic option besides transplantation in a subset of patients with CHF, severe functional limitation, and an otherwise dismal prognosis.
Severe mitral regurgitation
ME two chamber view demonstrating significant mitral regurgitation and left ventricle dilatation. The mitral annulus measured > 5cm. Note the dilated, hypokinetic, basal segments.
Carpentier- Edward ring annuloplasty
Is the same patient as above, following a #28 Carpentier-Edward ring annuloplasty.
Mitral repair in rheumatic disease
The symptoms of patients with some degree of leaflet pliability can be relieved by open commissurotomy and chordal fenestration in lieu of replacement (Fig. 10.10). The anterolateral commissure is often fused to a greater degree than the posteromedial commissure. With a nerve hook distracting either leaflet edge, the fused portions of the leaflets/commissures are divided; great care must be taken to respect the chordal attachments to the papillary muscle heads. This incision can be carried down from the leaflet through the fused chords. In minimally calcified valves with good pliability on echocardiography, comparable results can be achieved with percutaneous balloon valvuloplasty (30).
FIG. 10.10. Transesophageal five-chamber view of the mitral valve depicting mitral stenosis with "smoke" (spontaneous contrast) in an enlarged left atrium (LA). Note the hockey stick deformity of the anterior leaflet (AL) and marked narrowing of the mitral orifice in diastole.
Repair of rheumatic MR is a very challenging endeavor. Leaflet restriction can be relieved through aggressive chordal fenestration with fanning of the involved papillary muscle heads. Leaflet decalcification and the transposition of chords from a secondary position back to the leaflet edge can give good results. Ring annuloplasty may be necessary, but care must be taken in mixed lesions that relief of MS is maintained.
Special Surgical Considerations
Calcified mitral annulus.
The presence of annular calcification considerably complicates mitral repair or replacement, increasing the risk for ventricular rupture, damage to the circumflex coronary artery, and postoperative paravalvular MR, and it must be identified in the TEE examination (31). Calcification is most commonly seen in the posterior annulus but can extend into the leaflet tissue or the ventricular myocardium, and rarely to the anterior annulus. It is distinguished from the calcification of rheumatic disease, in which primary leaflet calcification may extend to the annulus with concomitant calcification of subchordal structures. Annular calcification in association with MR occurs most frequently in the elderly and in patients with Marfan syndrome or Barlow disease. Carpentier et al. (32) reported successful en bloc resection of the entire calcium deposit with subsequent repair in 98% of cases, with a 3.3% mortality (Fig 10.11). Once the calcium is resected, the atrioventricular groove is repaired with vertical mattress sutures. The posterior leaflet (or its remnants in the case of a P2 resection) is then reattached.
FIG. 10.11. P2 segment with adjacent annular calcium. The patient was a 72-year-old woman with marked calcium deposition in the posterior annulus and P2 prolapse with severe mitral regurgitation. En bloc resection was carried out with repair, as described in the text.
Cases at high risk for systolic anterior motion.
The surgical approach to MV repair may be modified in cases identified to be at high risk for SAM. In the case of dominant posterior leaflet prolapse, sliding leaflet plasty can be carried out after P2 resection and the excessive height of the remnants of the posterior leaflet reduced by the resection of leaflet tissue from the annulus-facing edge (33). If an anteriorly displaced line of coaptation is identified after leaflet resection has been performed, some modification can be achieved by bending a rigid ring so that the anteroposterior diameter is increased, which reduces the volume of anterior leaflet tissue available to obstruct the LVOT. Accurate ring sizing and avoidance of undersizing the annuloplasty ring also reduce the risk for LVOTO secondary to SAM. Finally, post-repair hemodynamic management should be attempted, as outlined later.
ASSESSMENT OF THE MITRAL VALVE AFTER REPAIR
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Surgical Valve Assessment
After packs and retraction sutures have been removed to prevent distortion of the valve and ventricle, the passive leak test is performed by forcefully injecting saline solution into the LV. This test remains useful in determining gross inadequacies of repair; a large leak by this test is generally confirmed as severe MR by TEE. Patients with a competent valve following the leak test may still have significant valvular insufficiency by TEE secondary to ischemic wall dysfunction or SAM in the beating, volume-loaded heart (34).
Transesophageal Echocardiographic Assessment of Adequacy of Repair
Post-repair assessment by TEE in the physiologically optimized heart has become the gold standard in determining the adequacy of MV repair. "Immediate failures" are detected in approximately 6% to 8% of patients, who then may undergo further reparative techniques or replacement during the same procedure (35,36). Post-repair MR of grade 1+ or 2+ increases the incidence of late reoperation threefold in comparison with trace or no MR after repair (37). Thus, post-repair TEE information is essential in determining whether immediate reintervention during the same surgery is warranted.
Transesophageal Echocardiographic Assessment of Complications of Mitral Valve Repair
Systolic anterior motion/left ventricular outlet tract obstruction.
SAM of the MV leaflets with resultant dynamic LV outflow tract obstruction is a known complication of MV repair, as discussed earlier. The echocardiographic findings demonstrate a characteristic systolic bending of the leaflet tips into the outflow tract, turbulent flow in the LVOT, and commonly MR (usually as a posteriorly directed jet) (Fig 10.12). Gradients across the LVOT are increased from baseline as a result of dynamic outflow obstruction. When SAM/LVOTO occurs after MV repair, hemodynamic maneuvers must be attempted before the results are declared inadequate. Inotropic agents, vasodilators, and low-volume states all exacerbate this condition and perhaps provoke it in susceptible patients. With the discontinuation of these agents and manipulation of the cardiovascular status by volume loading with or without the administration of alpha agents, SAM/LVOTO often resolves. In some patients with a significant LVOT gradient, beta-blockers may be useful in resolving the LVOTO (38). With persistent SAM/LVOTO, surgical reintervention may be necessary.
FIG. 10.12. Transesophageal longitudinal view depicting obstruction of the left ventricular outflow tract (LVOT) by leaflet tips during systole (systolic anterior motion with left ventricular outflow tract obstruction). Color Doppler in this situation would show turbulence in the left ventricular outflow tract and a posteriorly directed mitral regurgitant jet. See Anatomical View in Appendix.
Coronary artery injury.
Injury to the circumflex coronary artery is a rare but frequently fatal complication of either mitral repair or mitral replacement (39). Intraoperative TEE findings of new segmental wall motion abnormalities in the lateral wall or inferoposterior regions may suggest circumflex injury, and grafting of the distal coronary artery may be indicated (40).
Disruption of the atrioventricular groove or rupture of the LV between the papillary muscle insertions and the atrioventricular groove is a feared and devastating complication of MV surgery. Factors predisposing to rupture include female sex, advanced age, annular calcification, and high-profile valve replacement devices in patients with a small LV cavity. Recognition of LV rupture can be aided by TEE, which often demonstrates continuous entrainment of intracardiac air. Repair by placement of an endocardial patch has been shown to be superior to attempts to stem the bleeding by placing external sutures or patches (41).
Aortic valve leaflet injury.
Deep suture placement in the anterior annulus can inadvertently injure the left or noncoronary leaflets of the aortic valve. Massive aortic insufficiency noted either clinically or by TEE alerts the surgeon to this possibility. Simple leaflet tethering may be relieved by suture removal and replacement, whereas tears in the aortic leaflets may require aortic valve replacement or more complex repair (42).
Pitfalls of Transesophageal Echocardiographic Examination after Mitral Valve Repair
Unreliability of pressure half-time results after repair of mitral stenosis.
A major assumption of the pressure half-time technique in valve area calculations is that LA and LV compliance does not significantly affect the rate of pressure decline across the stenotic orifice. In clinically stable MS, this assumption appears valid, but immediately following MV repair, LA and LV compliance is markedly altered and does not reach equilibrium for 24 to 72 hours. Thus, the pressure half-time method of calculating the MV area after MS repair may not be accurate in the immediate postoperative period.
Inadequacy of hemodynamic state inadequate to expose mitral regurgitation.
General anesthesia can effectively mask MR by lowering preload, decreasing afterload, and decreasing the inotropic state of the heart. Before TEE assessment of the MV, manipulation (volume loading, administration of an inotrope or alpha agonist) should be attempted to attain hemodynamics that approximate those of the ambulatory state. This detail is critical in both pre-repair and post-repair TEE evaluations to assess the degree of mitral insufficiency accurately.
DECISION TO REINTERVENE
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The decision to reintervene because of an imperfect result is a difficult one, in part because of a conflicting literature concerning the significance of mild-moderate residual MR. Fix et al. (36) found no increase in long-term mortality in patients with grade 1 to 2+ MR after repair, although a trend to increased late reoperation was noted. In contrast, Sheikh et al. (43) noted an increase in postoperative morbidity and mortality in patients with grade 2+ or higher residual MR. Interpretation of the post-repair TEE data may reveal the cause of residual MR, and cooperation between the echocardiographer and surgeon will allow a determination of the likelihood of a more successful repair. The decision to reintervene must also take into account the condition of the heart, the potential for injury during a second cross-clamp period, and the potential need for valve replacement with its attendant costs. These decisions must be made in the "heat of battle" and require echocardiographers with a firm and confident grasp of TEE interpretation, surgeons with an awareness of their capabilities, and a clear understanding by the entire team of the short-term implications of reintervention and the long-term implications of residual MR.
Prolapsing P2 segment of the mitral valve
Demonstrates a patient who had an isolated repair of a prolapsing P2 segment with resection and a ring annuloplasty. The annular sutures failed (see Fig. 10.7) resulting in annular dilatation and posterior movement of the posterior leaflet. (Arrow) A return to cardiopulmonary bypass is warranted.
Prolapsing P2 segment of the mitral valve, color Doppler
Color flow Doppler evaluation of the same patient as above.
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The establishment of intraoperative TEE as the standard of care in MV repair places the intraoperative echocardiographer and the surgeon in a close working relationship in which real-time decisions with tremendous implications for the patient are made on a daily basis.
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Which of the following is true about ischemic papillary muscle rupture?
Rupture is caused by fewer chordal attachments to the posteromedial papillary muscle.
Rupture most commonly involves the anterior papillary muscle.
A lack of dual blood supply to the myocardium subtending the posterior papillary muscle makes it the one most commonly involved in ischemic papillary rupture.
Rupture most commonly involves the entire papillary muscle.
Rupture usually results in bileaflet flail.
Mitral ring annuloplasty
Can increase the risk for SAM if the ring is oversized
Improves the durability of repair techniques
Decreases the risk for atrioventricular groove disruption
Improves visualization of the mitral apparatus by TEE after MV repair
Increases the risk for MS after MV repair
After MV repair, SAM/LVOTO
Can be identified before surgery
Can be successfully treated by increasing the afterload
Should be treated with dopaminergic agents
Can be treated by undersizing the mitral annuloplasty ring
Is more likely in patients with a preoperative AL/PL ratio greater than 3
Anterior leaflet prolapse repair
May involve resection of P2
Is the most durable of all leaflet repairs
Requires at least a small triangular resection of a large anterior leaflet
Results are improved with chordal-shortening procedures
Long-term results are poor after chordal replacement with Gore-Tex
Intraoperative TEE evaluation for mitral repair
Fails to depict localized leaflet prolapse accurately
Accurately measures postrepair stenosis by the pressure half-time technique after open commissurotomy
Allows inexperienced observers to identify normal and abnormal leaflet segments accurately
Does not correlate well with postoperative TTE findings
Improves the long-term durability of mitral repair
In type III leaflet abnormality
Of both leaflets, one would expect an eccentric jet of MR
Of the posterior leaflet, one would expect a posteriorly directed MR jet
Of the anterior leaflet, one would expect a posteriorly directed MR jet
Effective resolution of MR by mitral repair does not alter the long-term outcome of patients with severe CHF before surgery
MR cannot be treated with a mitral annuloplasty ring alone
In MS of rheumatic origin
Adequate repair is achieved in more than 90% of cases with good long-term results
Repair is commonly complicated by annular calcification
Balloon mitral commissurotomy may provide adequate treatment
TEE is unable to predict the degree of stenosis accurately before surgery with the pressure half-time method
Chordal fenestration has been shown to improve long-term durability.
The surgical view of the MV
Places the P3 and A3 segments to the surgeon's right
Allows accurate assessment of leaflet prolapse after the administration of cardioplegia
Is most easily replicated with the echocardiographer's head tilted to the right and the TEE image in the fish mouth view
Easily demonstrates the continuity of the posterior leaflet with the LVOT and aortic valve apparatus
Reliably demonstrates a competent valve if the passive leak test result is negative
Late MV repair failure
Is rarely caused by the progression of valvular disease
Is rarely a consequence of procedure-related failures
Is most often caused by endocarditis
Is more likely with the use of an annuloplasty ring
And reoperation are more likely when the trenching technique of chordal shortening is used
The American College of Cardiology/American Heart Association practice guidelines recommend MV repair
For patients with severe MR and marked LV dysfunction only
For asymptomatic patients with severe MR and LV dilation
Over percutaneous balloon valvuloplasty for patients with severe MS and pliable leaflets
For patients with MS, functional class II symptoms, and an MV area of 2 cm2
For patients with severe MR so long as atrial fibrillation is absent