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Address reprint requests to Edwin C. McGee, Jr., MD, Assistant Professor of Surgery, Northwestern University’s Feinberg School of Medicine, Division of Cardiothoracic Surgery, Galter 10-105, 201 East Huron Street, Chicago, IL 60611-2908.
1 Dr. McCarthy is a consultant for Edwards Lifesciences, Irvine, CA, and co-inventor of the IMR ETlogix ring.
Patrick M. McCarthy
Footnotes
1 Dr. McCarthy is a consultant for Edwards Lifesciences, Irvine, CA, and co-inventor of the IMR ETlogix ring.
Affiliations
Bluhm Cardiovascular Institute, Division of Cardiothoracic Surgery, Northwestern University’s Feinberg School of Medicine, Northwestern Memorial Hospital, Chicago, IL, USA.
Unlike myxomatous mitral regurgitation (MR), the management of chronic ischemic mitral regurgitation (IMR) remains a contentious issue. Numerous questions abound. Is revascularization enough? When should repair be undertaken? Should a partial or complete ring be used? Should the annulus be downsized? Is outright valve replacement ever indicated and, if so, what type of valve should be used? With the rise in percutaneous interventions, straightforward coronary revascularizations are becoming less frequent. Without question, we are operating on patients with more advanced coronary artery disease with frequently associated ventricular dysfunction. As our patients become older and less healthy, we will be required to deal with chronic IMR more frequently. In this article, we present the rationale we use when we consider how to best manage these patients, and will outline the preoperative and operative approach that we undertake when dealing with chronic IMR.
A thorough understanding of the underlying pathophysiology of IMR is necessary. The function of the normal mitral valve results from a complex interplay among the annulus, valvular, and subvalvular elements. In his classification scheme, Carpentier delineates chronic IMR as type IIIb
(Fig. 1). IMR results when posterolateral scar leads to a tethered posteromedial papillary muscle.
Figure 1Carpentier classification of mitral regurgitation. (I) Normal leaflet motion. (II) Increased leaflet motion. (III) Restricted leaflet motion. (A) Diastolic and systolic restriction. (B) Systolic restriction. (Color version of figure is available online at http://www.us.elsevierhealth.com/optechstcvs/.)
New evidence has been presented indicating that even more moderate amounts of MR in patients undergoing coronary artery bypass do not resolve after coronary bypass alone
Ischemic mitral valve regurgitation grade II-III correction in patients with impaired left ventricular function undergoing simultaneous coronary revascularization.
However, the reports of adding mitral valve surgery to coronary artery bypass to improve survival and late functional class are controversial, because other reports have failed to show any benefit.
Repair of ischemic mitral regurgitation does not increase mortality or improve long-term survival in patients undergoing coronary artery revascularization A propensity analysis.
Survival after coronary revascularization, with and without mitral valve surgery, in patients with ischemic mitral valve surgery, in patients with ischemic mitral regurgitation.
indicate that untreated MR would lead to a decreased survival. All of these studies, however, suffer from the common critique that they include a relatively small sample size and have limitations of retrospective studies (although attempts are made to account for this with propensity matching and multivariable analysis).
An increasing number of our patients have more advanced coronary disease and worse ventricular function. We believe that in such patients significant IMR is unlikely to improve with revascularization alone, and that a conservative approach is outdated. An aggressive approach should be taken when treating IMR and in preventing its recurrence.
The largest series in the literature to examine recurrent ischemic MR comes from the Cleveland Clinic Foundation and includes 585 patients who underwent annuloplasty performed over a 17-year period.
Nearly one third of patients had return of 3 to 4+ MR at 1 year.
Three concepts explain the recurrence of IMR. First, there has been a long held dogma that the intertrigonal distance is fixed. Recent work from several investigators has shown that the intertrigonal distance is subject to dilation.
Second, Miller’s laboratory has shown that fixation of the septal-lateral dimension, or distance from the anterior annulus to the posterior annulus, is important in preventing return of MR after repair. Third, the annulus asymmetrically dilates at the medial commissure, or P3 region. Although partial rings can provide good immediate repair of IMR, they provide protection from dilation of neither the intertrigonal nor septal-lateral dimension. In addition, standard complete rings do not address the asymmetric dilation found in ischemic MR.
Our belief that type IIIb MR would be best treated by a complete remodeling ring that provides additional reduction to the tethered P3 region led to the development of the Carpentier-McCarthy-Adams IMR ETlogix annuloplasty ring (Edwards Lifesciences, Irvine, CA).
Is there ever a role for outright valve replacement in ischemic MR? Calafiore and coworkers have shown that mitral valve coaptation depth, or the distance between the mitral valve annular plane and the coaptation point of the mitral leaflets, is a strong predictor of recurrent MR.
An increased coaptation depth is associated with a more spherical ventricle, and in their series, Calafiore reported that values greater than 10 mm were at high risk of recurrent MR after repair with a nonring suture annuloplasty. In the Cleveland Clinic series that looked at repair versus replacement for IMR, repair was associated with improved survival except in the least healthy subset of patients.
In severely compromised individuals with extensive leaflet tethering, we strongly consider proceeding directly to chordal sparing mitral valve replacement using a bioprosthetic valve. We believe that in patients with limited long-term survival, there is no place for a mechanical prosthesis.
Operative Approach
Figure 2Intraoperative transesophageal echocardiography (TEE) is performed as conduits are being harvested. The anatomy of the valve and subvalvular apparatus is carefully assessed, and the mechanism of the MR is confirmed. A “normal” valvular and subvalvular apparatus characterizes ischemic MR. Most commonly, a central or posterior jet is noted, but careful study of the jet will reveal a larger jet arising from the P2/P3 region and a smaller jet comes from the anterolateral commissure. Our practice has evolved to the routine repair of 2+ or greater MR. If lesser degrees of MR are noted, we will pharmacologically increase the blood pressure to a mean of 90 to 100 mm Hg and then reassess the MR. If the MR increases to 2+ or greater, we repair the mitral valve. Most patients require concomitant coronary artery revascularization and mitral valve repair. A full median sternotomy is used. Standard aortic and bicaval cannulation is performed. We have found that vacuum-assisted venous drainage allows us to use smaller venous cannulae and still have a bloodless field. Normothermic bypass is established, and the heart is arrested with a combination of antegrade and retrograde cold blood–modified Buckberg cardioplegia (4°C). Distal vein or radial artery anastomoses are completed and then connected to the cardioplegia manifold. Cardioplegia is administered retrograde and down grafts at least every 15 minutes to maintain myocardial protection. Caval isolation is achieved, and a standard left atriotomy is performed after developing the interatrial groove. The atriotomy is extended under the superior vena cava and inferior vena cava. Placing traction on the caval tourniquets, which are subsequently attached to the operative drape, can facilitate additional exposure. Left-side pericardial well sutures are removed. We use a self-retaining mitral retractor for all cases. The table is rotated away from the surgeon. If the view is still inadequate, a sponge on a ring forceps can be placed on top of the heart to depress the medial commissure. A small, metal-tip basket suction is placed in the left superior pulmonary vein to scavenge blood returning through the pulmonary bed. (Color version of figure is available online at http://www.us.elsevierhealth.com/optechstcvs/.)
Figure 3Although intraoperative TEE is always performed, direct inspection of the mitral valve is necessary to confirm pathology. Cold saline solution is infused into the ventricle under pressure to demonstrate the leak. The valve and the subvavular apparatus are carefully studied. With type IIIb ischemic MR, typically the posteromedial papillary muscle is tethered and the annulus is asymmetrically deformed at the P3 region. Findings may be subtle depending on the amount of tethering present. (Color version of figure is available online at http://www.us.elsevierhealth.com/optechstcvs/.)
Figure 4We generally start placing nonpledgeted sutures of 2-0 braided suture in the middle of the posterior annulus. Traction on these sutures sets up exposure of the entire valve. Generally, 8 sutures are placed in the posterior annulus and 6 sutures are placed in the anterior annulus. We size the ring to the surface area of the anterior leaflet. Unlike myxomatous disease, the leaflets are not elongated. (Color version of figure is available online at http://www.us.elsevierhealth.com/optechstcvs/.)
Figure 5The 26-mm or 28-mm Carpentier-McCarthy-Adams IMR ETLogix ring is typically used. Sutures are passed through the ring with appropriate spacing, and then the ring is lowered into the annulus after moistening the sutures with saline solution. The ring is sized to the anterior leaflet. (Color version of figure is available online at http://www.us.elsevierhealth.com/optechstcvs/.)
Figure 6We usually tie the sutures along the anterior annulus first and tie the sutures over P3 last to allow for as much remodeling as possible. The left atrial appendage is excluded with an over and over or purse string stitch of 4-0 polypropolene. (Color version of figure is available online at http://www.us.elsevierhealth.com/optechstcvs/.)
Figure 7The ventricle is pressurized with cold saline solution to test for a residual leak. Occasionally, an edge-to-edge repair with 4-0 braided suture may be required if a residual leak is noted, usually at the medial commissure. (Color version of figure is available online at http://www.us.elsevierhealth.com/optechstcvs/.)
Figure 8De-airing maneuvers are performed as the atrium is closed. The left internal mammary artery to left anterior descending coronary artery anastomosis is constructed, and proximal anastomoses are fashioned (Fig 8). Further de-airing maneuvers are performed. The cross clamp is released with flow diminished and the aortic vent on suction. If indicated, left ventricular reconstruction (modified Dor procedure) and tricuspid repair are performed while the heart reperfuses. After weaning from bypass, TEE is used to assess the adequacy of repair. MR greater that 1+ is not accepted and is dealt with by additional repair or choral sparing mitral valve replacement. (Color version of figure is available online at http://www.us.elsevierhealth.com/optechstcvs/.)
Figure 9For mitral valve replacement, the exposure and setup are the same as for mitral valve repair. The anterior leaflet usually is split at its midpoint. The midportion of the anterior leaflet can be removed if it is bulky, but this is rare in ischemic MR. (Color version of figure is available online at http://www.us.elsevierhealth.com/optechstcvs/.)
Figure 10Pledgetted 2-0 braided sutures are placed with the pledgets on the atrial side. Sutures are placed so as to incorporate annulus and the leaflet, and act to plicate the chords to the annulus. (Color version of figure is available online at http://www.us.elsevierhealth.com/optechstcvs/.)
Figure 11A dental mirror is useful to determine the midpoint of the left ventricular outflow tract. The landmark for this is the left and noncoronary commissural post of the aortic valve. The struts of the bioprosthesis are oriented so that they straddle the outflow tract and do not impinge on it. This is accomplished by passing the sutures that lie in the middle of the left ventricular outflow tract between the struts on the valve. (Color version of figure is available online at http://www.us.elsevierhealth.com/optechstcvs/.)
Figure 12The bioprosthetic valve (bovine Carpentier-Edwards PERIMOUNT pericardial bioprosthesis [Edwards Lifesciences, Irvine, CA]) is carefully seated. Sutures are tied first at each of the struts, and then over the circumference of the valve. The holder is not removed until all sutures are tied. The atrium is closed and de-aired in the standard fashion. We avoid lifting the heart if a valve has been placed, especially in frail elderly patients. (Color version of figure is available online at http://www.us.elsevierhealth.com/optechstcvs/.)
Figure 13Completed valve replacement with struts straddling the left ventricular outflow tract. Note the position of the black marks on the valve sewing ring at 1230 and 0800 that mark the position of the valve struts and aid in orientation of the valve. (Color version of figure is available online at http://www.us.elsevierhealth.com/optechstcvs/.)
IMR is a serious problem. It is often associated with advanced coronary artery disease and diminished left ventricular function. We believe it warrants an aggressive treatment philosophy. It is important to completely eliminate MR in the operating room and to take measures to limit its recurrence. We feel that IMR is primarily a ventricular problem and is best dealt with by using a complete annuloplasty ring that fixes both the intertrigonal and septal-lateral dimension, and remodels the tethered P3 region. In those individuals with severe MR and a severely depressed left ventricle, a chordal sparing mitral valve replacement with a bioprosthetic valve is a reasonable alternative.
Ischemic mitral valve regurgitation grade II-III correction in patients with impaired left ventricular function undergoing simultaneous coronary revascularization.
Repair of ischemic mitral regurgitation does not increase mortality or improve long-term survival in patients undergoing coronary artery revascularization.
Survival after coronary revascularization, with and without mitral valve surgery, in patients with ischemic mitral valve surgery, in patients with ischemic mitral regurgitation.
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