Standard techniques of monitoring (arterial line, central venous access, Foley catheter...) are used in patients undergoing a combined mitral valve reconstruction and coronary bypass grafting. A Swan-Ganz catheter should be inserted in every patient. Initially a transesophageal echocardiogram should be performed. It is a key element to determine the functional type of mitral regurgitation and to assess left ventricular size and function. At the completion of cardiopulmonary bypass, it allows the surgeons to assess the quality of valve reconstruction, to detect residual air in left side cavities, and to monitor ventricular filling. An epiaortic scan of the ascending aorta is recommended to rule out the presence of atherosclerotic lesion prior to arterial cannulation.
Surgical approaches, cardio pulmonary bypass, and myocardial protection
Median sternotomy is the surgical approach of choice in patients undergoing combined mitral valve reconstruction and myocardial revascularization. In reoperative setting ( e.g. mitral valve surgery after previous coronary artery bypass grafting), a right thoracotomy approach is a viable alternative. Femoral vessels exposure is recommended if severe mediastinal adhesions are suspected (recent reoperation, multiple previous sternotomies, mediastinitis, and mediastinal radiation) and in patients with patent left internal mammary graft. Mitral valve surgery is classically performed with cannulation of both vena cava and the aorta, intermittent antegrade or a combined antegrade and retrograde cardioplegic arrest with cold blood high potassium cardioplegia for myocardial protection. Further myocardial protection can be obtained by moderate systemic hypothermia between 28-30oC and local hypothermia with topical ice.
Exposure of the mitral valve and valve analysis
Following completion of coronary bypass grafting, the perfect exposition of the mitral valve is essential before undertaking any type of mitral valve surgery. The most commonly used approach is the interatrial approach through the Sondergaard's groove.
The valvular apparatus is inspected and then examined with a nerve hook in order to assess tissue pliability and to identify the functional type of mitral regurgitation. The anterior paracommissural scallop of the posterior leaflet (P1) constitutes the reference point. Applying traction to the free edge of other valvular segments and comparing them to P1 determines the extent of leaflet prolapse in patients with papillary muscle rupture. This technique is, however, not very reliable to assess the severity of leaflet tethering in the arrested heart. The presence and severity of annular dilatation/deformation is also evaluated. In postero-lateral myocardial infarction, this dilatation is asymmetrical, involving mostly the p2, p3 and posterior commissural area. In antero-septal infarction, the annulus is symmetrically dilated.
Mitral valve reconstructive Surgery
Type I mitral regurgitation
Type I mitral regurgitation is best treated with a remodeling annuloplasty. The ring is downsized by one size.
Type II mitral regurgitation
Mitral valve replacement with the preservation of the subvalvular apparatus is the surgical treatment of choice in patients with complete rupture of a papillary muscle.
Papillary muscle reimplantation can be attempted in selected patients, provided that necrosis of the supporting myocardial wall is limited and in the absence of akinetic or dyskinetic wall. The non-prolapsed area of the valve serves as a reference point to determine the site and level of implantation of the papillary muscle remnant. At this site a 5mm deep trench is created in the muscular wall. The papillary muscle remnant is trimmed in order to preserve only the fibrous cuff. The papillary muscle remnant is buried in the trench using interrupted 4/0 polypropylene sutures. The trench is then closed around the papillary muscle remnant using a figure of eight suture. The procedure should be completed with a remodeling annuloplasty.
Elongated papillary muscle can be treated by its plication or resection of its extra length followed by reconstitution of the continuity of the remaining segments. The procedure is completed with a slightly downsized ring annuloplasty to reduce the tension on the reconstructed valve. If the papillary muscle is too thin and the anatomic conditions are not favorable, mitral valve replacement should be preferred.
Type IIIb mitral regurgitation
Remodeling annuloplasty using a downsized ring is the technique of choice in type IIIb dysfunction. The goals of valve reconstruction are: preserving leaflet mobility, restoring a large surface of coaptation by reducing the septo-lateral dimension, and stabilizing the annulus to ensure long-term stability.
From Carpentier A, Adams DH, Filsoufi F. Carpentier's Reconstructive Valve Surgery. Saunders (Elsevier), 2010
The prosthetic ring should be downsized by one size or two sizes depending on the severity of leaflet tethering. The use of double-row annuloplasty suture technique is recommended to reduce the risk of ring dehiscence.
From Carpentier A, Adams DH, Filsoufi F. Carpentier's Reconstructive Valve Surgery. Saunders (Elsevier), 2010
Additional procedure such as the resection of a large aneurysm or dyskinetic plaque may be necessary to enhance the results of valve reconstruction.
During the last decade, adjunct techniques including the closure of the indentation between p2-p3 segments, resection of secondary chordae, patch extension of the posterior leaflet and papillary muscle sling have been described to minimize the risk of residual or recurrent mitral regurgitation. Clinical experience with these procedures remains limited and there are no long-term data available.
Finally, it is important to stress that in selected patients particularly those with severe bileaflet tethering and enlarged left ventricle with an end diastolic diameter greater than 65 mm, mitral valve replacement with a bioprosthesis may be the surgical procedure of choice.
The results of the operative procedure depends on the acuity of the presentation, the functional type of mitral regurgitation and valvular lesions, and the ventricular function.
Operative mortality in patients with type II dysfunction and papillary muscle rupture who require an emergent operation has traditionally been high. During the last two decades, significant advances in the perioperative management of these patients have significantly contributed in reducing the operative mortality to 10-15%. Concomitant coronary revascularization at the time of mitral valve surgery has also been identified as a key factor in improving long-term outcomes. Major postoperative complications such as respiratory failure, stroke or renal failure requiring dialysis occur in about 20 % of patients. Late results including long-term survival (about 70% at 7 years) and quality of life are good among these patients. This is mainly explained by the fact that the size of the myocardial infarction is often limited and the overall left ventricular function is preserved at the time of initial presentation.
Operative mortality in patients with type IIIb chronic mitral regurgitation undergoing a combined mitral valve reconstruction and coronary bypass grafting is less than 4 % in experienced centers. The surgical outcomes for this group of patients have also dramatically improved during the last two decades.
Advanced age, extensive coronary artery disease, prior myocardial infarction and severely depressed left ventricular function are predictors of early mortality. Respiratory failure and stroke are the most serious postoperative complications among these patients affecting long term survival. Several clinical studios have reported a 5-year survival of 60 to 70 % in these patients. Left ventricular size and function are among the strongest predictors of long term outcome. The addition of left ventricular aneurysmectomy to the procedure also affects negatively long-term survival.
In patients with type IIIb dysfunction, the persistence of mitral regurgitation following an annuloplasty has been incriminated as a risk factor compromising late results. Several studies have shown that the type of annuloplasty plays a key role in the incidence of this complication. The rate of residual mitral regurgitation is significantly higher after annuloplasty using flexible bands or rings than after the implantation of a remodeling ring. Another possible explanation for residual mitral regurgitation is inadequate downsizing. The anteroposterior dimension of the annulus must be aggressively reduced to bring the tethered posterior leaflet close enough to the anterior leaflet to allow adequate coaptation. Other possible mechanisms for residual regurgitation include unsuspected mild prolapse and enlarged posterior leaflet indentations in patients with severe leaflet tethering. The significant impact of even mild degrees of residual mitral regurgitation on survival should challenge surgeons to make every effort to minimize the incidence of this complication following mitral annuloplasty.
The recurrence of mitral regurgitation has also been identified as a risk factor impacting long term outcome. This is mostly due to the continuous process of ventricular dilatation which produces severe leaflet tethering and subsequently recurrent mitral regurgitation. Several echocardiographic variables such as depth of coaptation, tenting height, tethering area, and posterior leaflet angle have been used to predict long-term durability of valve repair. In patients at risk (coaptation depth greater than 11mm, tethering area greater than 22mm2, posterior leaflet angle greater than 45 degrees), some have advocated the use of adjunct techniques such as posterior leaflet extension or papillary muscle slings to minimize the risk of recurrent mitral regurgitation. In selected patients, mitral valve replacement with a bioprosthesis is an acceptable alternative.
Carpentier A. Cardiac valve surgery--the "French correction". J Thorac Cardiovasc Surg1983;86(3):323-337
Carpentier A, Adams DH, Filsoufi F. Carpentier's reconstructive valve surgery. Philadelphia, Elsevier (Saunders), 2010
Adams DH, Filsoufi F, Byrne JG, et al. Mitral valve repair in redo cardiac surgery. J Card Surg 2002;17(1): 40-5
Bax JJ, Braun J, Somer ST, et al. Restrictive annuloplasty and coronary revascularization in ischemic mitral regurgitation results in reverse left ventricular remodeling. Circulation 2004;110(11 Suppl 1):II103-II108
Daimon M, Fukuda S, Adams DH, et al. Mitral valve repair with Carpentier-McCarthy-Adams IMR ETlogix ring for ischemic mitral regurgitation: Early echocardiographic results from a multi-center study. Circulation 2006;114(I Suppl):I588-93
Messas E, Pouzet B, Touchot B, et al. Efficacy of chordal cutting to relieve chronic persistent ischemic mitral regurgitation. Circulation 2003;108 Suppl 1:II111-115
Kron IL, Green GR, Cope JT. Surgical relocation of the posterior papillary muscle in chronic ischemic mitral regurgitation. Ann.Thorac.Surg 2002;74(2):600-601
Hvass U, Tapia M, Baron F, et al. Papillary muscle sling: a new functional approach to mitral repair in patients with ischemic left ventricular dysfunction and functional mitral regurgitation. Ann Thorac Surg 2003;75(3):809-811
Gillinov AM, Wierup PN, Blackstone EH, et al. Is repair preferable to replacement for ischemic mitral regurgitation? J Thorac Cardiovasc Surg 2001;122:1125-41
Grossi EA, Goldberg JD, LaPietra A, et al. Ischemic mitral valve reconstruction and replacement: comparison of long-term survival and complications. J Thorac Cardiovasc Surg 2001;122:1107-24
Tavakoli R, Weber A, Vogt P, et al. Surgical management of acute mitral valve regurgitation due to post-infarction papillary muscle rupture. J Heart Valve Dis 2002;11:20-6
Filsoufi F, Aklog L, Byrne JG, et al. Current results of combined CABG and mitral annuloplasty in patients with moderate ischemic mitral regurgitation. J Heart Valve Dis 2004; 13(5): 747-753
Filsoufi F, Castillo JG, Rahmanian PB, et al. Anuloplastia remodeladora mediante un anillo especifico para la reparacion de la regurgitacion mitral isquemica de tipo IIIb. Rev Esp Cardiol 2007;60(11):1051-8
Braun J, Bax JJ, Versteegh MI, et al. Preoperative left ventricular dimensions predict reverse remodeling following restrictive mitral annuloplasty in ischemic mitral regurgitation. Eur J Cardiothorac Surg 2005; 27(5):847-853
Klein P, Bax JJ, Shaw LJ, et al. Early and late outcome of left ventricular reconstruction surgery in ischemic heart disease. Eur J Cardiothorac Surg 2008;34(6):1149-57
Ciarka A, Braun J, Delgado V, et al. Predictors of mitral regurgitation recurrence in patients with heart failure undergoing mitral valve annuloplasty. Am J Cardiol 2010;106(3):395-401