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Interact CardioVasc Thorac Surg 2008;7:368-371. doi:10.1510/icvts.2008.175125 © 2008 European Association of Cardio-Thoracic Surgery
Papillary muscle realignment and mitral annuloplasty in patients with severe ischemic mitral regurgitation and dilated heartDepartment of Cardiovascular Surgery, Sakakibara Heart Institute, 3-16-1 Asahi-cho, Fuchu City, Tokyo 183-0003, Japan Received 4 January 2008; received in revised form 7 March 2008; accepted 9 March 2008
*Corresponding author. Tel.: +81-42-314-3111; fax: +81-42-314-3133.
Chronic ischemic mitral regurgitation (IMR) is one of the leading causes of congestive heart failure and death. It is controversial whether mitral annuloplasty (MAP) per se can improve the long-term survival because IMR has been considered a disease of the left ventricle. We reviewed our experience of papillary muscle realignment in conjunction with MAP in patients with IMR. Between September 2004 and October 2007, seven patients were treated with papillary muscle realignment and MAP with coronary bypass grafting. The mean age was 60.3±3.5 years. The mean number of distal anastomoses was 3.6±1.9. Procedural success without in-hospital complications was achieved in all cases, except one patient who had a stroke and another patient with prolonged ventilation. Echocardiographic examination revealed that postoperative coaptation depth (10.2±3.1 mm preoperatively vs. 6.5±2.0 mm postoperatively), tenting area (1.8±0.8 cm2 vs. 0.6±0.1 cm2), end-diastolic interpapillary muscle distance (36.4±4.7 mm vs. 27.1±4.6 mm) and the grade of MR (3.3±0.5 vs. 0.4±0.5) significantly improved. Furthermore, a six-month echocardiographic examination demonstrated that these improvements remained unchanged. The combination of papillary muscle realignment and MAP seems to be effective in patients with IMR. The duration of the effect may be expected to be long-term with these methods.
Key Words: Cardiomyopathy; Ischemic heart disease; Ischemic mitral regurgitation
Chronic ischemic mitral regurgitation (IMR) is one of the leading causes of congestive heart failure and death. Severe IMR has been considered to be best corrected at the time of CABG. The main method of repair of IMR has been ‘downsizing’ annuloplasty [1]. Although early postoperative results after downsizing annuloplasty have improved, long-term outcomes are not clear. More recently, Mihaljevic et al. reported CABG with mitral valve annuloplasty did not improve long-term functional status or survival in patients with severe IMR compared with CABG alone [2]. They also concluded that mitral valve annuloplasty (MAP) without addressing fundamental ventricular pathology is not sufficient to improve long-term clinical outcomes. It is the general consensus that IMR occurs not from the valve itself but from the left ventricular muscle. Infero-posterior infarction is more likely to cause IMR than anterior infarction [3]. Dislocation of the papillary muscle (PM) because of myocardial infarction is one of the factors causing IMR as well as annular dilatation. The dislocated PM then causes apical displacement and tethering of the mitral leaflets. Several additional procedures to annuloplasty have been proposed to secure leaflet coaptation, including secondary chordal cutting [4], infarct plication [5], PM imbrication [6], PM sling [7] and surgical relocation of the posterior PM [8]. We have employed PM realignment and MAP. This report consists of a review of our experiences, with echocardiographic evaluation after PM realignment.
2.1. Patient population Between September 2004 and October 2007, we performed CABG and MAP in 40 patients with IMR. Of these, seven patients underwent PM realignment as an adjunctive method to treat IMR. We have performed this procedure in patients with moderate to severe or severe IMR caused by leaflet tethering with left ventricular dysfunction. Preoperative patient characteristics are listed in Table 1. The age range was from 55 to 66 years (mean 60.3±3.5 years). The number of patients with New York Heart Association class III or IV was 4 (mean 2.7±0.8). The mean preoperative ejection fraction (EF) was 31.1±10.4%. All patients except one had inferior old myocardial infarction (MI) confirmed with cardiac scintigraphy. All patients had triple vessel disease.
2.2. Surgical technique The operation was performed through median sternotomy in all patients. Cardiopulmonary bypass and aortic cross-clamp was used in all patients. An arterial cannula was inserted via the ascending aorta and a venous cannula via both the superior and inferior vena cavae. Cardioplegic solution was administered in both antero- and retrograde fashion. Distal coronary anastomoses with the exception of the left anterior descending artery (LAD) were performed first. Secondly, papillary muscle realignment was performed (Fig. 1). Two or three mattress 3-0 polypropylene sutures with PTFE pledget were passed through the base and body of the anterior and posterior PMs. A deep bite was kept so as not to tear the muscles. We did not use this suture at the fibrous portion of the PM tip. We tied the sutures until both PMs came into contact with each other. Papillary muscle realignment was performed through a superior septal incision in all patients. A left ventricular incision was not done in any patient. Thirdly, MAP was performed with a semi-rigid ring in all patients (size 26 in five patients and 28 in two patients). Finally, anastomosis of the LAD with the left internal thoracic artery was done, followed by proximal anastomoses of free grafts to the aorta or internal thoracic artery.
2.3. Echocardiographic examination Two-dimensional imaging of the intracardiac structure and blood flow estimations were performed using HP Sonos (Hewlett-Packard Co, Andover, MA). Preoperative and early postoperative transthoracic echocardiography (TTE) was performed in all patients. Quantitative analysis was conducted by experienced echocardiographers and reviewed by two cardiologists. Mitral regurgitation was assessed using the color-flow Doppler method with TTE. The estimation of the MR grade was based on the size and the distance of the regurgitant jet. Mitral regurgitation was graded as none (0), trivial or mild (1), mild to moderate or moderate (2), moderate to severe (3) or severe (4). Tenting area (defined as the area enclosed by the mitral leaflets and the plane of the mitral annulus) and coaptation depth (defined as the distance between the mitral annular plane and the coaptation point of the mitral leaflets) was also measured. Furthermore, the effective regurgitant orifice area was calculated by the proximal isovelocity surface area method. Both diastolic and systolic inter-papillary muscle distances were measured as an evaluation of the papillary muscle realignment. The left ventricular short-axis view was used to measure the distance between the PMs. Follow-up echocardiographic examinations were performed in our outpatient clinic. Routine examinations were performed after six months and every year after operation. Medical records were reviewed and mortality and morbidity of each patient were determined. Postoperative complications included the following: myocardial infarction (new Q wave in the electrocardiogram or creatine kinase MB>10%), low cardiac output (a newly placed intra-aortic balloon pumping or the use of inotropes, dopamine or dobutamine, over 5 µg/kg/min), ventricular tachycardia or fibrillation, bleeding requiring re-exploration, stroke, respiratory failure (intubation time over 48 h), renal failure, and mediastinitis. Data are presented as mean±S.D. Continuous data were analyzed by the paired Student's t-test and discrete variables were compared by the  2-test or Fisher's exact test. Differences were considered statistically significant at P<0.05. Statistical analyses were performed using the StatView 5.0 software package (SAS Institute Inc., Cary, NC).
3.1. Clinical outcomes Seven patients underwent the PM realignment operation along with CABG and MAP. Intraoperative and postoperative data are listed in Table 2. The number of distal anastomoses per patient ranged from 2 to 7 (mean 3.6±1.9).
There were no in-hospital deaths. Postoperative atrial fibrillation was temporarily observed in three patients. Major complications occurred in two patients. The need for prolonged ventilation (72 h) was observed in one patient. Another patient suffered a postoperative permanent stroke. Mean in-hospital stay was 25.0±11.5 days. There have been no late deaths or cardiac events during the follow-up period (mean 14.8±7.0 months). 3.2. Echocardiographic evaluation Preoperative and early postoperative echocardiographic data were available for all patients. The mean duration between the operation and the early postoperative echocardiographic examination was 8.1±2.6 days (range 7 to 14 days). Preoperative and postoperative data are listed in Table 3. Both diastolic and systolic left ventricular volume were reduced postoperatively, however, this was not statistically significant. Coaptation depth and tenting area significantly improved as well as the grade of mitral regurgitation. Both diastolic and systolic inter-papillary muscle distances were reduced significantly.
Interval echocardiographic data were available in four patients. When preoperative and 6-month postoperative data were compared in these four patients, there was a significant difference in coaptation depth (10.0±2.4 mm vs. 6.0±2.0 mm, P=0.001), tenting area (1.7±0.7 cm2 vs. 0.5±0.2 cm2, P=0.024), diastolic inter-papillary muscle distance (39.3±4.3 mm vs. 24.0±7.1 mm, P=0.014), systolic inter-papillary muscle distance (31.8±4.0 mm vs. 21.3±5.6 mm, P=0.008) and the grade of MR (3.3±0.5 vs. 0.8±0.5, P=0.015), but there was no difference in diastolic left ventricular volume (214.3±62.9 ml vs. 168.0±50.3 ml, P=0.234) and systolic left ventricular volume (155.3±48.5 mm vs. 122.0±50.7 mm, P=0.176).
There has been a great debate among surgeons on surgical treatment of IMR. However, it is considered that moderate to severe or severe MR should be treated simultaneously with CABG. Recently, the cause of IMR has been explained by not only an annular dilatation but also a deformation of the left ventricle and subvalvular apparatus. Borger et al. detailed precisely the mechanism of IMR after MI in their review article [9]. Left ventricular distortion and remodeling after MI displaces PMs away from the mitral annulus. The displacement puts excessive tension on the chordae, resulting in apical mitral leaflet tethering, restricting their coaptation during systole. Once IMR is initiated, end-diastolic left ventricular volume and wall stress increase in tandem with preload. Increased wall stress causes more left ventricular dysfunction, which in turn results in further PM displacement and leaflet tethering. The longer the interpapillary muscle distance becomes, the further MR deteriorates. Chronic IMR begets MR in a self-perpetuating manner. Therefore, moderate to severe or severe MR should be repaired at the time of CABG in patients with left ventricular dysfunction. A number of mitral procedures have been performed to treat IMR. Mitral valve replacement should be considered only in patients with acute IMR and multiple comorbidities, complex regurgitant jets, or severe tethering of both mitral valve leaflets [9]. The most common technique for repair of IMR has been an undersized annuloplasty ring [1]. However, some reports revealed that a long-term survival benefit has not been realized with MAP [2]. Since the pathology of IMR is closely related to the subvalvular apparatus and infarcted ventricle, a downsized MAP per se has been considered to be insufficient. More recently, several surgical procedures on the subvalvular apparatus and left ventricle with or without MAP have been proposed to treat IMR. Borger et al. [4] reported that chordal cutting improved mitral valve leaflet mobility and reduced MR recurrence in patients with IMR. However, there is a skepticism about this operation because clinical experience is very limited. Several techniques of repositioning or relocation of PM have been developed. Lifting the PM toward the mitral annuals with or without a direct suture between the annulus and PM has been reported from some institutes [8]. The surgery was successfully performed and early results were acceptable. Another intervention in PM is approximation or realignment [6, 7, 10–13]. Reestablishing a more normal annulus-to-PM alignment was expected to relieve the excess tethering on the mitral leaflets, and significantly restore leaflet mobility [7]. Leaflet tethering is considered to be improved by shortening the distance between both papillary muscles. This leads to the improvement of MR. This method would modify the shape of the left ventricle from spherical to elliptical. We have also followed this concept. In the present and other studies, early clinical and echocardiographic results were favorable. In the present study, the severity of IMR was expressed by coaptation depth and tenting area. The coaptation depth has been used by Calafiore and colleagues as the parameter of the severity of IMR [14]. If this depth exceeded 10 mm, patients were considered poor repair candidates. In our study, patients had severe IMR by their definition because mean preoperative coaptation depth was 10.2±3.1 mm. Srichai et al. demonstrated that tenting area has also been a powerful independent predictor of the severity of IMR [15]. In their study, however, tenting area was measured by magnetic resonance imaging while echocardiographic measurement was used in our study. The assessment of the tenting area may not have matched between the studies. We believe the echocardiographic evaluation is more easily obtained and less invasive than magnetic resonance imaging. The correct distance between papillary muscles has never been established, however, Hvass et al. [7] described normal values of 2.5±0.3 cm in their report. We have measured diastolic and systolic values of inter-papillary muscle distance. These data significantly improved postoperatively. Furthermore, we found that the distance between PMs changed during the cardiac cycle even after this operation. The limitations of this clinical study are that the number of patients is small and the length of clinical follow-up was short. The major weakness of this study is that the follow-up echocardiography could be obtained in only four patients. Furthermore, there was no control group in this study. In conclusion, the combination of papillary muscle realignment and MAP seems to be an effective technique for patients with IMR. The duration of the effect may be expected to be long-term with these methods.
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Abstract
1. Introduction
