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J Thorac Cardiovasc Surg 2006;131:99-106
© 2006 The American Association for Thoracic Surgery
Surgery for Acquired Cardiovascular Disease |
Department of Thoracic and Cardiovascular Surgery, Johann Wolfgang Goethe University, Frankfurt/Main, Germany
Received for publication March 10, 2005; revisions received July 20, 2005; accepted for publication July 21, 2005. * Address for reprints: Tayfun Aybek, MD, Department of Thoracic and Cardiovascular Surgery, Johann Wolfgang Goethe University, Theodor Stern Kai 7, 60590 Frankfurt at Main, Germany (Email: Tayfun{at}Aybek.de).
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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METHODS: Between 1996 and 2003, 222 elective consecutive patients (58.1% males; age, 59 ± 14 years) underwent simple or complex mitral valve repair. Minimal invasive reconstruction was performed in 150 patients. For correction of annular dilatation, we used double-running 2-0 polytetrafluoroethylene sutures to reinforce the posterior circumference of the annulus. Patients were investigated prospectively by means of transthoracic echocardiography before discharge and 1 and 5 years after the operation. The mean follow up was 32 ± 21 months (range 1-77 months).
RESULTS: The operative mortality was 3.1%. Hemodynamic performance at 1 and 5 years showed low mean transvalvular gradients (2.1 ± 0.9 and 2.0 ± 0.8 mm Hg, respectively) and a calculated mitral valve orifice area of 3.3 ± 0.9 cm2 and 3.1 ± 0.6 cm2, respectively, with progressive annular dilatation from 31.2 ± 3 mm to 33.9 ± 4 mm at 1 year and 35.7 ± 4 mm at 5 years (P < .01). Clinical status improved from New York Heart Association class 3.0 ± 0.4 to 0.6 ± 0.8 at 1 year and 0.8 ± 0.8 at 5 years. Freedom form nontrivial residual mitral regurgitation was 82.3%, freedom from reoperation was 95.1% and actuarial survival was 87.2%, all at 77 months.
CONCLUSIONS: The midterm results show satisfactory hemodynamic performance and clinical improvement. Valve competence and reoperation rates are comparable with those of other reports. Durability of the mural annulus shortening suture procedure for mitral valve repair is questioned because progressive annular redilatation occurs.
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Mitral valve repair has been reported to be superior over valve replacement in terms of operative mortality,
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late survival,
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valve-related complications,
3,4
and preservation of mitral valve function and left ventricular performance.
5
The most common repair procedures are completed with annuloplasty that not only decreases the diameter of the annulus to increase leaflet coaptation but also reinforces the annulus to prevent future dilatation. In addition, the mitral valve annulus has a sphincter-like function that enlarges its area during diastole by 26%.
6
This physiologic flexibility is important for uncompromised left ventricular function and should be preserved in repair attempts. Flexible and partial rings have been introduced to maintain this physiology.
7,8
A similar strategy, reinforcement of the posterior mitral annulus with sutures, should create minimal rigidity of the mitral ring. In an attempt to avoid the drawbacks of prosthetic ring annuloplasty, like left ventricular outflow tract obstruction
9,10
or posterior leaflet movement restriction,
11
suture annuloplasty is still performed by some groups.
12-14
In 1990, Frater and Sisto
15
described the mural annulus shortening suture (MASS) technique for stabilizing the posterior mitral annulus, a modification of the Paneth-Burr annuloplasty reported earlier.
16
We adapted this technique and found excellent early results. The hemodynamic performance was superior after suture annuloplasty compared with that seen after rigid ring annuloplasty in the short-term follow-up, mainly because of the preservation of the intrinsic flexibility of the annulus.
17
The objective of this report was to assess the midterm durability of the MASS procedure and to present our 7-year experience regarding valve function, hemodynamic performance, and clinical outcome.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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In 150 patients minimally invasive mitral valve reconstruction was performed through the fourth intercostal space through a small right anterior thoracotomy incision (7 cm). In these patients the right femoral vessels were used for arterial and venous cannulation. In 15 patients the Port Access System was used (Heartport, Inc, Redwood City, Calif), including an endoaortic balloon catheter for aortic occlusion and aortic root venting. In 135 patients cardiac arrest was induced by using the technique first described by Chitwood and associates
18
using a transthoracic crossclamp (Scanlan International, Inc, Minneapolis, Minn) introduced through a 5-mm incision in the third right intercostal space.
As summarized in Table 2, concomitant leaflet procedures were necessary in most patients and were performed by using techniques described by Carpentier and coworkers.
19,20
The most common procedure was a quadrangular resection of the posterior leaflet. Operations considered complex mitral valve procedures were as follows: additional repair of the anterior leaflet, papillary muscles, or both; artificial chordae implantation; sliding plasty; pericardial patch reconstruction of the anterior leaflet; an additional operation on of the left atrium like volume reduction; the maze procedure; and combined procedures with tricuspid valve repair. Complex mitral valve procedures were performed in 79.7% of the patients.
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as an alternative to prosthetic ring implantation. A 2-0 expanded polytetrafluoroethylene (ePTFE) running suture (Gore-Tex, CV-2; W. L. Gore & Associates, Inc, Flagstaff, Ariz) was passed through the right fibrous trigone and forwarded as a semicircular running suture around the posterior annulus as far as the left fibrous trigone. The same suture was then stepped backward, passing the needle between the stitches of the first suture line and ending at the right fibrous trigone. In general, the amount of tissue compression caused by the running suture resulted in a ring size matching the size and form of the anterior leaflet. Varying the distance between stitches and further tightening or loosening enabled some adjustment of the mitral annulus size, leaving some place for slight overcorrection. Intraventricular injection of saline solution and intraoperative transesophageal echocardiography were performed in all patients to confirm mitral valve competence (5.0-MHz multiplane transducer, Vingmed System Vived Five ultrasound instrument; Vingmed Sound, Horton, Norway). The other surgical details, concomitant procedures, and mean operating, bypass, and aortic crossclamp times are shown in Table 2.
Postoperative Anticoagulation
All patients received warfarin at least for the first 6 postoperative weeks; the medication was discontinued in patients with sinus rhythm. In patients with atrial fibrillation, oral anticoagulation was maintained; however, medication during follow-up was at the discretion of referring cardiologists.
Follow-up and Echocardiographic Evaluation
Follow-up was prospectively and systematically collected by means of annual mailed questionnaires or telephone interview. Clinical and echocardiographic examination in our outpatient clinic was planned at 1 and 5 years after discharge. Functional status was determined according to NYHA classification.
For the purposes of the study, echocardiographic examination was performed intraoperatively, at discharge, and at 1 and 5 years after surgical intervention. Examination included 2-dimensional, M-mode, continuous-wave, continuous, and pulsed, as well as color, Doppler analyses. The examinations were performed with a 3.5-MHz transducer (GE Medical Systems, New Berlin, Wis). All evaluations were carried out according to standard techniques recommended by the American Society of Echocardiography.
21
Parameters obtained included mean mitral transvalvular gradient, mitral valve opening area as estimated by the pressure half-time method, degree of mitral valve regurgitation, mitral annulus diameter in 4-chamber view, and septolateral dimension during diastole, as well as left ventricular end-diastolic diameter. All parameters were measured 3 times to obtain a mean value by 2 experienced ultrasonographers. The severity of regurgitation was classified as trivial (degree I), mild (degree II), moderate (degree III), or severe (degree IV) and was assessed in a semiquantitative manner by means of color Doppler flow mapping. Morbidity and mortality are reported as currently recommended.
22
Data Analysis
Statistical analysis of the data was performed by using the StatView software package, version 5.0 (SAS Institute Inc, Cary, NC). The Student t test was applied to analyze normally distributed continuous data. Specific differences were isolated by using the Bonferroni correction for multiple comparisons. Values were expressed as means ± standard deviation. Survival and freedom from event probabilities were estimated with the standard nonparametric Kaplan-Meier method.
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Results |
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The mean operating, cardiopulmonary bypass, and aortic crossclamp times averaged to 242 ± 58 minutes, 143 ± 56 minutes, and 84 ± 33 minutes, respectively.
Four patients had possible damage of the circumflex artery intraoperatively, as suspected on the basis of electrocardiographic and transesophageal echocardiographic findings. Three (1.4%) of them had angiographically proved lesions of the circumflex artery. One of these patients had severe ischemia of the posterior wall in the early postoperative course, resulting in emergency coronary bypass grafting to the circumflex artery. The other 3 patients had increased serum cardiac enzymes in stable hemodynamic conditions. A minimally invasive approach was used for their procedures. These patients were clinically and hemodynamically stable and did not undergo an additional revascularization procedure.
Eight (3.6%) patients underwent valve replacement during a second pump run after failed mitral valve repair and moderate residual mitral regurgitation. All of them had complex repair attempts as annulus decalcification in 1 patient, restrictive anterior leaflet in 2 patients, and geometric coaptation problems after extensive resection of the posterior leaflet in 3 patients. Six of them were approached in a minimally invasive fashion; SAM was the reason for conversion to replacement in 2 patients. Altogether, we experienced systolic anterior motion (SAM) in 15 patients, as seen with intraoperative transesophageal echocardiography. In 9 of them, the phenomenon disappeared after volume substitution and cessation of inotropic management. Four of the remaining six (2.8%) were treated with additional repair.
On the third postoperative day, there was 1 embolic event associated with atrial fibrillation; this resulted in a permanent neurologic deficit. Thus far, there has been no additional thromboembolic event of any type.
Patient Survival and Clinical Follow-up
Two hundred two surviving patients were included in the follow-up. Patients with intraoperative valve replacements after failed repair were excluded. Patients were followed for a total of 573 patient-years. The mean clinical follow-up was 32 ± 21 months (range 1-77 months) and was complete in 97.1% of the surviving patients.
There were 6 late deaths. In 2 patients the reason for death remained unknown; 2 experienced sudden cardiac death. Other causes of death were severe pneumonia and lung cancer, respectively. Actuarial survival at 77 months, including early mortality, was 87.2% (Figure 1).
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Reoperation
Five (2.3%) patients required reoperation during follow-up. The causes were repair related in all cases, including annulus redilatation in all patients, additional prolapse of the posterior leaflet in 2 patients, and restriction of the posterior leaflet in 1 patient. All patients had initially minimally invasive mitral valve repair or primary imperfect results. At reoperation, all valves were repaired again except one. Overall freedom from reoperation was 95.1% at 77 months (Figure 2). The PTFE sutures remained in situ and within a thick strip of scar, and no detachment at the trigones could be observed. Ring dilatation occurred by straightening of the continuous suture.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Disadvantages seen with ring annuloplasty include impairment of overall annular contraction during systole and therefore left ventricular systolic function.
5,6
As reported by Van Rijk-Zwikker and coworkers,
24
a rigid ring significantly restricts the motion of the basal left ventricular wall as well. This finding has been confirmed in experimental settings by the Stanford group.
11
In contrast, the potential advantages of suture annuloplasty over ring annuloplasty are believed to include better preservation of overall annular motion, as well as a lack of effect on posterior leaflet mobility.
25
It avoids the possibility of distortion of the anterior leaflet, as well as pushing up a commissure. The costs of the procedure are reduced by avoiding an implant, and the risk of infection or hemolysis might be decreased.
In March 1996, semicircular suture annuloplasty was introduced in our institution as an alternative to prosthetic ring annuloplasty. This technique, known as the MASS procedure, was first reported in 1990 by Frater and Sisto.
15
It should offer flexibility to the mitral annulus and preserve the physiologic function and geometry of the mitral valve while stabilizing the annulus, as well as reducing the mitral orifice to the same size as the anterior leaflet. We have modified this technique by using ePTFE (Gore-Tex) sutures instead of polypropylene sutures. In contrast to polypropylene sutures, the ePTFE suture allows tissue ingrowth, potentially ensuring long-term durability. Others have come to the same finding.
26,27
The correct size of the mitral annulus was determined by varying the distance between the stitches and varying the tension, although in general the running suture, limited by tissue compressibility, matched the ring size to the size of the anterior leaflet. Mostly, diameter reduction appeared sufficient after completing one circumference of the suture line. When necessary, the second line could further tighten the ring. In fact, secondary readjustment of the suture after testing with intraventricular injection of saline solution was only exceptionally necessary in our hands. In contrast to our first impression, this technique is not a means to completely avoid SAM situations.
Our early results
17
showed superior hemodynamic performance after the MASS procedure over ring annuloplasty in terms of mean valve gradients and mitral valve opening areas. As the etiology of the groups operated on either by using sutures or ring annuloplasty was different, we preferentially implanted prosthetic rings in ischemic or secondary mitral incompetence due to ventricular dilatation. Thus, the homogeneity of the groups was lost. Therefore we could not include comparative follow-up data in this report. However, the persistence of satisfactory hemodynamic performance was confirmed by the 1- and 5-year follow-up echocardiographic examinations and might be due to preservation of the flexibility and physiologic function of the mitral valve.
The operative mortality rate of 3.1% is well comparable with rates cited in the literature.
19,20
In 3 patients functional occlusion of the circumflex artery was proved by means of postoperative angiography. Two of them had an anomalous course of the circumflex artery and extensive anterior commissure resection, respectively. Bulking of the tissue between the mitral annulus at the P1 segment and the base of the left atrial appendage might well be associated with a higher incidence of left circumflex artery injury. Concomitant exclusion of the left atrial appendage also bears this risk. However, we have observed circumflex occlusion in a pediatric patient with partial suture annuloplasty. By this, we attribute this complication to suture annuloplasty. To our knowledge, this complication with the MASS procedure has not been reported elsewhere yet. However, there are reports of a significantly higher incidence of myocardial ischemia after mitral repair (5.4%) in comparison with replacements (0%) in a series on 335 patients.
28
All of the ischemic events involved the inferior wall. The authors attributed this complication to air embolism at the time of testing valve competence with saline injection into the left ventricle.
We used a minimally invasive approach in 150 patients through a right-sided minithoracotomy. Although being technically more demanding, operative times were not prolonged. Suture annuloplasty might be a technique that is simpler to perform in minimally invasive mitral valve surgery. Annulus stabilization is performed by using a single running suture with less need for knot tying as required for prosthetic ring implantation. In 8 patients we detected unacceptable residual mitral regurgitation intraoperatively. All underwent complex mitral valve repair, and 6 of them had a minimally invasive approach. Intraoperative secondary valve replacement might be as well attributable to the learning curve for the limited approach.
In our study the patients had predominantly a degenerative cause of mitral regurgitation. Degenerative valves have been shown to have the best perioperative outcomes and superior midterm and long-term repair prognoses in comparison with valves with other causes of mitral regurgitation. To date, 5 (2.3%) patients have returned for reoperation because of progressive valve regurgitation. They all had primarily nontrivial regurgitation.
Overall, freedom from nontrivial mitral regurgitation was 83.2% at 77 months after the operation, a score not comparable with best results from ring annuloplasty.
19,20
In addition, we found significant and progressive postoperative mitral annulus dilatation in the years of follow-up. These facts have raised some doubts about the durability of the procedure. There are insufficient data to make a definite statement regarding the durability of this procedure, and a longer follow-up is warranted. Deloche and associates
20
reported an early reoperation rate of 4.3%, whereas Galloway and coworkers
29
noted a rate of reoperation of 2.9% with the Carpentier-Edwards annuloplasty ring, which is comparable with our results. The lack of ring annuloplasty was found by Cohn and colleagues
30
to be a risk factor for reoperation. Overall freedom from reoperation was 95.1% at 77 months.
Most of our patients undergoing reoperation had annular dilatation and recurrent changes of the leaflets. Stable annuloplasty reduces mitral valve area to less than natural size. As load calculates from pressure by area, stable annuloplasty should constantly reduce leaflet stress. Therefore in the meantime we changed our technique and use a partial flexible prosthetic band.
In conclusion, the present study demonstrates that by reinforcing the mitral ring with a suture annuloplasty, similar perioperative results as with prosthetic ring implantation can be achieved. Transvalvular gradients are consistently low, and midterm stability of repair and reoperation rates are comparable with those seen in other series. Continuous redilatation of the annulus raises concerns about further long-term stability. Additionally, there is an increased risk of circumflex artery injury. The present study suggests that the MASS procedure might not be a durable annular remodeling technique. At midterm, the majority of repairs do not depend on a stable ring size reduction.
| See related editorial on page 9.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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