|Year : 2002 | Volume
| Issue : 4 | Page : 5
New Ideas About Atrial Fibrillation 50 Years On
Michele De Bonis1, Elisabetta Lapenna1, Ottavio Alfieri2
1 Division of Cardiac Surgery, San Raffaele University Hospital, Milan, Italy
2 Professor and Chairman, Division of Cardiac Surgery, San Raffaele University Hospital, Milan, Italy
|Date of Web Publication||22-Jun-2010|
Ottavio Alfieri, MD, Department of Cardiac Surgery, San Raffaele Univ. Hospital, Via Olgettina 60, 20132, Milano
Source of Support: None, Conflict of Interest: None
| Abstract|| |
The "edge-to-edge" is a relatively new technique to treat mitral regurgitation. First introduced in 1991, it has been widely used in patients with severe mitral regurgitation due to complex lesions requiring demanding surgical techniques for correction or with expected low chances of successful repair. This alternative surgical approach consists of anchoring the free edge of the diseased leaflet to the corresponding edge of the opposing leaflet. Because of its effectiveness and durability, the "edge-to-edge" technique can be a useful addition to the surgical armamentarium in mitral valve reconstruction. Indications, results, controversies and future perspectives of this type of repair are discussed.
Keywords: mitral regurgitation, mitral valve repair, edge-to-edge technique
|How to cite this article:|
De Bonis M, Lapenna E, Alfieri O. New Ideas About Atrial Fibrillation 50 Years On. Heart Views 2002;3:5
| Introduction|| |
Since the introduction by Carpentier and coworkers, mitral valve repair has become the preferred treatment of mitral regurgitation (MR) because of its superior results over valve replacement  . Surgical techniques for correcting mitral regurgitation have evolved to address a wide spectrum of mitral disease providing durable and predictable results in most patients , . However, anterior mitral leaflet defects, bileaflet prolapse, commissural lesions, MR in presence of annular calcification, ischemic mitral insufficiency and MR due to restricted leaflet motion, still represent challenging mitral pathology for which a conventional conservative approach can be technically demanding and/or associated with suboptimal results ,,,,.
To extend the feasibility of reconstructive mitral valve surgery to such a complex group of mitral defects, we introduced in the early nineties a simple and effective surgical technique called "edge-to-edge", which consists of anchoring the free edge of the diseased leaflet to the corresponding edge of the opposing leaflet, just at the site of the regurgitant jet , . When the jet of regurgitation is located in the central part of the mitral valve, the application of the "edge-to-edge" technique produces a double orifice valve configuration. On the other hand, when the mitral lesion is commissural, the plication of this area creates a single orifice mitral valve with a relatively smaller area.
The surgical techniques, indications, results and controversial issues of the "edge-to-edge" technique are reported and discussed in this review.
| Surgical technique|| |
The "edge-to-edge" mitral-valve repair is performed during total normothermic cardiopulmonary by-pass, through a conventional midline sternotomy. Recently a minimally invasive approach has been used with Heart-port cannulation and a small right thoracotomy (15 pts) or with the adoption of Robotic technology (3 pts). Myocardial protection is accomplished by intermittent antegrade cold-blood cardioplegia; retrograde cardioplegia is associated only in presence of aortic regurgitation. After dissection of the interatrial groove, the mitral valve is approached through the left atrium and carefully inspected. Once the prolapsing or flailing segment of one or both leaflets is identified, the free edge of the diseased leaflet is anchored to the corresponding edge of the opposing leaflet with a 4-0 polypropylene running suture.
When the mitral defect (prolapse, flail, edge erosion, restricted motion) is located in the middle portion of the leaflet, the "edge-to-edge" technique creates a double orifice valve [Figure 1]. In this case, it is mandatory to identify correctly the middle portion of the leaflets to avoid valve distortion and residual leakage. The subvalvular apparatus is inspected with a nerve hook and the chordae connected to the anterolateral and posteromedial papillary muscles are identified: the convergence point of the two groups of chordae is defined as the middle portion of each leaflet. A stay stitch is placed at this site through both the anterior and posterior leaflets and the symmetry of the two orifices created is immediately checked. A running suture is then passed in a standardized manner along the whole free edge of the middle scallop of the anterior and posterior leaflets (A2-P2) to complete the repair.
Minimal technical modifications are adopted according to the single case anatomy and pathology.
In Barlow's disease, for instance, big bites should be taken to enhance the strength of the repair and reduce the leaflets height in the middle of the double-orifice valve. In the presence of flail segments, on the other hand, the position of the stitch may be somewhat asymmetric, corresponding to the center of the flail portion of the leaflet. Finally, if the mitral valve area is relatively small, as in the case of rheumatic or ischemic mitral disease, a shorter running suture should be placed to avoid the risk of stenosis.
After reconstruction, the residual mitral area is always measured by introducing Hegar valve dilators into the orifices: a global valve area of more than 2.5 cm2 is usually considered acceptable for "normal size" patients. Competence is evaluated by forceful saline filling of the left ventricle.
When the mitral valve lesion is localized in the proximity of a commissure, its surgical correction by the "edge-to-edge" technique results in a valve with a single orifice but a smaller area: this is usually defined paracommissural repair [Figure 2].
Transesophageal echo-Doppler reassessment of the valve is routinely performed after weaning from cardiopulmonary by-pass with the measurement of the planimetric area, Doppler-derived effective orifice area, transmitral flows and competence analysis.
| Indication|| |
The "edge-to-edge" technique can be used for the correction of different complex mitral valve lesions. Since its application always decreases the original mitral valve area of about 50%, the main indication for the "edge-to-edge" technique is the degenerative mitral regurgitation with anterior or bileaflet prolapse typical of Barlow's disease, where the mitral valve area is usually larger than 7 cm2  . In patients with the severe form of this pathology, all the components of the mitral valve apparatus are involved by myxomatous degeneration, which eventually lead to severe generalized prolapse of both the anterior and posterior leaflets. In such context, a conventional anatomical reconstructive approach would require a long operation addressing the multiple mitral defects at annular, valvular and subvalvular level. This type of correction, although successfully performed by many experienced surgeons, is technically demanding, not easily reproducible and results are sometimes suboptimal. The "edge-to-edge" technique, on the other hand, allows a standardized correction of this complex condition just by suturing the middle scallop of the anterior and posterior leaflet (A2 to P2) followed by ring annuloplasty: The aim is to have a post-repair mitral valve area of at least 2.5 cm2 in patients with normal body surface. This simple, standardized and easily reproducible surgical technique allows the effective treatment of multiple and generalized anatomical mitral defects. It is a new functional approach rather than a conventional anatomical correction.
In degenerative mitral valve disease the mechanism of the regurgitation is mainly the prolapse whereas in ischemic and rheumatic mitral disease, restricted leaflet motion of one or both leaflets is usually responsible for the incompetence of the valve. In those conditions, the "edge-to-edge" approach has been successfully used as a double orifice technique in case of central regurgitant jet or as a paracommissural "edge-to-edge" repair when the site of regurgitation was located in correspondence of a commissure, usually the postero-medial.
In ischemic mitral insufficiency due to tethering of the leaflets, valve repair with an undersized annuloplasty is effective in most cases. However, in our experience, to enhance the likelihood of a successful and durable correction, a central or paracommissural "edge-to-edge" can be added placing the approximating stitch according to the location of the regurgitant jet as seen on echocardiography.
In selected cases of rheumatic mitral regurgitation, the "edge-to-edge" technique can be used as well, but careful judgment is required to avoid the potential risk of inducing a mitral stenosis.
Finally, a new emerging indication for the "edge-to-edge" technique is functional mitral regurgitation secondary to dilated cardiomyopathy. The severe left ventricular enlargement produces a tethering effect on the mitral leaflets, which is responsible for significant mitral insufficiency. The regurgitant jet is usually central in location as seen on echocardiography. Indeed, in very large hearts or in the presence of severe valve deformity, annuloplasty alone, even though undersized, might not be sufficient to guarantee a long lasting effective mitral correction. A possible alternative to MV replacement in such context could the addition of a central edge-to-edge repair to a slightly undersized annuloplasty. In case of excessive tethering, the edge-to-edge approach could force coaptation of the leaflets, stabilizing the repair and reducing the incidence of early and mid-term failure. Preliminary experience with this strategy has produced encouraging results but longer follow-up is obviously needed.
| Clinical experience|| |
From 1991, out of 1478 consecutive patients with pure MR undergoing valve surgery, 1403 (94.9%) were submitted to valve repair at our institution. The "edge-to-edge" technique was adopted in 619 cases (44.1%) [Table 1], [Table 2]. So far the mean follow-up is 2.8 + 2.0 years (range 1 month - 11 years), with a cumulative follow-up of 797 pt/year.
The double orifice repair was carried out in 483 pts (78.1 %), while the paracommissural repair was performed in 136 pts (21.9 %). In most of the cases, the technique has been used for degenerative mitral regurgitation (78%), whereas in the remaining 22% of patients it has been successfully adopted for the treatment of ischemic, endocarditic and rheumatic lesions. Indeed the "edge-to-edge" technique can be equally effective in both type II and III mitral regurgitation according to Carpentier's classification.
In 75 % of the patients, the "edge-to-edge" technique alone was sufficient to correct MR whereas, in one fourth of the patients, additional reconstructive procedures (leaflet resection, artificial chordae implant, patch repair of perforation, chordal transposition etc.) were concomitantly performed as indicated.
The simplicity of this approach makes it possible to perform complex mitral valve repair with very short cross-clamp times, which is one of the main determinant of the operative result. In our experience, mean cardiopulmonary by-pass time and aortic cross clamp time were 54 ± 13.8 min and 39 ± 6.7 min, respectively. Excluding patients undergoing associated cardiac procedures, mean cardiopulmonary by-pass and ischemic times were 47 ± 9.1 min and 33 ± 3.9 min.
The overall hospital mortality was 0.9% and the freedom from reoperation 91+ 2.7% at 5 years [Figure 3]. No patients required late reoperation for mitral valve stenosis. Freedom from reoperation was 91% ± 3.4% at 5 years in the degenerative disease group; 76% ± 12.9% in the rheumatic group and 96% ± 4.1 % in the endocarditis group. No patient with ischemic etiology of MR required reoperation during the follow-up period (p=0.04) [Figure 4]. According to the results reported by other authors, the durability of the repair in case of rheumatic mitral disease has been the lowest compared to any other etiology. This can be explained by the severe anatomical abnormalities of the valvular and subvalvular apparatus present in the rheumatic mitral valve and by the progression of such a chronic disease, which jeopardizes the durability of any mitral reconstruction.
There was no significant difference in freedom from reoperation when the different mechanisms of MR were considered.
Considering the unfavorable anatomical features and the complexity of the mitral valve lesions of the patients selected for the "edge-to-edge" correction, we believe that the reported results are very satisfactory.
Functional status at latest follow up was obtained in 329 patients: 225 patients (69 %) were in NYHA class I; 80 (24 %) were in class II; 20 (6 %) were in class III and 4 (1 %) were in class IV. No important mitral valve dysfunction was documented in patients with persisting symptoms.
| Controversial issues|| |
The opportunity to combine an annuloplasty procedure to every "edge-to-edge" repair has been debated for many years, particularly because of the potential risk of stenosis. Based on our experience, we would recommend to add an annuloplasty to the "edge-to-edge" repair whenever possible. We believe that the annuloplasty stabilizes the reconstruction reducing the stress on the "edge-to-edge" suture and increases the coaptation surface of the leaflets enhancing the competence of the valve. Moreover, the possibility of subsequent annular dilatation is prevented by the annuloplasty and this can potentially improve the long-term results of the mitral correction. Indeed, a ring or pericardial annuloplasty has been combined to the "edge-to-edge" technique in more than 80% of our cases. In the remaining 20%, it has not been performed either for the presence of severe annular calcification or because of the small size of the mitral valve area to avoid the risk of stenosis. The Kaplan-Meier freedom from reoperation in our experience has been 92+3% at 5 years in the presence of annuloplasty and 79+10% when the annuloplasty was not associated to the "edge-to-edge" technique (p=0.02) [Figure 5]: this statistically significant difference confirms its importance for the effectiveness and durability of the repair.
When the "edge-to-edge" technique is adopted as a double orifice repair, the morphology of the mitral valve becomes that of a double orifice valve, which raises several controversial issues. In particular, a matter of concern is the possible implication of a non-physiological mitral orifice configuration on the hemodynamics of the valve during ventricular filling. Moreover, the distribution of the trans-mitral flow through the two orifices, which can be of significantly different sizes, has generated doubts regarding the assessment of mitral valve hemodynamics with Doppler. A computational model, together with clinical experience, however, has clearly demonstrated that the double orifice configuration of the valve does not have any influence on mitral hemodynamics, which depends exclusively on the total valve area and on the cardiac output  .
In double-orifice valve configuration, the velocity of the flow through each orifice is very similar to the one observed through a single orifice valve area whose area equals the sum of the areas of the two orifices. Moreover, the flow velocities through the two orifices are exactly the same, even when the orifice sizes are significantly different, which means that the Doppler sampling of any of the two orifices is sufficient to assess the hemodynamic of the mitral valve. Our clinical experience confirms these findings: in a series of ten patients, previously submitted to double orifice repair, in sinus rhythm, the velocities recorded at each orifice by Doppler examination did not differ by more than 5%.
Therefore, the hemodynamic performance of a double-orifice mitral valve is the same of that of a single orifice of equivalent effective orifice area; the ratio between the orifice areas does not influence the hemodynamic of the valve and Doppler-derived velocities are a good indicator of pressure loss through the valve.
The risk of increased thromboembolic complications due to the higher flow turbulence generated by the double orifice configuration has been postulated: we do not have in our experience any evidence supporting such a concern.
Another major concern regarding this type of repair was the potential for creating functional mitral stenosis, especially with exercise. Low mitral gradients have been measured at rest in patients at short to medium-term follow-up  . However no data were available on the hemodynamics of the double orifice valve under stress conditions. To address this issue, we performed an exercise echocardiographic study to evaluate valve function and hemodynamics in patients who underwent central double orifice mitral repair.
| Exercise echocardiographic evaluation of double orifice mitral valve reserve.|| |
Thirty patients submitted to double orifice mitral valve repair for degenerative mitral regurgitation were randomly taken from our database. A ring annuloplasty had been associated in twenty-eight cases (93%). Time from surgery was 2 + 0.6 years. At rest none of them had residual mitral regurgitation (degree > moderate), atrial fibrillation, left ventricular dysfunction (left ventricular ejection fraction < 40%) and severe pulmonary hypertension (systolic pulmonary pressure > 45 mmHg). All were asked to undergo bicycle ergometer stress test. Exercise testing was performed in supine position increasing the workload of 10 watts per minute until at least 80% of the predicted heart rate was reached or until symptoms occurred. The echocardiographic exam was performed at baseline and at peak of the stress. During exercise, blood pressure, heart rate and cardiac output significantly increased. The mitral valve area was derived by planimetry of each single orifice in parasternal short axis view. The total mitral valve area was calculated as the sum of the two individual geometric orifice areas. The planimetric valve area increased from 3.5 + 0.7 cm2 to 4.4 + 0.8 cm2 (p=0.0003), peak mitralgradient from 6 + 3.1 mmHg to 11 + 5 mmHg (p=0.001) and mean gradient from 3 + 1.6 mmHg to 4 + 2.1 mmHg (p=0.002). The systolic pulmonary artery pressure increased as well but remaining in a normal physiologic range (from 22 + 6.4 mmHg to 28 + 11.2 mmHg, p=0.03). The data collected in this study show that during physical exercise the mean transmitral gradient after double orifice mitral valve repair remains below 5 mmHg and the peak transmitral gradient does not exceed 10 mmHg. Moreover, the pulmonary pressure does not increase up to pathologic levels and the mean planimetric mitral valve area at peak of the stress is more than 4 cm2. Therefore the artificially created double orifice valves follow a physiologic behavior during physical exercise, showing a good valvular reserve in response to the increased cardiac output. Functional mitral stenosis does not develop either at baseline or under stress conditions even with concomitant ring annuloplasty.
| Conclusions|| |
We strongly believe that the "edge-to-edge" technique can be a very useful addition to the surgical armamentarium in mitral valve reconstruction. It can be particularly effective in the following situations: Barlow's disease (as a double-orifice technique), ischemic mitral regurgitation (central or paracommissural edge-to-edge), and mitral regurgitation due to commissural lesions. Mitral regurgitation with severe annular calcification when decalcifying would be too risky. It can be applied as well in selected cases of endocarditis and rheumatic disease. Functional mitral regurgitation secondary to advanced dilated cardiomyopathy is a new emerging indication.
This technique has been shown to be reproducible with effective long-term results  . Reliability and simplicity are the main advantages of the "edge-to-edge" technique and has led to its application in minimally invasive and robotic assisted mitral surgery. The next step forward would be application of the technique in beating heart mitral repair, possibly percutaneously. Specific devices have been designed for this purpose and preliminary experience in experimental animal setting have been successfully performed. The non-surgical application of this approach is only a matter of time.®
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2]