Mitral valve repair using a flexible and adjustable annuloplasty ring

Development of In-Vitro Evaluation System for Annuloplasty Rings

An in-vitro system was devised to study the performance of newly developed annuloplasty rings as well as various conventional rings. The Duran Flexible Annuloplasty Ring was tested to define its characteristics and to validate the system for comparative testing. It was possible to obtain quantitative data using a microscope and a load cell to respectively measure valve orifice area and tensile load on the valve annulus. The results suggest that this apparatus could be employed to characterize the features and functional performance of other types of annuloplasty ring.

The viable mitral annular dynamics and left ventricular function after mitral valve repair by biological rings

OBJECTIVE

Considering the importance of annular dynamics in the valvular and ventricular function, we sought to evaluate the effects of treated pericardial annuloplasty rings on mitral annular dynamics and left-ventricular (LV) function after mitral valve repair. The results were compared with the mitral annular dynamics and LV function in patients with rigid and flexible rings and also in those without any heart problems.

MATERIALS AND METHODS

One hundred and thirty-six consecutive patients with a myxomatous mitral valve and severe regurgitation were prospectively enrolled in this observational cohort study. The patients underwent comparable surgical mitral valve reconstruction; of these 100 received autologous pericardium rings (Group I), 20 were given flexible prosthetic rings (Group II), and 16 received rigid rings (Group III). Other repair modalities were also performed, depending on the involved segments. The patients were compared with 100 normal subjects in whom an evaluation of the coronary artery was not indicative of valvular or myocardial abnormalities (Group IV). At follow-up, LV systolic indices were assessed via two-dimensional echocardiography at rest and during dobutamine stress echocardiography. Mitral annular motion was examined through mitral annulus systolic excursion (MASE). Peak transmitral flow velocities (TMFV) and mitral valve area (MVA) were also evaluated by means of continuous-wave Doppler.

RESULTS

A postoperative echocardiographic study showed significant mitral regurgitation (>=2+) in one patient in Group I, one patient in Group II, and none in Group III. None of the patients died. There was a noteworthy increase in TMFV with stress in all the groups, the increase being more considerable in the prosthetic ring groups (Group I from 1.10 ± 0.08 to 1.36 ± 0.13 m/s, Group II from 1.30 ± 0.11 to 1.59 ± 0.19 m/s, Group III from 1.33 ± 0.09 to 1.69 ± 0.21 m/s, and Group IV from 1.08 ± 0.08 to 1.21 ± 0.12 m/s). Recruitment of LVEF reserve during stress was observed in the pericardial ring and normal groups (Group I from 54.6±6.2 to 64.6±7.3%, P<0.005; and Group IV from 55.3 ± 5.7 to 66 ± 6.2%, P<0.05), but no significant changes were detected in the prosthetic ring groups (Group II from 50.4 ± 5 to 55.0 ± 5.1, and Group III from 51.1 ± 6.6 to 53.8 ± 4.7). There was a significant MASE increase in both of the studied longitudinal segments at rest and during stress in Groups I and IV compared with the prosthetic ring groups. There was no calcification of the pericardial rings.

CONCLUSIONS

The use of treated autologous pericardium rings for mitral valve annuloplasty yields excellent mitral annular dynamics, preserves LV function during stress conditions, and leaves no echocardiographic signs of degeneration.

Mitral Annular Remodeling with Varying Degrees and Mechanisms of Chronic Mitral Regurgitation

HYPOTHESES

Degree of mitral annular remodeling is directly associated with severity of chronic mitral regurgitation (MR). Mitral annular remodeling occurs in a symmetric fashion, regardless of MR severity. In addition to MR severity, MR mechanism plays a significant role in mitral annular remodeling.

BACKGROUND

Limited data exists on mitral annular remodeling in patients with MR. Identification of annular changes may be important in aiding surgical repair.

METHODS

Mitral annular dimensions (anteroposterior, intercommissural, surface area, and circumference) were measured in end systole and diastole using 3-dimensional reconstructive software in 83 patients: trace to no MR (23), mild MR (15), moderate MR (26), and severe MR (19). Annular sphericity indices were determined by dividing intercommissural by anteroposterior dimensions. Patients were further subgrouped by mechanism of MR.

RESULTS

With increasing MR severity, there was a corresponding increase in all annular measurements, most pronounced in the anteroposterior dimension, circumference, and area. Larger increases were seen in patients with prolapse/flail and dilated mechanisms. Furthermore, the mitral annulus became more circular (sphericity index approached 1.0) with increasing MR severity. Patients with prolapse/flail mechanisms exhibited normal left ventricular volumes despite significant annular enlargement.

CONCLUSIONS

Mitral annular remodeling is directly associated with MR severity and occurs in an asymmetric fashion, yet is not limited to one region of the annulus. Mechanism of MR plays a significant role in annular remodeling. Annular remodeling can occur independently of left ventricular remodeling.

Relationship of Mitral Annular Remodeling to Severity of Chronic Mitral Regurgitation

HYPOTHESES

(1) Mitral regurgitation (MR) severity is directly associated with mitral annular remodeling as evidenced by mitral annular enlargement. (2) Increasing severity of chronic MR will result in symmetric enlargement of the mitral annulus as measured by annular shape indices.

BACKGROUND

Limited data exist on mitral annular remodeling for patients with MR. Identification of annular changes may be important in aiding surgical repair.

METHODS

The mitral annulus was measured in several planes using transthoracic echocardiography in 173 patients: trace to no MR (34), mild MR (48), moderate MR (45), and severe MR (46). Patients were subgrouped by mechanism of MR and annular shape indices were determined.

RESULTS

With increasing MR severity, there was a corresponding symmetric increase in all systolic and diastolic measurements, but no significant differences in annular shape indices between subgroups by MR severity or by MR mechanism.

CONCLUSIONS

Mitral annular remodeling is symmetric, regardless of degree or mechanism of MR.

Multiple purpose simulator using a natural porcine mitral valve

An in vitro pulsatile simulator with a porcine mitral valve was developed in order to simulate physiologic and diseased mitral valve conditions. Evaluation of these conditions was conducted from a hydrodynamic and annulus behavior point of view. We found it possible to simulate mild "mitral valve prolapse" and to obtain quantitative data related to the condition. The diseased condition produced a 40% greater regurgitant volume than that observed under the normal condition (p < 0.0001). Regarding the leakage volume, the diseased condition exhibited about 2.6 times more leakage than the normal condition. The mitral valve simulator proposed in this study is considered fairly stable with respect to both hemodynamics and the behavior of the annulus, and it is an adequate simulator for modeling various types of normal and diseased mitral valve conditions.

Use of expanded polytetrafluoroethylene sutures as artificial tendinous cords in children with congenital mitral regurgitation

OBJECTIVE

To determine the efficacy in the intermediate term of artificial cords inserted in children with congenital mitral regurgitation.

METHODS

We reconstructed the tendinous cords using expanded polytetrafluoroethylene (ePTFE) sutures in 11 children with severe mitral regurgitation. In these patients, the aortic (anterior) leaflet of the mitral valve had been markedly prolapsed, the tendinous cords being partially lacking in seven, and elongated in the remaining four. In addition, one of the papillary muscles was hypoplastic in five and absent in three. The number of artificial cords constructed varied from two to six. Conventional annuloplasty was performed in all to plicate the dilated annular attachment of the valve. Ventricular septal defect was present in four patients, and other associated malformations in another two. Age at operation ranged from 9 months to 9 years old, with a mean of 4.5 years.

RESULTS

All patients survived the operation. No reoperation has been needed thus far. No complications were encountered related to the use of the prosthetic materials or anticoagulation. As judged by echocardiography, regurgitation became trivial or slight immediately after the repair. In two patients, however, regurgitation recurred within 1 year of the operation. Coaptation between the leaflets was maintained by a compensatory growth at the site of attachment of the artificial cords. Catheterization demonstrated significant improvements in the end-diastolic volume of the left ventricle.

CONCLUSION

Expanded polytetrafluoroethylene sutures can be used as artificial cords when attempting to repair the malformed mitral valve in children, providing excellent results in the short- and the intermediate-term after the surgical procedure.

Mitral valve repair vs replacement. Current recommendations and long-term results

Techniques now exist to correct abnormalities of all components of the mitral valvular apparatus except extensive loss of pliable leaflet area. Thus, paradoxically, myxomatous valves with redundant leaflets represent the ideal candidates for mitral valve repair. Repair for mitral insufficiency can be performed for some rheumatic valves, but patient selection is critical. Loss of leaflet area, leaflet thickening, and extensive calcification of the leaflets or commissures are contraindications to repair. The abnormalities of the subvalvular apparatus are less important because a complete set of new chordae can be reconstructed using PTFE suture material. Some cases of endocarditis are ideal for repair using localized débridement and pericardial patch repair with or without PTFE chordal replacement. True ischemic mitral regurgitation of the Carpentier type I category is still something of a surgical enigma. Because it is a restrictive leaflet motion problem, annuloplasty alone is not always effective, and the outcome of any given repair attempt is less predictable. Repairs in patients with small annuli and multiple leaflet defects requiring complex series of maneuvers have a low probability of success. Furthermore, such patients with small left ventricular cavities are more prone to experience SAM. Several factors contributing to which therapy is chosen for mitral valve disease are summarized in Table 1. Patient selection, accurate evaluation of the cause or causes of mitral regurgitation, and well-executed application of the appropriate techniques for repair are all critical factors in the early and late success of mitral valve repair.

Cosgrove-Edwards mitral ring dynamics measured with transesophageal three-dimensional echocardiography

BACKGROUND

Flexible rings have been introduced for improved mitral valve annuloplasty. These rings allow systolic-diastolic variation of both the shape and the area of the valve orifice, mimicking the normal dynamics of the mitral valve ring. In humans, information on the functional behavior of the Cosgrove-Edwards ring during the cardiac cycle is limited at present.

METHODS

We used transesophageal three-dimensional echocardiography to analyze mitral valve rings in 19 consecutive patients who underwent annuloplasty because of severe (grade III to IV) mitral regurgitation. Fifteen patients received a Cosgrove-Edwards ring and 4 received a Carpentier ring. The acquisition for three-dimensional reconstruction was performed using the transesophageal rotational technique, immediately after operation. Horizontal cross-sections through the mitral valve ring were selected from the data sets for measurement of the dimensions and surface area of the mitral valve orifice at end-systole and end-diastole. Measurements of the flexible Cosgrove-Edwards ring and the rigid Carpentier ring were compared.

RESULTS

Adequate images for measurements were obtained in 17 of 19 patients. The end-systolic orifice area of the Cosgrove-Edwards ring was 4.21 +/- 1.50 cm2 (mean +/- standard deviation) and the end-diastolic area was 4.81 +/- 1.56 cm2 (p < 0.0001). No significant change in the orifice area of the Carpentier ring was observed.

CONCLUSIONS

Three-dimensional transesophageal echocardiography allows the functional assessment in vivo of mitral valve annuloplasty rings. The Cosgrove-Edwards ring maintains its flexibility early after implantation and demonstrates significant systolic-diastolic changes in the orifice area during the cardiac cycle.

Mitral annular flexibility

An analysis of three-dimensional movement of the mitral valve annulus (MVA) may address the question of geometrical change after mitral valve repair to preserve mitral annular function. Conventionally, annular contraction has been studied for this purpose. We investigated this geometrical change occurring in the anterior half of the MVA and discuss its clinical significance. Three-dimensional images of the MVA during systole were reconstructed from magnetic resonance images of eight normal subjects. The posterior half of the MVA exhibited translational motion. We assume that this portion, exhibiting translational motion as well as contraction, purely follows the motion of the left ventricular contraction. Compensating for the discrepancy between the motion of the aortic root and that of the posterior half of the MVA, the anterior half exhibited a flexible change in shape during systole, thus maintaining a sufficient left ventricular outflow tract (LVOT). The increase in the extent of displacement of the anterior MVA from the posterior half of the MVA during systole, which was 3.6 +/- 1.0 mm (mean +/- SD), indicates the annular flexibility. The preservation of annular flexibility may prevent LVOT obstruction. Further geometrical analysis of patients after mitral repair will clarify annular function as presented in this article.

Mitral valve repair is superior to valve replacement for the early preservation of cardiac function: relation of ventricular geometry to function

The immediate effect or mitral valve repair (MVP) or replacement (MVR) on cardiac function was compared in patients with mitral regurgitation in relation to the changes in left ventricular (LV) function and geometry by using intraoperative transesophageal echocardiography in 29 patients with MVP and 21 patients with MVR, before and immediately after cardiopulmonary bypass. The LV volumes, ejection fraction, and long-axis and short-axis lengths and eccentricity index (ratio of long axis to short axis) at end-systole and end-diastole were measured. After both MVP and MVR, there were significant decreases in LV end-diastolic volume (p < 0.0001). However, the ejection fraction did not change after MVP, whereas it decreased after MVR (p < 0.0001). After MVP, there was an increase in eccentricity index at end-systole (p < 0.0001). After MVR, there was no decrease in end-systolic volume, and the eccentricity index was lower than that after MVP (p < 0.0001). The change in LV ejection fraction correlated with the changes in eccentricity index at end-systole (r = 0.55; p < 0.0001) and end-diastole (r = 0.42; p < 0.0003). Immediate intraoperative LV function is preserved after MVP but is depressed after MVR for mitral regurgitation. The changes in ejection fraction correlate with changes in ventricular geometry.

Mitral valve remodeling: long-term results with posterior pericardial annuloplasty

BACKGROUND

We studied the long-term results of a technique of mitral annuloplasty using autologous pericardium.

METHODS

Between June 1989 and December 1994, 113 mitral valvuloplasties were performed for myxomatous degenerative disease. Repair of isolated anterior leaflet prolapse was performed in 26 patients (23%), posterior leaflet prolapse in 38 (33.6%), and prolapse of both leaflets in 49 (43.4%). Posterior pericardial annuloplasty was performed in all patients. In 20 patients, the pericardial graft was marked with metal clips for postoperative cinefluoroscopic assessment of annulus motion.

RESULTS

The operative mortality rate was 2.7% (3/113). One patient died of myocardial infarction and 2 of low cardiac output syndrome. One patient required replacement of the mitral valve 2 days after operation because of dehiscence of the annular plication. Follow-up (average length, 32.41 +/- 20.09 months; range 1 to 71 months) was 97% complete and revealed good clinical and functional results: 95 patients (84.1%) were in New York Heart Association class I and had no regurgitation or only mild residual regurgitation. Postoperative transmitral flow indices were almost normal (mitral valve area = 3.7 +/- 0.4 cm2; peak flow velocity = 1.06 +/- 0.2 m/s). Only 3 patients had reoperation within 3 years (actuarial 5-year reoperation-free rate, 89.7%) and event-free survival at 5 years was 91%. In patients with metal clips marking autologous pericardium, planimetry of the area derived by fluoroscopic examination showed systolic narrowing of annulus size (8.5% +/- 6.4%; p < 0.01) and a slight systolic fall in the anteroposterior diameter of the annulus contour (5.9% +/- 3.8%; p < 0.01).

CONCLUSIONS

Posterior pericardial annuloplasty seems to be a safe, effective and easily performed technique and a more physiologic correction that preserves mitral annulus motion.

Early results of a simplified method of mitral valve annuloplasty

BACKGROUND

We hypothesized that a simple, unmeasured posterior annuloplasty technique (two thirds of a 27-mm Duran ring) offered advantages of standardization and ease of insertion.

METHODS AND RESULTS

A consecutive series of all patients (n = 418; median age, 67 years) having mitral valve repair performed by two surgeons was analyzed to determine the outcome of three different annuloplasty techniques: commissural annuloplasty (n = 124), complete ring annuloplasty (n = 113), and an unmeasured, posterior, partial ring annuloplasty (n = 181). Intraoperatively, before repair, severity of mitral regurgitation as measured by double sampling dye curves and transesophageal echocardiography was similar in all three groups; after mitral valve repair, intraoperative assessment showed a similar degree of reduction in regurgitation in the three annuloplasty groups. Before hospital dismissal, transthoracic echocardiography demonstrated that the mean mitral valve areas and gradients were similar in the three groups; more patients having commissural annuloplasty were classified as having grade II or greater regurgitation. Mortality (n = 7, 1.7%) and need for reoperation (n = 8, 1.9%) was low in all groups despite the fact that additional procedures were performed in 48.8% of patients. Durations of cardiopulmonary bypass and aortic cross-clamping were significantly less in patients having commissural or posterior annuloplasties compared with those receiving a complete ring annuloplasty.

CONCLUSIONS

These early results indicate that the posterior annuloplasty method is reproducible and expeditious. Postoperative valve function as assessed by degree of regurgitation, transvalvular gradient, and valve area was similar to that obtained by measured, complete ring annuloplasty and superior to that found in patients having commissural annuloplasty.