Ring annuloplasty prevents delayed leaflet coaptation and mitral regurgitation during acute left ventricular ischemia

The Use of a Preoperative Mitral Valve Model to Guide Mitral Valve Repair

BACKGROUND

Mitral valve repair is commonly used to address degenerative or functional changes to the mitral valve apparatus and surrounding ventricular anatomy. Preoperative transoesophageal echocardiogram (TOE) is routinely used to evaluate and identify the precise anatomic location of mitral valve pathology in order to guide repair. However, surgeons currently lack specific guidance regarding the approximate dimensions of the mitral valve they should aim for in order to achieve optimal valve function and avoid adverse outcomes. Therefore, through an observational study, we aimed to develop and test the accuracy of a preliminary mathematical model which represents the geometric relationship between various clinically relevant components of the mitral valve and its surrounding structures.

METHODS

Using established trigonometric principles, the geometric relationship shared between several mitral valve components was represented in a two-dimensional (2D) model and described in a mathematical equation. The output variable of the model is the anteroposterior diameter of the mitral valve. To assess the accuracy of the mathematical model, we compared the model-predicted anteroposterior (AP) diameter against AP diameter measured by postoperative TOE in 42 cases.

RESULTS

The root mean squared error (RMSE) of model predicted AP diameter compared to measured AP diameter was 0.43 cm. The mean absolute percentage error (MAPE) of the model was 17.7%. In 34 out of 42 cases, model-predicted AP diameters were within 25% of AP diameters measured by postoperative TOE.

CONCLUSIONS

Preliminary testing of a simple mathematical model has shown its relative accuracy in representing the geometric relationship between several mitral valve variables. Further research and refinement of the model is required in order to improve its accuracy. We are encouraged that, with further improvement, the model has the potential for clinical application.

The correlation between the coaptation height of mitral valve and mitral regurgitation after mitral valve repair

Background

To investigate the association between the coaptation height of mitral valve and mitral regurgitation after mitral valve repair.

Methods

From Sep 2014 to Jun 2015, 20 patients underwent mitral valve valvuloplasty for mitral regurgitation were included. Ring annuloplasty was performed in all cases. Mitral valve short-axis dimension (MVd), coaptation height (CH), Left ventricular ejection fraction (LVEF) were measured by the transesophageal echocardiography before the operation in operation room and 3 months and 12 months after the operation by the transthoracic echocardiography. A degree from 0 to 4 was used to measure the degree of mitral regurgitation.

Results

There were 14 patients with 0, 3 patients with 1, 3 patients with 2 of mitral regurgitation 12 months after the operation. CH (3.53 ± 1.91 mm) increased significantly at 3 months (5.05 ± 1.09 mm) and 12 months after operation (5.22 ± 1.15 mm) (p < 0.05). MVd and LVEF were not significantly changed after mitral valve repair. Furthermore, CH after resuscitation have a statistically significant negative correlation with the degree of mitral regurgitation 12 months after operation.

Conclusion

The mitral valve repair with mitral valve ring induce the morphologic change of the mitral valve structure. The increase of CH after mitral valve repair may be one of the main factors in regulation of mitral regurgitation.

Long-term results of suture annuloplasty for degenerative mitral valve disease: a propensity-matched analysis

AIMS

Ring annuloplasty is the gold standard of surgical repair in degenerative mitral valve disease. However, prosthetic annuloplasty has some drawbacks and potential hazards. Suture annuloplasty theoretically is able to preserve annular leaflet dynamics and left ventricular performance, but experience is limited. The aim of the study was to review the early and long-term outcome of the posterior double-suture annuloplasty (DSA) technique for degenerative mitral valve repair.

METHODS

From January 2002 to December 2008, 400 patients underwent primary mitral valve repair for degenerative disease either with posterior DSA [n = 147 (37%)] or with flexible posterior annuloplasty band [n = 253 (63%)]. Differences in patient characteristics were addressed by propensity-score matching (132 pairs). A composite end-point of mitral valve failure (MVF) was calculated as the incidence of mitral valve regurgitation greater than 2+ or need for mitral valve replacement at follow-up.

RESULTS

After propensity-score matching, the distribution of preoperative variables among matched pairs was, on average, equal. Isolated annuloplasty and leaflet repair techniques were similarly performed in both groups (P = 0.20). In-hospital mortality was comparable between the two study groups (P = 0.48). Predischarge echocardiography showed excellent results regarding valve hemodynamics (P = 0.71). At a mean follow-up of 11 ± 3 years, all-cause mortality (P = 0.12), need for mitral valve replacement (P = 0.49), and cardiac re-hospitalization rate (P = 0.57) resulted comparable between the two groups. Ten-year survival (75 vs. 71%, P = 0.51) and freedom from MVF (92 vs. 84%, P = 0.39) were similar between posterior annuloplasty band and DSA groups.

CONCLUSION

Suture annuloplasty demonstrated comparable results with posterior flexible band repair and could be a viable option for mitral valve surgery in selected patients, such as in the minimally invasive approach, in endocarditis, and in developing countries.

Comparison of the novel Medtentia double helix mitral annuloplasty system with the Carpentier-Edwards Physio annuloplasty ring: morphological and functional long-term outcome in a mitral valve insufficiency sheep model

Background

The prevalence of mitral regurgitation in cardiac diseases requires annuloplasty systems that can be implanted without excessive patient burden. This study was designed to examine the morphological and functional outcome of a new double helix mitral annuloplasty ring in an ovine model in comparison to the classical Carpentier-Edwards (CE) annuloplasty ring as measured by reduction of mitral regurgitation and tissue integration. The Medtentia annuloplasty ring (MAR) is a helical device that is rotated into the annulus self-restoring the valve geometry, enabling a faster fixation without the need of elaborate repair of the valve geometry. The ventricular part of the helical ring encircles the valve chords.

Methods

Twenty adult sheep were overpaced until 2+ level mitral valve regurgitation was achieved. Seven animals per group received either the MAR or the CE ring. Implantation was performed on-pump in a beating heart through the left atrial appendix. The animals were sacrificed 3.6 ± 0.3 months after surgery following an echocardiography for assessing mitral regurgitation as primary endpoint. The annuloplasty rings with surrounding tissue were harvested for histological analyses as secondary endpoints. The remaining six sheep received the MAR system and were sampled seven, nine or 12 months after surgery.

Results

Implantation time (p < 0.01) and perfusion time (p < 0.001) as clinical secondary endpoints were significantly shorter in the MAR group. Echocardiography follow-ups showed sufficient valve function repair in nearly all animals with a normalization of the ventricle diameters in both groups (group difference: p = 0.147). The weights of the hearts did not differ significantly. Histology revealed adequately covered atrial annuloplasty rings with functional endothelium and lack of excessive granulation tissue or fibrosis in all specimens. The ventricular projections of the MAR systems encircling the chordae tendineae were not completely covered with neointimal tissue, although in no case were microthrombi detected and no thromboembolic events were recorded.

Conclusions

The new MAR system is an easy to use annuloplasty system with a functional outcome comparable to that of the well–proven CE ring. Mitral valve regurgitation is effectively stopped both by restricting the pathological expansion of the annulus and by gathering the chords without thrombus formation.

Mitral Valve Finite Element Modeling: Implications of Tissues’ Nonlinear Response and Annular Motion

Finite element modeling represents an established method for the comprehension of the mitral function and for the simulation of interesting clinical scenarios. However, current models still do not include all the key aspects of the real system. We implemented a new structural finite element model that considers (i) an accurate morphological description of the valve, (ii) a description of the tissues’ mechanical properties that accounts for anisotropy and nonlinearity, and (iii) dynamic boundary conditions that mimic annulus and papillary muscles’ contraction. The influence of such contraction on valve biomechanics was assessed by comparing the computed results with the ones obtained through an auxiliary model with fixed annulus and papillary muscles. At the systolic peak, the leaflets’ maximum principal stress contour showed peak values in the anterior leaflet at the strut chordae insertion zone (300 kPa) and near the annulus (200–250 kPa), while much lower values were detected in the posterior leaflet. Both leaflets underwent larger tensile strains in the longitudinal direction, while in the circumferential one the anterior leaflet experienced nominal tensile strains up to 18% and the posterior one experienced compressive strains up to 23% associated with the folding of commissures and paracommissures, consistently with tissue redundancy. The force exerted by papillary muscles at the systolic peak was equal to 4.11 N, mainly borne by marginal chordae (76% of the force). Local reaction forces up to 45 mN were calculated on the annulus, leading to tensions of 89 N/m and 54 N/m for its anterior and posterior tracts, respectively. The comparison with the results of the auxiliary model showed that annular contraction mainly affects the leaflets’ circumferential strains. When it was suppressed, no more compressive strains could be observed and peak strain values were located in the belly of the anterior leaflet. Computational results agree to a great extent with experimental data from literature. They provided insight into some of the features characterizing normal mitral function, such as annular contraction and leaflets’ tissue anisotropy and nonlinearity. Some of the computed results may be useful in the design of surgical devices and techniques. In particular, forces applied on the annulus by the surrounding tissues could be considered as an indication for annular prostheses design.

The effect of pure mitral regurgitation on mitral annular geometry and three-dimensional saddle shape

OBJECTIVE

Chronic ischemic mitral regurgitation is associated with mitral annular dilatation in the septal-lateral dimension and flattening of the annular 3-dimensional saddle shape. To examine whether these perturbations are caused by the ischemic insult, mitral regurgitation, or both, we investigated the effects of pure mitral regurgitation (low pressure volume overload) on annular geometry and shape.

METHODS

Eight radiopaque markers were sutured evenly around the mitral annulus in sheep randomized to control (CTRL, n = 8) or experimental (HOLE, n = 12) groups. In HOLE, a 3.5- to 4.8-mm hole was punched in the posterior leaflet to generate pure mitral regurgitation. Four-dimensional marker coordinates were obtained radiographically 1 and 12 weeks postoperatively. Mitral annular area, annular septal-lateral and commissure-commissure dimensions, and annular height were calculated every 16.7 ms.

RESULTS

Mitral regurgitation grade was 0.4 +/- 0.4 in CTRL and 3.0 +/- 0.8 in HOLE (P < .001) at 12 weeks. End-diastolic left ventricular volume index was greater in HOLE at both 1 and 12 weeks; end-systolic volume index was larger in HOLE at 12 weeks. Mitral annular area increased in HOLE predominantly in the commissure-commissure dimension, with no difference in annular height between HOLE versus CTRL at 1 or 12 weeks, respectively.

CONCLUSION

In contrast with annular septal-lateral dilatation and flattening of the annular saddle shape observed with chronic ischemic mitral regurgitation, pure mitral regurgitation was associated with commissure-commissure dimension annular dilatation and no change in annular shape. Thus, infarction is a more important determinant of septal-lateral dilatation and annular shape than mitral regurgitation, which reinforces the need for disease-specific designs of annuloplasty rings.

Ischemic mitral regurgitation: revascularization alone versus revascularization and mitral valve repair

BACKGROUND

In this study we compared the surgical management of ischemic mitral regurgitation (IMR) by revascularization alone and by revascularization combined with mitral valve repair.

METHODS

We studied 355 patients who underwent revascularization alone (n = 168) or revascularization combined with mitral valve repair (n = 187) for IMR from March 1994 to September 2003. Preoperative and operative characteristics, postoperative mitral regurgitation severity, operative mortality, and late survival were examined for each surgical group.

RESULTS

No differences were noted between the two groups in age, sex, history of diabetes or hypertension, and number of bypass grafts. The combined surgical group had a lower preoperative left ventricular ejection fraction (0.38 +/- 0.14 versus 0.44 +/- 0.15), greater severity of IMR, higher frequency of prior myocardial infarction, and longer cross-clamp and pump times (p < 0.01). The combined surgical group had a greater reduction in IMR grade (2.7 +/- 0.1 grades versus 0.2 +/- 0.1 grade), a lower postoperative IMR grade (0.9 +/- 0.1 versus 2.3 +/- 0.1), and a higher success with reduction of IMR by two or more grades (89% versus 11%) (p < 0.001). In patients with 3+ or 4+ IMR, both groups had similar operative mortality (11.0% in the combined group compared with 4.7% for revascularization alone, p = 0.11) and actuarial survival at 5 years (44% +/- 5% versus 41% +/- 7%, p = 0.53). Independently predictive of higher early mortality (< or = 30 days) by Cox analysis were longer pump time (p < 0.001) and older age (p < 0.02). Predictive of late mortality (> 30 days) were older age (p < 0.001), fewer bypass grafts (p < 0.01), and lower ejection fraction (p < 0.01). After adjustment for these variables, there was a trend (p = 0.08) toward a higher late survival with the combined surgical procedure.

CONCLUSIONS

In patients with IMR, combined mitral valve repair and revascularization resulted in less postoperative mitral regurgitation and similar 5-year survival when compared with revascularization alone. Attempts to reduce pump time by using off-pump techniques may reduce early mortality in these high-risk patients.

Acute geometric changes of the mitral annulus after coronary occlusion: a real-time 3D echocardiographic study

We performed real-time 3D echocardiography in sixteen sheep to compare acute geometric changes in the mitral annulus after left anterior descending coronary artery (LAD, n=8) ligation and those after left circumflex coronary artery (LCX, n=8) ligation. The mitral regurgitation (MR) was quantified by regurgitant volume (RV) using the proximal isovelocity surface area method. The mitral annulus was reconstructed through the hinge points of the annulus traced on 9 rotational apical planes (angle increment=20 degrees). Mitral annular area (MAA) and the ratio of antero-posterior (AP) to commissure-commissure (CC) dimension of the annulus were calculated. Non-planar angle (NPA) representing non-planarity of the annulus was measured. After LCX occlusion, there were significant increases of the MAA during both early and late systole (p<0.01) with significant MR (RV: 30+/-14 mL), while there was neither a significant increase of MAA, nor a significant MR (RV: 4+/-5 mL) after LAD occlusion. AP/CC ratio (p<0.01) and NPA (p<0.01) also significantly increased after LCX occlusion during both early and late systole. The mitral annulus was significantly enlarged in the antero-posterior direction with significant decrease of non-planarity compared to LAD occlusion immediately after LCX occlusion.

Evaluation of the Mitral Valve Leaflet Morphology After Mitral Valve Reconstruction with a Concept "Coaptation Length Index"

BACKGROUND

In clinical settings, information on morphology of mitral valve leaflet after mitral valve reconstruction is limited.

METHODS

Between January 1996 and June 2000, 36 patients underwent mitral valve repair for mitral regurgitation (MR). The etiology of mitral insufficiency was prolapse, dilated annulus, and ischemia. Ring annuloplasty was performed in all cases. Mitral valve short-axis dimension (MVd), vertical distance between annular line and closing point (Vd), coaptation length (CL), and coaptation length index (CLI) were measured by two-dimensional transesophageal echocardiography for the present 11 cases.

RESULTS

In 11 cases, residual MR, using a scale from 0 to 4, was 0 in 5 patients, 1 in 4 patients, 2 in 2 patients whose etiology of regurgitation was cardiomyopathy. MVd and Vd decreased significantly (38.7+/- 6.2 to 27.0 +/- 5.6 mm, 10.1 +/- 7.7 to 6.5 +/- 4.6 mm, respectively). CL and CLI increased significantly (6.4 +/- 2.4 to 11.6 +/- 4.6 mm, 0.16 +/- 0.06 to 0.44 +/- 0.21, respectively). Among those indices, only CLI has a statistically significant negative correlation with the degree of residual MR.

CONCLUSION

Mitral valve ring annuloplasty produces the morphologic change of the mitral apparatus, especially increase of CLI, which may be one of the main factors in regulation of regurgitation.

Annular Height-to-Commissural Width Ratio of Annulolasty Rings In Vivo

Background— A “saddle-shaped” mitral annulus with an optimal ratio between annular height and commissural diameter may reduce leaflet and chordal stress and is purported to be conserved across mammalian species. Whether annuloplasty rings maintain this relationship is unknown.

Methods and Results— Twenty-three adult sheep underwent implantation of radiopaque markers on the left ventricle and mitral annulus. Eight animals underwent implantation of a Carpentier-Edwards Physio ring, 7 underwent a Medtronic Duran flexible ring, and 8 served as controls. Animals were studied with biplane videofluoroscopy 7 to 10 days postoperatively. Annular height and commissural width (CW) were determined from 3D marker coordinates, and annular height:CW ratio (AHWCR) was calculated. Annular height was similar in Control and Duran animals but significantly lower in the Physio group at end diastole (8.4±3.8, 6.7±2.3, and 3.4±0.6 mm, respectively, for Control, Duran, and Physio; ANOVA=0.005) and at end systole (14.5±6.2, 10.5±5.5, and 5.8±2.5 mm, respectively, for Control, Duran, and Physio; ANOVA=0.004). Both ring groups reduced CW significantly relative to Control. AHCWR did not differ between Control and Duran but was lower in Physio (23±11%, 24±7%, and 12±2% at end diastole and 42±17%, 37±17%, and 21±10% at end systole, respectively, for Control, Duran, and Physio, respectively; ANOVA <0.05 for both).

Conclusions— Mitral annular height and AHWCR of the native valve were unchanged by a Duran ring, whereas the Physio ring led to a lower AHWCR. Theoretically, such a flexible annuloplasty ring may provide better leaflet stress distribution by maintaining normal AHWCR.

Sovering annuloplasty rings: experimental pathology in the sheep model

INTRODUCTION

A new flexible annuloplasty ring (Sovering, Sorin Biomedica Cardio), both closed and open, has been designed and consists of radiopaque silicone core impregnated with barium sulfate and covered by a knitted polyester fabric coated with Carbofilm. The aim of the study was to test the biological compatibility of the new device in large animals in orthotopic position.

METHODS

Ten Sovering rings were implanted in 10 female adult sheep, 7 mitral (3 open, 4 closed) and 3 tricuspid (all open). The size was 23-25 mm in the mitral and 28-30 mm in the tricuspid position, and the time in place varied from 63 to 110 days (mean = 89 +/- 14) and from 58 to 63 days (mean = 61 +/- 3), respectively. The morphological analysis consisted of gross, histological, immunohistochemical and ultrastructural investigations.

RESULTS

The prosthetic ring appeared well implanted in the valve atrioventricular (AV) junction, encapsulated by a thin fibrous sheath without any evidence of thrombus deposition, fibrinous lining or exuberant fibrous tissue overgrowth. No adverse inflammatory reaction was observed, but rare lymphocytes, macrophages and foreign body giant cells. At electron microscopy, the fibrous tissue appeared to permeate deeply within the fabric network; reendothelization on the surface was noted and confirmed by immunohistochemistry. Sirius red staining at polarized light revealed a higher content of collagen type III in the mitral than in the tricuspid position.

CONCLUSIONS

Sovering annuloplasty rings implanted in the AV valves of adult sheep showed excellent biocompatibility, fibrous encapsulation and reendothelization. The absence of thrombosis and exuberant fibrous tissue reaction supports the effective use of Carbofilm covering in annuloplasty devices.

Evaluation of the Mitral Valve Leaflet Morphology after Mitral Valve Reconstruction with a Concept "Coaptation Length Index"

BACKGROUND

In clinical settings, information on morphology of mitral valve leaflet after mitral valve reconstruction is limited.

METHODS

Between January 1996 and June 2000, 36 underwent mitral valve repair for mitral regurgitation (MR). The etiology of mitral insufficiency was prolapse, dilated annulus, and ischemic. Ring annuloplasty was performed in all cases. Mitral valve short-axis dimension (MVd), vertical distance between annular line and closing point (Vd), coaptation length (CL), coaptation length index (CL/MVd) were measured by the two-dimensional transesophageal echocardiography for the present 11 cases.

RESULTS

In 11 cases, residual MR, using a scale from 0 to 4, was 0 in 5 patients, 1 in 4 patients, 2 in 2 patients whose etiology of regurgitation was cardiomyopathy. MVd and Vd decreased significantly (38.7 +/- 6.2 to 27.0 +/- 5.6 mm, 10.1 +/- 7.7 to 6.5 +/- 4.6 mm, respectively). CL and CLI increased significantly (6.4 +/- 2.4 to 11.6 +/- 4.6 mm, 0.16 +/- 0.06 to 0.44 +/- 0.21, respectively). Among those index, only CLI have a statistically significant negative correlation with the degree of residual MR.

CONCLUSION

The mitral valve ring annuloplasty produce the morphologic change of mitral apparatus, especially the increase of CLI, which may be one of the main factors in regulation of regurgitation.

Annular remodeling in chronic ischemic mitral regurgitation: ring selection implications

BACKGROUND

More precise understanding of annular remodeling in the evolution of chronic ischemic mitral regurgitation is needed to provide a more rational basis for optimal annuloplasty ring sizing and selection as well as the design of new reparative techniques. Three-dimensional in vivo data describing these geometric perturbations however are lacking. Using an ovine model of chronic myocardial infarction we determined the three-dimensional distortions of the mitral annulus associated with the development of chronic ischemic mitral regurgitation.

METHODS

Ten sheep underwent placement of radiopaque markers on the left ventricle and mitral annulus as well as placement of snares around the second and third obtuse marginal coronary arteries. After 8 days biplane cinefluoroscopy provided three-dimensional marker data and snare occlusion created an inferior infarction. After 7 more weeks the animals were studied again.

RESULTS

Severity of mitral regurgitation increased (0.6 +/- 0.5 to 2.5 +/- 0.7). Septal-lateral (2.99 +/- 0.20 cm to 3.64 +/- 0.35 cm, maximum dimension) and commissure-commissure (3.71 +/- 0.32 cm to 4.40 +/- 0.30 cm) mitral annular diameters and the lengths of the muscular (7.77 +/- 0.39 cm to 9.51 +/- 0.72 cm) and fibrous annular perimeters (3.36 +/- 0.37 cm to 3.85 +/- 0.39 cm, p < 0.0001 for all) increased while the height of the annular "saddle horn" above a best-fit plane fell (0.73 +/- 0.52 cm to 0.57 +/- 0.42 cm, minimum dimension, p = 0.01).

CONCLUSIONS

These three-dimensional in vivo data reflect annular remodeling in chronic ischemic mitral regurgitation and suggest that mitral repair in this context should be aimed at preventing further lengthening of the intertrigonal distance, reducing the septal-lateral annular diameter to reestablish adequate leaflet coaptation, and restoring the saddle shape of the annulus.

Percutaneous mitral valve repair: A feasibility study in an ovine model of acute ischemic mitral regurgitation

Annuloplasty is the cornerstone of surgical mitral valve repair. A percutaneous transvenous catheter-based approach for mitral valve repair was tested by placing a novel annuloplasty device in the coronary sinus of sheep with acute ischemic mitral regurgitation. Mitral regurgitation was reduced from 3-4+ to 0-1+ in all animals (P < 0.03). The annuloplasty functioned by reducing septal-lateral mitral annular diameter (30 +/- 2.1 mm preinsertion vs. 24 +/- 1.7 mm postinsertion; P < 0.03). These preliminary experiments demonstrate that percutaneous mitral annuloplasty is feasible. Further study is necessary to demonstrate long-term safety and efficacy of this novel approach.

Paneth suture annuloplasty abolishes acute ischemic mitral regurgitation but preserves annular and leaflet dynamics

BACKGROUND

Ring annuloplasty, the standard treatment for ischemic mitral regurgitation (IMR), abolishes normal annular dynamics and freezes the posterior leaflet. We examined the impact of Paneth suture annuloplasty during acute IMR on motion of the mitral annulus and leaflets in an ovine model.

METHODS AND RESULTS

Eight sheep had radiopaque markers placed on the left ventricle, anterior mitral leaflet, posterior mitral leaflet, and mitral annulus. A Paneth suture annuloplasty that could be reversibly tightened was anchored to each fibrous trigone and externalized through the mid-lateral mitral annulus. Acute IMR was induced by proximal circumflex artery occlusion. Transesophageal echocardiography assessed the degree of IMR, and biplane cinefluoroscopy measured 3-dimensional marker coordinates before and during circumflex ischemia, and tightening of the Paneth suture. Paneth suture annuloplasty eliminated acute IMR, and reduced septal-lateral and commissure-commissure mitral annular dimensions. Tightening of the annuloplasty sutures, even beyond the degree necessary to eliminate mitral regurgitation (MR), did not reduce septal-lateral or commissure-commissure annular shortening, shortening of the muscular annular perimeter, annular flexion, or angular excursion of the anterior or posterior leaflets relative to ischemic conditions.

CONCLUSIONS

In contrast to ring annuloplasty, annular reduction sufficient to restore mitral competence during acute IMR can be achieved with a Paneth suture annuloplasty while simultaneously maintaining normal annular and leaflet dynamic motion. These findings should prompt additional investigation and design of repair methods that preserve the mobility of the mitral apparatus.

Geometric distortions of the mitral valvular-ventricular complex in chronic ischemic mitral regurgitation

BACKGROUND

Better understanding of the precise 3-dimensional geometric changes of the mitral valvular-ventricular complex in chronic ischemic mitral regurgitation (CIMR) is needed in order to devise better surgical repair techniques. We hypothesized that changes after inferior myocardial infarction would be different in hearts that developed CIMR compared with those that did not.

METHODS AND RESULTS

Twenty-four sheep underwent coronary snare and marker placement (annulus, papillary muscles, and anterior and posterior leaflets). After 8 days, cinefluoroscopy provided 3-dimensional marker data, and snare occlusion of obtuse marginal branches created inferior myocardial infarction, including the posterior papillary muscle. After 7 weeks, the 16 surviving animals were studied again and grouped by mitral regurgitation grade (>or= 2+, n=10 versus <or= 1+, n=6). End-systolic mitral annulus dimensions, components of papillary muscle and leaflet displacement, were calculated. After inferior myocardial infarction, total displacement of the posterior papillary muscle from the midseptal annulus ("saddle horn") was greater in CIMR(+) animals: 6.5+/-3.2 versus 3.1+/-2.7 (P=0.02), with the posterior papillary muscle moving more laterally (6.8+/-3.4 versus 2.5+/-3.5 mm, P=0.01). Increase in mitral annular septal-lateral diameter was greater in animals with CIMR (4.9+/-2.7 versus 2.3+/-2.0, P=0.02), and apical displacement of the posterior leaflet (PL) margin was also greater in the CIMR(+) group (1.7+/-1.0 versus 0.3+/-0.5, P=0.01).

CONCLUSIONS

The CIMR(+) group had greater septal-lateral annular dilatation, lateral posterior papillary muscle displacement, and apical PL restriction, indicating that these associated geometric alterations may be important in the pathogenesis of CIMR. Treatment of CIMR should address both annular septal-lateral dilatation and lateral displacement of the posterior papillary muscle.

Atrial contraction and mitral annular dynamics during acute left atrial and ventricular ischemia in sheep

In six sheep, radiopaque markers were placed on the left ventricle (LV), the mitral annulus, the left atrium (LA), and the central edge of both mitral leaflets to investigate the effects of acute LV ischemia on atrial contraction, mitral annular area (MAA), and mitral regurgitation (MR). Animals were studied with biplane videofluoroscopy and transesophageal echocardiography before and during balloon occlusion of the left anterior descending (LAD), distal circumflex (dLCX), and proximal circumflex (pLCX) coronary arteries. MAA and LA area were calculated from the corresponding markers. LAD occlusion did not alter LA area reduction or presystolic MAA reduction, whereas dLCX occlusion resulted in a mild decrease in the former with no change in the latter. Neither occlusion resulted in MR. pLCX occlusion, however, significantly decreased LA area and presystolic MAA reduction and resulted in increased end-diastolic MAA, delayed valve closure from end diastole, and MR. Decreased atrial contractile function, as observed during acute posterolateral ischemia, is linked to diminished presystolic mitral annular reduction, a larger mitral annular size at end diastole, and MR.

Septal-lateral annular cinching abolishes acute ischemic mitral regurgitation

OBJECTIVE

Ring annuloplasty prevents acute ischemic mitral regurgitation in sheep, but it also abolishes normal mitral annular and posterior leaflet dynamics. We investigated a novel surgical approach of simple septal-lateral annular cinching with sutures to treat acute ischemic mitral regurgitation.

METHODS

Nine adult sheep underwent implantation of multiple radiopaque markers on the left ventricle, mitral anulus, and mitral leaflets. A septal-lateral transannular suture was anchored to the midseptal mitral anulus and externalized to a tourniquet through the midlateral mitral anulus and left ventricular wall. Open-chest animals were studied immediately postoperatively. Acute ischemic mitral regurgitation was induced by means of proximal left circumflex artery snare occlusion, and 3 progressive steps of septal-lateral annular cinching (each 2-3 mm suture tightening for 5 seconds) were performed with the transannular suture. Biplane videofluoroscopy for 3-dimensional marker coordinates and transesophageal echocardiography were performed continuously before and during left circumflex ischemia and septal-lateral annular cinching.

RESULTS

Acute left circumflex ischemia caused ischemic mitral regurgitation (+0.5 +/- 0.4 [baseline] vs +2.0 +/- 0.7 [ischemia]; P =.005; scale, +0-4), which decreased progressively with each step of septal-lateral annular cinching and was eliminated during the third step (ischemic mitral regurgitation, +0.6 +/- 0.5; P = not significant vs baseline). The third step of septal-lateral annular cinching decreased the septal-lateral diameter by 6.0 +/- 2.6 mm (P =.005); however, mitral anulus area reduction (8.5% +/- 1.0% and 6.9% +/- 1.9% for ischemic mitral regurgitation and septal-lateral annular cinching step 3, respectively; P =.006) and posterior leaflet excursion (50 degrees +/- 9 degrees and 44 degrees +/- 11 degrees for regurgitation and annular cinching step 3, respectively; P =.002) throughout the cardiac cycle were affected only mildly. Normal mitral annular 3-dimensional shape was maintained with septal-lateral annular cinching.

CONCLUSIONS

Isolated 22% +/- 10% reduction in mitral annular septal-lateral dimension abolished acute ischemic mitral regurgitation in normal sheep hearts while allowing near-normal mitral annular and posterior leaflet dynamic motion. Septal-lateral annular cinching may represent a simple method for the surgical treatment of ischemic mitral regurgitation, either as an adjunctive technique or alone, which helps preserve physiologic annular and leaflet function.

The effects of ring annuloplasty on mitral leaflet geometry during acute left ventricular ischemia

BACKGROUND

The perturbed mitral leaflet geometry that leads to acute ischemic mitral regurgitation during acute left ventricular ischemia has not been quantified, nor is it known whether annuloplasty rings affect these detrimental changes in leaflet geometry.

METHODS

Radiopaque markers were implanted on both mitral leaflets and around the anulus in 3 groups of sheep: one group without rings served as the control group (n = 7); the others underwent Duran (n = 6; Medtronic Heart Valve Division, Minneapolis, Minn) or Carpentier-Edwards Physio (n = 5; Baxter Cardiovascular Division, Santa Ana, Calif) ring annuloplasty. After recovery, 3-dimensional marker coordinates were obtained by means of biplane videofluoroscopy before and during acute posterolateral left ventricular ischemia. Leaflet geometry was defined by measuring distances between annular and leaflet markers and perpendicular distances to the leaflet markers from a best-fit annular plane.

RESULTS

In all control animals, left ventricular ischemia was associated with acute ischemic mitral regurgitation and apical displacement (away from the annular plane) of the posterior leaflet edge and base markers by 0.6 +/- 0.4 mm (P =.01) and 0.7 +/- 0.2 mm (P <.001), respectively. The distance between the posterior leaflet markers and the mid-posterior anulus did not change significantly during ischemia. The anterior leaflet edge marker extended 1.0 +/- 0. 5 mm (P =.01) away from the mid-anterior anulus during ischemia, but compared with its nonischemic position, the anterior leaflet was not displaced apically away from the annular plane. In all animals in the Duran and Physio groups, leaflet geometry was unchanged during ischemia, and acute ischemic mitral regurgitation was not detected.

CONCLUSION

Acute ischemic mitral regurgitation was associated with restricted motion of the posterior leaflet and extension of the anterior leaflet. Annuloplasty rings prevented these geometric perturbations of the mitral leaflets during acute left ventricular ischemia and preserved valvular competence.