Restricted posterior leaflet motion after mitral ring annuloplasty

Impact of papillary muscle relocation as adjunct procedure to mitral ring annuloplasty in functional ischemic mitral regurgitation

BACKGROUND

The optimal surgical treatment in functional ischemic mitral regurgitation (FIMR) remains controversial. Recently, a posterior papillary muscle relocation (PMR) technique as adjunct procedure to ring annuloplasty has been proposed to prevent recurrent FIMR. In the present study, we used 3D cardiac MRI to assess the impact of relocating both papillary muscles as adjunct procedure to downsized ring annuloplasty on mitral leaflet coaptation geometry in FIMR pigs.

METHODS AND RESULTS

Eleven FIMR pigs were randomized to downsized ring annuloplasty (RA; n=6) or RA combined with PMR (RA+PMR, n=5). In the RA+PMR group, a 2-0 Gore-Tex suture was attached to each trigone, exteriorized through the corresponding papillary muscle, mounted on an epicardial pad, and tightened to relocate the myocardium adjacent to the anterior and posterior papillary muscles 5 and 15 mm, respectively. Using 3D MRI, the impact from these interventions on leaflet geometry was assessed. The distance from the posterior papillary muscle to the anterior trigone was reduced significantly more (median values) in the RA+PMR compared with RA animals at end-diastole (-7.9% versus 3.8%, P<0.01) and end-systole (-9.7% versus 2.5%, P=0.02). Accordingly, lateral tethering of the coaptation point (median values) was reduced significantly more in RA+PMR compared with RA animals (-42.8% versus -29.1%, P<0.01).

CONCLUSIONS

Adding papillary muscle relocation to downsized ring annuloplasty reduced lateral leaflet tethering in a porcine experimental model of FIMR. Therefore, this technique holds promise for reducing persistent and recurrent FIMR in patients.

Effect of mitral valve geometry on valve competence

The aim of the investigation was to vary certain geometrical features of the mitral valve in vitro, in order to understand their role in valve function. Geometrical changes to mitral valve components are known to affect valve function, but complete understanding of how geometrical changes influence valve function is far from complete. Test apparatus has been used to apply pressure to porcine mitral valves. Porcine mitral valve specimens were tested both in their intact state and with a specific aspect of their geometry altered. The geometric parameters of the mitral valve varied were (1) the length between the papillary muscles and the mitral annulus (termed the annulo-papillary length), (2) the diameter of the left ventricle at the level of the papillary muscles, and (3) the mitral annular area. Six specimens were tested for each parameter investigated. A minimum annulo-papillary length was necessary to allow chordae tendineae to pull on the valve leaflets in order to prevent mitral valve failure; increasing this length further improved valve closure. Over the experimental range tested, left ventricular dilation at the level of the papillary muscles did not induce failure (P not significant). Increasing the mitral annular area was found to induce failure (P = 0.030 and P = 0.018 for medium and large annular diameters, respectively). The results demonstrate the importance of the geometry of mitral valve components on its function, and give insights into further experiments required to provide further understanding of the role of mitral valve geometry in its function. The results demonstrate that this in vitro method can be used to vary selected features of the geometry of the mitral valve.

Preoperative Posterior Leaflet Angle Accurately Predicts Outcome After Restrictive Mitral Valve Annuloplasty for Ischemic Mitral Regurgitation

Background— Ischemic mitral regurgitation (MR) often persists after restrictive mitral valve annuloplasty, in which case it is associated with worse clinical outcomes. The goal of the present study was to determine whether persistence of MR and/or clinical outcome could be predicted from preoperative analysis of mitral valve configuration.

Methods and Results— In 51 consecutive patients undergoing restrictive annuloplasty for ischemic MR, posterior leaflet (PL) angle, anterior leaflet angle, coaptation distance, and tenting area were quantified by echocardiography before surgery (6±3 days), and MR severity was assessed before and early after surgery (9±4 days). Postoperatively, persistence of mild to moderate MR (vena contracta >3 mm) was observed in 11 (22%) of the patients. The best predictor of postoperative persistence of MR was a PL angle ≥45 degrees (sensitivity 100%, specificity 97%, positive predictive value 92%, negative predictive value 100%). Patients with persistent MR had markedly lower 3-year event-free survival (26±20%) compared with those with nonpersistent MR (75±12%, P =0.01). Preoperative presence of a PL angle ≥45 degrees also was associated with a markedly lower 3-year event-free survival (22±17% versus 76±12%; P <0.001).

Conclusions— In patients undergoing restrictive annuloplasty for ischemic MR, persistence of MR and 3-year event-free survival can accurately be predicted by preoperative analysis of mitral valve configuration. Patients with a PL angle ≥45 degrees (ie, with high PL restriction) should thus be considered poor candidates for this procedure, and concomitant or alternative procedures should be contemplated.

Mechanism of Recurrent/Persistent Ischemic/Functional Mitral Regurgitation in the Chronic Phase After Surgical Annuloplasty

Background— Surgical annuloplasty can potentially hoist the posterior annulus anteriorly, exaggerate posterior leaflet (PML) tethering, and lead to recurrent ischemic/functional mitral regurgitation (MR). Characteristics of leaflet configurations in late postoperative MR were investigated.

Methods and Results— In 30 patients with surgical annuloplasty for ischemic MR and 20 controls, the anterior leaflet (AML) and PML tethering angles relative to the line connecting annuli, posterior and apical displacement of the coaptation and the MR grade were measured by echocardiography before, early after, and late after surgery. Early after surgery, grade of MR and AML tethering generally decreased ( P <0.01), whereas PML tethering significantly worsened ( P <0.01). Nine of the 30 patients showed recurrent/persistent MR late after surgery. Compared with patients without late MR, those with the MR showed similar reduction in the annular area, significant re-increase in posterior displacement of the coaptation, and progressive worsening in PML tethering ( P <0.05) late after surgery in comparison to the early phase. Both preoperative MR and late postoperative MR were significantly correlated with all tethering variables in univariate analysis. Although apical displacement of the coaptation was the primary determinant of preoperative MR ( r 2 =0.60, P <0.0001), increased PML tethering was the primary determinant of late MR ( r 2 =0.75, P <0.0001).

Conclusions— Whereas both leaflets tethering is related to preoperative ischemic MR, both leaflets tethering but with predominant contribution from augmented and progressive PML tethering is related to recurrent/persistent ischemic/functional MR late after surgical annuloplasty.

Effects of Undersized Mitral Annuloplasty on Regional Transmural Left Ventricular Wall Strains and Wall Thickening Mechanisms

Background— Undersized mitral annuloplasty, widely used for ischemic and functional mitral regurgitation (MR), has been proposed as an “annular solution to a ventricular problem.” Beyond relief of MR, it is thought to improve global left ventricular (LV) shape, hence potentially reducing myocardial stress and promoting beneficial reverse LV remodeling. We previously observed that undersized annuloplasty inhibited systolic wall thickening at the LV base near the mitral annulus. In this study, we measured the effects of undersized annuloplasty on regional transmural LV wall fiber and sheet strains and wall thickening mechanisms.

Methods and Results— Nine sheep had transmural radiopaque beadsets surgically inserted into anterobasal and lateral equatorial LV regions, with additional markers silhouetting the LV and mitral annulus. 4-Dimensional marker dynamics were studied with biplane videofluoroscopy before and after tightening an adjustable Paneth-type mitral annuloplasty suture. Transmural circumferential, longitudinal, and radial systolic and remodeling strains in the subepicardium (20% depth), midwall (50%), and subendocardium (80%) in both regions were computed. Fiber and sheet angles from quantitative regional histology allowed transformation of these strains into local fiber (f), sheet (s), and sheet-normal (n) coordinates. Further analysis calculated the transmural contributions of sheet extension (E ssc ), sheet thickening (E nnc ), and sheet shear (E snc ) to systolic wall thickening (E 33 ). In the anterobasal region, undersized annuloplasty reduced systolic wall thickening (E 33 ) by &50% at all transmural depths by inhibiting: (1) subendocardial systolic fiber shortening (−0.10±0.05 versus −0.04±0.05; P <0.05); (2) subepicardial (0.16±0.15 versus 0.09±0.08; P <0.05) and subendocardial (0.45±0.40 versus 0.19±0.18; P <0.05) systolic sheet thickening; (3) midwall sheet extension (0.22±0.12 versus 0.11±0.06; P <0.05); and (4) transmural sheet shear (subepicardium, −0.14±0.07 versus −0.08±0.07; midwall, 0.21±0.12 versus 0.10±0.11; subendocardium, −0.19±0.23 versus −0.11±0.16; P <0.05). In the remote lateral equatorial region, fiber-sheet strains and E 33 were unchanged.

Conclusions— In this acute animal study, undersized annuloplasty inhibited systolic wall thickening in the anterobasal region by reducing subendocardial systolic fiber shortening and laminar sheet wall thickening, but had no effects in a more distant LV region. This suggests that undersized mitral annuloplasty may have potentially deleterious effects on local myocardial mechanics.

Chronic Ischemic Mitral Regurgitation: Repair, Replace or Rethink?

Ischemic mitral regurgitation (IMR) is a common complication of coronary artery disease and is the focus of a rapidly increasing amount of research. Mechanistic studies have determined that IMR is caused by apical displacement and tethering of the mitral valve leaflets after myocardial infarction, resulting in incomplete coaptation. Despite the relatively high prevalence of IMR, most centers have only a small surgical experience with this disorder. The result is that a number of different procedures have been recently developed without clear improvement in patient outcomes. The current review will examine the myriad surgical options for IMR with a focus on clinical outcomes.

Mechanism of persistent ischemic mitral regurgitation after annuloplasty: importance of augmented posterior mitral leaflet tethering

BACKGROUND

We hypothesized that surgical annuloplasty for ischemic mitral regurgitation (MR) that displaces the posterior annulus anteriorly can potentially augment posterior leaflet (PML) tethering, leading to persistent MR. Relationships between leaflet configurations and persistent ischemic MR after the annuloplasty were investigated.

METHODS AND RESULTS

In 31 patients with surgical annuloplasty for ischemic MR and 20 controls, posterior and apical displacement of the leaflet coaptation, the anterior leaflet (AML) and PML tethering angles relative to the line connecting annuli, coaptation length (CL), and the MR grade were quantified before and early after surgery in echocardiographic left ventricular long-axis views. Six of the 31 patients showed persistent MR despite annuloplasty. Compared with patients without persistent MR, those with MR showed no improvement in the left ventricular ejection fraction and systolic volume, similar reduction in the annular area, significant increase in posterior displacement of the coaptation (P<0.01), no improvement in AML tethering, greater worsening in PML tethering (P<0.01), and no increase in the CL. All tethering variables were significantly correlated with both preoperative and postoperative MR in univariate analysis, and reduced CL was the primary independent determinant of both preoperative and postoperative MR. Although increased AML tethering was the primary determinant of the preoperative CL (r2=0.46, P<0.0001), increased PML tethering was the primary determinant afterward (r2=0.60, P<0.0001).

CONCLUSIONS

Although tethering of both leaflets is the major determinant of ischemic MR before surgical annuloplasty, both leaflets tethering but with predominant and augmented PML tethering is related to persistent ischemic MR after the annnuloplasty.

Seven years’ experience with suture annuloplasty for mitral valve repair

OBJECTIVE

Our early experience with the mural annulus shortening suture procedure for mitral valve repair showed superior hemodynamic performance over ring annuloplasty. The aim of this study was to assess the durability of the mural annulus shortening suture procedure and evaluate our 7-year experience regarding valve function, hemodynamic performance, and clinical outcome.

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.

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.

Experimental stenting of the posterior mitral leaflet to correct prolapse in mitral valve insufficiency

OBJECTIVE

This study investigated the use of a new concept of mitral valve reconstruction using a novel device to stent the posterior mitral leaflet in combination with semicircular annuloplasty. Modern mitral valve repair is an accepted modality and a routine procedure for treatment of degenerative mitral valve insufficiency. One of the most common mechanisms of mitral valve insufficiency is leaflet prolapse. In the majority of cases the posterior leaflet is dysfunctional and therapeutic reconstruction of the PII flail leaflet segment involves quadrangular resection which is usually combined to mitral annulo-plasty with a ring. A new time-saving concept of mitral valve reconstruction by stenting the posterior mitral leaflet in combination with semicircular annuloplasty is presented.

METHODS

The new mitral valve reconstruction device (Shelhigh MitroFast, Shelhigh, Inc., Union, NJ, USA) was implanted in four adult sheep. It is constructed as an annuloplasty ring in combination with a posterior leaflet stent. The device has the shape of a closed posterior leaflet and forms a "buttress" against which the anterior leaflet can coapt.

RESULTS

Every implantation of a MitroFast device could be performed in less than 30 minutes. After implantation of the device, all animals could be successfully weaned from CPB. Invasively measured left atrial pressure was below 12 mm Hg in all animals. After chest closure, transoesophageal echocardiography revealed a competent mitral valve in all animals, without any inflow restriction in three animals, and suspected mild stenosis in one animal.

CONCLUSIONS

In this experimental model, implantation of the newly designed annuloplasty ring with stenting the posterior mitral leaflet avoids extensive and time-consuming reconstructive surgery on a flail posterior leaflet. Implantation of the device resulted in favorable short-term hemodynamic effects. Implantation technique of the device is simple, the potential for minimal invasive implantation of a conceptual similar device will be further investigated.

Mechanism of recurrent ischemic mitral regurgitation after annuloplasty: continued LV remodeling as a moving target

BACKGROUND

Patients who undergo ring annuloplasty for ischemic mitral regurgitation (MR) often have persistent or recurrent MR. This may relate to persistent leaflet tethering from left ventricle (LV) dilatation that is not relieved by ring annuloplasty. Therefore, the purpose of this study was to test the hypothesis that recurrent MR in patients after ring annuloplasty relates to continued LV remodeling.

METHODS AND RESULTS

Serial echoes were reviewed in 30 patients (aged 72+/-11 years) who showed recurrent MR late (47+/-27 months) versus early (3.8+/-5.8 months) after ring annuloplasty for ischemic MR during coronary artery bypass grafting without interval infarction. Patients with intrinsic mitral valve disease were excluded. Echocardiographic measures of MR (vena contracta and jet area/left atrial area) and LV remodeling (LV dimensions, volumes, and sphericity) were assessed at each stage. The degree of MR increased from mild to moderate, on average, from early to late postoperative stages, without significant change in LV ejection fraction. Changes in MR paralleled increases in LV volumes and sphericity index at end-systole and end-diastole. The only independent predictor of late postoperative MR was LV sphericity index at end-systole.

CONCLUSIONS

Recurrent MR late after ring annuloplasty is associated with continued LV remodeling, emphasizing its dynamic relation to the LV.

Mitral regurgitation: overview of current surgical techniques and future developments

Mitral regurgitation is a complex disease with many different etiologies, underlying dysfunctions and histologic alterations. Surgical correction of this condition dramatically improves the life expectancy and life quality of affected patients. The structure of the mitral valve lends itself to many surgical techniques. The purpose of this review is to offer readers an overview on this subject.

Optimal Mitral Annular and Subvalvular Shape Change Created by the Coapsys Device to Treat Functional Mitral Regurgitation

We have reported that the Myocor Coapsys (Myocor, Inc, Maple Grove, MN) device treated functional mitral regurgitation (MR) by reducing mitral annular dimension and repositioning papillary muscles. This study was conducted to evaluate the optimal Coapsys device sizing level. The Coapsys device was implanted in seven dogs after induction of MR by rapid ventricular pacing. The device consists of anterior and posterior pads connected by a subvalvular cord. The device was tightened in 5% increments of the left ventricular epicardial to epicardial dimension up to 40%. Hemodynamic and echocardiographic measurements were repeated at each tightening level. The Coapsys significantly reduced or eliminated functional MR, and the reduction was maximized at the 30% tightening level or lower in all cases. Although the left ventricular end diastolic volume decreased significantly, forward stroke volume was maintained until the 35% tightening level. The forward ejection fraction significantly increased from 33 +/- 24% at baseline to 62 +/- 42% at 40% tightening level. Mean aortic pressure decreased slightly but significantly. The Coapsys device can be applied over a broad range of tightening levels with significant reduction in MR without negative physiologic impact. This feature makes the device usable [corrected] in a variety of clinical settings.

Off-pump mitral valve repair using the Coapsys device: a pilot study in a pacing-induced mitral regurgitation model

PURPOSE

The purpose of this study was to evaluate the ability of the Myocor Coapsys device to restore leaflet apposition and valve competency off-pump in a canine model of functional mitral regurgitation (MR).

DESCRIPTION

The Coapsys device was surgically implanted in 10 dogs after MR induction by rapid ventricular pacing. The Coapsys consists of anterior and posterior epicardial pads connected by a subvalvular chord. The annular head of the posterior pad was positioned at the annular level to draw the posterior leaflet and annulus toward the anterior leaflet. Final device size was selected when MR was minimized or eliminated as assessed by color flow Doppler echocardiography.

EVALUATION

All implants were placed off-pump without atriotomy, and mean MR grade was reduced from 2.9 +/- 0.7 to 0.6 +/- 0.7 (p < 0.001) acutely. No hemodynamic compromise was noted.

CONCLUSIONS

The Coapsys device consistently and significantly reduced or eliminated functional MR acutely. Further study will be required to assess the chronic stability of the repair in this animal model.

Does septal-lateral annular cinching work for chronic ischemic mitral regurgitation?

OBJECTIVES

Ring annuloplasty, the current treatment of choice for chronic ischemic mitral regurgitation, abolishes dynamic annular motion and immobilizes the posterior leaflet. In a model of chronic ischemic mitral regurgitation, we tested septal-lateral annular cinching aimed at maintaining normal annular and leaflet dynamics.

METHODS

Twenty-five sheep had radiopaque markers placed on the mitral annulus and anterior and posterior mitral leaflets. A transannular suture was anchored to the midseptal mitral annulus and externalized through the midlateral mitral annulus. After 7 days, biplane cinefluoroscopy provided 3-dimensional marker data (baseline) prior to creating inferior myocardial infarction by snare occlusion of obtuse marginal branches. After 7 weeks, the 9 animals that developed chronic ischemic mitral regurgitation were restudied before and after septal-lateral annular cinching. Anterior and posterior mitral leaflet angular excursion and annular septal-lateral and commissure-commissure dimensions and percent shortening were computed.

RESULTS

Septal-lateral annular cinching reduced septal-lateral dimension (baseline: 3.0 +/- 0.2; chronic ischemic mitral regurgitation: 3.5 +/- 0.4 [P <.05 vs baseline by repeated measures analysis of variance and Dunnett's test]; septal-lateral annular cinching: 2.4 +/- 0.3 cm; maximum dimension) and eliminated chronic ischemic mitral regurgitation (baseline: 0.6 +/- 0.5; chronic ischemic mitral regurgitation: 2.3 +/- 1.0 [P <.05 vs baseline by repeated measures analysis of variance and Dunnett's test]; septal-lateral annular cinching: 0.6 +/- 0.6; mitral regurgitation grade [0 to 4+]) but did not alter dynamic annular shortening (baseline: 7 +/- 3; chronic ischemic mitral regurgitation: 10 +/- 5; septal-lateral annular cinching: 6 +/- 2, percent septal-lateral shortening) or posterior mitral leaflet excursion (baseline: 46 degrees +/- 8 degrees; chronic ischemic mitral regurgitation: 41 degrees +/- 13 degrees; septal-lateral annular cinching: 46 degrees +/- 8 degrees ).

CONCLUSIONS

In this model, septal-lateral annular cinching decreased chronic ischemic mitral regurgitation, reduced annular septal-lateral diameter (but not commissure-commissure diameter), and maintained normal annular and leaflet dynamics. These findings provide additional insight into the treatment of chronic ischemic mitral regurgitation.

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.

Modified technique for mitral repair without ring annuloplasty

Mitral valve repair is the procedure of choice to correct mitral regurgitation. Most operative techniques use an annuloplasty ring to provide stability and durability to the correction. We present a modification of existing repair techniques, without the use of an annuloplasty ring, in which plication sutures allow both annular remodeling and stability. Clinical and echocardiographic follow-up in our series of 60 patients with a mean follow-up of 29 months is presented.

Hemodynamic performance of an unstented xenograft mitral valve substitute

OBJECTIVE

Stentless mitral xenografts offer potential clinical benefits because they mimic the normal bileaflet mitral valve. How best to implant them and their hemodynamic performance and durability, however, remain unknown.

METHODS

A stentless porcine mitral xenograft valve (Medtronic physiologic mitral valve) was implanted in 7 sheep with papillary muscle sewing tubes attached with transmural left ventricular sutures. Radiopaque markers were inserted on the leaflets, annular cuff, papillary tips, and left ventricle. After 10 +/- 5 days, the animals were studied with biplane videofluoroscopy to determine 3-dimensional marker coordinates at baseline and during dobutamine infusion. Transesophageal echocardiography assessed mitral regurgitation and valvular gradients. Mitral annular area was calculated from the annular markers. Physiologic mitral valve leaflet and annular dynamics were compared with 8 native sheep valves.

RESULTS

Average mitral regurgitation grade at baseline was 1.2 +/- 1.0 (range, 0-4), and the mean transvalvular pressure gradients were 3.6 +/- 1.3 and 6.2 +/- 2.2 mm Hg during baseline and dobutamine infusion, respectively. Xenograft mitral annular area contraction throughout the cardiac cycle was reduced (6% +/- 6% vs 13% +/- 4% for physiologic mitral valve and control valve, respectively; P =.03). Physiologic mitral valve leaflet geometry during closure differed from the native valve, with the anterior leaflet being convex to the atrium and with little motion of the posterior leaflet. Three animals survived more than 3 months; good healing of the annular cuff and papillary muscle tubes was demonstrated.

CONCLUSION

This stentless xenograft mitral valve substitute had low gradients at baseline and during stress conditions early postoperatively, with mild mitral regurgitation. Preliminary analysis of healing characteristics appeared favorable at 3 months. Additional studies are needed to determine long-term xenograft mitral valve performance and resistance to calcification.

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.

Three-dimensional geometric comparison of partial and complete flexible mitral annuloplasty rings

BACKGROUND

It has previously been shown in sheep that mitral annular physiologic dynamics during the cardiac cycle are abolished by complete ring annuloplasty, but recent clinical studies suggest that flexible partial ring annuloplasty preserves normal mitral annular dynamics.

METHODS

Eight radiopaque markers were sutured equidistantly around the mitral anulus in 3 groups of sheep: no-ring control animals (n = 16); animals with a flexible Tailor partial ring annuloplasty (n = 6; St Jude Medical, Inc, St Paul, Minn); and animals with a flexible Duran ring annuloplasty (n = 7; Medtronic, Inc, Minneapolis, Minn). After 7 to 10 days' recovery, 3-dimensional marker coordinates were measured by biplane cinefluoroscopy. Mitral annular area and folding (defined as displacement of the mitral anulus from a least-squares plane) and mitral annular septal-lateral and commissure-commissure dimensions were calculated from the 3-dimensional marker coordinates throughout the cardiac cycle every 17 ms.

RESULTS

In the no-ring control group mitral annular area varied from 8.0 +/- 0.2 to 7.2 +/- 0.2 cm(2) (10% +/- 2%), and the septal-lateral and commissure-commissure dimensions varied from 27.7 +/- 0.4 to 25.9 +/- 0.4 mm (7% +/- 1%) and from 38.2 +/- 0.8 to 36.4 +/- 0.8 mm (5% +/- 1%), respectively (mean +/- standard error of the mean, P <.001 for all comparisons). In the Duran ring annuloplasty and Tailor partial ring annuloplasty groups, the anulus was fixed in size throughout the cardiac cycle (area = 4.8 +/- 0.1 and 5.3 +/- 0.3 cm(2), septal-lateral = 21.8 +/- 0.7 and 22.0 +/- 0.8 mm, and commissure-commissure = 27.7 +/- 0.7 and 31.2 +/- 1.7 mm). Mitral annular folding did not differ significantly between the control and Tailor partial ring annuloplasty groups but was dampened in the Duran ring annuloplasty group.

CONCLUSIONS

Partial Tailor flexible ring annuloplasty fixed mitral annular area and dimensions throughout the cardiac cycle in sheep; however, it preserved physiologic mitral annular folding dynamics, which might be important in terms of long-term valve function and prevention of left ventricular outflow tract obstruction.

Edge-to-edge mitral repair: gradients and three-dimensional annular dynamics in vivo during inotropic stimulation

OBJECTIVE

The edge-to-edge (Alfieri) mitral repair technique appears to be clinically promising, but the potential for functional mitral stenosis, especially with exercise, remains a concern. We used the myocardial marker method combined with Doppler echocardiography to evaluate mitral annular (MA) three-dimensional (3-D) dynamics and transvalvular gradients after leaflet approximation before and during dobutamine infusion.

METHODS

Eight adult sheep underwent implantation of eight myocardial markers around the MA and nine in the left ventricle. Mitral leaflet edges were approximated at the valve center and micromanometers were placed in the left ventricle and atrium. The animals were studied with biplane videofluoroscopy to determine 3-D marker coordinates for computation of precise 3-D MA area and left ventricular (LV) volume. Epicardial Doppler echocardiography measured peak and mean diastolic mitral valve gradients at baseline and during dobutamine infusion (10 microg/kg per min).

RESULTS

During dobutamine stimulation, left ventricular dP/dt increased from 1776+/-712 to 3390+/-618 mmHg/s (P=0.002), and cardiac output (CO) increased from 2.7+/-1.1 to 5.1+/-1.2 l/min (P=0.009). Mitral annular area (MAA) at end-diastole (ED) fell from 8.6+/-1.4 to 7.0+/-1.8 cm(2) (P=0.001) with inotropic stimulation, but only a modest increase was observed in mean (1.4+/-0.4 vs. 2.4+/-1.0 mmHg, P=0.046) and peak (2.7+/-0.8 vs. 4.9+/-2.5 mmHg, P=0.03) diastolic mitral valve gradients. MAA changed dynamically throughout the cardiac cycle, reflecting normal physiology, but the magnitude of MAA change was augmented during inotropic stimulation (18+/-5% and 27+/-4% for control and dobutamine, respectively; P=0.004).

CONCLUSION

Dobutamine increased CO by 89% and decreased ED annular area by 19% after edge-to-edge repair, yet only a small increase in valve gradient occurred. Marker analysis showed enhanced dynamic motion of the mitral annulus. Thus, the edge-to-edge mitral valve repair was not associated with substantial transvalvular obstruction during high flow conditions and did not perturb normal MA 3-D dynamics in normal ovine hearts.

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.