Subvalvular repair: the key to repairing ischemic mitral regurgitation?

Interpapillary muscle distance independently predicts recurrent mitral regurgitation

OBJECTIVE

Ischaemic secondary mitral regurgitation (ISMR) after surgery is due to the displacement of papillary muscles resulting from progressive enlargement of the left ventricle end-diastolic diameter (LVEDD). Our aim was to prove that if the interpapillary muscle distance (IPMD) is surgically stabilized, an increase in LVEDD will not lead to a recurrence of ischaemic mitral regurgitation (MR).

METHODS

Ninety-six patients with ISMR, who underwent surgical revascularisation and annuloplasty, were randomly assigned in a 1:1 ratio to undergo papillary muscle approximation (PMA). At the 5-year follow-up, we assessed the correlation between PMA and echocardiographic improvements, the effect size of PMA on echocardiographic improvements, and a prediction model for recurrent MR using inferential tree analysis.

RESULTS

There was a significant correlation between PMA and enhancements in both the α and β angles (Spearman's rho > 0.7, p < 0.01). The α angle represents the angle between the annular plane and either the A2 annular-coaptation line or the P2 annular-coaptation line. The β angle indicates the angle between the annular plane and either the A2 annular-leaflet tip line or the P2 annular-leaflet tip line. PMA led to substantial improvements in LVEDD, tenting area, α and β angles, with a large effect size (Hedge's g ≥ 8, 95% CI ORs ≠ 1). The most reliable predictor of recurrent MR grade was the interpapillary distance, as only patients with an interpapillary distance greater than 40 mm developed ≥ 3 + grade MR. For patients with an IPMD of 40 mm or less, the best predictor of recurrent MR grade was LVEDD. Among the patients, only those with LVEDD greater than 62 mm showed moderate (2+) MR, while only those with LVEDD less than or equal to 62 mm had absent to mild (1+) MR.

CONCLUSION

Prediction of recurrent ischaemic MR is not independent of progressive LVEDD increase. PMA-based surgical procedure stabilises IPMD.

Characterization of 3-dimensional papillary muscle displacement in in vivo ovine models of ischemic/functional mitral regurgitation

OBJECTIVE

Papillary muscle (PM) displacement contributes to ischemic/functional mitral regurgitation (IMR/FMR). The displaced PMs pull the mitral leaflets into the left ventricle (ie, toward the apex) thus hampering leaflet coaptation. Intuitively apical leaflet tethering results from apical PM displacement. The 3-dimensional directions of PM displacement are, however, incompletely characterized.

METHODS

Data from in vivo ovine models of IMR (6-8 weeks of posterolateral infarction, n = 12) and FMR (9-21 days of rapid left ventricular pacing, n = 11) were analyzed. All sheep had radiopaque markers implanted on the anterior and posterior PM (PPM) tips, around the mitral annulus, and on the left ventricular apex. To explore 3-dimensional PM displacement directions, differences in marker coordinates were calculated at end-systole before and during IMR/FMR using a right-handed coordinate system centered on the mitral annular "saddle horn" with the y-axis passing through the apical marker.

RESULTS

No apical PM displacement was observed during either IMR or FMR. The anterior PM displaced laterally during FMR. Posterolateral PPM displacement was observed during IMR and FMR.

CONCLUSIONS

Experimental in vivo ovine models suggest posterolateral PPM displacement as a predominant pathomechanism leading to apical leaflet tethering during IMR/FMR.

Functional mitral regurgitation: an overview for surgical management framework

Functional mitral regurgitation (FMR) is one the most common complications of myocardial infarction (MI) in adults carrying a significant clinical and economic burden. Despite specific randomized controlled studies to address its treatment have been performed, there are still a number of questions remained unanswered. Outcomes of surgical repair of FMR are still hampered by a significant rate of recurrence of regurgitation and need for reoperation. Mechanisms underlying failure of repairs still need to be completely clarified and questions regarding the indications and optimal timing for intervention as well as the best suitable operative technique to be applied are still debated. This work will review the current knowledge on FMR including its pathogenic mechanisms, the available treatment strategies, the evidences from trials and observational studies and the potential future directions to address the issues related to its treatment.

Ischemic mitral regurgitation

Ischemic mitral regurgitation (IMR) is a frequent complication of left ventricular (LV) global or regional pathological remodeling due to chronic coronary artery disease. It is not a valve disease but represents the valvular consequences of increased tethering forces and reduced closing forces. IMR is defined as mitral regurgitation caused by chronic changes of LV structure and function due to ischemic heart disease and it worsens the prognosis. In this review, we discuss on etiology, pathophysiology, and mechanisms of IMR, its classification, evaluation, and therapeutic corrective methods of IMR.

Mitral valve repair and subvalvular intervention for secondary mitral regurgitation: a systematic review and meta-analysis of randomized controlled and propensity matched studies

BACKGROUND

Combining a ring annuloplasty (Ring) with a mitral subvalvular intervention (Ring + subvalvular) in patients with secondary mitral regurgitation (MR) may improve mitral valve (MV) repair durability. However, the outcomes of this strategy compared with a Ring only, have not been clearly defined.

METHODS

A systematic review and meta-analysis was performed utilizing randomized controlled and propensity matched studies which compared a Ring + subvalvular versus Ring MV repair for the treatment of secondary MR. Risk ratio (RR), weighted mean difference (MD), and the 95% confidence interval (CI) were calculated by the Mantel-Haenszel and inverse-variance methods, for clinical outcomes and echocardiographic measures of follow-up MR, left ventricular (LV) reverse remodeling, and MV apparatus geometry.

RESULTS

Five studies were identified, with a total of 397 patients. Baseline characteristics were similar between groups, and all patients had moderate to severe secondary MR, with the vast majority in the setting of ischemic cardiomyopathy. A Ring + subvalvular repair consisted of papillary muscle approximation (n=2), papillary muscle relocation (n=2), or secondary chordal cutting (n=1). Follow-up ranged from 10.1 (mean range =0.25-42) to 69 [interquartile range (IQR) =23-82] months. When compared with Ring only at last follow-up, a Ring + subvalvular MV repair was associated with: (I) a smaller MR grade (MD =-0.44, 95% CI -0.69 to -0.19; P=0.0005); (II) a reduced risk of moderate or greater recurrent MR (RR =0.43, 95% CI, 0.27-0.66; P=0.0002); (III) a smaller mean LV end-diastolic diameter (MD =-3.56 mm, 95% CI -5.40 to -1.73; P=0.0001) and a greater ejection fraction (MD =2.64%, 95% CI, 0.13-5.15; P=0.04); and, (IV) an improved MV apparatus geometry. There were no differences in operative mortality, post-operative morbidity, or follow-up survival between surgical approaches.

CONCLUSIONS

When compared with Ring only, a Ring + subvalvular MV repair is associated with greater LV reverse remodeling and systolic function, less recurrence of moderate or greater MR, and an improved geometry of the MV apparatus at short and mid-term follow-up.

The role of papillary muscle approximation in mitral valve repair for the treatment of secondary mitral regurgitation

Secondary mitral regurgitation (MR) is present in up to half of patients with dilated cardiomyopathy, and is associated with a poor prognosis. It primarily results from progressive left ventricular remodelling, papillary muscle displacement and tethering of the mitral valve leaflets. Mitral valve repair with an undersized ring annuloplasty is the reparative procedure of choice in the treatment of secondary MR. However, this technique is associated with a 30-60% incidence of recurrent moderate or greater MR at mid-term follow-up, which results in progressive deterioration of left ventricular function and increased morbidity. Combined mitral valve repair and papillary muscle approximation has been applied in order to address both the annular and subvalvular dysfunction that coexist in secondary MR, which include graft and suture-based techniques. Herein, we provide a systematic review of the published literature regarding the technical aspects, clinical application, and outcomes of mitral valve repair with combined ring annuloplasty and papillary muscle approximation for the treatment of secondary MR.

Ischemic mitral valve prolapse

Ischemic mitral prolapse (IMP) is a pathologic entity encountered in about one-third among the patients undergoing surgery for ischemic mitral regurgitation (IMR). IMP is generally the result of a papillary muscle injury consequent to myocardial, but the recent literature is progressively unveiling a more complex pathogenesis. The mechanisms underlying its development regards the impairment of one or more components of the mitral apparatus, which comprises the annulus, the chordae tendineae, the papillary muscle and the left ventricular wall. IMP is not only a disorder of valvular function, but also entails coexistent aspects of a geometric disturbance of the mitral valve configuration and of the left ventricular function and dimension and a correct understanding of all these aspects is crucial to guide and tailor the correct therapeutic strategy to be adopted. Localization of prolapse, anatomic features of the prolapsed leaflets and the subvalvular apparatus should be carefully evaluated as also constituting the major determinants defining patient's outcomes. This review will summarize our current understanding of the pathophysiology and clinical evidence on IMP with a particular focus on the surgical treatment.

Is subvalvular repair worthwhile in severe ischemic mitral regurgitation? Subanalysis of the Papillary Muscle Approximation trial

OBJECTIVE

The symmetry of mitral valve tethering and regional left ventricle wall dysfunction are reported to play a fundamental role in the outcomes and long-term durability of surgical repair in ischemic mitral regurgitation (IMR). We recently demonstrated in a randomized clinical trial (the Papillary Muscle Approximation trial) the superiority of papillary muscle approximation (PMA) in combination with standard restrictive annuloplasty (RA) in severe IMR over annuloplasty alone in terms of adverse left ventricular remodeling and mitral regurgitation (MR) recurrence. This approach, however, failed to produce a survival advantage and was still plagued by a high incidence of reoperation. We therefore performed a subanalysis of the PMA trial on the basis of preoperative parameters to elucidate the value of subvalvular surgery in certain subcategories of patients with the aim of creating a decisional algorithm on the best operative strategy.

METHODS

We performed a subanalysis of PMA trial, evaluating 96 patients with severe IMR and eligible for myocardial revascularization randomized to PMA + RA (n = 48) versus RA alone (n = 48) in association with coronary artery bypass grafting. Endpoints included left ventricular remodeling, MR recurrence, overall mortality, reoperation, and a composite cardiac endpoint (cardiac death, stroke, reintervention, hospitalization for heart failure, or New York Heart Association class worsening). Stratification variables were preoperative symmetry of mitral valve tethering and regional wall motion abnormality.

RESULTS

PMA improved ventricular remodeling and recurrence of MR in both preoperative symmetric and asymmetric tethering and in case of inferior wall dyskinesia but did not produce an additional benefit in anterolateral wall dysfunction.

CONCLUSIONS

Preoperative symmetric and asymmetric tethering and isolated inferior wall dyskinesia are an indication for subvalvular apparatus surgery in IMR.

Mitral valve disease--morphology and mechanisms

Mitral valve disease is a frequent cause of heart failure and death. Emerging evidence indicates that the mitral valve is not a passive structure, but--even in adult life--remains dynamic and accessible for treatment. This concept motivates efforts to reduce the clinical progression of mitral valve disease through early detection and modification of underlying mechanisms. Discoveries of genetic mutations causing mitral valve elongation and prolapse have revealed that growth factor signalling and cell migration pathways are regulated by structural molecules in ways that can be modified to limit progression from developmental defects to valve degeneration with clinical complications. Mitral valve enlargement can determine left ventricular outflow tract obstruction in hypertrophic cardiomyopathy, and might be stimulated by potentially modifiable biological valvular-ventricular interactions. Mitral valve plasticity also allows adaptive growth in response to ventricular remodelling. However, adverse cellular and mechanobiological processes create relative leaflet deficiency in the ischaemic setting, leading to mitral regurgitation with increased heart failure and mortality. Our approach, which bridges clinicians and basic scientists, enables the correlation of observed disease with cellular and molecular mechanisms, leading to the discovery of new opportunities for improving the natural history of mitral valve disease.

Geometric perturbations in multiheaded papillary tip positions associated with acute ovine ischemic mitral regurgitation

BACKGROUND

Novel surgical approaches are focusing on the "ventricular disease" of ischemic mitral regurgitation (IMR), to correct altered papillary muscle (PM) tip positions (apical displacement) and ameliorate leaflet tethering. Due to the anatomic complexity of the subvalvular apparatus, however, the precise geometric perturbations of the multiheaded PM tips associated with IMR remain uncharacterized.

METHODS

In 6 adult sheep, we implanted 3 markers on each PM. To specifically identify distinct PM tips, 1 marker was placed on the PM origin of the dominant chord to the anterior, posterior, and commissural leaflets. Nine markers were placed on the edge of the posterior mitral leaflet, and 5 on the edge of the anterior mitral leaflet. Eight markers were sewn around the mitral annulus. Animals were studied immediately postoperatively, with biplane videofluoroscopy and transesophageal echocardiography, before and during acute snare occlusion of the proximal left circumflex coronary artery, to induce IMR. Papillary muscle tip and leaflet edge geometry was expressed as the orthogonal distance of each respective marker to the least-squares mitral annulus plane at end-systole. In addition, the distance from each PM tip marker to the mitral annulus "saddle horn" was calculated.

RESULTS

Acute left circumflex occlusion significantly increased mitral regurgitation from a baseline of 0.7 ± 0.3 to 2.5 ± 0.5 (P < .05). The IMR was associated with posterior leaflet restriction near the central leaflet edge, with simultaneous prolapse of both leaflets near the posterior commissure. No apical displacement of PM tips was observed during IMR, although the posterior PM moved farther away from the midseptal annulus.

CONCLUSIONS

During acute ischemia, no apical displacement of any PM tip was observed. Posterior PM movement away from the annular saddle horn, and toward the annulus, was associated with IMR and leaflet prolapse near the posterior commissure, and with restriction near the valve center. These data may help guide development of surgical interventions aimed at PM repositioning.

Posterior papillary muscle anchoring affects remote myofiber stress and pump function: finite element analysis

BACKGROUND

The role of posterior papillary muscle anchoring (PPMA) in the management of chronic ischemic mitral regurgitation (CIMR) is controversial. We studied the effect of anchoring point direction and relocation displacement on left ventricular (LV) regional myofiber stress and pump function.

METHODS

Previously described finite element models of sheep 16 weeks after posterolateral myocardial infarction (MI) were used. True-sized mitral annuloplasty (MA) ring insertion plus different PPM anchoring techniques were simulated. Anchoring points tested included both commissures and the central anterior mitral annulus; relocation displacement varied from 10% to 40% of baseline diastolic distance from the PPM to the anchor points on the annulus. For each reconstruction scenario, myofiber stress in the MI, border zone, and remote myocardium as well as pump function were calculated.

RESULTS

PPMA caused reductions in myofiber stress at end-diastole and end-systole in all regions of the left ventricle that were proportional to the relocation displacement. Although stress reduction was greatest in the MI region, it also occurred in the remote region. The maximum 40% displacement caused a slight reduction in LV pump function. However, with the correction of regurgitation by MA plus PPMA, there was an overall increase in forward stroke volume. Finally, anchoring point direction had no effect on myofiber stress or pump function.

CONCLUSIONS

PPMA reduces remote myofiber stress, which is proportional to the absolute distance of relocation and independent of anchoring point. Aggressive use of PPMA techniques to reduce remote myofiber stress may accelerate reverse LV remodeling without impairing LV function.

Five-year real world outcomes of GeoForm ring implantation in patients with ischemic mitral regurgitation

BACKGROUND

Reductive ring annuloplasty represents the current standard surgical therapy for ischemic mitral regurgitation (IMR); however, the clinical results have been suboptimal. Etiology-specific prostheses such as the GeoForm annuloplasty ring have been designed to better address the annular and subvalvular perturbations associated with IMR. However, clinical experience is limited, and mid-term results are lacking.

METHODS

We reviewed the clinical outcomes of 86 patients who had undergone implantation of a GeoForm ring at our center from 2005 to 2011. Perioperative mortality and clinical parameters were derived from The Society of Thoracic Surgeons database. Follow-up survival was assessed using the Social Security Death Index. Surviving patients were interviewed by telephone for valve-specific follow-up data and to complete the Medical Outcomes Study, short-form, 36-item, quality-of-life questionnaire.

RESULTS

The mean grade of IMR preoperatively was 3.1±0.8 (range, 1-4+), 0.2±0.4 in the immediate postoperative period, and 0.7±0.7 at the last mean follow-up point of 41 months; only 2 patients developed ≥2+IMR during the follow-up period, for a 5-year freedom from recurrent 2+ IMR of 86%. The mean left ventricular end-diastolic and end-systolic diameters decreased from before to after surgery from 6.0±0.0 cm to 5.3±09 cm and 5.0±0.9 cm to 4.3±1.1 cm, respectively (P<.001). Perioperative mortality was 5.8% (5 of 86), and 1-, 3-, and 5-year survival was 87%, 81%, and 75%, respectively. At the last follow-up point, 80% of patients were in New York Heart Association class I and II, and their quality of life was equal to, or better than, age-matched controls from the general population.

CONCLUSIONS

Implantation of the GeoForm ring offers very good control of IMR, with low rate of recurrent IMR at mid-term follow-up. The use of this prosthesis was associated with good perioperative mortality, mid-term survival, and quality of life.

Another multidisciplinary look at ischemic mitral regurgitation

Ischemic mitral regurgitation (IMR) continues to challenge surgeons and scientists alike. This vexing clinical entity frequently complicates myocardial infarction and carries a poor prognosis both in the setting of coronary disease and idiopathic dilated cardiomyopathy. Ischemic mitral regurgitation encompasses a difficult patient population that is characterized by high operative mortality, poor long term outcomes, and frequent recurrent insufficiency after standard surgical repair. Yet optimal surgical repair and improved clinical outcomes can only be achieved with better knowledge of the pathophysiology of IMR which is still incompletely understood. The causative mechanism of IMR appears to lie in the annular and subvalvular frame of the valve rather than leaflet or chordal structure leading to such labels as "ischemic," "functional," "non-organic," and "cardiomyopathy associated" being applied in the clinical literature. Although ischemic mitral regurgitation is a prevailing clinical entity, it has not been consistently defined in the literature, contributing to considerable confusion and contradictory results of clinical studies. As the mechanisms of pathophysiology have been better elucidated, novel surgical and interventional strategies have been developed recently to provide better treatment for this difficult patient population. In this review, we undertake a multidisciplinary update of the pathophysiology, classification, and surgical and interventional treatment of ischemic mitral regurgitation in today's clinical practice.

Mechanism of valvular regurgitation

PURPOSE OF REVIEW

Despite improvements in surgical techniques, valvular regurgitation results in major morbidity in children with heart disease. Functional anatomy, mechanisms of valve closure and adaptation to changing hemodynamic stress in normal mitral and tricuspid valves are complex and only partially understood. As well, pathology of atrioventricular valve regurgitation is further complicated by congenital valve abnormalities involving leaflet tissue, supporting chordal apparatus and displaced papillary muscles. This review provides a current understanding of the mechanisms that result in atrioventricular valve failure.

RECENT FINDINGS

Mitral valve leaflets have contractile elements, in addition to atrial muscle modulation of leaflet tension. When placed under mechanical tethering stress, the mitral valve adapts by leaflet expansion, which increases coaptation surface reserve and chordal thickening. Both pediatric and adult studies are increasingly reporting on the importance of subvalvar apparatus function in maintaining valve competency.

SUMMARY

The maintenance of efficient valve function is accomplished by a complex series of events involving atrial and annular contraction, annular deformation, active leaflet tension, chordal transmission of papillary muscle contractions and ventricular contraction.

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.

Echocardiographic evaluation of mitral geometry in functional mitral regurgitation

Objectives

We sought to evaluate the geometric changes of the mitral leaflets, local and global LV remodeling in patients with left ventricular dysfunction and varying degrees of Functional mitral regurgitation (FMR).

Background

Functional mitral regurgitation (FMR) occurs as a consequence of systolic left ventricular (LV) dysfunction caused by ischemic or nonischemic cardiomyopathy. Mitral valve repair in ischemic MR is one of the most controversial topic in surgery and proper repairing requires an understanding of its mechanisms, as the exact mechanism of FMR are not well defined.

Methods

136 consecutive patients mean age of 55 with systolic LV dysfunction and FMR underwent complete echocardiography and after assessing MR severity, LV volumes, Ejection Fraction, LV sphericity index, C-Septal distance, Mitral valve annulus, Interpapillary distance, Tenting distance and Tenting area were obtained.

Results

There was significant association between MR severity and echocardiogarphic indices (all p values < 0.001). Severe MR occurred more frequently in dilated cardiomyopathy (DCM) patients compared to ischemic patients, (p < 0.001). Based on the model, only Mitral valve tenting distance (TnD) (OR = 22.11, CI 95%: 14.18 – 36.86, p < 0.001) and Interpapillary muscle distance (IPMD), (OR = 6.53, CI 95%: 2.10 – 10.23, p = 0.001) had significant associations with MR severity.

Mitral annular dimensions and area, C-septal distance and sphericity index, although greater in patients with severe regurgitation, did not significantly contribute to FMR severity.

Conclusion

Degree of LV enlargement and dysfunction were not primary determinants of FMR severity, therefore local LV remodeling and mitral valve apparatus deformation are the strongest predictors of functional MR severity.

Effects of acute ischemic mitral regurgitation on three-dimensional mitral leaflet edge geometry

BACKGROUND

Improved quantitative understanding of in vivo leaflet geometry in ischemic mitral regurgitation (IMR) is needed to improve reparative techniques, yet few data are available due to current imaging limitations. Using marker technology we tested the hypotheses that IMR (1) occurs chiefly during early systole; (2) affects primarily the valve region contiguous with the myocardial ischemic insult; and (3) results in systolic leaflet edge restriction.

METHODS

Eleven sheep had radiopaque markers sutured as five opposing pairs along the anterior (A(1)-E(1)) and posterior (A(2)-E(2)) mitral leaflet free edges from the anterior commissure (A(1)-A(2)) to the posterior commissure (E(1)-E(2)). Immediately postoperatively, biplane videofluoroscopy was used to obtain 4D marker coordinates before and during acute proximal left circumflex artery occlusion. Regional mitral orifice area (MOA) was calculated in the anterior (Ant-MOA), middle (Mid-MOA), and posterior (Post-MOA) mitral orifice segments during early systole (EarlyS), mid systole (MidS), and end systole (EndS). MOA was normalized to zero (minimum orifice opening) at baseline EndS. Tenting height was the distance of the midpoint of paired markers to the mitral annular plane at EndS.

RESULTS

Acute ischemia increased echocardiographic MR grade (0.5+/-0.3 vs 2.3+/-0.7, p<0.01) and MOA in all regions at EarlyS, MidS, and EndS: Ant-MOA (7+/-10 vs 22+/-19 mm(2), 1+/-2 vs 18+/-16 mm(2), 0 vs 17+/-15 mm(2)); Mid-MOA (9+/-13 vs 25+/-17 mm(2), 3+/-6 vs 21+/-19 mm(2), 0 vs 25+/-17 mm(2)); and Post-MOA (8+/-10 vs 25+/-16, 2+/-4 vs 22+/-13 mm(2), 0 vs 23+/-13 mm(2)), all p<0.05. There was no change in MOA throughout systole (EarlyS vs MidS vs EndS) during baseline conditions or ischemia. Tenting height increased with ischemia near the central and the anterior commissure leaflet edges (B(1)-B(2): 7.1+/-1.8mm vs 7.9+/-1.7 mm, C(1)-C(2): 6.9+/-1.3mm vs 8.0+/-1.5mm, both p<0.05).

CONCLUSIONS

MOA during ischemia was larger throughout systole, indicating that acute IMR in this setting is a holosystolic phenomenon. Despite discrete postero-lateral myocardial ischemia, Post-MOA was not disproportionately larger. Acute ovine IMR was associated with leaflet restriction near the central and the anterior commissure leaflet edges. This entire constellation of annular, valvular, and subvalvular ischemic alterations should be considered in the approach to mitral repair for IMR.