Early systolic mitral leaflet "loitering" during acute ischemic mitral regurgitation

Acute Ischaemic Mitral Valve Regurgitation

Acute ischaemic mitral regurgitation (IMR) is an increasingly rare and challenging complication following acute myocardial infarction. Despite recent technical advances in both surgical and percutaneous interventions, a poor prognosis is often associated with this challenging patient cohort. In this review, we revisit the diagnosis and typical echocardiographic features, and evaluate current surgical and percutaneous treatment options for patients with acute IMR.

Complicating Acute Myocardial Infarction. Current Status and Unresolved Targets for Subsequent Research

Mechanical reperfusion with primary angioplasty, as the treatment of choice in acute myocardial infarction (MI), is associated not only with a high percentage of full epicardial and tissue reperfusion but also with a very good immediate and long-term clinical outcome. However, the Achilles heel of MI treatment is its ensemble of complications, such as cardiogenic shock due to severe systolic and/or diastolic dysfunction or MI mechanical complications, including perforation of the left ventricular free wall, papillary muscle rupture with acute mitral regurgitation and ventricular septal rupture. They are associated with an increased or, sometimes, with an extremely high mortality rate, determining the overall mortality in an MI patient population. In this review we summarize the mechanisms of MI complications, current therapeutic management and alternative directions for overcoming their devastating consequences. Moreover, we have sought to indicate gaps in the evidence on current treatments as the potential targets for further clinical research. From the perspective of mortality trends that are not improving, the forthcoming therapeutic management of complicated MI will require an individualized and novel approach based on their thorough pathobiology.

Surgical access via right thoracotomy facilitates tricuspid valve surgery in sheep

In quadrupeds, the three-dimensional orientation of the heart with respect to the thorax is fundamentally different from that in humans. In this study, we assessed the best surgical approach to the tricuspid valve in sheep. Firstly, different surgical access sites to the tricuspid valve were tested in sheep cadavers, the anatomy was analyzed, and the optimal surgical approach to the tricuspid valve was determined. Secondly - along with cardiopulmonary bypass and cardioplegic arrest -the chosen approach was tested in six adult sheep in vivo. Anatomical analyses revealed that a left thoracotomy provided optimal access to the aorta and left heart. However, visualization of the right heart was significantly impaired. In contrast, a right thoracotomy provided good access to the right heart, but the ascending aorta was difficult to approach. Therefore, in the in vivo studies, arterial cannulation was performed through a carotid (n = 4) or femoral (n = 2) artery. In conclusion, a right-sided thoracotomy allows good visualization of all components of the tricuspid valve complex in sheep, but not of the ascending aorta. Consequently, peripheral vessels are preferred for arterial cannulation. This work may stimulate the investigation of pathomechanisms and/or novel treatment options for tricuspid valve pathologies.

Mitral valve coaptation and its relationship to late diastolic flow: A color Doppler and vector flow map echocardiographic study in normal subjects

BACKGROUND

Three competing theories about the mechanism of mitral coaptation in normal subjects were evaluated by color Doppler and vector flow mapping (VFM): (1) beginning of ventricular (LV) ejection, (2) "breaking of the jet" of diastolic LV inflow, and (3) returning diastolic vortices impacting the leaflets on their LV surfaces.

METHODS AND RESULTS

We analyzed 80 color Doppler frames and 320 VFM measurements. In all 20 normal subjects, coaptation occurred before LV ejection, 78±16 ms before onset. On color Doppler frames the larger anterior, and smaller posterior vortices circle back and, in all cases, strike the ventricular surfaces of the leaflets. On the first closing-begins frame, for the first time, vortex velocity normal to the ventricular surface of the anterior leaflet (AML) is greater than that in the mitral orifice, and the angle of attack of LV vortical flow onto the AML is twice as high as the angle of flow onto the valve in orifice. Thus, at the moment coaptation begins, vortical flow strikes the mitral leaflet with higher velocity, and higher angle of attack than orifice flow, and thus with greater force. According to the "breaking of the jet" theory, one would expect to see de novo LV flow perpendicular to the leaflets beginning after transmitral flow terminates. Instead, the returning continuous LV vortical flow that impacts the valve builds continuously after the P-wave.

CONCLUSIONS

Late diastolic vortices strike the ventricular surfaces of the mitral leaflets and contribute to valve coaptation, permitted by concomitant decline in transmitral flow.

Immediate Improvement in Severe Mitral Regurgitation After Aortic Valve Replacement for Severe Aortic Insufficiency

A 57-year-old male with ascending aortic aneurysm, severe aortic regurgitation, and severe mitral regurgitation (MR) underwent ascending aortic replacement and aortic valve replacement. MR in this patient with normal mitral valve morphology was considered secondary to aortic valve incompetency. Consequently, a surgical approach to restore aortic valve function was adopted with successful MR resolution. This case report demonstrates the possibility of reversing early functional mitral regurgitation without surgically approaching the mitral valve.

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.

Tension to passively cinch the mitral annulus through coronary sinus access: an ex vivo study in ovine model

INTRODUCTION

The transcatheter mitral valve repair (TMVR) technique utilizes a stent to cinch a segment of the mitral annulus (MA) and reduces mitral regurgitation. The cinching mechanism results in reduction of the septal-lateral distance. However, the mechanism has not been characterized completely. In this study, a method was developed to quantify the relation between cinching tension and MA area in an ex vivo ovine model.

METHOD

The cinching tension was measured from a suture inserted within the coronary sinus (CS) vessel with one end tied to the distal end of the vessel and the other end exited to the CS ostium where it was attached to a force transducer on a linear stage. The cinching tension, MA area, septal-lateral (S-L) and commissure-commissure (C-C) diameters and leakage was simultaneously measured in normal and dilated condition, under a hydrostatic left ventricular pressure of 90 mm Hg.

RESULTS

The MA area was increased up to 22.8% after MA dilation. A mean tension of 2.1 ± 0.5 N reduced the MA area by 21.3 ± 5.6% and S-L diameter by 24.2 ± 5.3%. Thus, leakage was improved by 51.7 ± 16.2% following restoration of normal MA geometry.

CONCLUSION

The cinching tension generated by the suture acts as a compensation force in MA reduction, implying the maximum tension needed to be generated by annuloplasty device to restore normal annular size. The relationship between cinching tension and the corresponding MA geometry will contribute to the development of future TMVR devices and understanding of myocardial contraction function.

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.

The mechanobiology of mitral valve function, degeneration, and repair

In degenerative valve disease, the highly organized mitral valve leaflet matrix stratification is progressively destroyed and replaced with proteoglycan rich, mechanically inadequate tissue. This is driven by the actions of originally quiescent valve interstitial cells that become active contractile and migratory myofibroblasts. While treatment for myxomatous mitral valve disease in humans ranges from repair to total replacement, therapies in dogs focus on treating the consequences of the resulting mitral regurgitation. The fundamental gap in our understanding is how the resident valve cells respond to altered mechanical signals to drive tissue remodeling. Despite the pathological similarities and high clinical occurrence, surprisingly little mechanistic insight has been gleaned from the dog. This review presents what is known about mitral valve mechanobiology from clinical, in vivo, and in vitro data. There are a number of experimental strategies already available to pursue this significant opportunity, but success requires the collaboration between veterinary clinicians, scientists, and engineers.

Effect of anterior strut chordal transection on the force distribution on the marginal chordae of the mitral valve

OBJECTIVES

Transection of the secondary chordae on the anterior leaflet of the mitral valve to relieve leaflet tethering and reduce regurgitation is an experimentally proven procedure to correct functional mitral regurgitation. In the present study, we sought to investigate whether transecting the secondary chordae would have an effect on the marginal chordal force on the same leaflet.

METHODS

Adult porcine mitral valves (n = 8) were studied in a pulsatile heart simulator, in which the papillary muscle positions can be precisely positioned. Miniature transducers were inserted into the anterior marginal chordae to measure the chordal forces. Each valve was studied under baseline conditions, 3 different tethering conditions (apical, apical-lateral, and apical-lateral-posterior), and after chordal cutting in the 3 tethering conditions. The temporal changes and peak and average marginal chordal forces under each condition are reported.

RESULTS

Apical tethering increased the marginal chordal force by an average of 96% but remained unchanged after chordal cutting. With apical-lateral tethering, the marginal chordal force increased by 210% from baseline and increased further to 350% of baseline after chordal cutting. After apical-lateral-posterior tethering, the marginal chordal force increased to 335% of baseline before transection and by 548% after transection.

CONCLUSIONS

The increase in the marginal chordal force after secondary chordal cutting depends on the location of the papillary muscles and the extent of leaflet tethering. Although chordal cutting might not alter the valve mechanics under minimal leaflet tethering, it significantly affects the mechanics when the leaflet tethering is more pronounced, which is typically seen in patients with functional mitral regurgitation.

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.

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.

Asynchronous movement of mitral annulus: an additional mechanism of ischaemic mitral regurgitation

In-coordinate mitral annulus movement might participate in the pathogenesis of functional mitral regurgitation. We evaluated a relationship between indices of mitral annulus systolic asynchrony and mitral regurgitation in patients after myocardial infarction in order to determine independent determinants of effective regurgitant orifice (ERO) area in a multivariate regression model. Tissue Doppler echocardiographic studies and quantitative analysis of mitral regurgitation were performed in 40 patients (33 men, 7 women, mean age 60.1 +/- 9.2 years) with a history of Q-wave myocardial infarction, with and without significant functional mitral regurgitation.A multivariate regression model showed that mitral annulus movement asynchrony index-difference between the longest and the shortest time from the R wave in the electrocardiogram to the cessation of systolic movement of the four aspects of mitral annulus, is an independent from ejection fraction, sphericity index, tenting, annulus diameter and infarct location, determinant of mitral regurgitation ERO area (r(2) change 0.72, p <or= 0.01). The only other independent predictor of ERO area was mitral annulus diameter (r(2) change 0.79, p <or= 0.01). Other variables were predictors of ERO only in univariate analyses: ejection fraction (r(2) change 0.59, p <or= 0.01), tenting area (r(2) change 0.76, p <or=0.01 ) and sphericity index (r(2) change 0.75, p <or=0.01). In conclusion, mitral annulus asynchrony is an additional mechanism contributing to the development of functional mitral regurgitation. This suggests, that cardiac resynchronization might be considered, either as a first line intervention in patients with mitral regurgitation not considered for mitral surgery or as a supplementary measure, when results of surgery are suboptimal.

Asynchronous movement of mitral annulus: an additional mechanism of ischaemic mitral regurgitation

In-coordinate mitral annulus movement might participate in the pathogenesis of functional mitral regurgitation. We evaluated a relationship between indices of mitral annulus systolic asynchrony and mitral regurgitation in patients after myocardial infarction in order to determine independent determinants of effective regurgitant orifice (ERO) area in a multivariate regression model. Tissue Doppler echocardiographic studies and quantitative analysis of mitral regurgitation were performed in 40 patients (33 men, 7 women, mean age 60.1 +/- 9.2 years) with a history of Q-wave myocardial infarction, with and without significant functional mitral regurgitation.A multivariate regression model showed that mitral annulus movement asynchrony index-difference between the longest and the shortest time from the R wave in the electrocardiogram to the cessation of systolic movement of the four aspects of mitral annulus, is an independent from ejection fraction, sphericity index, tenting, annulus diameter and infarct location, determinant of mitral regurgitation ERO area (r(2) change 0.72, p <or= 0.01). The only other independent predictor of ERO area was mitral annulus diameter (r(2) change 0.79, p <or= 0.01). Other variables were predictors of ERO only in univariate analyses: ejection fraction (r(2) change 0.59, p <or= 0.01), tenting area (r(2) change 0.76, p <or=0.01 ) and sphericity index (r(2) change 0.75, p <or=0.01). In conclusion, mitral annulus asynchrony is an additional mechanism contributing to the development of functional mitral regurgitation. This suggests, that cardiac resynchronization might be considered, either as a first line intervention in patients with mitral regurgitation not considered for mitral surgery or as a supplementary measure, when results of surgery are suboptimal.

The Geoform disease-specific annuloplasty system: a finite element study

BACKGROUND

Functional mitral regurgitation (FMR) is the inability of mitral leaflets to coapt due to a combination of functional and geometrical factors. Valve competence is commonly restored by undersized annuloplasty, reducing the native annulus anteroposterior dimension. In case of severe FMR, this solution may be inadequate. The use of rings specific for the correction of FMR may lead to better results.

METHODS

The performance of the Geoform ring, a recently designed FMR-specific prosthesis, was compared with that of a standard Physio annuloplasty ring. Finite element modeling was used to simulate dilated cardiomyopathy-related FMR and compare, at the systolic peak, the valve's pathologic condition with the postoperative scenario corresponding to both devices. Three degrees of the pathology were simulated by progressively displacing papillary muscles apically, up to 5 mm. Three ring sizes were modeled.

RESULTS

Regurgitant area, coaptation length, and stresses acting on valve structures were assessed. When the use of the Geoform was modeled, coaptation length was always longer than 7 mm. In the most unfavorable case, the regurgitant area reduction was 74% with respect to baseline, and leaflets stresses were reduced by 20% when undersizing was simulated. When Physio ring implantation was simulated, coaptation length maximum extent was equal to 4.3 mm, the maximum regurgitant area reduction was equal to 60%, and leaflet stress reduction was observed.

CONCLUSIONS

Disease-specific prostheses may allow for restoration of valve competence even for significant degrees of leaflets tethering and avoid the need for aggressive undersizing, thus leading to more durable results.

Systematic Reductive Annuloplasty of the Mitral and Tricuspid Valves in Patients With End-Stage Ischemic Dilated Cardiomyopathy

OBJECTIVE

Patients with ischemic dilated cardiomyopathy exhibit extensive remodeling of the left ventricle, annular dilation, and significant mitral and tricuspid regurgitation. These changes increase per operative morbidity and mortality, and emphasize patient candidacy for heart transplantation. The aim of this study is to show immediate and long-term results after reductive annuloplasty of double (mitral and tricuspid) orifices, performed at the time of coronary artery bypass grafting, as an alternative to heart transplantation.

METHODS

There were 226 consecutive patients (205 males, 21 females) with ischemic dilated cardiomyopathy, mean ejection fraction below 30% [(26.6 +/- 3.1)%], and mean left ventricle end-diastolic internal diameter greater than 7.0 cm (7.3 +/- 0.3 cm). In addition to myocardial revascularization, Carpentier's mitral annuloplasty and posterior semicircular reductive annuloplasty were performed in 37 and 189 patients, respectively. In all 226 patients, a modified De Vega's tricuspid annuloplasty was performed.

RESULTS

Postoperative 30-day mortality was 7.5% (17 patients). Survival rates after 5 and 10 years were (61.5 +/- 4.0)% and (38.05 +/- 8.0)%, respectively.

CONCLUSION

Reductive annuloplasty of mitral and tricuspid orifices performed at the time of myocardial revascularization could be beneficial in selective patients with ischemic dilated cardiomyopathy. Results indicate that this method should not be recognized as a valve repair, but ventricular repair procedure also.

Preoperative and late postoperative mitral regurgitation in ventricular reconstruction: role of local left ventricular deformation

BACKGROUND

We sought to analyze the characteristics of local left ventricular deformation related to functional mitral regurgitation (MR) in post-anterior myocardial infarction scar, and to evaluate how local remodeling contributes to late development of MR after surgical ventricular reconstruction by endoventricular circular patch plasty repair.

METHODS

Two hundred twenty-one consecutive patients (aged 60 +/- 9 years; 193 males) with previous transmural anterior infarction underwent heart catheterization both before and 1 year after endoventricular circular patch plasty repair. Preoperative global left ventricular shape determinants (eccentricity and circularity indexes), regional curvature and wall motion (centerline), and both preoperative and 1-year postoperative hemodynamic parameters (volumes, ejection fraction, capillary wedge and pulmonary artery pressures) were calculated.

RESULTS

Forty-eight patients had (MR patients), and 173 did not have (NoMR patients) angiographic MR grade 2 or more preoperatively; at follow-up, 30 NoMR patients had MR (late MR [LMR]). Before surgery, MR patients had larger left ventricular volumes, higher capillary wedge and mean pulmonary artery pressures, and lower ejection fraction and cardiac index. The LMR patients had similarly high capillary wedge and pulmonary artery pressures as MR patients; otherwise, they did not differ from NoMR patients. Mitral regurgitation patients had wider lateral wall akinesia and greater inferior wall asynergy; the inferobasal region was hypokinetic in LMR patients. In MR patients, inferior wall systolic curvature was less negative; the inferobasal region had a more positive curvature in LMR patients.

CONCLUSIONS

Local deformation of the inferior wall with loss of systolic inward bending is associated with functional MR, while asynergy and systolic deformation of the inferobasal region and high capillary wedge pressure are prognostic signs of MR development late after endoventricular circular patch plasty repair.

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.

Mitral valve repair for functional mitral regurgitation in end-stage dilated cardiomyopathy: role of the "edge-to-edge" technique

BACKGROUND

The aim of this study was to assess the results of mitral valve (MV) repair in functional mitral regurgitation because of end-stage dilated cardiomyopathy (DCM).

METHODS AND RESULTS

Seventy-seven patients with end-stage idiopathic (26 patients) or ischemic (51 patients) DCM underwent MV repair for functional mitral regurgitation (3 to 4+/4+). Fifty-eight patients (75.3%) were in New York Heart Association class III, and 19 (24.6%) were in IV. In 23 patients (29.8%) with a coaptation depth <1 cm, an isolated undersized annuloplasty was used. In the remaining 54 (70.1%), with a coaptation depth > or =1 cm, the "edge-to-edge" technique was associated with the annuloplasty. In most of the cases (88.3%), a complete rigid/semirigid ring was used. Concomitant coronary artery bypass graft was performed in 39 patients (50.6%). Hospital mortality was 3.8% (3 of 77). Actuarial survival was 90.7+/-3.64%, and freedom from cardiac events was 81.8+/-7.96% at 2.7 years. At a mean follow-up of 18.4+/-9.8 months (range, 1 month to 5 years) New York Heart Association class improved from 3.4+/-0.4 to 1.4+/-0.6 (P<0.0001). Mitral repair failure (recurrence of MR > or =3+/4+) was documented in 7 patients (9%): 2 in the edge-to-edge (2 of 54, 3.7%) and 5 in the isolated annuloplasty group (5 of 23, 21.7%) (P=0.03). Freedom from repair failure at 1.5 years was 95.0+/-3.4% and 77+/-12.1%, respectively (P=0.04). The absence of the edge-to-edge was the only predictor of repair failure (P=0.03). When residual MR was absent or mild, a reverse left ventricular remodeling was clearly documented.

CONCLUSIONS

In patients with end-stage DCM, MV repair is feasible with low hospital mortality and important symptomatic improvement. The association of the edge-to-edge technique to the undersized annuloplasty can significantly improve the durability of the repair.

Exercise-induced changes in mitral regurgitation in patients with prior myocardial infarction and left ventricular dysfunction: relation to mitral deformation and left ventricular function and shape

AIMS

The aim of this study was to assess the relationship between exercise-induced changes in mitral regurgitation (MR) and echocardiographic characteristics of mitral deformation, global left ventricular (LV) function and shape at rest and after exercise.

METHODS AND RESULTS

Forty consecutive patients with ischaemic MR due to prior myocardial infarction (MI), ejection fraction <45% in sinus rhythm underwent exercise-echocardiographic testing. Exercise-induced changes in effective regurgitant orifice (ERO) were compared with baseline and exercise-induced changes in mitral deformation and global LV function and shape. There was significant correlation between exercise-induced changes in ERO and changes in coaptation distance (r=0.80, P<0.0001), tenting area (r=0.79, P<0.0001) and mitral annular diameter (r=0.65, P<0.0001), as well as in end-systolic sphericity index (r=-0.50, P=0.001, respectively), and wall motion score index (r=0.44, P=0.004). In contrast, exercise-induced changes in ERO were not related to the echocardiographic features at rest. By stepwise multiple regression model, the exercise-induced changes in mitral deformation were found to independently correlate with exercise-induced changes in ERO (generalized r(2)=0.80, P<0.0001).

CONCLUSION

Exercise-induced changes in severity of ischaemic MR in patients with LV dysfunction due to prior MI were independently related to changes in mitral deformation.

Cutting second-order chords does not prevent acute ischemic mitral regurgitation

BACKGROUND

Cutting anterior mitral leaflet second-order chordae has been proposed for repair in ischemic mitral regurgitation (IMR). We examined the efficacy of such chordal cutting in preventing acute IMR.

METHODS AND RESULTS

Six sheep underwent radiopaque marker placement (left ventricle, mitral annulus, papillary muscles [PMs], and leaflets). The largest second-order chord from each PM was encircled with exteriorized wire snares. Three-dimensional marker coordinates were obtained with biplane videofluoroscopy before and during acute ischemia (80 seconds of mid-circumflex occlusion). Color Doppler transesophageal echocardiography was used to grade MR on a 0 to 4+ scale. Data were acquired immediately before and after dividing second-order chordae. Slope of the end-diastolic volume-stroke work relationship (PRSW) was calculated to assess systolic function. Chordal cutting increased anterior leaflet inflection angle (155+/-12 versus 162+/-9 degrees; P=0.03), resulting in a flatter leaflet, but did not increase effective leaflet length (1.97+/-0.24 versus 2.08+/-0.23 cm; P=0.15); PRSW decreased (63+/-15 versus 56+/-12 mm Hg; P=0.008). Both before and after chordal cutting, ischemia caused: Septal-lateral annular dilation (P=0.005), posterior PM displacement away from the mid-septal annulus (P=0.06), increased leaflet tenting area (P=0.001), and increased leaflet tenting volume (P=0.002). Before chordal cutting, MR increased significantly during ischemia (0.5+/-0.3 versus 1.7+/-0.4; P<0.001), and IMR increased similarly even after the second-order chords were cut (0.7+/-0.4 versus 1.9+/-0.9; P<0.001).

CONCLUSIONS

Cutting second-order chordae resulted in LV systolic dysfunction and neither prevented nor decreased the severity of acute IMR, septal-lateral annular dilation, leaflet tenting area, or leaflet tenting volume.

An Annular Prosthesis for the Treatment of Functional Mitral Regurgitation: Finite Element Model Analysis of a Dog Bone–Shaped Ring Prosthesis

BACKGROUND

Undersized annuloplasty is commonly used in the treatment of functional mitral regurgitation. However, in the case of severely dilated ventricles, annuloplasty may be inadequate to counteract leaflet tethering. My colleagues and I hypothesized that modifying the shape of the annular prosthesis to account for the specific anatomy of functional mitral regurgitation could challenge extreme leaflet tethering.

METHODS

Using finite element model simulations, we tested valve competence after the implantation of conventional D-shaped versus dog bone-shaped annuloplasty rings, the latter of which was designed to selectively reduce the septolateral dimension of the annulus. Three models were compared: model A, simulating the native mitral valve; model B, simulating the same valve after annuloplasty with a conventional D-shaped annuloplasty; and model C, simulating a dog-bone annuloplasty ring implantation. Each model was then challenged by progressively pulling the tip of the papillary muscles away from the annulus plane to simulate ventricular remodeling and leaflet tethering. Valve competence was compared in each model for each degree of leaflet tethering.

RESULTS

After maximal leaflet tethering simulation (4-mm apical displacement of the papillary tips), the regurgitant area increase was 70.4 mm2 for model A and 52.9 mm2 for model B. In model C, the regurgitant area was only negligibly affected by papillary displacement, increasing to 3.9 mm2.

CONCLUSIONS

An annular prosthesis with selective reduction in the septolateral dimension is more effective than a conventional prosthesis for treating leaflet tethering in functional mitral regurgitation. Use of disease-specific annular prostheses is needed to improve the results of valve reconstruction.

Haemodynamic determinants of the mitral valve closure sound: a finite element study

Automatic acoustic classification and diagnosis of mitral valve disease remain outstanding biomedical problems. Although considerable attention has been given to the evolution of signal processing techniques, the mechanics of the first heart sound generation has been largely overlooked. In this study, the haemodynamic determinants of the first heart sound were examined in a computational model. Specifically, the relationship of the transvalvular pressure and its maximum derivative to the time-frequency content of the acoustic pressure was examined. To model the transient vibrations of the mitral valve apparatus bathed in a blood medium, a dynamic, non-linear, fluid-coupled finite element model of the mitral valve leaflets and chordae tendinae was constructed. It was found that the root mean squared (RMS) acoustic pressure varied linearly (r2= 0.99) from 0.010 to 0.259 mmHg, following an increase in maximum dP/dt from 415 to 12470 mm Hg s(-1). Over that same range, peak frequency varied non-linearly from 59.6 to 88.1 Hz. An increase in left-ventricular pressure at coaptation from 22.5 to 58.5mm Hg resulted in a linear (r2= 0.91) rise in RMS acoustic pressure from 0.017 to 1.41mm Hg. This rise in transmitral pressure was accompanied by a non-linear rise in peak frequency from 63.5 to 74.1 Hz. The relationship between the transvalvular pressure and its derivative and the time-frequency content of the first heart sound has been examined comprehensively in a computational model for the first time. Results suggest that classification schemes should embed both of these variables for more accurate classification.

Effects of Paracommissural Septal-Lateral Annular Cinching on Acute Ischemic Mitral Regurgitation

BACKGROUND

Previous experimental studies demonstrated that central septal-lateral (SL) annular cinching (SLAC) abolishes acute ischemic mitral regurgitation (IMR), but whether localized cinching near the anterior (ACOM) or posterior (PCOM) commissure is equally effective is unknown.

METHODS

Six adult sheep underwent implantation of 9 radiopaque markers on the left ventricle, 8 around the mitral annulus (MA) and 1 on each papillary muscle (PM) tip. Transannular SL sutures were placed at the valve center (CENT) and near ACOM and PCOM and externalized. Acute IMR was induced by proximal circumflex coronary snare occlusion. Biplane videofluoroscopy and transesophageal echocardiography were performed before and continuously during 3 episodes of myocardial ischemia including 20 seconds of SLAC at each different location. End-systolic MA SL dimension at each suture location and distances between the anterior and posterior PM tips and mid-septal annulus ("saddle horn") were calculated from the 3-dimensional (3D) marker coordinates.

RESULTS

SLAC interventions in all 3 locations reduced the degree of IMR, but cinching at the center, SLAC(CENT), had a significantly greater effect on reducing the magnitude of IMR than SLAC(PCOM) or SLAC(ACOM) (mean grade of IMR reduction=1.0+/-0.5, 1.8+/-0.5, and 0.9+/-0.2 for SLAC(ACOM), SLAC(CENT), and SLAC(PCOM), respectively; P=0.044). Although ACOM and PCOM cinching reduced SL(CENT) somewhat, only SLAC(CENT) simultaneously reduced both SL(ACOM) and SL(PCOM) and also repositioned both PM tips closer to the annular saddle horn.

CONCLUSIONS

SLAC in all 3 positions reduced acute IMR, but central SLAC cinching was most effective, reduced all mitral annular SL dimensions, and relocated both PM tips closer to the mid-septal annulus. Central SLAC is most capable of correcting the annular and subvalvular perturbations accompanying acute left ventricular ischemia that lead to IMR.

Computer-generated three-dimensional animation of the mitral valve

OBJECTIVE

Three-dimensional motion-capture data offer insight into the mechanical differences of mitral valve function in pathologic states. Although this technique is precise, the resulting time-varying data sets can be both difficult to interpret and visualize. We used a new technique to transform these 3-dimensional ovine numeric analyses into an animated human model of the mitral apparatus that can be deformed into various pathologic states.

METHODS

In vivo, high-speed, biplane cinefluoroscopic images of tagged ovine mitral apparatus were previously analyzed under normal and pathologic conditions. These studies produced serial 3-dimensional coordinates. By using commercial animation and custom software, animated 3-dimensional models were constructed of the mitral annulus, leaflets, and subvalvular apparatus. The motion data were overlaid onto a detailed model of the human heart, resulting in a dynamic reconstruction.

RESULTS

Numeric motion-capture data were successfully converted into animated 3-dimensional models of the mitral valve. Structures of interest can be isolated by eliminating adjacent anatomy. The normal and pathophysiologic dynamics of the mitral valve complex can be viewed from any perspective.

CONCLUSION

This technique provides easy and understandable visualization of the complex and time-varying motion of the mitral apparatus. This technology creates a valuable research and teaching tool for the conceptualization of mitral valve dysfunction and the principles of repair.

The effect of regional ischemia on mitral valve annular saddle shape

BACKGROUND

The mitral valve annulus has a distinctive saddle shape. Recent finite element analysis indicates this shape may contribute to normal valve function by increasing leaflet curvature and reducing leaflet stress. This study tests the hypothesis that acute ischemic mitral regurgitation (AIMR) is associated with loss of annular saddle shape.

METHODS

Sonomicrometry array localization (SAL) measured the three-dimensional geometry of the mitral annulus in 6 sheep before and after 30 min of posterior ischemia that produced severe AIMR. Using this SAL data the annular height to commissural width ratio (AHCWR), a measure of annular saddle shape, was calculated throughout the cardiac cycle and reported as a percentage.

RESULTS

The normal mitral annulus accentuated its saddle shape rapidly during isovolemic contraction: AHCWR increased from 11.6% +/- 1.1%-13.9% +/- 1.6% (p < 0.001). During ejection AHCWR remained relatively constant ranging from a minimum of 14.1% +/- 1.5% to a maximum of 14.9% +/- 1.3%. During ischemia AHCWR was found to be significantly smaller (p < 0.05) during isovolemic contraction, ejection, and isovolemic relaxation, but not during diastolic filling. Whereas ischemia did not affect AHCWR at end diastole (11.6% +/- 2.8%), the isovolemic accentuation of the saddle shape was lost.

CONCLUSIONS

The normal mitral annulus accentuates its saddle shape during systole. This accentuation is eliminated during ischemia that causes AIMR. These data suggest an association between annular saddle shape and valve competency.

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.

Mild to moderate mitral regurgitation in patients undergoing coronary bypass grafting: effects on operative mortality and long-term significance

BACKGROUND

Patients undergoing bypass grafting (CABG) often present with mitral regurgitation (MR). While surgical strategy for patients with either trace or severe MR is well established, the need for a valve procedure with mild (2) to moderate (3+) mitral regurgitation is controversial.

METHODS

We reviewed 1,939 consecutive CABG patients (1987 to 1999). A preoperative echocardiogram performed when clinically indicated graded MR from 1 to 4+. Patient characteristics, hospital mortality, and long-term survival were compared between 167 patients with grade 2 to 3+ MR and controls. A multivariate analysis identified independent predictors for long-term mortality.

RESULTS

The MR patients were more often female and older; had increased comorbidities including hypertension, diabetes, and heart failure; had more extensive coronary disease and worse left ventricular (LV) function; and required urgent surgery more often. Operative mortality was 0.8% in no MR patients and 1.8% in MR patients (p not significant). Long-term survival for MR patients with poor LV function (LV grade 3 to 4) was significantly lower (53% versus 75% at 10 years, p = 0.001). Independent predictors of poor long-term survival were advanced age, LV dysfunction, heart failure, diabetes, prior cerebrovascular accident, peripheral vascular disease, and no left internal mammary artery use.

CONCLUSIONS

Coronary artery bypass graft patients with mild or moderate MR have worse baseline characteristics but operative mortality with CABG alone is not significantly increased. Long-term prognosis for MR patients with poor LV function is worse compared with patients with no MR but MR was not an independent predictor of long-term mortality. To determine whether surgical correction of MR would improve results, a prospective randomized trial seems warranted.

Edge-to-edge mitral valve repair without ring annuloplasty for acute ischemic mitral regurgitation

BACKGROUND

Alfieri edge-to-edge mitral repair has been used clinically with ring annuloplasty to correct ischemic mitral regurgitation (IMR), but its efficacy without concomitant ring annuloplasty has not been described in this setting.

METHODS

Seventeen sheep underwent implantation of 9 radiopaque markers on the left ventricle, 8 on the mitral annulus (MA), 1 on each papillary muscle (PM) tip, and 1 on the anterior and posterior leaflet edges near the anterior and posterior commissures. Alfieri repair was performed in 7 animals, and 10 were controls. Biplane videofluoroscopy and transesophageal echocardiography (TEE) were performed (open chest) before and continuously during left circumflex coronary artery occlusion to induce acute IMR. MA area (MAA), anterior (APM), and posterior (PPM) papillary muscle tip distances to midseptal MA ("saddle horn"), and distance of each leaflet marker to the mitral annular plane were calculated from 3-dimensional marker coordinates at end-systole (ES).

RESULTS

Severity of IMR was not different between groups (+1.9+/-0.7 versus +1.4+/-0.5 for Control and Alfieri, respectively; P=not significant [NS]). Mitral annular area (MAA; 21+/-15 versus 19+/-9%; P =NS) and septal-lateral (SL) annular diameter (12+/-6 versus 12+/-11%; P =NS) increased similarly during ischemia. While PPM-saddle horn distance increased in both groups (1.5+/-1.3 and 1.6+/-1.4 mm for Control and Alfieri, respectively; P<0.05 versus preischemia), APM-saddle horn distance increased in Control (1.0+/-1.2 mm; P=0.03) but not in the Alfieri animals (0.8+/-08 mm; P=0.07). Leaflet edge displacements from the annular plane during ischemia were similar in both groups.

CONCLUSIONS

Alfieri repair did not prevent acute IMR nor alter ischemic valvular or subvalvular geometric perturbations. Adjunct surgical procedures, such as ring annuloplasty, are also necessary.

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.

Geometric differences of the mitral apparatus between ischemic and dilated cardiomyopathy with significant mitral regurgitation: real-time three-dimensional echocardiography study

BACKGROUND

This study was conducted to elucidate the geometric differences of the mitral apparatus in patients with significant mitral regurgitation caused by ischemic cardiomyopathy (ICM-MR) and by idiopathic dilated cardiomyopathy (DCM-MR) by use of real-time 3D echocardiography (RT3DE).

METHODS AND RESULTS

Twenty-six patients with ICM-MR caused by posterior infarction, 18 patients with DCM-MR, and 8 control subjects were studied. With the 3D software, commissure-commissure plane and 3 perpendicular anteroposterior (AP) planes were generated for imaging the medial, central, and lateral sides of the mitral valve (MV) during mid systole. In 3 AP planes, the angles between the annular plane and each leaflet (anterior, Aalpha; posterior, Palpha) were measured. In ICM-MR, Aalpha measured in the medial and central planes was significantly larger than that in the lateral plane (39+/-5 degrees, 34+/-6 degrees, and 27+/-5 degrees, respectively; P<0.01), whereas Palpha showed no significant difference in any of the 3 AP planes (61+/-7 degrees, 57+/-7 degrees, and 56+/-7 degrees, P>0.05). In DCM-MR, both Aalpha (38+/-8 degrees, 37+/-9 degrees, and 36+/-7 degrees, P>0.05) and Palpha (59+/-6 degrees, 58+/-5 degrees, and 57+/-6 degrees, P>0.05) revealed no significant differences in the 3 planes.

CONCLUSIONS

The pattern of MV deformation from the medial to the lateral side was asymmetrical in ICM-MR, whereas it was symmetrical in DCM-MR. RT3DE is a helpful tool for differentiating the geometry of the mitral apparatus between these 2 different types of functional mitral regurgitation.

Ischemia in three left ventricular regions: Insights into the pathogenesis of acute ischemic mitral regurgitation

BACKGROUND

Acute posterolateral left ventricular ischemia in sheep results in ischemic mitral regurgitation, but the effects of ischemia in other left ventricular regions on ischemic mitral regurgitation is unknown.

METHODS

Six adult sheep had radiopaque markers placed on the left ventricle, mitral annulus, and anterior and posterior mitral leaflets at the valve center and near the anterior and posterior commissures. After 6 to 8 days, animals were studied with biplane videofluoroscopy and transesophageal echocardiography before and during sequential balloon occlusion of the left anterior descending, distal left circumflex, and proximal left circumflex coronary arteries. Time of valve closure was defined as the time when the distance between leaflet edge markers reached its minimum plateau, and systolic leaflet edge separation distance was calculated on the basis of left ventricular ejection.

RESULTS

Only proximal left circumflex coronary artery occlusion resulted in ischemic mitral regurgitation, which was central and holosystolic. Delayed valve closure (anterior commissure, 58 +/- 29 vs 92 +/- 24 ms; valve center, 52 +/- 26 vs 92 +/- 23 ms; posterior commissure, 60 +/- 30 vs 94 +/- 14 ms; all P <.05) and increased leaflet edge separation distance during ejection (mean increase, 2.2 +/- 1.5 mm, 2.1 +/- 1.9 mm, and 2.1 +/- 1.5 mm at the anterior commissure, valve center, and posterior commissure, respectively; P <.05 for all) was seen during proximal left circumflex coronary artery occlusion but not during left anterior descending or distal left circumflex coronary artery occlusion. Ischemic mitral regurgitation was associated with a 19% +/- 10% increase in mitral annular area, and displacement of both papillary muscle tips away from the septal annulus at end systole.

CONCLUSIONS

Acute ischemic mitral regurgitation in sheep occurred only after proximal left circumflex coronary artery occlusion along with delayed valve closure in early systole and increased leaflet edge separation throughout ejection in all 3 leaflet coaptation sites. The degree of left ventricular systolic dysfunction induced did not correlate with ischemic mitral regurgitation, but both altered valvular and subvalvular 3-dimensional geometry were necessary to produce ischemic mitral regurgitation during acute left ventricular ischemia.

Tachycardia-induced cardiomyopathy in the ovine heart: mitral annular dynamic three-dimensional geometry

BACKGROUND

Ring annuloplasty has been used to correct annular dilatation and mitral regurgitation in dilated cardiomyopathy, but little is known about the dynamic precise 3-dimensional geometry of the mitral annulus in this condition.

METHODS

Nine sheep had radiopaque markers sewn to the mitral annulus, creating 8 distinct segments beginning at the posterior commissure (segments 1-4, septal mitral annulus; segments 5-8, lateral mitral annulus). Biplane videofluoroscopy and transesophageal echocardiography were performed before and after rapid pacing (180-230 min(-1) for 15 +/- 6 days) sufficient to develop tachycardia-induced cardiomyopathy and mitral regurgitation. Mitral annular segment contraction was defined as the percentage difference between maximum and minimum lengths. Mitral annular area and mitral annular septal-lateral and commissure-commissure diameters and 3-dimensional shape were determined from marker coordinates.

RESULTS

With tachycardia-induced cardiomyopathy, end-diastolic mitral annular area, septal-lateral diameter, and commissure-commissure diameter increased by 36% +/- 14%, 25% +/- 12%, and 9% +/- 5%, respectively (P <.01), whereas mitral regurgitation increased from 0.3 +/- 0.2 to 2.2 +/- 0.9 (P <.0001). All annular segments dilated at end-diastole with tachycardia-induced cardiomyopathy, except the segment between the midseptal annulus and the left fibrous trigone. Annular segment contraction was significantly decreased with tachycardia-induced cardiomyopathy in the lateral, but not in the septal, regions. Three-dimensional reconstruction of annular shape revealed a saddle shape of the annulus at baseline; this shape was also measured with tachycardia-induced cardiomyopathy, but there was some flattening of the septal annulus.

CONCLUSIONS

With tachycardia-induced cardiomyopathy, the mitral annulus dilated substantially, being more in the septal-lateral than in the commissure-commissure dimension. Greater annular segmental dilatation and decreased contraction occurred in the lateral annulus. The saddle shape of the annulus was retained but flattened.