Reverse ventricular remodeling reduces ischemic mitral regurgitation: echo-guided device application in the beating heart

Utilization of Engineering Advances for Detailed Biomechanical Characterization of the Mitral-Ventricular Relationship to Optimize Repair Strategies: A Comprehensive Review

The geometrical details and biomechanical relationships of the mitral valve-left ventricular apparatus are very complex and have posed as an area of research interest for decades. These characteristics play a major role in identifying and perfecting the optimal approaches to treat diseases of this system when the restoration of biomechanical and mechano-biological conditions becomes the main target. Over the years, engineering approaches have helped to revolutionize the field in this regard. Furthermore, advanced modelling modalities have contributed greatly to the development of novel devices and less invasive strategies. This article provides an overview and narrative of the evolution of mitral valve therapy with special focus on two diseases frequently encountered by cardiac surgeons and interventional cardiologists: ischemic and degenerative mitral regurgitation.

Mechanical effects of MitraClip on leaflet stress and myocardial strain in functional mitral regurgitation - A finite element modeling study

Purpose

MitraClip is the sole percutaneous device approved for functional mitral regurgitation (MR; FMR) but MR recurs in over one third of patients. As device-induced mechanical effects are a potential cause for MR recurrence, we tested the hypothesis that MitraClip increases leaflet stress and procedure-related strain in sub-valvular left ventricular (LV) myocardium in FMR associated with coronary disease (FMR-CAD).

Methods

Simulations were performed using finite element models of the LV + mitral valve based on MRI of 5 sheep with FMR-CAD. Models were modified to have a 20% increase in LV volume (↑LV_VOLUME) and MitraClip was simulated with contracting beam elements (virtual sutures) placed between nodes in the center edge of the anterior (AL) and posterior (PL) mitral leaflets. Effects of MitraClip on leaflet stress in the peri-MitraClip region of AL and PL, septo-lateral annular diameter (SLAD), and procedure-related radial strain (E_rr) in the sub-valvular myocardium were calculated.

Results

MitraClip increased peri-MitraClip leaflet stress at end-diastole (ED) by 22.3±7.1 kPa (p<0.0001) in AL and 14.8±1.2 kPa (p<0.0001) in PL. MitraClip decreased SLAD by 6.1±2.2 mm (p<0.0001) and increased E_rr in the sub-valvular lateral LV myocardium at ED by 0.09±0.04 (p<0.0001)). Furthermore, MitraClip in ↑LV_VOLUME was associated with persistent effects at ED but also at end-systole where peri-MitraClip leaflet stress was increased in AL by 31.9±14.4 kPa (p = 0.0268) and in PL by 22.5±23.7 kPa (p = 0.0101).

Conclusions

MitraClip for FMR-CAD increases mitral leaflet stress and radial strain in LV sub-valvular myocardium. Mechanical effects of MitraClip are augmented by LV enlargement.

Application of polymer-mesh device to remodel left ventricular-mitral valve apparatus in ischemic mitral regurgitation

OBJECTIVES

Ischemic mitral regurgitation (IMR) results from ischemic left ventricular (LV) distortion and remodeling, which displaces the papillary muscles and tethers the mitral valve leaflets apically. The aim of this experimental study was to examine efficacy of an adjustable novel polymer filled mesh (poly-mesh) device to reverse LV remodeling and reduce IMR.

METHODS

Acute (N = 8) and chronic (8 weeks; N = 5) sheep models of IMR were studied. IMR was produced by ligation of circumflex branches to create myocardial infarction. An adjustable poly-mesh device was attached to infarcted myocardium in acute and chronic IMR models and compared with untreated sham sheep. Two- and 3-dimensional echocardiography and hemodynamic measurements were performed at baseline, post IMR, and post poly-mesh (humanely killed).

RESULTS

In acute models, moderate IMR developed in all sheep and decreased to trace/mild (vena contracta: 0.50 ± 0.09 cm to 0.26 ± 0.12 cm; P < .01) after poly-mesh. In chronic models, IMR decreased in all sheep after poly-mesh, and this reduction persisted over 8 weeks (vena contracta: 0.42 ± 0.09 cm to 0.08 ± 0.12 cm; P < .01) with significant increase in the slope of end-systolic pressure-volume relationship (1.1 ± 0.5 mm Hg/mL to 2.9 ± 0.7 mm Hg/mL; P < .05). There was a significant reduction in LV volumes from chronic IMR to euthanasia stage with poly-mesh compared with sham group (%end-diastolic volume change -20 ± 11 vs 15% ± 16%, P < .01; %end-systolic volume change -14% ± 19% vs 22% ± 22%, P < .05; poly-mesh vs sham group) consistent with reverse remodeling.

CONCLUSIONS

An adjustable polymer filled mesh device reduces IMR and prevents continued LV remodeling during chronic follow-up.

[Impact of mitral annuloplasty combined with surgical revascularization in ischemic mitral regurgitation]

INTRODUCTION

Ischemic Mitral Regurgitation (IMR) is a serious complication of coronary artery disease and is associated with a poor prognosis. The optimal surgical treatment of IMR involves controversies in its indications and modalities.

OBJECTIVES

To determine whether mitral annuloplasty associated with surgical revascularization improved short and mid terms outcomes compared with revascularization alone in patients with IMR.

METHODS

Between January 2007 and January 2011, 81 patients operated on Department of Cardiovascular Surgery "B" were included in this study divided into 3 groups. Group 1: 28 patients with IMR had mitral valve surgery associated with surgical revascularization. Group 2: 26 patients with IMR had surgical revascularization without mitral valve surgery. Group 3: 27 patients without IMR had isolated revascularization. Clinical end-points were operative mortality, late mortality, postoperative functional status (NYHA), and the Effective Regurgitant Orifice (ERO) at last follow-up. The mean follow-up was 5 years for groups 1 and 2 and 4 years for group 3.

RESULTS

There was no difference between the 3 groups regarding age, sex, cardiovascular risk factors, and extension of coronary artery disease. The Left Ventricle End Diastolic Diameter (LVEDD) and the Left Ventricle Ejection Fraction (LVEF) were slightly different. Late and operative mortality were higher in group 2 compared to groups 1 and 3. Postoperative functional status (NYHA) improved both in groups 1 and 2. In group 1, there was a decrease in ERO.

CONCLUSION

Mitral annuloplasty combined to revascularization improves symptoms, postoperative ERO and short- and mid-term survival compared with revascularization alone.

Echocardiographic Assessment of Ischaemic Mitral Regurgitation, Mechanism, Severity, Impact on Treatment Strategy and Long Term Outcome

Introduction:

The commonest mitral regurgitation etiologies are degenerative (60%), rheumatic post-inflammatory, 12%) and functional (25%). Due to the large number of patients with acute MI, the incidence of ischaemic MR is also high. Ischaemic mitral regurgitation is a complex multifactorial disease that involves left ventricular geometry, the mitral annulus, and the valvular/subvalvular apparatus. Ischaemic mitral regurgitation is an important consequence of LV remodeling after myocardial infarction.

Research Objectives:

The objective of this study is to determine the role of echocardiography in detecting and assessment of mitral regurgitation mechanism, severity, impact on treatment strategy and long term outcome in patients with myocardial infarction during the follow up period of 5 years. Also one of objectives to determine if the absence or presence of ischaemic MR is associated with increased morbidity and mortality in patients with myocardial infarction.

Patients and methods:

The study covered 138 adult patients. All patients were subjected to echocardiography evaluation after acute myocardial infarction during the period of follow up for 5 years. The patients were examined on an ultrasound machine Philips iE 33 xMatrix, Philips HD 11 XE, and GE Vivid 7 equipped with all cardiologic probes for adults and multi-plan TEE probes. We evaluated mechanisms and severity of mitral regurgitation which includes the regurgitant volume (RV), effective regurgitant orifice area (EROA), the regurgitant fraction (RF), Jet/LA area, also we measured the of vena contracta width (VC width cm) for assessment of IMR severity, papillary muscles anatomy and displacement, LV systolic function ± dilation, LV regional wall motion abnormality WMA, LV WMI, Left ventricle LV remodeling, impact on treatment strategy and long term mortality.

Results:

We analyzed and follow up 138 patients with previous (>16 days) Q-wave myocardial infarction by ECG who underwent TTE and TEE echocardiography for detection and assessment of ischaemic mitral regurgitation (IMR) with baseline age (62 ± 9), ejection fraction (EF 41±12%), the regurgitant volume (RV) were 42±21 mL/beat, and effective regurgitant orifice area (EROA) 20±16 mm², the regurgitant fraction (RF) were 48±10%, Jet/LA area 47±12%. Also we measured the of vena contracta width (VC width cm) 0,4±0,6 for assessment of IMR severity. During 5 years follow up, total mortality for patients with moderate/severe IMR–grade II-IV (54.2±1.8%) were higher than for those with mild IMR–grade I (30.4±2.9%) (P<0.05), the total mortality for patients with EROA ≥20 mm²(54±1.9%) were higher than for those with EROA <20 mm²(27.2±2.7%) (P<0.05), and the total mortality for patients with RVol ≥30 mL (56.8±1.7%) were higher than for those with RVol<30ml (29.4±2.9%) (P<0.05). After assessment of IMR and during follow up period 64 patients (46%) underwent CABG alone or combined CABG with mitral valve repair or replacement. In this study, the procedure of concomitant down-sized ring annuloplasty at the time if CABG surgery has a failure rate around 24% in terms of high late recurrence rate of IMR during the follow period especially after 18–42 months.

Conclusion:

The presence of ischaemic MR is associated with increased morbidity and mortality. Chronic IMR, an independent predictor of mortality with a reported survival of 40–60% at 5 years. Ischaemic mitral regurgitation has important prognosis implications in patients with coronary heart disease. Recognizing the mechanism of valve incompetence is an essential point for the surgical planning and for a good result of the mitral repair. It is important that echocardiographers understand the complex nature of the condition. Despite remarkable progress in reparative surgery, further investigation is still necessary to find the best approach to treat ischaemic mitral regurgitation.

Repair or replace for severe ischemic mitral regurgitation: prospective randomized multicenter data

Ischemic mitral regurgitation (IMR) is a subset of functional mitral regurgitation (MR) that has the potential to impact an increasing number of patients in the future. This is in the context of a worldwide population, which continues to live longer with improved survival after myocardial infarction. Substantial data have accumulated over the past few decades demonstrating the negative effects of IMR. Further, significant research has been done to define the optimal surgical approach and several studies have compared mitral repair versus replacement for patients with severe mitral regurgitation (SMR). Studies supporting performance of mitral repair cite superior operative morbidity and mortality rates, while proponents of mitral replacement cite improved long-term durability and correction of MR. Lack of clinically robust Level I randomized controlled trial data have curtailed attempts to better define appropriate surgical treatment allocation over the past few decades. Recently, however, the Cardiothoracic Surgical Trials Network (CTSN) conducted the first randomized controlled trial, funded by the National Heart, Lung, and Blood Institute, the National Institute for Neurological Diseases and Stroke and the Canadian Institute for Health Research, to compare the performance of mitral repair versus replacement for SMR. Herein, the present review describes the design, results and implications of the CTSN SMR trial and its efforts to identify the most efficacious surgical approach to SMR. This review also describes CTSN investigation to predict the recurrence of MR after mitral repair.

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.

Surgical management of moderate ischemic mitral valve regurgitation: Where do we stand?

Ischemic mitral regurgitation (IMR) represents a common complication after myocardial infarction. The valve is anatomically normal and the incompetence is the result of papillary muscles displacement and annular dilatation, causing leaflets tethering. Functionally the leaflets present a restricted systolic motion due to tethering forces that displaces the coaptation surface toward the left ventricle apex. The patients present poor left ventricular function at the time of surgery and the severity of the mitral regurgitation increases the risk of mortality. Currently there is general agreement to treat surgically severe IMR nevertheless strong evidences for patient with moderate insufficiency remains poor and proper treatment debated. The most effective surgical approach for the treatment of IMR remains debated. Some authors demonstrated that coronary artery bypass graft (CABG) alone is beneficial in patients with IMR. Conversely, in most patients, moderate IMR will persist or worsen after CABG alone which translate in higher long-term mortality as a function of residual mitral regurgitation severity. A probable reason for this unclear surgical management of functional MR is due to the contemporary suboptimal results of reparative techniques. The standard surgical treatment of chronic IMR is CABG associated with undersized annuloplasty using complete ring. Though, the recurrence of mitral regurgitation remains high (> 30%) because of continous left ventricle remodeling. To get better long term results, in the last decade, several subvalvular procedures in adjunct to mitral anuloplasty have been developed. Among them, surgical papillary muscle relocation represents the most appreciated option capable to restore normal left ventricle geometry. In the next future new preoperative predictors of increased mitral regurgitation recurrence are certainly needed to find an individual time period of treatment in each patient with moderate IMR.

Echocardiographic assessment of ischemic mitral regurgitation

Ischemic mitral regurgitation is an important consequence of LV remodeling after myocardial infarction. Echocardiographic diagnosis and assessment of ischemic mitral regurgitation are critical to gauge its adverse effects on prognosis and to attempt to tailor rational treatment strategy. There is no single approach to the echocardiographic assessment of ischemic mitral regurgitation: standard echocardiographic measures of mitral regurgitation severity and of LV dysfunction are complemented by assessments of displacement of the papillary muscles and quantitative indices of mitral valve deformation. Development of novel approaches to understand mitral valve geometry by echocardiography may improve understanding of the mechanism, clinical trajectory, and reparability of ischemic mitral regurgitation.

Basic mechanisms of mitral regurgitation

Any structural or functional impairment of the mitral valve (MV) apparatus that exhausts MV tissue redundancy available for leaflet coaptation will result in mitral regurgitation (MR). The mechanism responsible for MV malcoaptation and MR can be dysfunction or structural change of the left ventricle, the papillary muscles, the chordae tendineae, the mitral annulus, and the MV leaflets. The rationale for MV treatment depends on the MR mechanism and therefore it is essential to identify and understand normal and abnormal MV and MV apparatus function.

Predictors and prognosis of early ischemic mitral regurgitation in the era of primary percutaneous coronary revascularisation

Background

Studies assessing ischemic mitral regurgitation (IMR) comprised of heterogeneous population and evaluated IMR in the subacute setting. The incidence of early IMR in the setting of primary PCI, its progression and clinical impact over time is still undetermined. We sought to determine the predictors and prognosis of early IMR after primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (STEMI).

Methods

Using our primary PCI database, we screened for patients who underwent ≥2 transthoracic echocardiograms early (1–3 days) and late (1 year) following primary PCI. The primary outcomes were: (1) major adverse events (MACE) including death, ischemic events, repeat hospitalization, re-vascularization and mitral repair or replacement (2) changes in quantitative echocardiographic assessments.

Results

From January 2006 to July 2012, we included 174 patients. Post-primary PCI IMR was absent in 95 patients (55%), mild in 60 (34%), and moderate to severe in 19 (11%). Early after primary PCI, IMR was independently predicted by an ischemic time > 540 min (OR: 2.92 [95% CI, 1.28 – 7.05]; p = 0.01), and female gender (OR: 3.06 [95% CI, 1.42 – 6.89]; p = 0.004). At a median follow-up of 366 days [34–582 days], IMR was documented in 44% of the entire cohort, with moderate to severe IMR accounting for 15%. During follow-up, MR regression (change ≥ 1 grade) was seen in 18% of patients. Moderate to severe IMR remained an independent predictor of MACE (HR: 2.58 [95% CI, 1.08 – 5.53]; p = 0.04).

Conclusions

After primary PCI, IMR is a frequent finding. Regression of early IMR during long-term follow-up is uncommon. Since moderate to severe IMR post-primary PCI appears to be correlated with worse outcomes, close follow-up is required.

Ischemic (functional) mitral regurgitation

Mitral regurgitation (MR) is a frequent complication of myocardial infarction and coronary artery disease that is associated with adverse prognosis. The main mechanism of ischemic MR relates to distortion of the spatial relationships between the mitral valve and papillary muscles secondary to ventricular remodeling. The evidence that treatment of ischemic MR improves long-term survival still remains unclear, and further studies are needed to determine whether correcting ischemic MR will improve survival and/or symptoms.

Ischemic mitral regurgitation: mechanisms, intraoperative echocardiographic evaluation, and surgical considerations

Ischemic mitral regurgitation (IMR) is a subcategory of functional rather than organic, mitral valve (MV) disease. Whether reversible or permanent, left ventricular remodeling creates IMR that is complex and multifactorial. A comprehensive TEE examination in patients with IMR may have important implications for perioperative clinical decision making. Several TEE measures predictive of MV repair failure have been identified. Current practice among most surgeons is to typically repair the MV in patients with IMR. MV replacement is usually reserved for situations in which the valve cannot be reasonably repaired, or repair is unlikely to be tolerated clinically.

Minimally invasive delivery of a novel direct epicardial assist device in a porcine heart failure model

OBJECTIVE

Despite advances in design, modern ventricular assist device placement involves median sternotomy and cardiopulmonary bypass and is associated with infectious/embolic complications. In this study, we examine the feasibility and function of a novel minimally invasive, non-blood-contacting epicardial assist device in a porcine ischemic cardiomyopathy model.

METHODS

Feasibility was first tested in an ex vivo thoracoscopic trainer box with slaughterhouse hearts. Five male Yorkshire swine underwent selective ligation of the circumflex artery to create a posterolateral infarct Twelve weeks after infarct, all animals underwent left minithoracotomy. A custom inflatable bladder was positioned over the epicardial surface of the infarct and firmly secured to the surrounding border zone myocardium with polypropylene mesh and minimally invasive mesh tacks. An external gas pulsation system actively inflated and deflated the bladder in synchrony with the cardiac cycle. All animals then underwent cardiac magnetic resonance imaging to assess ventricular function.

RESULTS

All subjects successfully underwent off-pump placement of the epicardial assist device via minithoracotomy. Ejection fraction significantly improved from 29.1% ± 4.8% to 39.6% ± 4.23% (P < 0.001) when compared with pretreatment. End-systolic volume decreased (76.6 ± 13.3 mL vs 62.4 ± 12.0 mL, P < 0.001) and stroke volume increased (28.6 ± 3.4 mL vs 37.9 ± 3.1 mL, P < 0.05) when assisted. No change was noted in end-diastolic volume (105.1 ± 11.4 vs 100.3 ± 12.7). On postmortem examination, mesh fixation and device position were excellent in all cases. No adverse events were encountered.

CONCLUSIONS

Directed epicardial assistance improves ventricular function in a porcine ischemic cardiomyopathy model and may provide a safe alternative to currently available ventricular assist device therapies. Further, the technique used for device positioning and fixation suggests that an entirely thoracoscopic approach is possible.

Mitral apparatus assessment by delayed enhancement CMR: relative impact of infarct distribution on mitral regurgitation

OBJECTIVES

This study sought to assess patterns and functional consequences of mitral apparatus infarction after acute myocardial infarction (AMI).

BACKGROUND

The mitral apparatus contains 2 myocardial components: papillary muscles and the adjacent left ventricular (LV) wall. Delayed-enhancement cardiac magnetic resonance (DE-CMR) enables in vivo study of inter-relationships and potential contributions of LV wall and papillary muscle infarction (PMI) to mitral regurgitation (MR).

METHODS

Multimodality imaging was performed: CMR was used to assess mitral geometry and infarct pattern, including 3D DE-CMR for PMI. Echocardiography was used to measure MR. Imaging occurred 27 ± 8 days after AMI (CMR, echocardiography within 1 day).

RESULTS

A total of 153 patients with first AMI were studied; PMI was present in 30% (n = 46 [72% posteromedial, 39% anterolateral]). When stratified by angiographic culprit vessel, PMI occurred in 65% of patients with left circumflex, 48% with right coronary, and only 14% of patients with left anterior descending infarctions (p <0.001). Patients with PMI had more advanced remodeling as measured by LV size and mitral annular diameter (p <0.05). Increased extent of PMI was accompanied by a stepwise increase in mean infarct transmurality within regional LV segments underlying each papillary muscle (p <0.001). Prevalence of lateral wall infarction was 3-fold higher among patients with PMI compared to patients without PMI (65% vs. 22%, p <0.001). Infarct distribution also impacted MR, with greater MR among patients with lateral wall infarction (p = 0.002). Conversely, MR severity did not differ on the basis of presence (p = 0.19) or extent (p = 0.12) of PMI, or by angiographic culprit vessel. In multivariable analysis, lateral wall infarct size (odds ratio 1.20/% LV myocardium [95% confidence interval: 1.05 to 1.39], p = 0.01) was independently associated with substantial (moderate or greater) MR even after controlling for mitral annular (odds ratio 1.22/mm [1.04 to 1.43], p = 0.01), and LV end-diastolic diameter (odds ratio 1.11/mm [0.99 to 1.23], p = 0.056).

CONCLUSIONS

Papillary muscle infarction is common after AMI, affecting nearly one-third of patients. Extent of PMI parallels adjacent LV wall injury, with lateral infarction-rather than PMI-associated with increased severity of post-AMI MR.

Directed epicardial assistance in ischemic cardiomyopathy: flow and function using cardiac magnetic resonance imaging

BACKGROUND

Heart failure after myocardial infarction (MI) is a result of increased myocardial workload, adverse left ventricular (LV) geometric remodeling, and less efficient LV fluid movement. In this study we utilize cardiac magnetic resonance imaging to evaluate ventricular function and flow after placement of a novel directed epicardial assist device.

METHODS

Five swine underwent posterolateral MI and were allowed to remodel for 12 weeks. An inflatable bladder was positioned centrally within the infarct and secured with mesh. The device was connected to an external gas exchange pump, which inflated and deflated in synchrony with the cardiac cycle. Animals then underwent cardiac magnetic resonance imaging during active epicardial assistance and with no assistance.

RESULTS

Active epicardial assistance of the infarct showed immediate improvement in LV function and intraventricular flow. Ejection fraction significantly improved from 26.0% ± 4.9% to 37.3% ± 4.5% (p < 0.01). End-systolic volume (85.5 ± 12.7 mL versus 70.1 ± 11.9 mL, p < 0.01) and stroke volume (28.5 ± 4.4 mL versus 39.9 ± 3.1 mL, p = 0.03) were also improved with assistance. End-diastolic volume and regurgitant fraction did not change with treatment. Regional LV flow improved both qualitatively and quantitatively during assistance. Unassisted infarct regional flow showed highly discoordinate blood movement with very slow egress from the posterolateral wall. Large areas of stagnant flow were also identified. With assistance, posterolateral wall blood velocities improved significantly during both systole (26.4% ± 3.2% versus 12.6% ± 1.2% maximum velocity; p < 0.001) and diastole (54.3% ± 9.3% versus 24.2% ± 2.5% maximum velocity; p < 0.01).

CONCLUSIONS

Directed epicardial assistance can improve LV function and flow in ischemic cardiomyopathy. This novel device may provide a valuable alternative to currently available heart failure therapies.

Mechanistic features associated with improvement in mitral regurgitation after cardiac resynchronization therapy and their relation to long-term patient outcome

BACKGROUND

Mechanisms of mitral regurgitation (MR) reduction with cardiac resynchronization therapy (CRT) are complex, and their association with long-term outcome is unclear. We sought to elucidate mechanistic features of reduction in MR with CRT, which impact long-term patient survival.

METHODS AND RESULTS

A prospective longitudinal study of 277 patients with heart failure with QRS width ≥ 120 ms and ejection fraction ≤ 35% for CRT was performed. Quantitative echocardiography, including dyssynchrony analysis, was performed at baseline. MR was quantified by color Doppler before and 6 months after CRT. Predefined end points of death, transplant, or left ventricular assist device were tracked during 4 years. There were 114 (48%) patients with CRT with significant MR (≥ moderate) at baseline; of whom 48 (42%) patients had MR improvement, and 24 (19%) patients had MR worsening after CRT. The 66 events (47 deaths, 10 transplantations, and 9 left ventricular assist devices) were strongly associated with significant MR after CRT (hazard ratio, 3.58; 95% confidence interval, 2.18-5.87; P<0.0001). Three echocardiographic features were independently associated with amelioration of significant MR after CRT by multivariable analysis: anteroseptal to posterior wall radial strain dyssynchrony >200 ms, lack of severe left ventricular dilatation (end-systolic dimension index <29 mm/m(2)), and lack of echocardiographic scar at papillary muscle insertion sites (all P<0.05) and, when combined, were additively associated with long-term survival (P=0.0001).

CONCLUSIONS

Significant MR after CRT was strongly associated with less favorable long-term survival. Echocardiographic mechanistic features were identified that were associated with improvement in MR after CRT and favorable long-term survival.

Anatomy of the mitral valve apparatus: role of 2D and 3D echocardiography

The mitral valve apparatus is a complex 3-dimensional (3D) functional unit that is critical to unidirectional heart pump function. This review details the normal anatomy, histology, and function of the main mitral valve apparatus components: mitral annulus, mitral valve leaflets, chordae tendineae, and papillary muscles. Two-dimensional and 3D echocardiography is ideally suited to examine the mitral valve apparatus and has provided important insights into the mechanism of mitral valve disease. An overview of standardized echocardiography image acquisition and interpretation is provided. Understanding normal mitral valve apparatus function is essential to comprehend alterations in mitral valve disease and the rationale for repair strategies.

Optimized local infarct restraint improves left ventricular function and limits remodeling

BACKGROUND

Preventing expansion and dyskinetic movement of a myocardial infarction (MI) can limit left ventricular (LV) remodeling. Using a device designed to produce variable alteration of infarct stiffness and geometry, we sought to understand how these parameters affect LV function and remodeling early after MI.

METHODS

Ten pigs had posterolateral infarctions. An unexpanded device was placed in 5 animals at the time of infarction and 5 animals served as untreated controls. One week after MI animals underwent magnetic resonance imaging to assess LV size and regional function. In the treatment group, after initial imaging, the device was expanded with 2, 4, 6, 8, and 10 mL of saline. The optimal degree of inflation was defined as that which maximized stroke volume (SV). The device was left optimally inflated in the treatment animals for 3 additional weeks.

RESULTS

One week after MI, device inflation to 6 mL or greater significantly (p < 0.05) decreased end-systolic volume (0 mL, 59.9 mL ± 3.8; 6 mL, 54.0 mL ± 3.1; 8 mL, 50.5 mL ± 4.8; and 10 mL, 46.1 mL ± 2.2) and increased ejection fraction (EF) (0 mL, 0.346 ± 0.016; 6 mL, 0.0397 ± 0.009; 8 mL, 0.431 ± 0.027; and 10 mL, 0.441 ± 0.009). Systolic volume significantly (p < 0.05) improved for the 6 mL and 8 mL volumes (0 mL, 31.2 mL ± 2.6; 6 mL, 35.7 mL ± 2.0; and 8 mL, 37.5 mL ± 1.9) but trended downward for 10 mL (36.6 mL ± 2.8). At 4 weeks after MI, end-diastolic volume and end-systolic volume were unchanged from 1-week values in the treatment group while the control group continued to dilate. Systolic volume (38.2 ± 4.4 mL vs 34.0.1 ± 4.8 mL, p = 0.08) and EF (0.360 ± 0.026 vs 0.276 ± 0.014, p = 0.04) were also better in the treatment animals.

CONCLUSIONS

Optimized isolated infarct restraint can limit adverse LV remodeling after MI. The tested device affords the potential for a patient-specific therapy to preserve cardiac function after MI.

Fiber architecture in remodeled myocardium revealed with a quantitative diffusion CMR tractography framework and histological validation

BACKGROUND

The study of myofiber reorganization in the remote zone after myocardial infarction has been performed in 2D. Microstructural reorganization in remodeled hearts, however, can only be fully appreciated by considering myofibers as continuous 3D entities. The aim of this study was therefore to develop a technique for quantitative 3D diffusion CMR tractography of the heart, and to apply this method to quantify fiber architecture in the remote zone of remodeled hearts.

METHODS

Diffusion Tensor CMR of normal human, sheep, and rat hearts, as well as infarcted sheep hearts was performed ex vivo. Fiber tracts were generated with a fourth-order Runge-Kutta integration technique and classified statistically by the median, mean, maximum, or minimum helix angle (HA) along the tract. An index of tract coherence was derived from the relationship between these HA statistics. Histological validation was performed using phase-contrast microscopy.

RESULTS

In normal hearts, the subendocardial and subepicardial myofibers had a positive and negative HA, respectively, forming a symmetric distribution around the midmyocardium. However, in the remote zone of the infarcted hearts, a significant positive shift in HA was observed. The ratio between negative and positive HA variance was reduced from 0.96 ± 0.16 in normal hearts to 0.22 ± 0.08 in the remote zone of the remodeled hearts (p < 0.05). This was confirmed histologically by the reduction of HA in the subepicardium from -52.03° ± 2.94° in normal hearts to -37.48° ± 4.05° in the remote zone of the remodeled hearts (p < 0.05).

CONCLUSIONS

A significant reorganization of the 3D fiber continuum is observed in the remote zone of remodeled hearts. The positive (rightward) shift in HA in the remote zone is greatest in the subepicardium, but involves all layers of the myocardium. Tractography-based quantification, performed here for the first time in remodeled hearts, may provide a framework for assessing regional changes in the left ventricle following infarction.

Functional mitral regurgitation: modern concepts for ventricular geometry reshaping

Functional mitral valve regurgitation (MR), a condition affecting millions of primarily elderly patients worldwide, is associated with poor clinical outcomes. Functional MR has traditionally been considered a disorder of regional or global left ventricular (LV) remodeling secondary to myocardial disease, in which anatomically normal leaflets fail to coapt adequately. The primary mechanisms of MR are mitral annular dilatation and leaflet restriction secondary to LV remodeling. Although annuloplasty is commonly used to correct valve incompetence, the effects of altered ventricular mechanics on MR need to be specifically addressed. This review focuses on current concepts of geometric reconfiguration of the LV and mitral-ventricular apparatus to reduce MR.

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.

Review of novel clinical applications of advanced, real-time, 3-dimensional echocardiography

Advances in computer processing speed and memory along with the advent of the microbeam former that can sample an entire crystal of the ultrasound transducer made possible the performance of 3-dimensional echocardiography in real time (RT3DE). The miniaturization of a 3-dimensional transducer permitting its extension to transesophageal mode rapidly expanded its use in a variety of conditions. Recent development of user-friendly automated/semiautomated cropping and display software may make it rather simple, even for the novice to gather useful information from RT3DE. We discuss the background, technique, and cutting-edge research and novel clinical applications of advanced RT3DE, including left ventricular dyssynchrony assessment, 3-D speckle tracking, myocardial contrast echocardiography, complete 4-dimensional (4-D) shape and motion analysis of the left ventricle, 4-D volumetric analysis of the right ventricle, 3-D volume rendering of the mitral valve, and other percutaneous and surgical procedural applications.

Relationship between mitral leaflets angles, left ventricular geometry and mitral deformation indices in patients with ischemic mitral regurgitation: imaging by echocardiography and cardiac magnetic resonance

Chronic ischemic mitral regurgitation (IMR) is associated with a markedly worse prognosis after myocardial infarction (MI).The study aimed to evaluate the relationship between anterior and posterior mitral leaflet angle (MLA) values, left ventricle remodeling and severity of ischaemic mitral regurgitation (IMR).

METHODS

Forty-two patients (age 63.5 ± 9.7 years, 36 men) with chronic IMR (regurgitant volume, RV > 20 ml; >6 months after MI) underwent transthoracic echocardiography (TTE) and cardiovascular magnetic resonance (CMR) imaging. Anterior and posterior MLA, determined by echocardiography, were correlated with indices of LV remodeling, mitral apparatus deformation and IMR severity by CMR. The anterior and posterior MLA was 25.41 ± 4.28 and 38.37 ± 8.89° (mean ± SD). In 5 patients (11.9%) the posterior MLA was ≥45°. There was a significant correlation between anterior MLA and RV (r = 0.74, P = 0.01). For patients with RV > 30 ml this correlation was stronger (r = 0.97, P = 0.005) and, in addition, there was a correlation between the RV and posterior MLA (r = 0.90, P = 0.037), between tenting area and posterior MLA (r = 0.90, P = 0.04), and between tenting area and anterior MLA (r = 0.82, P = 0.08). With regard to LV remodeling parameters, there was weaker but significant correlation between posterior MLA and LV end-diastolic volume index (r = 0.35, P = 0.031), LV end-systolic volume index (r = 0.37, P = 0.021), stroke volume (r = 0.35, P = 0.03), sphericity index (r = 0.33, P = 0.041). Anterior MLA correlated with wall motion score index (r = 0.41, P = 0.019). Besides, there was a correlation between posterior MLA and left atrial volume (r = 0.41, P = 0.012). Measurement of anterior and posterior MLA may play an important role in evaluating patients with IMR.

Optimal surgical management of severe ischemic mitral regurgitation: to repair or to replace?

BACKGROUND

Ischemic mitral regurgitation, a complication of myocardial infarction and coronary artery disease more generally, is associated with a high mortality rate and is estimated to affect 2.8 million Americans. With 1-year mortality rates as high as 40%, recent practice guidelines of professional societies recommend repair or replacement, but there remains a lack of conclusive evidence supporting either intervention. The choice between therapeutic options is characterized by the trade-off between reduced operative morbidity and mortality with repair versus a better long-term correction of mitral insufficiency with replacement. The long-term benefits of repair versus replacement remain unknown, which has led to significant variation in surgical practice.

METHODS AND RESULTS

This article describes the design of a prospective randomized clinical trial to evaluate the safety and effectiveness of mitral valve repair and replacement in patients with severe ischemic mitral regurgitation. This trial is being conducted as part of the Cardiothoracic Surgical Trials Network. This article addresses challenges in selecting a feasible primary end point, characterizing the target population (including the degree of mitral regurgitation) and analytical challenges in this high mortality disease.

CONCLUSIONS

The article concludes by discussing the importance of information on functional status, survival, neurocognition, quality of life, and cardiac physiology in therapeutic decision making.

Saddle-shaped mitral valve annuloplasty rings improve leaflet coaptation geometry

OBJECTIVES

The mitral valve annulus naturally conforms to a saddle shape in systole. This configuration is believed to put the leaflets into a lower-energy equilibrium with the annulus and subvalvular apparatus. Conventional flat annuloplasty rings restrict posterior leaflet motion, which may result in a "monocusp" valve, affecting valvular stress distribution. It is hypothesized that saddle-shaped annuloplasty rings cause less distortion of the physiologic leaflet geometry than do flat rings.

METHODS

Twelve pigs were studied in an acute setting with 3-dimensional echocardiography and sonomicrometry before and after implantation of rigid flat (n = 5) and saddle-shaped (n = 7) annuloplasty rings. The rings were true sized to the annulus with equal anterior-posterior and commissure-commissure circumferential dimensions. The saddle-shaped rings had an annular height to commissural width ratio of 15%.

RESULTS

Saddle-shaped rings maintained both leaflets operational (P < .01). Flat rings made the posterior leaflet immobile and the anterior leaflet aligned flat along the annulus in systole, effectively resulting in monoleaflet function. The average distance from the papillary muscle tips to the posterior annulus decreased by 2.4 ± 0.4 mm after flat ring implantation (P < .01).

CONCLUSIONS

Saddle-shaped annuloplasty rings provide better leaflet coaptation geometry than do flat rings by not hoisting the papillary muscles toward the posterior annulus through the commissural chordae, allowing greater leaflet mobility. This entails a potentially beneficial impact on valvular stress distribution that could affect durability of the repaired valve.

Right ventricular remodeling determines tricuspid valve geometry and the severity of functional tricuspid regurgitation: a real-time 3-dimensional echocardiography study

Background and Objectives

Right ventricle (RV) remodeling can determine tricuspid valve (TV) geometry and the severity of functional tricuspid regurgitation (TR).

Subjects and Methods

In 53 patients with various degrees of functional TR and in sinus rhythm, RV and TV geometries were analyzed using real-time 3-dimensional echocardiography, including tenting angles of 3 leaflets, septal-lateral and antero-posterior tricuspid annulus diameters and inlet RV dimensions, mid-RV septal-lateral dimension, and the distance between annulus and apex. A mid-systole frame when the TV tenting is smallest was selected for the analysis. RV end-diastolic and end-systolic volumes were measured. The severity of functional TR was determined by distal jet area.

Results

TR distal jet area was mainly determined by septal-lateral annulus diameter (p<0.001) RV inlet dimension (p=0.015), RV end-systolic volume (p=0.010), septal (p=0.019), and anterior leaflet tenting angles (p=0.045) by multiple stepwise linear regression analysis. Leaflet tenting angles were mainly determined by septal-lateral RV inlet dimension. Septal-lateral annulus diameter was determined by septal-lateral RV inlet dimension (p<0.001) and mid RV dimension (p=0.033), whereas antero-posterior annulus diameter was determined by antero-posterior RV inlet dimension (p<0.001).

Conclusion

Functional TR severity is determined by septal-lateral annulus and RV dilation, and tenting of septal and anterior leaflets. TV leaflet tenting is mainly determined by septal-lateral RV inlet dilation, and tricuspid annulus dilation is closely linked with inlet RV dilation.

Primary percutaneous coronary intervention lowers the incidence of ischemic mitral regurgitation in patients with acute ST-elevated myocardial infarction

BACKGROUND

The impact of primary percutaneous coronary intervention (PCI) for acute ST-elevated myocardial infarction (STEMI) on the incidence of ischemic mitral regurgitation (IMR) is unclear.

METHODS AND RESULTS

Between January 2000 and December 2004, 318 patients presenting with first acute STEMI were enrolled in this study. Two hundred and twelve (66.67%) patients received PCI (PCI group), and 106 age- and Killip class-matched patients received medical management (non-PCI group). The median duration of follow up was 40.46 months. Compared to the non-PCI group, the PCI group had 14.6% (9.9% vs 24.5%) fewer patients with moderate or severe IMR (P<0.001). Univariate analysis demonstrated IMR was significantly associated with advanced age, higher Killip score, and posterior myocardial infarction (MI). Moreover, IMR was strongly associated with a lower left ventricular (LV) ejection fraction, larger left atrial dimension (LAd), and a larger LV end-systolic and LV end-diastolic volumes (LVEDV) (all P<0.01). Multivariate analysis revealed the odds of IMR in the PCI group was 0.208 times those of the non-PCI group (P<0.001). Additionally, moderate or severe IMR was independently correlated with advanced age, inferior MI, Killip class ≥3, larger LAd, and larger LVEDV (all P<0.05). Furthermore, long-term survival time was longer in the PCI group without IMR than in the non-PCI group with IMR (all P<0.01).

CONCLUSIONS

PCI for first acute STEMI was associated with lower incidence of IMR. Advanced age, inferior MI, Killip class ≥3, larger LAd and LVEDV were risk factors associated with IMR development.

Polymer injection therapy to reverse remodel the papillary muscles: efficacy in reducing mitral regurgitation in a chronic ischemic model

BACKGROUND

Ischemic mitral regurgitation (MR) results from displacement of the papillary muscles caused by ischemic ventricular distortion. Progressive left ventricular (LV) remodeling has challenged therapy. Our hypothesis is that repositioning of the papillary muscles can be achieved by injection of polyvinyl-alcohol (PVA) hydrogel polymer into the myocardium in chronic MR despite advanced LV remodeling.

METHODS AND RESULTS

Ten sheep underwent ligation of the circumflex branches to produce chronic ischemic MR over 8 weeks. PVA was injected into the myocardium underlying the infarcted papillary muscle. Two-dimensional and 3D echocardiograms and hemodynamic data were obtained before infarct (baseline), before PVA (chronic MR), and after PVA. PVA injection significantly decreased MR from moderate to severe to trace (MR vena contracta, 5.8±1.2 to1.8±1.3 mm; chronic MR to post-PVA stage; P=0.0003). This was associated with a decrease in infarcted papillary muscle-to-mitral annulus tethering distance (30.3±5.7 to 25.9±4.6 mm, P=0.02), tenting volume (1.8±0.7 to 1.4±0.5 mL, P=0.01), and leaflet closure area (8.8±1.3 cm(2)to 7.6±1.3 cm(2), P=0.004) from chronic MR to post-PVA stages. PVA was not associated with significant decreases in LV ejection fraction (41±3% versus 40±3%, P=NS), end-systolic elastance, τ (82±36 ms to 72±26, P=NS), or LV stiffness coefficient (0.05±0.04 to 0.03±0.01).

CONCLUSIONS

PVA hydrogel injections improve coaptation and reduce remodeling in chronic MR without impairing LV systolic and diastolic function. This new approach offers a potential alternative for relieving tethering and ischemic MR by correcting papillary muscle position.

Gene delivery of sarcoplasmic reticulum calcium ATPase inhibits ventricular remodeling in ischemic mitral regurgitation

BACKGROUND

Mitral regurgitation (MR) doubles mortality after myocardial infarction (MI). We have demonstrated that MR worsens remodeling after MI and that early correction reverses remodeling. Sarcoplasmic reticulum Ca(+2)-ATPase (SERCA2a) is downregulated in this process. We hypothesized that upregulating SERCA2a might inhibit remodeling in a surgical model of apical MI (no intrinsic MR) with independent MR-type flow.

METHODS AND RESULTS

In 12 sheep, percutaneous gene delivery was performed by using a validated protocol to perfuse both the left anterior descending and circumflex coronary arteries with occlusion of venous drainage. We administered adeno-associated virus 6 (AAV6) carrying SERCA2a under a Cytomegalovirus promoter control in 6 sheep and a reporter gene in 6 controls. After 2 weeks, a standardized apical MI was created, and a shunt was implanted between the left ventricle and left atrium, producing regurgitant fractions of ≈30%. Animals were compared at baseline and 1 and 3 months by 3D echocardiography, Millar hemodynamics, and biopsies. The SERCA2a group had a well-maintained preload-recruitable stroke work at 3 months (decrease by 8±10% vs 42±12% with reporter gene controls; P<0.001). Left ventricular dP/dt followed the same pattern (no change vs 55% decrease; P<0.001). Left ventricular end-systolic volume was lower with SERCA2a (82.6±9.6 vs 99.4±9.7 mL; P=0.03); left ventricular end-diastolic volume, reflecting volume overload, was not significantly different (127.8±6.2 vs 134.3±9.4 mL). SERCA2a sheep showed a 15% rise in antiapoptotic pAkt versus a 30% reduction with the reporter gene (P<0.001). Prohypertrophic activated STAT3 was also 41% higher with SERCA2a than in controls (P<0.001). Proapoptotic activated caspase-3 rose >5-fold during 1 month in both SERCA2a and control animals (P=NS) and decreased by 19% at 3 months, remaining elevated in both groups.

CONCLUSIONS

In this controlled model, upregulating SERCA2a induced better function and lesser remodeling, with improved contractility, smaller volume, and activation of prohypertrophic/antiapoptotic pathways. Although caspase-3 remained activated in both groups, SERCA2a sheep had increased molecular antiremodeling "tone." We therefore conclude that upregulating SERCA2a inhibits MR-induced post-MI remodeling in this model and thus may constitute a useful approach to reduce the vicious circle of remodeling in ischemic MR.

Mechanism of decrease in mitral regurgitation after cardiac resynchronization therapy: optimization of the force-balance relationship

BACKGROUND

Cardiac resynchronization therapy (CRT) has been shown to reduce functional mitral regurgitation (MR). It has been proposed that the mechanism of MR reduction relates to geometric change or, alternatively, changes in left ventricular (LV) contractile function. Normal mitral valve (MV) function relies on a balance between tethering and closing forces on the MV leaflets. Functional MR results from a derangement of this force-balance relationship, and CRT may be an important modulator of MV function by its ability to enhance the force-balance relationship on the MV. We hypothesized that CRT improves the comprehensive force balance acting on the valve, including favorable changes in both geometry and LV contractile function.

METHODS AND RESULTS

We examined the effect of CRT on 34 patients with functional MR before and after CRT (209+/-81 days). MR regurgitant volume, closing forces on MV (derived from Doppler transmitral pressure gradients), including dP/dt and a factor (closing pressure ratio) expressing how long the peak closing gradient is maintained over systole (closing pressure ratio=velocity time integral/MR peak velocityxmitral regurgitation time), and dyssynchrony by tissue Doppler were measured. End-diastolic volume, end-systolic volume, mitral valve annular area (MAA) and contraction (percent change in MAA from end-diastole to midsystole), leaflet closing area (leaflet area during valve closure), and tenting volume (volume under leaflets to annular plane) were measured by 3D echocardiography. After CRT, end-diastolic volume (253+/-111 versus 221+/-110 mL, P<0.001) and end-systolic volume (206+/-97 versus 167+/-91 mL, P<0.001) decreased and ejection fraction (19+/-6 versus 27+/-9%, P<0.001) increased. MR regurgitant volume decreased from 35+/-17 to 23+/-14 mL (P<0.001), MAA from 11.6+/-3.5 to 10.5+/-3.1 cm(2) (P<0.001), leaflet closing area from 15.4+/-5 to 13.7+/-3.8 cm(2) (P<0.001), and tenting volume from 5.7+/-2.6 to 4.6+/-2.2 mL (P<0.001). Peak velocity (and therefore transmitral closing pressure) was more sustained throughout systole, as reflected by the increase in the closing pressure ratio (0.77+/-0.1 versus 0.84+/-0.1 before CRT versus after CRT, P=0.01); dP/dt also improved after CRT. There was no change in dyssynchrony or MAA contraction.

CONCLUSIONS

Reduction in MR after CRT is associated with favorable changes in MV geometry and closing forces on the MV. It does so by favorably affecting the force balance acting on the MV in 2 ways: reducing tethering through reversal of LV remodeling and increasing the systolic duration of peak transmitral closing pressures.

Mitral leaflet adaptation to ventricular remodeling: prospective changes in a model of ischemic mitral regurgitation

BACKGROUND

Ischemic mitral regurgitation is caused by systolic traction on the mitral leaflets related to ventricular distortion. Little is known about how chronic tethering affects leaflet area, in part because it cannot be measured repeatedly in situ. Recently, a new method for 3D echocardiographic measurement of mitral leaflet area was developed and validated in vivo against sheep valves, later excised. Clinical studies (n=80) showed that mitral leaflet area increased by >30% in patients with inferior myocardial infarction and dilated cardiomyopathy versus normal; greater adaptation independently predicted less mitral regurgitation. This study explored whether mitral valve area changes over time within the same heart with ischemic mitral regurgitation.

METHODS AND RESULTS

Twelve sheep were studied at baseline and 3 months after inferior myocardial infarction by 3D echocardiography; 6 were untreated and 6 were treated initially with an epicardial patch to limit left ventricular dilation and mitral regurgitation. Untreated sheep developed left ventricular dilation at 3 months, with global dysfunction (mean+/-SD ejection fraction, 24+/-10% versus 44+/-10% with patching, P=0.02) and moderate mitral regurgitation (vena contracta, 5.0+/-1.0 versus 0.8+/-1.0 mm, P<0.0002). In untreated sheep, total diastolic leaflet area increased from 13.1+/-1.3 to 18.1+/-2.5 cm(2) (P=0.0001). In patched sheep, leaflet area at 3 months was not significantly different from baseline sheep values (13.0+/-1.1 versus baseline, 12.1+/-1.8 cm(2), P=0.31).

CONCLUSIONS

Mitral valve area, independent of systolic stretch, increases over time as the left ventricular remodels after inferior myocardial infarction. This increase, however, fails to compensate adequately for tethering to prevent mitral regurgitation. Understanding the mechanism of valve adaptation can potentially suggest new biological and surgical therapeutic targets.

Initial results of posterior leaflet extension for severe type IIIb ischemic mitral regurgitation

BACKGROUND

Management of severe ischemic mitral regurgitation remains difficult with disappointing early and intermediate-term surgical results of valve repair.

METHODS AND RESULTS

Forty-four patients with severe (4+) Carpentier type IIIb ischemic mitral regurgitation underwent mitral valve repair, with or without surgical revascularization, by posterior leaflet extension with a patch of bovine pericardium and a remodeling annuloplasty. Serial echocardiography was performed preoperatively, intraoperatively, and postoperatively to assess mitral valve competence. The postoperative functional status of patients was assessed. The average Parsonnet score was 38+/-13. Thirty-day mortality was 11%, and late mortality was 14%. Mean follow-up was 38 months. The actuarial freedom from moderate or severe recurrent mitral regurgitation was 90% at 2 years, whereas 90% of patients were in New York Heart Association class I at 2 years.

CONCLUSIONS

Posterior leaflet extension with annuloplasty of the mitral valve for severe type IIIb ischemic regurgitation is a safe, effective method that provides good early and intermediate-term competence of the mitral valve and therefore good functional status.

Mitral regurgitation

Mitral regurgitation affects more than 2 million people in the USA. The main causes are classified as degenerative (with valve prolapse) and ischaemic (ie, due to consequences of coronary disease) in developed countries, or rheumatic (in developing countries). This disorder generally progresses insidiously, because the heart compensates for increasing regurgitant volume by left-atrial enlargement, causes left-ventricular overload and dysfunction, and yields poor outcome when it becomes severe. Doppler-echocardiographic methods can be used to quantify the severity of mitral regurgitation. Yearly mortality rates with medical treatment in patients aged 50 years or older are about 3% for moderate organic regurgitation and about 6% for severe organic regurgitation. Surgery is the only treatment proven to improve symptoms and prevent heart failure. Valve repair improves outcome compared with valve replacement and reduces mortality of patient with severe organic mitral regurgitation by about 70%. The best short-term and long-term results are obtained in asymptomatic patients operated on in advanced repair centres with low operative mortality (<1%) and high repair rates (>/=80-90%). These results emphasise the importance of early detection and assessment of mitral regurgitation.

Mitral regurgitation and cardiac resynchronization therapy

Secondary mitral regurgitation (MR) is frequent in patients with severely depressed left ventricular function. It increases mortality, and decreases exercise capacity. Its main mechanisms are multifactorial, related to apical and outward displacement of the papillary muscles, secondary to an enlarged and a more spherical left ventricle, causing increased subvalvar traction; mitral annular dilatation; and poor contraction of the left ventricle, with a slowed rate of rise of intraventricular pressure and slow closure of the leaflets. Since mechanical dyssynchrony is a major contributor factor to secondary MR, cardiac resynchronization therapy (CRT) could be considered as an alternative therapeutic option for MR, alone or in combination with surgical correction. Effects of CRT on secondary MR are acute and long-term, due to the reverse remodeling of the left ventricle. CRT reduces systolic MR by 30-40%, both at rest and during exercise, and abolishes diastolic MR, by increase of the closing forces and decrease of the tethering forces, acting on the mitral valve; decrease of the mitral annular dilatation represents a minor mechanism. Patients more likely to benefit should have moderate-to-severe MR (but not too severe), of nonischemic etiology, and high interpapillary muscles dyssynchrony. Effects are similar in patients with sinus rhythm and in patients with atrial fibrillation, and in patients with broad and narrow QRS complexes, provided that they have similar extent of dyssynchrony. Biventricular mode is the pacing modality of choice.