Determinants of the degree of functional mitral regurgitation in patients with systolic left ventricular dysfunction: A quantitative clinical study

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.

Ischemic mitral regurgitation: pathophysiology, diagnosis and surgical treatment

Ischemic mitral valve regurgitation often complicates acute myocardial infarction and also represents a negative prognostic factor for long-term survival in patients undergoing surgical myocardial revascularization. While severe mitral regurgitation should always be corrected during a coronary artery bypass operation, the decision making is more difficult in patients with a mild-to-moderate degree of regurgitation. Recent studies and experimental protocols have elucidated the pathophysiological mechanisms leading to mitral regurgitation with great interest in annular modifications and subvalvular alterations. These data suggest that new and integrated surgical approaches that address annuloplasty ring sizing, ring type selection and tethering phenomenon (i.e., chordal cutting, 'edge-to-edge' technique and left-ventricular plasty techniques) are required for a safer and durable valve repair. Transthoracic and transesophageal echocardiography are useful in determining the etiology and the degree of mitral regurgitation, to assess mitral deformation and to measure indexes of global and regional left-ventricular remodeling. Stress echocardiography may unmask higher degrees of mitral regurgitation. More data are needed in order to confirm the promising and interesting preliminary experimental findings of magnetic resonance imaging in diagnosis and clinical evaluation of ischemic mitral regurgitation.

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.

Mitral-valve repair versus replacement for severe ischemic mitral regurgitation

BACKGROUND

Ischemic mitral regurgitation is associated with a substantial risk of death. Practice guidelines recommend surgery for patients with a severe form of this condition but acknowledge that the supporting evidence for repair or replacement is limited.

METHODS

We randomly assigned 251 patients with severe ischemic mitral regurgitation to undergo either mitral-valve repair or chordal-sparing replacement in order to evaluate efficacy and safety. The primary end point was the left ventricular end-systolic volume index (LVESVI) at 12 months, as assessed with the use of a Wilcoxon rank-sum test in which deaths were categorized below the lowest LVESVI rank.

RESULTS

At 12 months, the mean LVESVI among surviving patients was 54.6±25.0 ml per square meter of body-surface area in the repair group and 60.7±31.5 ml per square meter in the replacement group (mean change from baseline, -6.6 and -6.8 ml per square meter, respectively). The rate of death was 14.3% in the repair group and 17.6% in the replacement group (hazard ratio with repair, 0.79; 95% confidence interval, 0.42 to 1.47; P=0.45 by the log-rank test). There was no significant between-group difference in LVESVI after adjustment for death (z score, 1.33; P=0.18). The rate of moderate or severe recurrence of mitral regurgitation at 12 months was higher in the repair group than in the replacement group (32.6% vs. 2.3%, P<0.001). There were no significant between-group differences in the rate of a composite of major adverse cardiac or cerebrovascular events, in functional status, or in quality of life at 12 months.

CONCLUSIONS

We observed no significant difference in left ventricular reverse remodeling or survival at 12 months between patients who underwent mitral-valve repair and those who underwent mitral-valve replacement. Replacement provided a more durable correction of mitral regurgitation, but there was no significant between-group difference in clinical outcomes. (Funded by the National Institutes of Health and the Canadian Institutes of Health; ClinicalTrials.gov number, NCT00807040.).

Growing matter: a review of growth in living systems

Living systems can grow, develop, adapt, and evolve. These phenomena are non-intuitive to traditional engineers and often difficult to understand. Yet, classical engineering tools can provide valuable insight into the mechanisms of growth in health and disease. Within the past decade, the concept of incompatible configurations has evolved as a powerful tool to model growing systems within the framework of nonlinear continuum mechanics. However, there is still a substantial disconnect between the individual disciplines, which explore the phenomenon of growth from different angles. Here we show that the nonlinear field theories of mechanics provide a unified concept to model finite growth by means of a single tensorial internal variable, the second order growth tensor. We review the literature and categorize existing growth models by means of two criteria: the microstructural appearance of growth, either isotropic or anisotropic; and the microenvironmental cues that drive the growth process, either chemical or mechanical. We demonstrate that this generic concept is applicable to a broad range of phenomena such as growing arteries, growing tumors, growing skin, growing airway walls, growing heart valve leaflets, growing skeletal muscle, growing plant stems, growing heart valve annuli, and growing cardiac muscle. The proposed approach has important biological and clinical applications in atherosclerosis, in-stent restenosis, tumor invasion, tissue expansion, chronic bronchitis, mitral regurgitation, limb lengthening, tendon tear, plant physiology, dilated and hypertrophic cardiomyopathy, and heart failure. Understanding the mechanisms of growth in these chronic conditions may open new avenues in medical device design and personalized medicine to surgically or pharmacologically manipulate development and alter, control, or revert disease progression.

Echocardiographic determinants of ischemic mitral regurgitation

OBJECTIVES

It is not clear whether the presence and degree of chronic ischemic mitral regurgitation (IMR) in patients with left ventricular (LV) dysfunction are related to LV dysfunction, local LV remodeling or mitral valve deformation. We sought to establish the strongest determinants of IMR severity in patients with LV dysfunction and IMR.

METHODS

We prospectively performed transthoracic echocardiography for 135 patients (mean age = 60.76 ± 9.69 years, 71.9% male) with LV dysfunction (ejection fraction ≤ 50%) and coronary artery disease (70% stenosis in ≥ 1 coronary artery and no myocardial infarction during the previous 16 days). Global and local LV remodeling and mitral deformity indices were measured. Using the vena contracta, MR severity was graded as no regurgitation; mild; moderate; and severe.

RESULTS

Mild regurgitation was found in 45 (33.3%) patients, moderate in 71 (52.6%), severe in 6 (4.4%), and no regurgitation in 13 (9.6%). By linear logistic multivariable analysis, the major echocardiographic determinants of MR severity were tenting area (TA), sphericity index (LV systolic length/width), and C-septal (distance between the leaflet coaptation and the septum). TA was best related to coaptation depth and annulus diameter. Mitral annular diameter was best correlated with left atrial surface area (r = 0.630, p < 0.001).

CONCLUSION

TA was significantly correlated with annulus diameter and, along with sphericity index and C-septal, were the independent echocardiographic determinants of MR severity. These findings warrant consideration when performing mitral valve repairs for patients with IMR.

The impact of segmental volumetric changes on functional mitral regurgitation: a study using three-dimensional regional time-volume analysis combined with low-dose dobutamine

PURPOSE

Using transthoracic three-dimensional (3D) echo regional volume analysis combined with low-dose dobutamine to investigate the effects on regional volume, mitral configuration and functional mitral regurgitation (FMR).

METHODS

Fifty-six patients with ischemic cardiomyopathy (ICM) were included in this study. The effective regurgitant orifice area (EROA) of FMR secondary to ICM with depressed left ventricular ejection fraction was compared with mitral tenting area and coaptation height (CH) before and after low-dose dobutamine (10 μg/kg per min). Using 3-DQ software we measured and calculated regional stroke-volumes (rSV), the ratio of the rSV to the whole left ventricular stroke volume (rgSVratio) in all 17 segments and the average rgSVratio of 4 anterior-PM attached segments (rgSVratio-aver anter-PM), 4 posterior-PM attached segments (rgSVratio-aver post-PM), 8 PMs attached segments (rgSVratio-aver PMs) and all 17 segments before and after dobutamine.

RESULTS

Compared with the resting condition, the SVr and rgSVratio on the basal and mid segments of anterior, lateral, inferior, and posterior walls were increased after dobutamine infusion (P < 0.05). EROA at rest was associated with tenting area, CH and rgSVratio-aver of PMs and the reduction in EROA caused by dobutamine was associated with reductions in tenting area, CH and increases in rgSVratio-aver of PMs. Tenting area was associated with rgSVratio-aver of PMs and reduction caused by dobutamine was associated with increases in rgSVratio-aver of PMs.

CONCLUSIONS

The FMR decreasing during low-dose dobutamine is quantitatively associated with the regional LV volume change of attached PMs. Real time transthoracic three-dimensional echocardiography may provide a simple and noninvasive approach to assess regional LV time-volume characteristic during FMR.

Criteria for mitral regurgitation classification were inadequate for dilated cardiomyopathy

Background

Mitral regurgitation (MR) is common in patients with dilated cardiomyopathy (DCM). It is unknown whether the criteria for MR classification are inadequate for patients with DCM.

Objective

We aimed to evaluate the agreement among the four most common echocardiographic methods for MR classification.

Methods

Ninety patients with DCM were included. Functional MR was classified using four echocardiographic methods: color flow jet area (JA), vena contracta (VC), effective regurgitant orifice area (ERO) and regurgitant volume (RV). MR was classified as mild, moderate or important according to the American Society of Echocardiography criteria and by dividing the values into terciles. The Kappa test was used to evaluate whether the methods agreed, and the Pearson correlation coefficient was used to evaluate the correlation between the absolute values of each method.

Results

MR classification according to each method was as follows: JA: 26 mild, 44 moderate, 20 important; VC: 12 mild, 72 moderate, 6 important; ERO: 70 mild, 15 moderate, 5 important; RV: 70 mild, 16 moderate, 4 important. The agreement was poor among methods (kappa = 0.11; p < 0.001). It was observed a strong correlation between the absolute values of each method, ranging from 0.70 to 0.95 (p < 0.01) and the agreement was higher when values were divided into terciles (kappa = 0.44; p < 0.01)

Conclusion

The use of conventional echocardiographic criteria for MR classification seems inadequate in patients with DCM. It is necessary to establish new cutoff values for MR classification in these patients.

Mechanics of healthy and functionally diseased mitral valves: a critical review

The mitral valve is a complex apparatus with multiple constituents that work cohesively to ensure unidirectional flow between the left atrium and ventricle. Disruption to any or all of the components-the annulus, leaflets, chordae, and papillary muscles-can lead to backflow of blood, or regurgitation, into the left atrium, which deleteriously effects patient health. Through the years, a myriad of surgical repairs have been proposed; however, a careful appreciation for the underlying structural mechanics can help optimize long-term repair durability and inform medical device design. In this review, we aim to present the experimental methods and significant results that have shaped the current understanding of mitral valve mechanics. Data will be presented for all components of the mitral valve apparatus in control, pathological, and repaired conditions from human, animal, and in vitro studies. Finally, current strategies of patient specific and noninvasive surgical planning will be critically outlined.

Determinants of functional mitral regurgitation severity in patients with ischemic cardiomyopathy versus nonischemic dilated cardiomyopathy

AIMS

Functional mitral regurgitation (MR) is prevalent among patients with left ventricular (LV) dysfunction and is associated with a poorer prognosis. Our aim was to assess the primary determinants of MR severity in patients with ischemic cardiomyopathy (ICM) and nonischemic dilated cardiomyopathy (DCM).

METHODS AND RESULTS

Patients with functional MR secondary to ICM (n = 55) and DCM (n = 48) were prospectively enrolled. Effective regurgitant orifice (ERO) area, global LV remodeling, regional wall-motion abnormalities, and mitral apparatus deformity indices were assessed utilizing conventional and tissue Doppler echocardiography. ICM patients had more severe MR compared with DCM patients despite similar ejection fraction and functional status (ERO = 0.16 ± 0.08 cm(2) vs. ERO = 0.12 ± 0.70 cm(2) , respectively, P = 0.002). Regional myocardial systolic velocities in mid-inferior and mid-lateral wall were negatively correlated with ERO in ICM and DCM patients, respectively. Multivariate analysis identified coaptation height as the only independent determinant of ERO in both groups. In a subset of ICM patients (n = 9) with relatively high ERO despite low coaptation height, a higher prevalence of left bundle branch block was detected (88.9% vs. 46.7%, P = 0.02).

CONCLUSIONS

Functional MR severity was chiefly determined by the extent of mitral apparatus deformity, and coaptation height can provide a rapid estimation of MR severity in heart failure patients. Additional contributory mechanisms in ICM patients include depressed myocardial systolic velocities in posteromedial papillary muscle attaching site and evidence of global LV dyssynchrony.

[Valvular surgery for an exercise-induced functional mitral regurgitation in heart failure and preserved ejection fraction: a case study]

We here report the case of a 67-year-old woman with moderate mitral regurgitation without significant structural abnormalities that get worse during severe recurrent heart failures and preserved ejection fraction with concomitant paroxysmal atrial fibrillation. Atrial fibrillation became permanent and despite a well-controlled cardiac frequency, new heart failure episodes occurred. Exercise doppler echocardiography showed that the mechanism of this mitral regurgitation was a two leaflet mitral tenting. We discuss here the different mechanisms that could induce these kinds of mitral regurgitation with excessive tenting. We emphasize the interest of early detection by exercise doppler echocardiography even when a triggering factor like atrial fibrillation seems to be involved. We also discuss the interest of mitral valve replacement for these patients.

Real-time 3-dimensional dynamics of functional mitral regurgitation: a prospective quantitative and mechanistic study

Background

Three‐dimensional transthoracic echocardiography (3D‐TTE) with dedicated software permits quantification of mitral annulus dynamics and papillary muscle motion throughout the cardiac cycle.

Methods and Results

Mitral apparatus 3D‐TTE was acquired in controls (n=42), patients with left ventricle dysfunction and functional mitral regurgitation (LVD‐FMR; n=43) or without FMR (LVD‐noMR, n=35). Annulus in both normal and LVD‐noMR subjects displayed saddle shape accentuation in early‐systole (ratio of height to intercommissural diameter, 10.6±3.7 to 13.5±4.0 in normal and 9.1±4.3 to 12.6±3.6 in LVD‐noMR; P<0.001 for diastole to early‐systole motion, P=NS between those groups). In contrast, saddle shape was unchanged from diastole in FMR patients (10.0±6.4 to 8.0±5.2; P=NS, P<0.05 compared to both other groups). Papillary tips moved symmetrically towards to the midanterior annulus in control and LVD‐noMR subjects, maintaining constant ratio of the distances between both tips to midannulus (PtAR) throughout systole. In LVD‐FMR patients midsystolic posterior papillary tip to anterior annulus distance was increased, resulting in higher PtAR (P=0.05 compared to both other groups). Mechanisms of early‐ and midsystolic FMR differed between different etiologies of LV dysfunction. In patients with anterior MI and global dysfunction annular function and dilatation were the dominant parameters, while papillary muscle motion was the predominant determinant of FMR in patients with inferior MI.

Conclusions

Inadequate early‐systolic annular contraction and saddle‐shape accentuation in patients with impaired LV contribute to early–mitral incompetency. Asymmetric papillary tip movement towards the midanterior annulus is a major determinant of mid‐ and late‐systolic functional mitral regurgitation.

LEFT VENTRICULAR REMODELLING AND MITRAL VALVE REMODELLING IN CORONARY HEART DISEASE PATIENTS WITH POST-SURGERY PROGRESSION OF MITRAL REGURGITATION

The progression of ischemic mitral regurgitation (MR) after coronary arty bypass graft (CABG) surgery remains one of the most complex and still unresolved problems in the treatment of coronary heart disease (CHD).

Aim. To study myocardial function, left ventricular (LV) remodelling, and mitral valve (MV) remodelling in CHD patients with MR progression after isolated CABG or CABG combined with LV reconstructive surgery.

Material and methods. In total, 101 CHD patients after CABG were included in the analysis.

Results. The mechanisms of MR progression after isolated CABG differ from those after CABG and LV reconstructive surgery. After the former, LV remodelling progresses both locally and globally, while after the latter, the LV remodelling progression is predominantly global. The patients with post-surgery MR progression differ from their peers without MR in terms of all key parameters of MV geometry.

Conclusion. The leading mechanism of MR progression is local and global LV remodelling, which leads to papillary muscle dislocation and MV leaflet tension and restricted motion. The categories of patients with a high risk of post-surgery MR progression are defined. 

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.

Quantitation of the mitral tetrahedron in patients with ischemic heart disease using real-time three-dimensional echocardiography to evaluate the geometric determinants of ischemic mitral regurgitation

BACKGROUND

Ischemic mitral regurgitation (IMR) is common in ischemic heart disease and results in poor prognosis. However, the exact mechanism of IMR has not been fully elucidated.

HYPOTHESIS

Quantitation of the mitral tetrahedron using three-dimentianl (3D) echocardiography is capable of evaluating the geometric determinants and mechanisms of IMR.

METHODS

Forty patients with a history of ST-elevation myocardial infarction at least 6 months earlier were studied. Parameters of mitral deformation and global left ventricular (LV) function and shape were evaluated by 2-dimensional echocardiography. The effective regurgitant orifice (ERO) of IMR was obtained by the quantitative continuous-wave Doppler technique. Three-dimensional (3D) echocardiography was applied to assess the mitral tetrahedron.

RESULTS

Mitral valvular tenting area (P < 0.001), mitral annular area (P = 0.032), dilation of the LV in diastole, impairment of the LV ejection fraction, and volume of the spherically shaped LV in systole were greater in patients with an ERO ≥20 mm(2) than in those with an ERO <20 mm(2). In the mitral tetrahedron, only the interpapillary muscle roots distance showed a significant difference (P = 0.004). Multivariate analysis with the logistic regression model showed the systolic mitral tenting area (odds ratio [OR]: 280.49, 95% confidence interval [CI]: 4.59-1.72 × 10(4), P = 0.007) and interpapillary muscle distance (OR: 1.50, 95% CI: 1.03-2.19, P = 0.036) to be independent factors in predicting significant IMR (ERO ≥20 mm(2)).

CONCLUSIONS

3D echocardiography can be effectively applied in measuring the mitral tetrahedron and evaluating the mechanism of IMR. Mitral valvular tenting and interpapillary muscle distance are 2 independent factors of significant IMR.

Mitral valve enlargement in chronic aortic regurgitation as a compensatory mechanism to prevent functional mitral regurgitation in the dilated left ventricle

OBJECTIVES

The aim of this study was to test the hypothesis that mitral valve (MV) enlargement occurring in chronic aortic regurgitation (AR) prevents functional mitral regurgitation (FMR).

BACKGROUND

Chronic AR causes left ventricular (LV) dilation, creating the potential for FMR. However, FMR is typically absent during compensated AR despite substantial LV enlargement. Increased mitral leaflet area has been identified in AR, but it is unknown whether increased MV size can represent a compensatory mechanism capable of preventing FMR.

METHODS

Database review of 816 patients with at least moderate AR evaluated the prevalence of FMR. A total of 90 patients were enrolled prospectively for 3-dimensional echocardiography (30 AR, 30 FMR, and 30 controls) to assess MV geometry including total leaflet area.

RESULTS

FMR was present in 5.6% of AR patients by database review. Prospectively, only 1 AR patient had more than mild FMR despite increased LV end-diastolic volume (82 ± 22, 86 ± 23, and 51 ± 12 cm(3)/m(2), respectively, for AR, FMR vs. control patients; p < 0.01) and similar sphericity index, annular area, and tethering distances compared with FMR. Total MV area was largest in AR (31.3% greater than normal), increasing significantly more than in FMR. The ratio of valve size to closure area was maintained in AR, whereas decreases in this ratio and LV ejection fraction independently predicted FMR.

CONCLUSIONS

FMR prevalence is low in chronic AR. MV leaflet area is significantly increased compared with control and FMR patients, preserving a normal relationship to the area needed for closure in the dilated LV. Understanding the mechanisms underlying this adaptation could lead to new therapeutic interventions to prevent FMR.

Devices in the management of advanced, chronic heart failure

Heart failure (HF) is a global phenomenon, and the overall incidence and prevalence of the condition are steadily increasing. Medical therapies have proven efficacious, but only a small number of pharmacological options are in development. When patients cease to respond adequately to optimal medical therapy, cardiac resynchronization therapy has been shown to improve symptoms, reduce hospitalizations, promote reverse remodelling, and decrease mortality. However, challenges remain in identifying the ideal recipients for this therapy. The field of mechanical circulatory support has seen immense growth since the early 2000s, and left ventricular assist devices (LVADs) have transitioned over the past decade from large, pulsatile devices to smaller, more-compact, continuous-flow devices. Infections and haematological issues are still important areas that need to be addressed. Whereas LVADs were once approved only for 'bridge to transplantation', these devices are now used as destination therapy for critically ill patients with HF, allowing these individuals to return to the community. A host of novel strategies, including cardiac contractility modulation, implantable haemodynamic-monitoring devices, and phrenic and vagus nerve stimulation, are under investigation and might have an impact on the future care of patients with chronic HF.

Contractile mitral annular forces are reduced with ischemic mitral regurgitation

OBJECTIVE

Forces acting on mitral annular devices in the setting of ischemic mitral regurgitation are currently unknown. The aim of this study was to quantify the cyclic forces that result from mitral annular contraction in a chronic ischemic mitral regurgitation ovine model and compare them with forces measured previously in healthy animals.

METHODS

A novel force transducer was implanted in the mitral annulus of 6 ovine subjects 8 weeks after an inferior left ventricle infarction that produced progressive, severe chronic ischemic mitral regurgitation. Septal-lateral and transverse forces were measured continuously for cardiac cycles reaching a peak left ventricular pressure of 90, 125, 150, 175, and 200 mm Hg. Cyclic forces and their rate of change during isovolumetric contraction were quantified and compared with those measured in healthy animals.

RESULTS

Animals with chronic ischemic mitral regurgitation exhibited a mean mitral regurgitation grade of 2.3 ± 0.5. Ischemic mitral regurgitation was observed to decrease significantly septal-lateral forces at each level of left ventricular pressure (P < .01). Transverse forces were consistently lower in the ischemic mitral regurgitation group despite not reaching statistical significance. The rate of change of these forces during isovolumetric contraction was found to increase significantly with peak left ventricular pressure (P < .005), but did not differ significantly between animal groups.

CONCLUSIONS

Mitral annular forces were measured for the first time in a chronic ischemic mitral regurgitation animal model. Our findings demonstrated an inferior left ventricular infarct to decrease significantly cyclic septal-lateral forces while modestly lowering those in the transverse. The measurement of these forces and their variation with left ventricular pressure contributes significantly to the development of mitral annular ischemic mitral regurgitation devices.

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.

Left ventricular mechanics following restrictive mitral annuloplasty for functional mitral regurgitation: two-dimensional speckle tracking echocardiographic study

BACKGROUND

Restrictive mitral annuloplasty (RMA) is widely employed for patients with functional mitral regurgitation (MR). Its improvement of left ventricular (LV) function has been demonstrated by only a gradual increase in LV ejection fraction (EF) in the chronic phase. However, the detailed evaluation of changes in LV function has not been fully elucidated in functional MR patients before and after RMA. Therefore, we performed two-dimensional speckle tracking echocardiography (2D-STE), which enables accurate evaluation of myocardial deformation and rotation that are undetectable by conventional echocardiography.

METHODS

We studied 13 patients (mean age 61 ± 10 years) with functional MR associated with cardiomyopathy undergoing RMA. In addition to conventional echocardiographic measurements, 2D-STE was performed to measure peak systolic radial (RS), circumferential (CS), and longitudinal (LS) strains and twist before and 4 ± 2 weeks after surgery. LV twist was defined as the difference between the apical and basal rotations.

RESULTS

After RMA, EF and LS remained unchanged, but RS and CS were significantly improved at the mid-LV (RS, 20.6 ± 10.8 vs 24.5 ± 11.6%; CS, -9.6 ± 5.2 vs -12.8 ± 5.6%) and at the apex (RS, 15.0 ± 12.2 vs 18.7 ± 8.6%; CS, -4.4 ± 3.0 vs -7.8 ± 4.8%). RS and CS were unchanged at the base. The apical and basal rotations changed significantly, from 3.5°± 0.7° to 9.2°± 2.1°, and -2.1°± 0.7° to -3.8°± 1.0°, respectively. Consequently, the LV twist increased significantly, from 5.6°± 1.0° to 13.0°± 1.9°.

CONCLUSIONS

Radial and circumferential strains and LV twist increased significantly in the early postoperative period in functional MR patients after RMA and concomitant procedures.

Evidence of adaptive mitral leaflet growth

Ischemic mitral regurgitation is mitral insufficiency caused by myocardial infarction. Recent studies suggest that mitral leaflets have the potential to grow and reduce the degree of regurgitation. Leaflet growth has been associated with papillary muscle displacement, but role of annular dilation in leaflet growth is unclear. We tested the hypothesis that chronic leaflet stretch, induced by papillary muscle tethering and annular dilation, triggers chronic leaflet growth. To decipher the mechanisms that drive the growth process, we further quantified regional and directional variations of growth. Five adult sheep underwent coronary snare and marker placement on the left ventricle, papillary muscles, mitral annulus, and mitral leaflet. After eight days, we tightened the snares to create inferior myocardial infarction. We recorded marker coordinates at baseline, acutely (immediately post-infarction), and chronically (five weeks post-infarction). From these coordinates, we calculated acute and chronic changes in ventricular, papillary muscle, and annular geometry along with acute and chronic leaflet strains. Chronic left ventricular dilation of 17.15% (p<0.001) induced chronic posterior papillary muscle displacement of 13.49 mm (p=0.07). Chronic mitral annular area, commissural and septal-lateral distances increased by 32.50% (p=0.010), 14.11% (p=0.007), and 10.84% (p=0.010). Chronic area, circumferential, and radial growth were 15.57%, 5.91%, and 3.58%, with non-significant regional variations (p=0.868). Our study demonstrates that mechanical stretch, induced by annular dilation and papillary muscle tethering, triggers mitral leaflet growth. Understanding the mechanisms of leaflet adaptation may open new avenues to pharmacologically or surgically manipulate mechanotransduction pathways to augment mitral leaflet area and reduce the degree of regurgitation.

Ischemic mitral regurgitation: not only a bystander

Ischemic mitral regurgitation (MR) is a common complication of left ventricular (LV) dysfunction related to chronic coronary artery disease. This complex multifactorial disease involves global and regional LV remodeling, as well as dysfunction and distortion of the components of the mitral valve including the chordae, the annulus, and the leaflets. Its occurrence is associated with a poor prognosis. The suboptimal results obtained with the most commonly used surgical strategy, involving mitral valve annuloplasty with coronary bypass grafting, emphasize the need to develop alternative surgical techniques targeting the causal mechanisms of the disease. A comprehensive preoperative assessment of mitral valve configuration and LV geometry and function and an accurate quantification of MR severity at rest and during exercise may contribute to improve risk stratification and to tailor the surgical strategy according to the individual characteristics of the patient.

Incremental value of global systolic dyssynchrony in determining the occurrence of functional mitral regurgitation in patients with left ventricular systolic dysfunction

AIMS

The aim of this study was to assess the contribution of left ventricular (LV) systolic dyssynchrony to functional mitral regurgitation (MR).

METHODS AND RESULTS

Patients (n = 136) with LV systolic dysfunction (ejection fraction <50%) and at least mild MR were prospectively recruited. The effective regurgitant orifice area (EROA) was assessed by the proximal isovelocity surface area method. Left ventricular global systolic dyssynchrony [the maximal difference in time to peak systolic velocity among the 12 LV segments (Ts-Dif)] and regional systolic dyssynchrony (the delay between the anterolateral and posteromedial papillary muscle attaching sites) were assessed by tissue Doppler imaging. Left ventricular global and regional remodelling, systolic function, indices of mitral valvular and annular deformation were also measured. The size of the EROA correlated with the degrees of mitral deformation, LV remodelling, systolic function, and systolic dyssynchrony. By multivariate logistic regression analysis, the mitral valve tenting area (OR = 1.020, P < 0.001) and the Ts-Dif (OR = 1.011, P = 0.034) were independent determinants of significant functional MR (defined by EROA ≥20 mm(2)). From the receiver-operating characteristic curve, the tenting area of 2.7 cm(2) (sensitivity 83%, specificity 82%, AUC 0.86, P < 0.001) and the Ts-Dif of 85 ms (sensitivity 66%, specificity 72%, AUC 0.74, P < 0.001) were associated with significant functional MR. The assessment of Ts-Dif showed an incremental value over the mitral valve tenting area for determining functional MR (χ(2) = 53.92 vs.49.11, P = 0.028).

CONCLUSION

This cross-sectional study showed that LV global, but not regional systolic dyssynchrony, is a determinant of significant functional MR in patients with LV systolic dysfunction, and is incremental to the tenting area that is otherwise the strongest factor for mitral valve deformation.

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.

Effect of obstructive sleep apnea on mitral valve tenting

Obstructive apneas produce high negative intrathoracic pressure that imposes an afterload burden on the left ventricle. Such episodes might produce structural changes in the left ventricle over time. Doppler echocardiograms were obtained within 2 months of attended polysomnography. Patients were grouped according to apnea-hypopnea index (AHI): mild/no obstructive sleep apnea (OSA; AHI <15) and moderate/severe OSA (AHI ≥15). Mitral valve tenting height and area, left ventricular (LV) long and short axes, and LV end-diastolic volume were measured in addition to tissue Doppler parameters. Comparisons of measurements at baseline and follow-up between and within groups were obtained; correlations between absolute changes (Δ) in echocardiographic parameters were also performed. After a mean follow-up of 240 days mitral valve tenting height increased significantly (1.17 ± 0.12 to 1.28 ± 0.17 cm, p = 0.001) in moderate/severe OSA as did tenting area (2.30 ± 0.41 to 2.66 ± 0.60 cm(2), p = 0.0002); Δtenting height correlated with ΔLV end-diastolic volume (rho 0.43, p = 0.01) and Δtenting area (rho 0.35, p = 0.04). In patients with mild/no OSA there was no significant change in tenting height; there was a borderline significant increase in tenting area (2.20 ± 0.44 to 2.31 ± 0.43 cm(2), p = 0.05). Septal tissue Doppler early diastolic wave decreased (8.04 ± 2.49 to 7.10 ± 1.83 cm/s, p = 0.005) in subjects with moderate/severe OSA but not in in those with mild/no OSA. In conclusion, in patients with moderate/severe OSA, mitral valve tenting height and tenting area increase significantly over time. This appears to be related, at least in part, to changes in LV geometry.

Shape Optimization of a Self-deployable Anchor Designed for Percutaneous Mitral Valve Repair

A new percutaneous annuloplasty technique for mitral regurgitation is proposed here. In this technique, inter-related anchors are first inserted around the annulus via a trans-septal catheter. The tethered wire passed through the anchors is then pulled to shrink the annulus and stop regurgitation. The anchors should withstand large deformation, applied during the delivery process, and should recover their original shape after being released inside the tissue. The shape of the anchors is, thus, optimized in an iterative process, to avoid stress concentration by minimizing the weighted rms value of the curvature along the anchor. The weight coefficients in each iteration are defined based on the stress distribution of the anchor obtained in the previous iteration. The procedure finally results in a structurally optimum anchor with a minimum in the maximum von Mises stress. This anchor is fabricated from Nitinol and tested in a cadaveric swine heart.

Core lab analysis of baseline echocardiographic studies in the STICH trial and recommendation for use of echocardiography in future clinical trials

BACKGROUND

The Surgical Treatment for Ischemic Heart Failure (STICH) randomized trial was designed to identify an optimal management strategy for patients with ischemic cardiomyopathy. Baseline echocardiographic examinations were required for all patients. The primary aim of this report is to describe the baseline STICH Echocardiography Core Laboratory data. The secondary aim is to provide recommendations regarding how echocardiography should be used in clinical practice and research on the basis of the experience gained from echocardiography in STICH.

METHODS

Between September 2002 and January 2006, 2,136 patients with ejection fractions (EFs) ≤ 35% and coronary artery disease amenable to coronary artery bypass grafting were enrolled. Echocardiography was acquired by 122 clinical enrolling sites, and measurements were performed by the Echocardiography Core Laboratory after a certification process for all clinical sites.

RESULTS

Echocardiography was available for analysis in 2,006 patients (93.9%); 1,734 (86.4%) were men, and the mean age was 60.9 ± 9.5 years. The mean left ventricular end-systolic volume index, measureable in 72.8%, was 84.0 ± 30.9 mL/m(2), and the mean EF was 28.9 ± 8.3%, with 18.5% of patients having EFs > 35%. Single-plane measurements of left ventricular and left atrial volumes were similar to their volumes by biplane measurement (r = 0.97 and r = 0.92, respectively). Mitral regurgitation severity by visual assessment was associated with a wide range of effective regurgitant orifice area, while effective regurgitant orifice area ≥ 0.2 cm(2) indicated at least moderate mitral regurgitation by visual assessment. Deceleration time of mitral inflow velocity had a weak correlation with EF (r = 0.25) but was inversely related to estimated pulmonary artery systolic pressure (r = -0.49).

CONCLUSIONS

In STICH patients with ischemic cardiomyopathy, Echocardiography Core Laboratory analysis of baseline echocardiographic findings demonstrated a wide spectrum of left ventricular shape, function, and hemodynamics, as well as the feasibility and limitations of obtaining essential echocardiographic measurements. It is critical that the use of echocardiographic parameters in clinical practice and research balance the strengths and weaknesses of the technique.

Mechanisms and predictors of mitral regurgitation after high-risk myocardial infarction

BACKGROUND

Mitral regurgitation (MR) has been associated with adverse outcomes after myocardial infarction (MI). Without structural valve disease, functional MR has been related to left ventricular (LV) remodeling and geometric deformation of the mitral apparatus. The aims of this study were to elucidate the mechanistic components of MR after high-risk MI and to identify predictors of MR progression during follow-up.

METHODS

The Valsartan in Acute Myocardial Infarction Echo substudy prospectively enrolled 610 patients with LV dysfunction, heart failure, or both after MI. MR at baseline, 1 month, and 20 months was quantified by mapping jet expansion in the left atrium in 341 patients with good-quality echocardiograms. Indices of LV remodeling, left atrial size, and diastolic function and parameters of mitral valve deformation, including tenting area, coaptation depth, anterior leaflet concavity, annular diameters, and contractility, were assessed and related to baseline MR. The progression of MR was further analyzed, and predictors of worsening among the baseline characteristics were identified.

RESULTS

Tenting area, coaptation depth, annular dilatation, and left atrial size were all associated with the degree of baseline MR. Tenting area was the only significant and independent predictor of worsening MR; a tenting area of 4 cm(2) was a useful cutoff to identify worsening of MR after MI and moderate to severe MR after 20 months.

CONCLUSIONS

Increased mitral tenting and larger mitral annular area are determinants of MR degree at baseline, and tenting area is an independent predictor of progression of MR after MI. Although LV remodeling itself contributes to ischemic MR, this influence is directly dependent on alterations in mitral geometry.