Influence of Chronic Tethering of the Mitral Valve on Mitral Leaflet Size and Coaptation in Functional Mitral Regurgitation

Fiberscope-Based Measurement of Coaptation Height for Intraoperative Assessment of Mitral Valve Repair

BACKGROUND

Restoring adequate coaptation height is a key principle of mitral valve (MV) repair. This study aimed to evaluate the utility of fiberscope (FS) technology to assess MV coaptation height for intraoperative use.

METHODS

Ex-vivo testing was performed on five adult porcine hearts. The left atrium (LA) was resected, and the left ventricle (LV) was pressurized retrograde to 27 ± 1mm Hg. An endoscope was inserted into the LV apex, centered under the MV orifice. An FS system (Milliscope II camera, LED light source, and 0.7 mm diameter × 15 cm long) 90° semirigid scope with 1.2 mm focal length) was mounted above the MV annulus in a custom alignment and measuring fixture. Three blinded measurements were taken at two locations on each MV, A2 and P2 segment, from the top of coaptation to the leaflet edge identified by the FS. Accurate positioning was verified using the LV endoscope. A control (metal rod of similar thickness) was used for comparison, with coaptation height recorded when the control was seen via the endoscope.

RESULTS

Coaptation heights were similar for the control and FS methods across all hearts at A2 (11.6 ± 2.6 mm control vs 11.8 ± 2.2 mm FS) and P2 (13.3 ± 2.6 mm control vs 13.4 ± 2.9 mm FS) segments, with similar measurement variability (control SD 0.1-1.0 mm; FS SD 0.1-0.9 mm). One outlier was excluded from analysis (n = 19/20). The maximum absolute difference and percent error between measurement methods were less than 1.1 mm (median [IQR], 0.6 [0.3-0.9] mm) and less than 14% (4.1 [2.2-7.6]%).

CONCLUSIONS

Utilization of a miniaturized FS enabled precise and accurate quantification of MV coaptation. This technique is promising for evaluating post-repair valve competence and coaptation height.

Echocardiographic quantification of mitral apparatus morphology and dynamics in patients with dilated cardiomyopathy

Mitral regurgitation is among the most common valvular heart diseases. Mitral regurgitation in patients with dilated cardiomyopathy is a complex pathology involving annular dilatation, papillary muscle displacement, systolic leaflet tethering, and left ventricular remodeling. Quantification of mitral apparatus damage in these patients is essential for successful interventional and surgical therapy. Mitral regurgitation in the presence of dilated cardiomyopathy is classified as Carpentier type IIIB, with restricted leaflet mobility as a standard feature. Echocardiography allows accurate evaluation of the complex anatomy and function of the mitral apparatus. Updated guidelines recommend two-dimensional followed by systematic three-dimensional echocardiographic evaluation in patients with mitral regurgitation. New three-dimensional echocardiographic software packages provide many parameters that help identify the precise morphology and function of the various components of the mitral apparatus, helping to determine the etiology of mitral regurgitation and evaluate disease severity. This review provides the first point-by-point approach to the assessment of all old and new echocardiographic methods, from the simplest to the most complex, used to examine the components of the mitral valve apparatus in patients with dilated cardiomyopathy. Although these parameters are still under research, this information will be helpful for establishing therapeutic procedures in a disease with a poor prognosis.

Secondary leaflet tethering in patients with severe degenerative mitral regurgitation and its association with the severity of mitral regurgitation

BACKGROUND

The purpose of the study was to determine the association between vena contracta area (VCA) and secondary leaflet tethering among mitral valve prolapse (MVP) patients, and thus to further identify and characterize an MVP with pathological leaflet tethering (MVPt+) phenotype.

METHODS

We prospectively evaluated 94 consecutive MVP patients with significant mitral regurgitation (MR) and 21 healthy controls. MVPt+ group was defined as tenting volume index (TVi) > .7 mL/m2 . The three-dimensional (3D) geometry of mitral valve apparatus and VCA was measured with dedicated quantification software.

RESULTS

Of the 94 patients with MVP and significant MR, 31 patients showed a TVi > .7 mL/m2 and entered the MVP with leaflet tethering (MVPt+) group. In stepwise multivariate analysis, only prolapse volume index and TVi were independently associated with 3D VCA. 3D VCA, annular area index, and plasma levels of NT-proBNP were independently correlated with the severity of leaflet tethering. ROC curve revealed that a 3D VCA ≥ .55 cm2 is the optimal cutoff point to predict MVPt+ phenotype.

CONCLUSIONS

Secondary leaflet tethering is a significant mechanism behind severe degenerative MR, resulting in an MVPt+ phenotype featuring more advanced morphological and hemodynamical characteristics.

Assessment of the mechanism of mitral valve prolapse in children: An echocardiography study

BACKGROUND

The high complexity of mitral valve anatomy and function in mitral valve prolapse (MVP) is not yet fully understood.

OBJECTIVE

The purpose of this study was to analyze each part of the mitral valve apparatus in children to determine its impact on the presence of MVP and to assess the interaction between the coaptation length (CL) and mitral regurgitation severity.

METHODS

We prospectively analyzed transthoracic echocardiograms of 60 patients with MVP (mean age 9.8 ± 3.1 years). We compared these patients with 60 control patients without disease. We determined length of leaflets, chordal length, tenting area, coaptation CL, the intrapapillary muscle distance (IPMD) and relation between CL and severity of mitral regurgitation (MR).

RESULTS

For patients with MVP, the posterior mitral leaflet (PML) was significantly enlarged 13.9 ± 4.1 mm versus 10.7 ± 3.5 mm (p < .01), the primary chordal length was significantly decreased 15.4 ± 3.61 mm versus 17.6 ± 3.8 mm (p < .02), and IPMD was significantly greater 18.1 ± 2.7 mm versus 16.6 ± 4.3 mm (p < .03). The difference between CL for both the anterior and posterior mitral leaflets correlated positively with MR (r = .249, p < .05). A greater than 4 mm CL correlated with at least MR (sensitivity 100%, specificity 72%) and greater than 5 mm correlated with at least moderate MR (sensitivity 100%, specificity 60%).

CONCLUSION

The majority of pediatric patients with mitral valve prolapse have structural abnormalities that are defined well by echocardiography. In addition to the presence of prolapse and regurgitation, routine assessment of leaflet length, thickness, chordal length and papillary muscle distance is fundamental for patients with MVP.

Functional anatomy and echocardiographic assessment in secondary mitral regurgitation

BACKGROUND

Mitral valve apparatus is complex and involves the mitral annulus, the leaflets, the chordae tendinae, the papillary muscles as well as the left atrial and ventricular myocardium. Secondary mitral regurgitation is a consequence of regional or global left ventricle remodeling due to an acute myocardial infarction (75% of cases) or idiopathic dilated cardiomyopathy (25% of cases). It is associated with an increase in mortality and poor outcome. There is a potential survival benefit deriving from the reduction in the degree of severity of mitral regurgitation. So the correction of the valve defect can change the clinical course and prognosis of the patient. The rationale for mitral valve treatment depends on the mitral regurgitation mechanism. Therefore, it is essential to identify and understand the pathophysiology of mitral valve regurgitation.

AIM OF THE STUDY

The aim of this review is to describe the crucial role of transthoracic and trans-esophageal echocardiography, in particular with three-dimensional echocardiography, for the assessment of the severity of secondary mitral regurgitation, anatomy, and hemodynamic changes in the left ventricle. Moreover, the concept that the mitral valve has no organic lesions has been abandoned. The echocardiography must allow a complete anatomical and functional evaluation of each component of the mitral valve complex, also useful to the surgeon in choosing the best surgical approach to repair the valve.

CONCLUSIONS

Echocardiography is the first-line imaging modality for a better selection of patients, according to geometrical modifications of mitral apparatus and left ventricle viability, especially in preoperative phase.

Wnt Site Signaling Inhibitor Secreted Frizzled‐Related Protein 3 Protects Mitral Valve Endothelium From Myocardial Infarction–Induced Endothelial‐to‐Mesenchymal Transition

Background

The onset and mechanisms of endothelial‐to‐mesenchymal transition (EndMT) in mitral valve (MV) leaflets following myocardial infarction (MI) are unknown, yet these events are closely linked to stiffening of leaflets and development of ischemic mitral regurgitation. We investigated whether circulating molecules present in plasma within days after MI incite EndMT in MV leaflets.

Methods and Results

We examined the onset of EndMT in MV leaflets from 9 sheep with inferior MI, 8 with sham surgery, and 6 naïve controls. Ovine MVs 8 to 10 days after inferior MI displayed EndMT, shown by increased vascular endothelial cadherin/α‐smooth muscle actin–positive cells. The effect of plasma on EndMT in MV endothelial cells (VECs) was assessed by quantitative polymerase chain reaction, migration assays, and immunofluorescence. In vitro, post‐MI plasma induced EndMT marker expression and enhanced migration of mitral VECs; sham plasma did not. Analysis of sham versus post‐MI plasma revealed a significant drop in the Wnt signaling antagonist sFRP3 (secreted frizzled‐related protein 3) in post‐MI plasma. Addition of recombinant sFRP3 to post‐MI plasma reversed its EndMT‐inducing effect on mitral VECs. RNA‐sequencing analysis of mitral VECs exposed to post‐MI plasma showed upregulated FOXM1 (forkhead box M1). Blocking FOXM1 reduced EndMT transcripts in mitral VECs treated with post‐MI plasma. Finally, FOXM1 induced by post‐MI plasma was downregulated by sFRP3.

Conclusions

Reduced sFRP3 in post‐MI plasma facilitates EndMT in mitral VECs by increasing the transcription factor FOXM1. Restoring sFRP3 levels or inhibiting FOXM1 soon after MI may provide a novel strategy to modulate EndMT in the MV to prevent ischemic mitral regurgitation and heart failure.

Differences in mitral valve geometry between atrial and ventricular functional mitral regurgitation in patients with atrial fibrillation: a 3D transoesophageal echocardiography study

AIMS

This study investigated geometric differences in mitral valve apparatus between atrial functional mitral regurgitation (A-FMR) and functional mitral regurgitation (FMR) with left ventricular (LV) dysfunction in patients with atrial fibrillation (AF) using 3D transoesophageal echocardiography (TOE).

METHODS AND RESULTS

In total, 135 moderate or greater FMR patients with persistent AF or atrial flutter underwent 3D TOE. Fifty-six patients had A-FMR, defined as preserved LV ejection fraction (LVEF) of ≥50% and normal LV wall motion. Seventy-nine patients had ventricular FMR (V-FMR), defined as LV dysfunction (LVEF of <50%) or LV wall motion abnormality. To evaluate mitral leaflet coaptation, the coapted area was calculated as follows: total leaflet area (TLA) in end-diastole - closed leaflet area in mid-systole. Although annular area (AA) did not significantly differ between the two groups, TLA was significantly smaller in A-FMR than in V-FMR (P = 0.005). TLA/AA, indicating the degree of the leaflet remodelling, was significantly smaller in A-FMR than in V-FMR (P < 0.001). A-FMR had significantly smaller posterior mitral leaflet tethering height and angle measured at three anteroposterior planes (lateral, central, and medial) than V-FMR (all P < 0.001). However, vena contracta width (VCW) measured on long-axis view on TOE and coapted area, which correlated with VCW (r = -0.464, P < 0.001), were similar between the two groups.

CONCLUSION

Mitral leaflet remodelling may be less in A-FMR compared with V-FMR. However, leaflet tethering was smaller in A-FMR than in V-FMR, and this may result in a similar degree of mitral leaflet coaptation and mitral regurgitation severity.

From secondary to tertiary mitral regurgitation: the paradigm shifts, but uncertainties remain

Secondary mitral regurgitation (MR) is the most common and undertreated form of MR, whose contribution to poor prognosis and indications to correction remains under discussion. MR has been characterized into 'proportionate' or 'disproportionate', based on left ventricle (LV) and regurgitant volumes, whereas 'tertiary' MR identifies conditions, in which regurgitation is pathologic per se and actively contributes to LV dysfunction. Echocardiographic and anatomo-pathological studies revealed that secondary MR prompts subtle leaflet maladaptive changes, actively contributing to the dynamic progression of secondary MR. We critically discuss the paradigm shift from secondary to tertiary MR and question the notion that MV leaflets play a passive role in secondary MR. We also review the role of standard transthoracic echocardiography for appraising and quantifying maladaptive MV leaflet changes and LV volumes and call for a more sophisticated and comprehensive imaging framework for classifying MR in future interventional studies.

Clinical and Echocardiographic Predictors of Reduced Survival in Patient with Functional Mitral Regurgitation

Functional mitral regurgitation (FMR) is associated with a poor outcome in patients with reduced left ventricular ejection fraction (LVEF). Two recent studies of percutaneous mitral valvular repair therapy reported disparate results, likely due in part to variable risk among FMR patients. The aim of this study is to define echocardiographic factors of prognostic significance in FMR patients, and particularly to compare ischemic and nonischemic FMR. We followed three hundred sixteen consecutive patients (age 60 ± 14 years, men 70%) with FMR and LVEF ≤ 35% between January 2010 and December 2015 (mean follow-up 3.7 years). Patients were categorized into ischemic (39.6%) and nonischemic (60.4%). MR was graded according to the American Society of Echocardiography guidelines. Although echo findings were similar between ischemic and nonischemic patient, the incidence of death, heart transplantation (HT), or LVAD implantation was higher in ischemic than in nonischemic patients (Log rank p = 0.001). In age and gender adjusted multivariate (11 variables) Cox regression analysis, left atrium volume index (LAVI) was associated with death, HT, or LVAD with hazard ratio of 2.1 for patients with FMR (p = 0.003). LAVI greater than 48.7 mL/m² predicts adverse outcome in both nonischemic and ischemic FMR (AUC 0.62, p < 0.001). Combined ischemic FMR with LAVI ≥ 48.7 mL/m² had the highest incident rate of all groups. In conclusion, despite similar LV function and MR severity, ischemic FMR patients had higher mortality than nonischemic patients. Of all echocardiographic parameters, an LAVI ≥ 48.7 mL/m² predicted adverse clinical outcome.

Guide to functional mitral regurgitation: a contemporary review

Functional mitral regurgitation (FMR) occurs in the absence of organic mitral valve (MV) disease and is a result of LV dysfunction due to ischemic vs. non ischemic etiologies. The prevalence of FMR is increasing, as 2.0-2.5 million people in the USA were diagnosed with FMR in 2000-and this number is expected to double to 4 million by 2030. FMR tends to develop in a significant number of patients after myocardial infarction (MI) and many develop heart failure (HF) subsequently with mortality rates ranging from 15-40% at 1 year. Therefore, there has been much interest and effort to develop optimized methods for quantifying and classifying the severity of FMR, as well as developing effective therapeutic interventions to improve outcomes in patients with significant FMR. Echocardiogram is typically the primary diagnostic method of assessment, however, there have been various technological advances including cardiac CT and cardiac MRI that can better guide quantification and management of this disease. Management of this disease is mostly aimed at optimizing left ventricular (LV) remodeling with surgical and transcatheter management gaining more popularity with recent times. The purpose of this paper is to provide a comprehensive review of the current evaluation methods and interventional strategies for FMR.

Optimal Quantification of Functional Mitral Regurgitation: Comparison of Volumetric and Proximal Isovelocity Surface Area Methods to Predict Outcome

Background

Effective orifice area (EOA) ≥0.2 cm² or regurgitant volume (Rvol) ≥30 mL predicts prognostic significance in functional mitral regurgitation (FMR). Both volumetric and proximal isovelocity surface area (PISA) methods enable calculation of these metrics. To determine their clinical value, we compared EOA and Rvol derived by volumetric and PISA quantitation upon outcome of patients with FMR.

Methods and Results

We examined the outcome of patients with left ventricular ejection fraction <35% and moderate to severe FMR. All had a complete echocardiogram including EOA and Rvol by both standard PISA and volumetric quantitation using total stroke volume calculated by left ventricular end‐diastolic volume×left ventricular ejection fraction and forward flow by Doppler method: EOA=Rvol/mitral regurgitation velocity time integral. Primary outcome was all‐cause mortality or heart transplantation. We examined 177 patients: mean left ventricular ejection fraction 25.2% and 34.5% with ischemic cardiomyopathy. Echo measurements were greater by PISA than volumetric quantitation: EOA (0.18 versus 0.11 cm²), Rvol (24.7 versus 16.9 mL), and regurgitant fraction (61 versus 37 %) respectively (all P value <0.001). During 3.6±2.3 years’ follow‐up, patients with EOA ≥0.2 cm² or Rvol ≥30 mL had a worse outcome than those with EOA <0.2 cm² or Rvol <30 mL only by volumetric (log rank P=0.003 and 0.004) but not PISA quantitation (log rank P=0.984 and 0.544), respectively.

Conclusions

Volumetric and PISA methods yield different measurements of EOA and Rvol in FMR; volumetric values exhibit greater prognostic significance. The echo method of quantifying FMR may affect the management of this disorder.

Mitral Valvular Coaptation-Zone Area Is Associated with the Severity of Atherosclerosis Assessed by Cardio-Ankle Vascular Index

Preservation of the mitral valve (MV) size is essential for valve function, and a reduced MV coaptation-zone area increases the risk of developing functional mitral regurgitation (FMR). We aimed to determine if the MV leaflet and coaptation-zone areas were associated with the severity of atherosclerosis assessed by cardio-ankle vascular index (CAVI) in patients with normal left ventricle (LV) systolic function and size by real-time 3D echocardiography (RT3DE).We performed RT3DE analysis in 66 patients with normal LV size and ejection fraction who underwent 2D echocardiography and CAVI. MV coaptation-zone areas were measured by custom 3D software and indexed by body surface area (BSA). The associations of clinical factors and mean CAVI with MV leaflet and coaptation-zone areas were evaluated by univariable and multivariable linear regression analyses.On univariable analysis, MV leaflet area/BSA was significantly associated with age (r = -0.335, P = 0.0069) and mean CAVI (r = -0.464, P < 0.001), and MV coaptation-zone area was significantly associated with age (r = -0.626, P < 0.001), hypertension (r = -0.626, P < 0.001), dyslipidemia (r = -0.626, P < 0.001), E/e' (r = -0.626, P < 0.001), and CAVI (r = -0.740, P < 0.001). On multivariable analysis, mean CAVI was independently associated only with MV leaflet area/BSA (standardized coefficient = -0.611, P < 0.001) and MV coaptation-zone area/BSA (standardized coefficient = -0.74, P < 0.001).In patients with normal LV systolic function and size, MV leaflet and coaptation-zone areas might be reduced according to advancing atherosclerosis. Patients with atherosclerosis might be at increased risk of developing FMR.

Impact of Leaflet Tethering on Residual Regurgitation in Patients With Degenerative Mitral Disease After Interventional Edge-to-Edge Repair

Background: Grade 2+ residual mitral regurgitation (MR 2+) is associated with the recurrence of MR and a lower survival rate in interventional mitral valve (MV) edge-to-edge (EE) repair. We sought to determine the MV anatomic factors affecting residual MR 2+ during interventional EE repair with the ValveClamp system in patients with degenerative MR (DMR).

Methods: In this multicenter study, 62 patients with significant (grade 3+ to 4+) DMR underwent ValveClamp implantation across eight centers from July 2018 to December 2019. Patient clinical, anatomical, and procedural characteristics were prospectively collected and retrospectively analyzed.

Results: A single clamp was implanted in 59 patients, and two clamps were implanted in three patients. Residual MR 2+ was found in 14 patients (22.6%) immediately after the ValveClamp procedure. Patients with residual MR 2+ showed significantly larger preoperative tenting sizes and annular dimensions than the residual MR ≤1+ group. Multivariate analysis identified tenting volume as the major determinant of residual MR 2+ after ValveClamp procedures (odds ratio, 1.410 per 0.1-mL/m² increase; 95% confidence interval, 1.167–1.705; P < 0.001). Receiver operating characteristic curves identified a tenting volume index ≥0.82 mL/m² as the optimal cutoff point to predict residual MR 2+ (area under curve, 0.84). Patients with a tenting volume index ≥0.82 mL/m² were more likely to develop recurrent 3+ MR or undergo MV surgery during short-term follow-up (P < 0.001).

Conclusions: Preoperative assessment of the tenting volume index will help to predict intraoperative residual MR 2+ in patients with DMR receiving EE-based interventional repair. Improvements in the interventional strategy are warranted for sustained MR reduction in patients with DMR with unfavorable anatomy.

Relationship Between Mitral Leaflet Size and Coaptation and Their Associated Factors in Patients with Normal Left Ventricular Size and Systolic Function

Enlargement of the mitral valve (MV) has gained attention as a compensatory mechanism for functional mitral regurgitation (FMR). We aimed to determine if MV leaflet area is associated with MV coaptation-zone area and identify the clinical factors associated with MV leaflet size and coaptation-zone area in patients with normal left ventricle (LV) systolic function and size using real-time 3D echocardiography (RT3DE).We performed RT3DE in 135 patients with normal LV size and ejection fraction. MV leaflet and coaptation-zone areas were measured using custom 3D software. The clinical factors associated with MV leaflet and coaptation-zone areas were evaluated using univariate and multivariate linear regression analyses.There was a significant relationship between MV leaflet and coaptation-zone areas (r = 0.499, P < 0.001). MV leaflet area was strongly associated with body surface area (BSA) (r = 0.905, P < 0.001) rather than LV size and age. MV leaflet area/BSA was independently associated with male gender (P = 0.002), lower diastolic blood pressure (P = 0.042), and LV end-diastolic volume (LVEDV) index (P = 0.048); MV coaptation-zone area/BSA was independently associated with lower LVEDV index (P = 0.01).In patients with normal LV systolic function and size, MV leaflet size has a significant impact on competent MV coaptation. MV leaflet area might be intrinsically determined by body size rather than age and LV size, and the MV leaflet area/BSA is relatively constant. On the other hand, some clinical factors might also influence MV leaflet and coaptation-zone area.

Longitudinal Evaluation of Mitral Valve Leaflet Remodeling After Acute Myocardial Infarction: Serial Quantitation of Valve Geometry Using Real-Time 3-Dimensional Echocardiography

BACKGROUND

Recent animal studies have suggested that mitral valve (MV) leaflet remodeling can occur even without significant tethering force and that the postinfarct biological reaction would contribute to the histopathologic changes of the leaflet. We serially evaluated the MV remodeling in patients with anterior and inferior acute myocardial infarction (MI), by using 2- and 3-dimensional transthoracic echocardiography. Additional histopathologic examinations were performed to assess the leaflet pathology.

METHODS

Sixty consecutive first-onset acute MI (anterior MI, n=30; inferior MI, n=30) patients who underwent successful primary percutaneous coronary intervention were examined (1) before primary percutaneous coronary intervention, (2) at 6-month follow-up, and (3) at follow-up 1 year or later after onset. MV complex geometry including MV leaflet area and thickness was analyzed using dedicated software. Additional histopathologic study compared 18 valves harvested during surgery for ischemic mitral regurgitation (MR).

RESULTS

MV area and thickness incrementally increased during the follow-up period. MV leaflet area significantly increased (anterior MI: 5.59 [5.28-5.98] to 6.54 [6.20-7.26] cm²/m², P<0.001; inferior MI: 5.60 [4.76-6.08] to 6.32 [5.90-6.90] cm²/m², P<0.001), and leaflet thickness also increased (anterior MI: 1.09 [0.92-1.24] to 1.45 [1.28-1.60] mm/m², P<0.001; inferior MI: 1.15 [1.03-1.25] to 1.44 [1.27-1.59] mm/m², P<0.001); data represent onset versus ≥1 year. Larger annuls, larger tenting, and a reduced leaflet area/annular ratio with smaller coaptation index were observed in patients with persistent ischemic MR compared with those without significant ischemic MR. Histopathologic examinations revealed that MV thickness was significantly greater in chronic ischemic MR compared with acute ischemic MR (1432.6±490.5 versus 628.7±278.7 μm; P=0.001), with increased smooth muscle cells and fibrotic materials.

CONCLUSIONS

MV leaflet remodeling progressed both in area and thickness after MI. This is the first clinical study to record the longitudinal course of MV leaflet remodeling by serial echocardiography.

Unique mechanism of mitral valve prolapse in atrial septal defect: Three-dimensional insights into mitral complex geometry using real-time transesophageal echocardiography

BACKGROUND

Mitral valve prolapse (MVP) is often identified in patients with atrial septal defect (ASD), which occasionally require surgical intervention at the time of ASD closure or even long after the surgery. Ventricular and valvular geometric characteristics in preoperative ASD patients were evaluated by three-dimensional (3D) transesophageal echocardiography.

METHODS AND RESULTS

Mitral valve (MV) complex geometry was quantitatively measured by 3D transesophageal echocardiography in 11 ASD patients (Qp/Qs > 1.5) and 11 controls. The ASD group had a significantly larger indexed prolapse volume and height, with a larger anterior mitral leaflet than controls (0.53 [0.33-0.75] vs 0.057 [0.027-0.11] mL/m² , P = .0001; 2.89 [2.13-3.50] vs 0.92 [0.48-1.32] mm/m² , P < .0001; 391.3 [346.4-445.1] vs 295.3 (281.9-330.0) mm² /m² , P = .011, respectively). The right ventricular (RV)-to-left ventricular (LV) end-systolic diameter ratio was larger in the ASD group than in the control group (1.34 [0.96-1.45] vs 0.85 [0.75-0.88], P = .004). The indexed inter-papillary muscle distance (IPMD) was significantly shorter in the ASD group than in the control group (7.77 [6.55-8.24] vs 9.71 [8.64-10.8] mm/m² , P = .011). IPMD was significantly correlated with the RV-LV end-systolic diameter ratio (r = -.70, P = .017).

CONCLUSIONS

Inward shift of the LV papillary muscle tips due to RV dilation may be a major mechanism of MV prolapse in ASD. At the same time, positive remodeling of the anterior leaflet was observed in the ASD group, which may compensate for the billowing leaflet geometry to maintain effective coaptation. Three-dimensional assessment of the MV apparatus geometry will help to further understand perioperative mitral regurgitation in patients with ASD.

Secondary mitral regurgitation: pathophysiology, proportionality and prognosis

Secondary mitral regurgitation (SMR) occurs as a result of multifactorial left atrioventricular dysfunction and maleficent remodelling. It is the most common and undertreated form of mitral regurgitation (MR) and is associated with a very poor prognosis. Whether SMR is a bystander reflecting the severity of the cardiomyopathy disease process has long been the subject of debate. Studies suggest that SMR is an independent driver of prognosis in patients with an intermediate heart failure (HF) phenotype and not those with advanced HF. There is also no universal agreement regarding the quantitative thresholds defining severe SMR and indeed there are challenges with echocardiographic quantification. Until recently, no surgical or transcatheter intervention for SMR had demonstrated prognostic benefit, in contrast with HF medical therapy and cardiac resynchronisation therapy. In 2018, the first two randomised controlled trials (RCTs) of edge-to-edge transcatheter mitral valve repair versus guideline-directed medical therapy in HF (Percutaneous Repair with the MitraClip Device for Severe (MITRA-FR), Transcather mitral valve repair in patients with heart failure (COAPT)) reported contrasting yet complimentary results. Unlike in MITRA-FR, COAPT demonstrated significant prognostic benefit, largely attributed to the selection of patients with disproportionately severe MR relative to their HF phenotype. Consequently, quantifying the degree of SMR in relation to left ventricular volume may be a useful discriminator in predicting the success of transcatheter intervention. The challenge going forward is the identification and validation of such parameters while in parallel maintaining a heart-team guided holistic approach.

Predictors and prognostic impact of secondary mitral regurgitation in myocardial infarction with preserved ejection fraction

BACKGROUND

Secondary or functional mitral regurgitation (FMR) has been reported associated with poor prognosis in patients with ischemic or non-ischemic cardiomyopathy. Prognostic impact of the FMR in myocardial infarction with preserved ejection fraction (MIpEF) is unknown. The aim of this study was to investigate predictors and prognostic impact of FMR in MIpEF.

METHODS

A total of 556 patients with MIpEF were selected from the Bell Land General Hospital MI (BELAMI) registry (n = 953). Patients were grouped according to the presence or absence of severe FMR. Clinical endpoint was all-cause death.

RESULTS

Severe FMR was present in 26 patients (4.7%) (FMR group) and absent in 530 patients (control). FMR group was older (77.5 ± 7.2 vs. 67.3 ± 11.3 years, P < 0.01) and had more female gender (54% vs. 28%, P < 0.01). By echocardiography, FMR group had larger left atrial diameter and left ventricular end-systolic volume. E and E/e' were significantly higher and deceleration time of E was significantly shorter in FMR group. By Kaplan-Meier analysis, survival was significantly lower in FMR group than in control (log-rank, P = 0.004).

CONCLUSION

Severe FMR is rare in MI patients with preserved EF but is associated with poor long-term prognosis.

Triangular resection versus neochordal replacement for posterior leaflet prolapse: a morphological assessment

OBJECTIVES

To evaluate the morphological reconstruction as assessed by 3D transoesophageal echocardiography after triangular resection and neochordal replacement in the treatment of posterior leaflet prolapse.

METHODS

We retrospectively selected 46 patients with isolated posterior leaflet prolapse who were undergoing mitral valve repair using triangular resection (n = 20) and neochordal replacement (n = 26) techniques. Sixty patients without valvular heart disease were also included as the control group. Thorough 3D transoesophageal echocardiography inspections were performed for the entire cohort, and morphological parameters of mitral valve complex were measured and compared. Mid-term repair durability was followed up by transthoracic echocardiography.

RESULTS

The baseline parameters, including annular size, leaflet tenting, leaflet area, coaptation line lengths and aortomitral angle, were significantly larger in prolapsed valves. After repair, tenting volume, exposed posterior leaflet area and coaptation line lengths were restored to the normal range. Baseline clinical characteristics and 3D transoesophageal echocardiography parameters were comparable in patients treated with 2 techniques, and all parameters remained comparable between the resection and the non-resection groups after repair, except for exposed posterior leaflet area and posterior leaflet ratio. At 62.2 ± 18.5 months after surgery, degrees of residual regurgitation were similar between 2 techniques.

CONCLUSIONS

Triangular resection and neochordal replacement can achieve comparable restoration to structural normality and functional competency of mitral valves with posterior leaflet prolapse. Resection of prolapsed segment does not significantly affect coaptation geometry but instead may aid in achieving normal posterior leaflet ratio.

Systolic characteristics and dynamic changes of the mitral valve in different grades of ischemic mitral regurgitation - insights from 3D transesophageal echocardiography

BACKGROUND

Mitral regurgitation in ischemic heart disease (IMR) is a strong predictor of outcome but until now, pathophysiology is not sufficiently understood and treatment is not satisfying. We aimed to systematically evaluate structural and functional mitral valve leaflet and annular characteristics in patients with IMR to determine the differences in geometric and dynamic changes of the MV between significant and mild IMR.

METHODS

Thirty-seven patients with IMR (18 mild (m)MR, 19 significant (moderate+severe) (s)MR) and 33 controls underwent TEE. 3D volumes were analyzed using 3D feature-tracking software.

RESULTS

All IMR patients showed a loss of mitral annular motility and non-planarity, whereas mitral annulus dilation and leaflet enlargement occurred in sMR only. Active-posterior-leaflet-area decreased in early systole in all three groups accompanied by an increase in active-anterior-leaflet-area in early systole in controls and mMR but only in late systole in sMR.

CONCLUSIONS

In addition to a significant enlargement and loss in motility of the MV annulus, patients with significant IMR showed a spatio-temporal alteration of the mitral valve coaptation line due to a delayed increase in active-anterior-leaflet-area. This abnormality is likely to contribute to IMR severity and is worth the evaluation of becoming a parameter for clinical decision-making. Further, addressing the leaflets aiming to increase the active leaflet-area is a promising therapeutic approach for significant IMR. Additional studies with a larger sample size and post-operative assessment are warranted to further validate our findings and help understand the dynamics of the mitral valve.

Assessment of the mitral valve coaptation zone with 2D and 3D transesophageal echocardiography before and after mitral valve repair

Background

Mitral valve (MV) coaptation is very important in MV repair patients. But accurate quantitation of the degree of MV coaptation remains challenging. This study aimed to evaluate the utility of two-dimensional (2D) and three-dimensional (3D) transesophageal echocardiography (TEE) to assess MV coaptation before and after MV repair.

Methods

Forty-eight patients [(age: 52.23±13.31 years; 26 men (54.17%)] undergoing MV repair for mitral regurgitation (MR) were studied. We assessed the utility of 2D and 3D TEE to assess MV coaptation before and after MV repair. Complete conventional 2D and 3D TEE studies were performed, and the degree of the MV coaptation defect before and after surgery was assessed by measuring the MV coaptation length (CL) and length index (CLI) with 2D TEE, and the coaptation area (CA) and coaptation area index (CAI) with 3D TEE.

Results

CL and CLI were measured successfully in 46 (95.83%) patients and CA and CAI in 39 (81.25%). Compared with preoperatively, postoperative CL, CLI, CA, and CAI were significantly increased (CL: 4.99±0.79 to 9.66±1.09 mm, P<0.05; CLI: 9.30%±2.66% to 38.24%±3.82%, P<0.05; CA: 158.49±64.17 to 371.33±143.57 mm², P<0.05; CAI: 9.71%±2.76% to 36.24%±7.26%, P<0.05). Spearman's rank correlation analysis revealed that the CLI and CAI had a significant negative correlation with the degree of MR (r=-0.97, P<0.01; r=-0.92, P<0.01, respectively). Furthermore, Pearson's correlation analysis revealed that the CLI was significantly correlated with the CAI both preoperatively (r=-0.66, P<0.01) and postoperatively (r=-0.67, P<0.01).

Conclusions

The coaptation variables increased significantly in patients undergoing MV repair. The CLI and CAI significantly correlated with MR severity. The CL and CLI determined with 2D TEE are more feasible than the CA and CAI determined with 3D TEE. Both 2D and 3D variables may complement each other for aiding MV repair. 2D CLI is an alternative to 3D CAI due to its simplicity.

Percutaneous Mitral Valve Interventions and Heart Failure

Mitral regurgitation (MR) is the most frequent Valvular Heart Disease (VHD) and is an important cause of heart failure. MR can be caused by primary valve abnormality (Degenerative MR/Primary MR) or it can be secondary to cardiomyopathy (Functional MR/Secondary MR). Medical management alleviates symptoms but does not alter the progression of the disease. Current guidelines recommend surgery for moderate-to-severe (Grade > 3) MR in patients with symptoms or evidence of left ventricular dysfunction. Despite current practice guidelines, the majority of patients with severe MR do not undergo surgery. The reasons include high surgical risk from advanced age or multiple comorbidities, and a lack of clear data supporting valve surgery for secondary MR with LV dysfunction. The recent emergence of percutaneous interventional approaches in treating MR has expanded therapeutic options for patients who are at high risk for conventional Mitral Valve (MV) surgery. In this chapter, we will review the novel advancements in the field of percutaneous MV interventions that could potentially become the standard of care for patients with MR and heart failure.

Assessment of deformation of the mitral valve complex during off-pump coronary artery bypass surgery using three-dimensional echocardiography in a porcine model

BACKGROUND

This study aimed to assess the deformation of the mitral valve complex during the displacement of the beating heart by using three-dimensional echocardiography in a porcine off-pump coronary artery bypass grafting (OPCAB) model.

METHODS

In nine healthy swine, we positioned the beating heart as an OPCAB model, i.e. control, left anterior descending artery (LAD), right coronary artery (RCA), and left circumflex artery (LCX) positions. In each position, three-dimensional echocardiography was performed to assess the mitral valve complex with hemodynamic parameters. We analyzed the deformation of the mitral valve and the three-dimensional coordinates of the papillary muscles.

RESULTS

There was a significant increase in maximum tenting length and tenting volume (control 0.70±0.30, LAD 0.65±0.27, RCA 0.79±0.23, LCX 0.95±0.34cm³, p<0.05) in the LCX position compared with the other positions. The posterior papillary muscle (PPM) angle had a significant relationship with the tenting volume (r=-0.643, p<0.001). The PPM was displaced to the medial side in the LAD and LCX positions (p<0.01).

CONCLUSIONS

The prime cause of the deformation of the mitral leaflets is suggested to be the displacement of the PPM associated with the change in geometry of the left ventricle in a porcine model.

Multimodality imaging assessment of mitral valve anatomy in planning for mitral valve repair in secondary mitral regurgitation

Secondary mitral regurgitation (MR) is frequent valvular heart disease and conveys worse prognostic. Therapeutic surgical or percutaneous options are available in the context of severe symptomatic secondary MR, but the best approach to treat these patients remains unclear, given the lack of clear clinical evidence of benefit. A comprehensive evaluation of the mitral valve apparatus and the left ventricle (LV) has the ability to clearly define and characterize the disease, and thus determine the best option for the patient to improve its clinical outcomes, as well as quality of life and symptoms. The current report reviews the mitral valve (MV) anatomy, the underlying mechanisms associated with secondary MR, the related therapeutic options available, and finally the usefulness of a multimodality imaging approach for the planning of surgical or percutaneous mitral valve intervention.

Exercise Dynamics in Secondary Mitral Regurgitation: Pathophysiology and Therapeutic Implications

Secondary mitral valve regurgitation (MR) remains a challenging problem in the diagnostic workup and treatment of patients with heart failure. Although secondary MR is characteristically dynamic in nature and sensitive to changes in ventricular geometry and loading, current therapy is mainly focused on resting conditions. An exercise-induced increase in secondary MR, however, is associated with impaired exercise capacity and increased mortality. In an era where a multitude of percutaneous solutions are emerging for the treatment of patients with heart failure, it becomes important to address the dynamic component of secondary MR during exercise as well. A critical reappraisal of the underlying disease mechanisms, in particular the dynamic component during exercise, is of timely importance. This review summarizes the pathophysiological mechanisms involved in the dynamic deterioration of secondary MR during exercise, its functional and prognostic impact, and the way current treatment options affect the dynamic lesion and exercise hemodynamics in general.

Advanced imaging in valvular heart disease

Although echocardiography remains the mainstay imaging technique for the evaluation of patients with valvular heart disease (VHD), innovations in noninvasive imaging in the past few years have provided new insights into the pathophysiology and quantification of VHD, early detection of left ventricular (LV) dysfunction, and advanced prognostic assessment. The severity grading of valve dysfunction has been refined with the use of Doppler echocardiography, cardiac magnetic resonance (CMR), and CT imaging. LV ejection fraction remains an important criterion when deciding whether patients should be referred for surgery. However, echocardiographic strain imaging can now detect impaired LV systolic function before LV ejection fraction reduces, thus provoking the debate on whether patients with severe VHD should be referred for surgery at an earlier stage (before symptom onset). Impaired LV strain correlates with the amount of myocardial fibrosis detected with CMR techniques. Furthermore, accumulating data show that the extent of fibrosis associated with severe VHD has important prognostic implications. The present Review focuses on using these novel imaging modalities to assess pathophysiology, early LV dysfunction, and prognosis of major VHDs, including aortic stenosis, mitral regurgitation, and aortic regurgitation.

Myocardial Infarction Alters Adaptation of the Tethered Mitral Valve

BACKGROUND

In patients with myocardial infarction (MI), leaflet tethering by displaced papillary muscles induces mitral regurgitation (MR), which doubles mortality. Mitral valves (MVs) are larger in such patients but fibrosis sets in counterproductively. The investigators previously reported that experimental tethering alone increases mitral valve area in association with endothelial-to-mesenchymal transition.

OBJECTIVES

The aim of this study was to explore the clinically relevant situation of tethering and MI, testing the hypothesis that ischemic milieu modifies mitral valve adaptation.

METHODS

Twenty-three adult sheep were examined. Under cardiopulmonary bypass, the papillary muscle tips in 6 sheep were retracted apically to replicate tethering, short of producing MR (tethered alone). Papillary muscle retraction was combined with apical MI created by coronary ligation in another 6 sheep (tethered plus MI), and left ventricular remodeling was limited by external constraint in 5 additional sheep (left ventricular constraint). Six sham-operated sheep were control subjects. Diastolic mitral valve surface area was quantified by 3-dimensional echocardiography at baseline and after 58 ± 5 days, followed by histopathology and flow cytometry of excised leaflets.

RESULTS

Tethered plus MI leaflets were markedly thicker than tethered-alone valves and sham control subjects. Leaflet area also increased significantly. Endothelial-to-mesenchymal transition, detected as α-smooth muscle actin-positive endothelial cells, significantly exceeded that in tethered-alone and control valves. Transforming growth factor-β, matrix metalloproteinase expression, and cellular proliferation were markedly increased. Uniquely, tethering plus MI showed endothelial activation with vascular adhesion molecule expression, neovascularization, and cells positive for CD45, considered a hematopoietic cell marker. Tethered plus MI findings were comparable with external ventricular constraint.

CONCLUSIONS

MI altered leaflet adaptation, including a profibrotic increase in valvular cell activation, CD45-positive cells, and matrix turnover. Understanding cellular and molecular mechanisms underlying leaflet adaptation and fibrosis could yield new therapeutic opportunities for reducing ischemic MR.

In vitro assessment of mitral valve function in cyclically pressurized porcine hearts

Recent approaches to the in vitro experimental study of cardiac fluid mechanics involve the use of whole biological structures to investigate in the lab novel therapeutic approaches for the treatment of heart pathologies. To enhance reliability and repeatability, the influence of the actuation strategy of the experimental apparatuses on the biomechanics of biological structures needs to be assessed. Using echography and intracardiac high-speed imaging, we compared the mitral valve (MV) anatomo-functional features (coaptation areas/lengths, papillary muscles-valvular plane distances) in two passive-beating-heart mock loops with internal (IPML) or external (EPML) pressurization of the ventricular chamber. Both apparatuses showed fluid dynamic conditions that closely resembled the physiology. The MVs analyzed in the EPML presented coaptation areas and lengths that were systematically higher, and exhibited greater variability from early-to peak-systole, as compared to those in the IPML. Moreover, in the EPML, the MV leaflets exhibited a convexity with high curvature toward the atrium. With the IPML, MV coaptation lengths ranged similar to available clinical data and the papillary muscles-valve plane distances were more stable throughout systole. In conclusion, both the apparatuses allow for reproducing in vitro the left heart hemodynamics, in terms of flow rates and pressures, with proper mitral valve continence. Results suggest that the IPML is more suitable for replicating the physiological MV functioning, while the EPML may have more potential as a model for the study of MV pathologies.

Renin-angiotensin system inhibitors in patients with myocardial infarction and secondary mitral regurgitation

OBJECTIVES

Secondary mitral regurgitation (MR) is negatively related to the prognosis of patients with myocardial infarction (MI). Renin-angiotensin system inhibitors (RASI) may favourably affect left ventricular remodelling and reduce afterload and thereby improve prognosis of secondary MR. The aim of this study was to investigate if use of RASI improves prognosis of patients with MI with secondary MR.

METHODS

A total of 953 patients with MI were enrolled in this study. Long-term prognosis was compared between patients with MI with no/mild MR (n=657), moderate MR (n=196) and severe MR (n=100). Patients with MI with significant (≥moderate) secondary MR were further divided into those treated with and without RASI. Survival and cardiac-event (all-cause death and congestive heart failure)-free survival were compared.

RESULTS

Long-term survival was significantly associated with severity of MR (log-rank, p<0.0001). In patients with significant MR (n=296), RASI was used in 130 patients (44%) and not used in 166 patients (56%). Ejection fraction (47.3±12.2 vs 46.6±13.4%, p=NS) and E/e' (18.4±8.1 vs 16.5±7.0, p=NS) were similar between the two groups. Kaplan-Meier curves for cardiac-event-free survival demonstrated that use of RASI was associated with better survival (p=0.006) as well as event-free survival (p=0.02). By univariable and multivariable Cox proportional hazard analysis, age (HR 1.046, 95% CI 1.002 to 1.091, p=0.039) and RASI (HR 0.480, 95% CI 0.231 to 0.995), p=0.048) were independent predictors of cardiac events.

CONCLUSIONS

Secondary MR affects prognosis in patients with MI. Use of RASI may be associated with better long-term prognosis in patients with MI with significant MR.

Elongation of chordae tendineae as an adaptive process to reduce mitral regurgitation in functional mitral regurgitation

AIMS

In functional mitral regurgitation (FMR), increased leaflet area has been described as a remodelling compensatory mechanism. We hypothesized that chordae tendineae elongation would also occur as part of this remodelling. In this study, the lengths of primary chords and measurements of mitral leaflets and annulus were compared with varying degrees of mitral regurgitation (MR).

METHODS AND RESULTS

We studied 58 patients who underwent three-dimensional (3D) transoesophageal echocardiography, including 38 with FMR and 20 with normal mitral valves (NL). The FMR group was divided into two subgroups according to two-dimensional vena contracta width (VCW). Three-dimensional datasets from transgastric or mid-oesophageal approach were used to measure primary chordal length, coaptation length, inter-papillary muscle distances, and quantitative 3D measurements of the annulus and leaflets. Leaflet surface area was increased and coaptation length was decreased in FMR compared with NL. While no difference in other 3D measurement of annulus/leaflets was noted between the FMR subgroups, averaged chordal length was shorter in patients with more severe FMR. Chords of the anterior leaflet in FMR with larger VCW were shorter compared with both NL and FMR with smaller VCW. In contrast, the chords of the posterior leaflet were longer in FMR with smaller VCW compared with the other two groups.

CONCLUSION

Our results suggest the posterior leaflet chords possibly remodel by elongating and contribute to reduced MR and that in a subgroup of FMR patients, the primary chords may remodel by shortening, resulting in augmented MR. This information could be useful in choosing strategy for FMR correction.

Echocardiographic assessment of takotsubo cardiomyopathy: beyond apical ballooning

It has been >25 years since the first report of the takotsubo cardiomyopathy (TC). Although left ventriculography was originally used to depict its typical and impressive wall motion abnormality mimicking "takotsubo", or octopus pot, echocardiography plays a pivotal role in detecting not only its left ventricular (LV) wall motion abnormality, apical ballooning, but also various other findings. First of all, apical ballooning is not an essential finding for TC anymore. Mid-ventricular LV asynergy with or without apical involvement is a basic pattern of the LV wall motion abnormality. Distribution and time course of the asynergy may be best detected by echocardiography and echo provides useful information to differentiate between TC and acute coronary syndrome or acute myocarditis. In addition to the wall motion assessment, echo detects complications of TC such as systolic anterior motion of the mitral leaflet with or without LV outflow obstruction, mitral regurgitation, LV thrombus, right ventricular (RV) involvement. In particular, RV involvement is not an uncommon finding and is associated with worse short-term as well as long-term prognosis. Finally, coronary flow measurements and speckle tracking by echo may offer additional and useful information about pathophysiology and prognosis of TC. In conclusion, echocardiography is a standard imaging modality for detecting various dynamic findings beyond apical ballooning in patients with TC.

Pregnancy-induced remodeling of heart valves

Recent studies have demonstrated remodeling of aortic and mitral valves leaflets under the volume loading and cardiac expansion of pregnancy. Those valves' leaflets enlarge with altered collagen fiber architecture, content, and cross-linking and biphasic changes (decreases, then increases) in extensibility during gestation. This study extends our analyses to right-sided valves, with additional compositional measurements for all valves. Valve leaflets were harvested from nonpregnant heifers and pregnant cows. Leaflet structure was characterized by leaflet dimensions, and ECM composition was determined using standard biochemical assays. Histological studies assessed changes in cellular and ECM components. Leaflet mechanical properties were assessed using equibiaxial mechanical testing. Collagen thermal stability and cross-linking were assessed using denaturation and hydrothermal isometric tension tests. Pulmonary and tricuspid leaflet areas increased during pregnancy by 35 and 55%, respectively. Leaflet thickness increased by 20% only in the pulmonary valve and largely in the fibrosa (30% thickening). Collagen crimp length was reduced in both the tricuspid (61%) and pulmonary (42%) valves, with loss of crimped area in the pulmonary valve. Thermomechanics showed decreased collagen thermal stability with surprisingly maintained cross-link maturity. The pulmonary leaflet exhibited the biphasic change in extensibility seen in left side valves, whereas the tricuspid leaflet mechanics remained largely unchanged throughout pregnancy. The tricuspid valve exhibits a remodeling response during pregnancy that is significantly diminished from the other three valves. All valves of the heart remodel in pregnancy in a manner distinct from cardiac pathology, with much similarity valve to valve, but with interesting valve-specific responses in the aortic and tricuspid valves.

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.

In vitro measurement of the coaptation force distribution in normal and functional regurgitant porcine mitral valves

Closure of the left atrioventricular orifice is achieved when the anterior and posterior leaflets of the mitral valve press together to form a coaptation zone along the free edge of the leaflets. This coaptation zone is critical to valve competency and is maintained by the support of the mitral annulus, chordae tendinae, and papillary muscles. Myocardial ischemia can lead to an altered performance of this mitral complex generating suboptimal mitral leaflet coaptation and a resultant regurgitant orifice. This paper reports on a two-part experiment undertaken to measure the dependence of coaptation force distribution on papillary muscle position in normal and functional regurgitant porcine mitral heart valves. Using a novel load sensor, the local coaptation force was measured in vitro at three locations (A1-P1, A2-P2, and A3-P3) along the coaptation zone. In part 1, the coaptation force was measured under static conditions in ten whole hearts. In part 2, the coaptation force was measured in four explanted mitral valves operating in a flow loop under physiological flow conditions. Here, two series of tests were undertaken corresponding to the normal and functional regurgitant state as determined by the position of the papillary muscles relative to the mitral valve annulus. The functional regurgitant state corresponded to grade 1. The static tests in part 1 revealed that the local force was directly proportional to the transmitral pressure and was nonuniformly distributed across the coaptation zone, been strongest at A1-P1. In part 2, tests of the valve in a normal state showed that the local force was again directly proportional to the transmitral pressure and was again nonuniform across the coaptation zone, been strongest at A1-P1 and weakest at A2-P2. Further tests performed on the same valves in a functional regurgitant state showed that the local force measured in the coaptation zone was directly proportional to the transmitral pressure. However, the force was now observed to be weakest at A1-P1 and strongest at A2-P2. Movement of the anterolateral papillary muscle (APM) away from both the annular and anterior-posterior (AP) planes was seen to contribute significantly to the altered force distribution in the coaptation zone. It was concluded that papillary muscle displacement typical of myocardial ischemia changes the coaptation force locally within the coaptation zone.

Basal chordae sites on the mitral valve determine the severity of secondary mitral regurgitation

OBJECTIVES

To evaluate the variation between individuals in terms of basal chordae (BC) attachment sites on the mitral valve (MV) and the influence of this variation on secondary mitral regurgitation (MR) severity.

BACKGROUND

BC-mediated MV tenting is the main cause of secondary MR.

METHODS

In this prospective cross-sectional study, 38 consecutive patients with dilated or ischaemic cardiomyopathy who were due for cardiac transplantation underwent preoperative 3D full volume/colour Doppler echocardiography in sinus rhythm, and MV apparatus geometry, LV volume and MR severity were assessed. The lengths and insertion sites of four BC in the explanted hearts were measured post-transplantation before fixation.

RESULTS

Multiple linear regression analyses revealed that the anterior leaflet systolic tenting angle and bending angle associated with the distance between the medial and lateral BC insertion sites. By contrast, the posterior leaflet tenting angle associated largely with LV volume indices. The mean longitudinal distance of the four BC from the MV edge was the main determinant of the distal length of the anterior MV from the angulation point. Square root of effective regurgitant orifice area (√EROA) only associated significantly with the mean longitudinal distance of the outer two BC from the MV edge (r=0.509, p=0.001) among pathological parameters, and the central MV tenting area (r=0.524, p=0.001) among echocardiographical parameters. √EROA did not correlate with LV volume indices, LVEF or BC lengths.

CONCLUSIONS

BC insertion sites were associated with systolic anterior MV configuration and secondary MR severity in dilated LV and severe systolic dysfunction.

Incremental value of 3-D transesophageal echocardiographic imaging of the mitral valve

Transesophageal echocardiography provides excellent visualization of the posteriorly located mitral valve. Over the last decade, 3-dimensional transesophageal echocardiography (3D TEE) has emerged as an exciting imaging modality, particularly of the mitral valve. The current generation matrix array technology allows the operator to perform 2D and 3D imaging with a single transducer. 3D TEE affords the unique ability to view the mitral valve and its surrounding structures "en face" in real time (RT), and provide contextual anatomical guidance during surgical and transcatheter interventions. Additionally, offline quantification has made significant contributions to our mechanistic understanding of the normal and diseased mitral valve, and alterations induced by therapeutic intervention such as surgical repair. This review will address recent advances in the incremental role of 3D TEE in mitral valve imaging.