Quantitative Assessment of Mitral Regurgitation

Fluid-Structure Interaction Analysis of Ruptured Mitral Chordae Tendineae

The chordal structure is a part of mitral valve geometry that has been commonly neglected or simplified in computational modeling due to its complexity. However, these simplifications cannot be used when investigating the roles of individual chordae tendineae in mitral valve closure. For the first time, advancements in imaging, computational techniques, and hardware technology make it possible to create models of the mitral valve without simplifications to its complex geometry, and to quickly run validated computer simulations that more realistically capture its function. Such simulations can then be used for a detailed analysis of chordae-related diseases. In this work, a comprehensive model of a subject-specific mitral valve with detailed chordal structure is used to analyze the distinct role played by individual chordae in closure of the mitral valve leaflets. Mitral closure was simulated for 51 possible chordal rupture points. Resultant regurgitant orifice area and strain change in the chordae at the papillary muscle tips were then calculated to examine the role of each ruptured chorda in the mitral valve closure. For certain subclassifications of chordae, regurgitant orifice area was found to trend positively with ruptured chordal diameter, and strain changes correlated negatively with regurgitant orifice area. Further advancements in clinical imaging modalities, coupled with the next generation of computational techniques will enable more physiologically realistic simulations.

Controversies in quantification of mitral valve regurgitation: role of cardiac magnetic resonance imaging

PURPOSE OF REVIEW

Mitral regurgitation remains a common problem, and when severe, is associated with significant morbidity and mortality. At present, echocardiography remains the primary modality for assessing both mechanism and severity of mitral regurgitation. However, recent studies demonstrate that the echocardiographic assessment of mitral regurgitation severity may be subject to variability as a result of semiquantitative parameters, dependence upon loading conditions and significant interobserver variability.

RECENT FINDINGS

Cardiac magnetic resonance (CMR) imaging is the gold standard in the assessment of cardiac function and structure, and offers an alternative method to estimate mitral regurgitation severity. Herein, we discuss the pitfalls of echocardiography in the assessment of mitral regurgitation and describe recent data demonstrating improved accuracy of CMR in the assessment of mitral regurgitation severity. Further, CMR derived regurgitant volume of ≤55 ml is associated with freedom from surgical intervention, in contrast to traditional volumetric measures, which fail to predict the need for surgical intervention.

SUMMARY

The CMR assessment of mitral regurgitation severity is easily performed and appears to be more accurate and predictive of the need for surgery than traditional echocardiography. These promising findings require further confirmation in larger outcome trials.

Misconceptions and Facts About Mitral Regurgitation

Mitral regurgitation is a common heart valve disease. It is defined to be primary when it results from the pathology of the mitral valve apparatus itself and secondary when it is caused by distortion of the architecture or function of the left ventricle. Although the diagnosis and management of mitral regurgitation rely heavily on echocardiography, one should bear in mind the caveats and shortcomings of such an approach. Clinical decision making commonly focuses on the indications for surgery, but it is complex and mandates precise assessment of the mitral pathology, symptom status of the patient, and ventricular performance (right and left) among other descriptors. It is important for healthcare providers at all levels to be familiar with the clinical picture, diagnosis, disease course, and management of mitral regurgitation.

Spectrum of cardiac lesions associated with Isolated Cleft Mitral Valve and their impact on therapeutic choices

Background

Isolated cleft mitral valve (ICMV) may occur alone or in association with other congenital heart lesions. The aim of this study was to describe the profile of cardiac lesions associated with ICMV and their potential impact on therapeutic management.

Methods

We conducted a descriptive study with data retrieved from the Congenital Heart Disease (CHD) single-center registry of our institution, including patients with ICMV registered between December 2008 and November 2014.

Results

Among 2177 patients retrieved from the CHD registry, 22 (1%) had ICMV. Median age at diagnosis was 5 years (6 days to 36 years). Nine patients (40.9%) had Down syndrome. Seventeen patients (77.3%) had associated lesions, including 11 (64.7%) with accessory chordae in the left ventricular outflow tract (LVOT) with no obstruction, 15 (88.2%) had ventricular septal defect (VSD), three had secundum atrial septal defect, and four had patent ductus arteriosus. Thirteen patients (59.1%) required surgical repair. The decision to proceed with surgery was mainly based on the severity of the associated lesion in eight patients (61.5%) and on the severity of the mitral regurgitation in four patients (30.8%). In one patient, surgery was decided based on the severity of both the associated lesion and mitral regurgitation.

Conclusion

Our study shows that ICMV is rare and strongly associated with Down syndrome. The most common associated cardiac abnormalities were VSD and accessory chordae in the LVOT. We conclude that cardiac lesions associated with ICMV are of major interest, since in this study patients with cardiac lesions were diagnosed earlier. The decision to operate on these patients must take into account the severity of both mitral regurgitation and associated cardiac lesions.

Advanced functional echocardiographic imaging of the failing heart in children

Over the past decade, new echocardiographic techniques such as three-dimensional echocardiography and the imaging of myocardial deformation (strain) have been developed, and are increasingly used in clinical practice. In this article, we describe the rationale and methodology, review available guidelines for practice, and discuss the advantages and limitations of each of these modalities. When available, we have also summarised the scientific evidence for the clinical application of these techniques to detect heart failure in children.

Three-dimensional versus two-dimensional echocardiographic assessment of functional mitral regurgitation proximal isovelocity surface area

BACKGROUND

The geometric shape of the mitral regurgitation (MR) proximal isovelocity surface area (PISA) is conventionally assumed to be a hemisphere (HS). However, in functional MR, PISA is frequently neither an HS nor a hemiellipse (HE) but is often asymmetric and crescent shaped. We used 3-dimensional transesophageal echocardiographic (3D TEE), full-volume data sets to directly measure the PISA and subsequently compared calculated values of effective regurgitant orifice area (EROA) with conventional 2D TEE techniques. EROA calculations from all PISA measurements were finally compared with the cross-sectional area at the vena contracta, a well-validated reference measure of the functional MR orifice area.

METHODS

Twenty-four cardiac surgical patients with functional MR, who underwent routine intraoperative TEE examinations with a 3D matrix array probe (X7-2t; IE33; Philips Healthcare, Inc., Andover, MA) were retrospectively evaluated for MR severity using quantitative 2D and 3D TEE-derived techniques. Conventional 2D TEE methods were used to estimate PISA assuming an HS shape and an HE shape. In addition, direct measurement of the 3D PISA was obtained (QLab, Philips Healthcare, Inc.) from corresponding full-volume, color-flow Doppler data sets. EROAs calculated from HS- and HE-PISA techniques were compared with the same values obtained from 3D TEE PISAs. EROAs obtained from all 3 PISA techniques were subsequently compared with vena contracta area.

RESULTS

Three-dimensional PISA was significantly larger than both HS-PISA and HE-PISA (mean ± SD: 4.65 ± 2.03 cm² vs 2.10 ± 1.58 cm² and 2.75 ± 1.42 cm²; both P < 0.0001), respectively. HE-PISA was also larger than HS-PISA (P = 0.042). In addition, 3D EROA was larger than both HS- and HE-acquired EROAs (mean ± SD: 0.44 ± 0.21 vs 0.19 ± 0.12 cm² and 0.26 ± 0.14; both P < 0.0001), respectively, while HE-EROA was larger than HS-EROA (P = 0.024). Vena contracta area correlated well with 3D EROA (Spearman r = 0.865), HS-EROA (Spearman r = 0.820; P < 0.001) and HE-EROA (Spearman r = 0.819). However, the difference between vena contracta area and 3D EROA was significantly less than the differences between vena contracta area and either 2D HS- or 2D HE-EROA (P < 0.0001).

CONCLUSIONS

Quantitative assessment of functional MR severity by 3D TEE may be superior to 2D methods by permitting more direct measures of PISA. Two-dimensional TEE techniques for assessing functional MR severity that rely on an HS- or HE-PISA shape may underestimate the EROA due to geometric assumptions that do not account for asymmetry.

Spectral Doppler interrogation of mitral regurgitation -spot diagnosis

Mitral regurgitation (MR) is one of the most common valvular lesions that are readily identified by transthoracic echocardiography. Color Doppler imaging is the modality of choice for the recognition of MR, and it plays an important role in the assessment of regurgitation severity. Continuous wave (CW) Doppler is commonly used to interrogate the MR signal, and this modality can provide highly useful data regarding several physiological and pathological parameters. In this manuscript, we present a series of cases that illustrate the various hemodynamic parameters that can be derived from analysis of the CW Doppler signal of MR.

Computational modeling of pathophysiologic responses to exercise in Fontan patients

Reduced exercise capacity is nearly universal among Fontan patients. Although many factors have emerged as possible contributors, the degree to which each impacts the overall hemodynamics is largely unknown. Computational modeling provides a means to test hypotheses of causes of exercise intolerance via precisely controlled virtual experiments and measurements. We quantified the physiological impacts of commonly encountered, clinically relevant dysfunctions introduced to the exercising Fontan system via a previously developed lumped-parameter model of Fontan exercise. Elevated pulmonary arterial pressure was observed in all cases of dysfunction, correlated with lowered cardiac output (CO), and often mediated by elevated atrial pressure. Pulmonary vascular resistance was not the most significant factor affecting exercise performance as measured by CO. In the absence of other dysfunctions, atrioventricular valve insufficiency alone had significant physiological impact, especially under exercise demands. The impact of isolated dysfunctions can be linearly summed to approximate the combined impact of several dysfunctions occurring in the same system. A single dominant cause of exercise intolerance was not identified, though several hypothesized dysfunctions each led to variable decreases in performance. Computational predictions of performance improvement associated with various interventions should be weighed against procedural risks and potential complications, contributing to improvements in routine patient management protocol.

Quantitative assessment of primary mitral regurgitation using left ventricular volumes: a three-dimensional transthoracic echocardiographic pilot study

AIMS

To investigate the value of assessment of mitral regurgitant fraction (RF) using left ventricular (LV) volumes obtained by three-dimensional echocardiography (3DE) to quantify primary mitral regurgitation (MR).

METHODS AND RESULTS

Sixty patients with primary MR in sinus rhythm were prospectively enrolled. RF was calculated using either 2DE or 3DE LV volumes obtained as follows: (LV total stroke volume - LV forward stroke volume by Doppler)/LV total stroke volume. Severity of MR was graded independently by two cardiologists blinded to LV volumetric data using an integrative approach, as recommended by current guidelines. Sixty patients with LV ejection fraction >50% and no MR were also studied. In patients without MR, 3D total LV stroke volume was more strongly correlated with LV forward stroke volume than 2D total LV stroke volume (r = 0.75, P < 0.0001 vs. r = 0.62, P < 0.0001, respectively). The 3D method had a feasibility of 90% in patients with MR. Inter-reader concordance for MR grading (four grades) was excellent with a Kappa-value of 0.90, P < 0.0001. A significant correlation was observed between grade of MR severity and 3D RF (r = 0.83, P < 0.0001) and 2D RF (r = 0.74, P < 0.0001). Comparisons between individual grades for 3D RF were significant (P < 0.05) except for 3+ vs. 4+ MR (P = 0.213). All patients with 3D RF ≥40% had ≥3+ or 4+ MR and those with 3D RF ≤30% had 1+ or 2+ MR with a 'grey' overlap zone between 30 and 40%.

CONCLUSIONS

RF can be routinely determined using 3D LV volumes with a high feasibility in patients with primary MR and is reliable for identification of Grade 3+ or Grade 4+ MR. The incorporation of this parameter into the currently recommended multiparametric integrative approach might be helpful to discriminate significant MR.

Role of cardiac magnetic resonance in the evaluation of dilated cardiomyopathy: diagnostic contribution and prognostic significance

Dilated cardiomyopathy (DCM) represents the final common morphofunctional pathway of various pathological conditions in which a combination of myocyte injury and necrosis associated with tissue fibrosis results in impaired mechanical function. Recognition of the underlying aetiology of disease and accurate disease monitoring may be crucial to individually optimize therapeutic strategies and stratify patient's prognosis. In this regard, CMR has emerged as a new reference gold standard providing important information for differential diagnosis and new insight about individual risk stratification. The present review article will focus on the role of CMR in the evaluation of present condition, analysing respective strengths and limitations in the light of current literature and technological developments.

Three-Dimensional Echocardiography: Advancements in Qualitative and Quantitative Analyses of Mitral Valve Morphology in Mitral Valve Prolapse

Degenerative mitral valve disease (MVD) is the leading cause of organic mitral regurgitation (MR), one of the most common valvular heart disease in western countries. Substantial progresses in the surgical treatment of degenerative MVD have improved life expectancy of patients with significant MR. However, prognosis, surgical decision and timing of surgery strongly depend on the accurate characterization of mitral valve (MV) anatomy and pathology and on the precise quantification of MR. Three-dimensional (3D) echocardiography, a major technological breakthrough in the field of cardiovascular imaging, provides several advantages over two-dimensional (2D) imaging in the qualitative and quantitative evaluations of MV apparatus. In this review, we focus on the contribution of this new modality to the diagnosis of degenerative MVD, the quantitative assessment of MR severity, the selection and monitoring of surgical and percutaneous procedures, the evaluation of procedural outcomes. The results of a systematic and exhaustive search of the existing literature, restricted to real-time 3D echocardiography in adults, are here reported.

Three-dimensional echocardiography of the mitral valve: lessons learned

Three-dimensional echocardiography has markedly improved our understanding of normal and pathologic mitral valve (MV) mechanics. Qualitative and quantitative analysis of three-dimensional (3D) data on the mitral valve could have a clinical impact on diagnosis, patient referral, surgical strategies, annuloplasty ring design and evaluation of the immediate and long-term surgical outcome. This review covers the contribution of 3D echocardiography in the diagnosis of MV disease, its role in selecting and monitoring surgical procedures, and in the assessment of surgical outcomes. Moreover, advantages of this technique versus the standard 2D modality, as well as future applications of advanced analysis techniques, will be reviewed.