Comparison of three-dimensional proximal isovelocity surface area to cardiac magnetic resonance imaging for quantifying mitral regurgitation

Echocardiography vs. CMR in the Quantification of Chronic Mitral Regurgitation: A Happy Marriage or Stormy Divorce?

Quantification of chronic mitral regurgitation (MR) is essential to guide patients’ clinical management and define the need and appropriate timing for mitral valve surgery. Echocardiography represents the first-line imaging modality to assess MR and requires an integrative approach based on qualitative, semiquantitative, and quantitative parameters. Of note, quantitative parameters, such as the echocardiographic effective regurgitant orifice area, regurgitant volume (RegV), and regurgitant fraction (RegF), are considered the most reliable indicators of MR severity. In contrast, cardiac magnetic resonance (CMR) has demonstrated high accuracy and good reproducibility in quantifying MR, especially in cases with secondary MR; nonholosystolic, eccentric, and multiple jets; or noncircular regurgitant orifices, where quantification with echocardiography is an issue. No gold standard for MR quantification by noninvasive cardiac imaging has been defined so far. Only a moderate agreement has been shown between echocardiography, either with transthoracic or transesophageal approaches, and CMR in MR quantification, as supported by numerous comparative studies. A higher agreement is evidenced when echocardiographic 3D techniques are used. CMR is superior to echocardiography in the calculation of the RegV, RegF, and ventricular volumes and can provide myocardial tissue characterization. However, echocardiography remains fundamental in the pre-operative anatomical evaluation of the mitral valve and of the subvalvular apparatus. The aim of this review is to explore the accuracy of MR quantification provided by echocardiography and CMR in a head-to-head comparison between the two techniques, with insight into the technical aspects of each imaging modality.

Spatiotemporal Complexity of Vena Contracta and Mitral Regurgitation Grading Using Three-Dimensional Echocardiographic Analysis

BACKGROUND

Spatiotemporal complexity of the color Doppler vena contracta challenging the assumption of a circular and constant orifice may lead to mitral regurgitation (MR) grading inconsistencies. Using 3D transesophageal echocardiography, we characterized spatiotemporal vena contracta complexity and its impact on MR severity grading.

METHODS

In 192 patients with suspected moderate or severe MR (100 primary MR [PMR]; 92 secondary MR [SMR]), we performed three-dimensional vena contracta area (VCA) quantification using single-frame (midsystolic or VCAmid, maximum or VCAmax) and multiframe (VCAmean) methods, as well as measures of orifice shape (shape index) and systolic variation of VCA. Vena contracta complexity and intermethod discrepancies were analyzed and correlated with functional class and pulmonary vein flow (PVF) patterns and with cardiac magnetic resonance (CMR) in a subset of cases (n = 20).

RESULTS

The vena contracta was noncircular (shape index > 1.5) in 90% of patients. Severe noncircularity (shape index > 3) was more prevalent in SMR than in PMR (32.4% vs 14.6%). Variations of the VCA were more prominent in SMR than in PMR. VCAmid showed a low grading agreement with VCAmax (62%) and high grading agreement with VCAmean (83.3%). Pulmonary vein flow systolic reversal was associated with MR severity by VCA in SMR but not in PMR. VCAmid and VCAmean showed a stronger association with systolic flow reversal than VCAmax (area under the curve, 0.88, 0.86, and 0.79, respectively). In the subset of patients with CMR quantification, severe MR by VCAmax was graded as nonsevere by CMR more frequently compared with VCAmid and VCAmean.

CONCLUSIONS

Highly prevalent spatiotemporal vena contracta complexity features in MR challenge the assumption of a circular and constant orifice. VCAmid seems the best single-frame approximation to multiframe quantification, and VCAmax may lead to severity overestimation.

Quantification of mitral regurgitation after transcatheter edge-to-edge repair: Comparison of echocardiography and patient-specific in silico models

BACKGROUND

Doppler echocardiographic (echo) assessment of residual mitral regurgitation (MR) after transcatheter edge-to-edge repair (TEER) is challenging and often subjective. This study aimed to evaluate the accuracy and feasibility of standardized quantitative echo methods for assessment of MR severity after MitraClip repair by comparing measurements against a reference MR severity obtained from patient-specific in silico models.

METHODS

Post-procedure hemodynamics were simulated under five different MitraClip configurations in previously validated patient-specific in silico models for the treatment of functional MR. The residual regurgitant volume was calculated as in clinical practice using four quantitative virtual echo methods: pulsed Doppler, volumetric, proximal isovelocity surface area (PISA) and vena contracta area (VCA). Multiple permutations were performed for each method. Virtual echo MR results were evaluated against reference MR values directly extracted from the 5 patient-specific in silico models.

RESULTS

The echo methods with the greatest accuracy were the three-dimensional (3D) volumetric method (r = 0.957, bias -0.8 ± 1.2 ml, p = 0.01), the 3D VCA method wherein velocity time integrals were evaluated for each jet assessed (r = 0.919, bias -1.5 ± 1.7 ml, p = 0.03), and the 3D PISA method integrating surface areas throughout systole (r = 0.98, bias -2.0 ± 0.9 ml, p = 0.003). The pulsed Doppler and 2D volumetric methods had technical limitations that may result in a high underestimation or overestimation of the MR severity after TEER. In the case of multiple regurgitant jets, a more accurate MR assessment was obtained when all significant jets were evaluated.

CONCLUSIONS

Clinically, the 3D volumetric, 3D VCA and 3D PISA methods gave the most accurate MR quantification after TEER. Three-dimensional echo technologies harbor the potential of becoming the non-invasive imaging tool of choice for MR quantification after complex transcatheter mitral interventions.

Transcatheter Mitral Valve Repair or Replacement: Competitive or Complementary?

Over the last two decades, transcatheter devices have been developed to repair or replace diseased mitral valves (MV). Transcatheter mitral valve repair (TMVr) devices have been proven to be efficient and safe, but many anatomical structures are not compatible with these technologies. The most significant advantage of transcatheter mitral valve replacement (TMVR) over transcatheter repair is the greater and more reliable reduction in mitral regurgitation. However, there are also potential disadvantages. This review introduces the newest TMVr and TMVR devices and presents clinical trial data to identify current challenges and directions for future research.

Clinical intra-cardiac 4D flow CMR: acquisition, analysis, and clinical applications

Identification of flow patterns within the heart has long been recognized as a potential contribution to the understanding of physiological and pathophysiological processes of cardiovascular diseases. Although the pulsatile flow itself is multi-dimensional and multi-directional, current available non-invasive imaging modalities in clinical practice provide calculation of flow in only 1-direction and lack 3-dimensional volumetric velocity information. Four-dimensional flow cardiovascular magnetic resonance imaging (4D flow CMR) has emerged as a novel tool that enables comprehensive and critical assessment of flow through encoding velocity in all 3 directions in a volume of interest resolved over time. Following technical developments, 4D flow CMR is not only capable of visualization and quantification of conventional flow parameters such as mean/peak velocity and stroke volume but also provides new hemodynamic parameters such as kinetic energy. As a result, 4D flow CMR is being extensively exploited in clinical research aiming to improve understanding of the impact of cardiovascular disease on flow and vice versa. Of note, the analysis of 4D flow data is still complex and accurate analysis tools that deliver comparable quantification of 4D flow values are a necessity for a more widespread adoption in clinic. In this article, the acquisition and analysis processes are summarized and clinical applications of 4D flow CMR on the heart including conventional and novel hemodynamic parameters are discussed. Finally, clinical potential of other emerging intra-cardiac 4D flow imaging modalities is explored and a near-future perspective on 4D flow CMR is provided.

Imaging and Patient Selection for Transcatheter Tricuspid Valve Interventions

With the emergence of transcatheter solutions for the treatment of tricuspid regurgitation (TR) increased attention has been directed to the once neglected tricuspid valve (TV) complex. Recent studies have highlighted new aspects of valve anatomy and TR etiology. The assessment of valve morphology along with quantification of regurgitation severity and RV function pose several challenges to cardiac imagers guiding transcatheter valve procedures. This review article aims to give an overview over the role of modern imaging modalities during assessment and treatment of the TV.

Assessment of mitral valve regurgitation by cardiovascular magnetic resonance imaging

Mitral regurgitation (MR) is a common valvular heart disease and is the second most frequent indication for heart valve surgery in Western countries. Echocardiography is the recommended first-line test for the assessment of valvular heart disease, but cardiovascular magnetic resonance imaging (CMR) provides complementary information, especially for assessing MR severity and to plan the timing of intervention. As new CMR techniques for the assessment of MR have arisen, standardizing CMR protocols for research and clinical studies has become important in order to optimize diagnostic utility and support the wider use of CMR for the clinical assessment of MR. In this Consensus Statement, we provide a detailed description of the current evidence on the use of CMR for MR assessment, highlight its current clinical utility, and recommend a standardized CMR protocol and report for MR assessment.

In this Consensus Statement, Garg and colleagues describe the current evidence on the use of cardiovascular magnetic resonance imaging for the assessment of mitral regurgitation, highlight its current clinical utility, and recommend a standardized imaging protocol and report.

3-Dimensional Echocardiography: Latest Developments and Future Directions

The ongoing refinements in 3-dimensional (3D) echocardiography technology continue to expand the scope of this imaging modality in clinical cardiology by offering new features that stem from the ability to image the heart in its complete dimensionality. Over the years, countless publications have described these benefits and tested new frontiers where 3D echocardiographic imaging seemed to offer promising ways to improve patients' care. These include improved techniques for chamber quantification and novel ways to visualize cardiac valves, including 3D printing, virtual reality, and holography. The aims of this review article are to focus on the most important developments in the field in the recent years, discuss the current utility of 3D echocardiography, and highlight several interesting future directions.

Automated Spectral Doppler Profile Tracing

OBJECTIVE

The authors hypothesized that automated tracings of both pulsed wave (PW) and continuous wave (CW) Doppler correlate well with manual measurements performed by an experienced echocardiographer.

DESIGN

The authors performed a retrospective analysis of spectral Doppler profile measurements performed by automated software and an echocardiographer.

SETTING

University hospital, single institution.

PARTICIPANTS

The authors reviewed transesophageal echocardiographic examinations from patients undergoing transcatheter aortic valve (AV) replacement procedures at their institution.

INTERVENTIONS

No interventions were performed solely for research purposes.

MEASUREMENTS AND MAIN RESULTS

PW and CW spectral envelopes at the left ventricular outflow tract (LVOT) and AV were analyzed. Blinded, a board-certified echocardiographer performed manual measurements of the identical spectral envelopes. Peak velocities, mean gradients, and velocity time integrals (VTI) were collected. A total of 33 PW as well as 33 CW Doppler spectral envelopes were evaluated. There was no significant difference between the measurements provided by the automated software and manual tracings. LVOT PW VTI automated versus manual: 18.2 cm versus 15.9 cm, p = 0.11. AV CW VTI automated versus manual: 65.8 cm versus 64.8 cm, p = 0.90. AV CW mean gradient automated versus manual: 24.3 mmHg versus 23.4 mmHg, p = 0.84. AV CW peak velocity automated versus manual: 3.00 m/s versus 2.98 m/s, p = 0.93. Correlation coefficients were all above 0.9.

CONCLUSIONS

Automated measurements of peak velocities, mean gradients, and VTI of spectral Doppler correlate closely with manual measurements performed by an experienced echocardiographer.

Quantification of Multiple Mitral Regurgitant Jets: An In Vitro Validation Study Comparing Two- and Three-Dimensional Proximal Isovelocity Surface Area Methods

BACKGROUND

The accuracy of the proximal isovelocity surface area (PISA) method for the quantification of mitral regurgitation (MR), in the case of multiple jets, is unknown. The aim of this study was to evaluate different two-dimensional (2D) and three-dimensional (3D) PISA methods using 3D color Doppler data sets.

METHODS

Several regurgitant volumes (Rvols) were simulated using a pulsatile pump connected to a phantom equipped with single and double regurgitant orifices of different sizes and interspaces. A flowmeter served as the reference method. Transthoracic (TTE) and transoesophageal echocardiography (TEE) were used to acquire the 3D data sets. Offline, Rvols were calculated by 2D PISA methods based on hemispheric and hemicylindric assumptions and by 3D integrated PISA.

RESULTS

A fusion of the PISA was observed in the setting of narrow-spaced regurgitant orifices; compared with flowmeter, Rvol was underestimated using the single hemispheric PISA model (TTE: Bland-Altman bias ± limit of agreement, -17.5 ± 8.9 mL; TEE: -15.9 ± 7.3 mL) and overestimated using the double hemispheric PISA model (TTE: +7.1 ± 14.6 mL; TEE: +10.4 ± 11.9 mL). The combined approach (hemisphere for single orifice, hemicylinder with two bases for nonfused PISAs, and hemicylinder with one base for fused PISAs) was more precise (TTE: -3.4 ± 6.3 mL; TEE: -1.9 ± 5.6 mL). Three-dimensional integrated PISA was the most accurate method to quantify Rvol (TTE: -2.1 ± 6.5 mL; TEE -3.2 ± 4.8 mL).

CONCLUSIONS

In the setting of double MR orifices, the 2D combined approach and integrated 3D PISA appear to be superior as compared with the conventional hemispheric method, thus providing tools for the challenging quantification of MR with multiple jets.

Cardiac Computed Tomography and Magnetic Resonance Imaging in the Evaluation of Mitral and Tricuspid Valve Disease

Transcatheter interventions to treat mitral and tricuspid valve disease are becoming increasingly available because of the growing number of elderly patients with significant comorbidities or high operative risk. Thorough clinical and imaging evaluation in these patients is essential. The latter involves both characterization of the mechanism and severity of valvular disease as well as determining the hemodynamic consequences and extent of ventricular remodeling, which is an important predictor of future outcomes. Moreover, an assessment of the suitability and risk of complications associated with device-specific therapies is also an important component of the preprocedural evaluation in this cohort. Although echocardiography including 2-dimensional and 3-dimensional methods has an important role in the initial assessment and procedural guidance, cross-sectional imaging, including both computed tomographic imagning and cardiac magnetic resonance imaging, is increasingly being integrated into the evaluation of mitral and tricuspid valve disease. In this review, we discuss the role of cross-sectional imaging in mitral and tricuspid valve disease, primarily valvular regurgitation assessment, with an emphasis on the preprocedural evaluation and implications for transcatheter interventions.

Quantitation of mitral regurgitation with cardiac magnetic resonance imaging: a systematic review

In this review discuss the application of cardiac magnetic resonance (CMR) to the evaluation and quantification of mitral regurgitation and provide a systematic literature review for comparisons with echocardiography. Using the 2015 Preferred Reporting Items for Systematic Reviews and Meta-Analyses methodology, we searched Medline and PubMed for original research articles published since 2000 that provided data on the quantification of mitral regurgitation by CMR. We identified 220 articles of which 33 were included. Four main techniques of mitral regurgitation quantification were identified. Reproducibility varied substantially between papers but was high overall for all techniques. However, quantification differed between the techniques studied. When compared with two-dimensional echocardiography, mitral regurgitation fraction and regurgitant volume measured by CMR were comparable but typically lower. CMR has high reproducibility for the quantification of mitral regurgitation in experienced centres, but further technological refinement is needed. An integrated and standardised approach that combines multiple techniques is recommended for optimal reproducibility and precise mitral regurgitation quantification. Definitive outcome studies using CMR as a basis for treatment are lacking but needed.