Assessing Regurgitation Severity, Adverse Remodeling, and Fibrosis with CMR in Primary Mitral Regurgitation.

PURPOSE OF REVIEW: This review offers an evidence-based analysis of established and emerging cardiovascular magnetic resonance (CMR) techniques used to assess the severity of primary mitral regurgitation (MR), identify adverse cardiac remodeling and its prognostic effect. The aim is to provide different insights regarding clinical decision-making and enhance the clinical outcomes of patients with MR. RECENT FINDINGS: Cardiac remodeling and myocardial replacement fibrosis are observed frequently in the presence of substantial LV volume overload, particularly in cases with severe primary MR. CMR serves as a useful diagnostic imaging modality in assessing mitral regurgitation severity, early detection of cardiac remodeling, myocardial dysfunction, and myocardial fibrosis, enabling timely intervention before irreversible damage ensues. Incorporating myocardial remodeling in terms of left ventricular (LV) dilatation and myocardial fibrosis with quantitative MR severity assessment by CMR may assist in defining optimal timing of intervention.

Assessing Regurgitation Severity, Adverse Remodeling, and Fibrosis with CMR in Aortic Regurgitation.

PURPOSE OF REVIEW: Cardiac magnetic resonance (CMR) is emerging as a valuable imaging modality for the assessment of aortic regurgitation (AR). In this review, we discuss the assessment of AR severity, left ventricular (LV) remodeling, and tissue characterization by CMR while highlighting the latest studies and addressing future research needs. RECENT FINDINGS: Recent studies have further established CMR-based thresholds of AR severity and LV remodeling that are associated with adverse clinical outcomes, and lower than current guideline criteria. In addition, tissue profiling with late gadolinium enhancement (LGE) and extracellular volume (ECV) quantification can reliably assess adverse myocardial tissue remodeling which is also associated with adverse outcomes. The strengths and reproducibility of CMR in evaluating ventricular volumes, tissue characteristics, and regurgitation severity position it as an excellent modality in evaluating and following AR patients. Advanced CMR techniques for the detection of tissue remodeling have shown significant potential and merit further investigation.

The Effect of Dobutamine Stress Testing on Vortex Formation Time in Patients Evaluated for Ischemia.

Vortex formation time (VFT) is a dimensionless index used to quantify duration of vortex ring formation during diastole. We sought to investigate the effect of pharmaceutical stress on VFT in patients evaluated for ischemia. For this purpose, a standard dobutamine stress echo (DSE) protocol was performed in 50 consecutive patients, and VFT was calculated at rest and at peak. VFT was calculated from echocardiography measurements using a previously developed mathematical equation. VFTi was calculated as the percentage of change of VFTpeak, compared with VFTrest. Mean VFTrest was 2.46 (0.73) and mean VFTpeak 1.67 (0.57) with mean VFTi - 30.0% (19.8). In 14 (28%) patients, an ischemic response (DSE+) was documented. VFTi was significantly lower in DSE+ patients a finding which remained significant in the multivariate analysis after adjusting for age, sex, hypertension, diabetes, history of coronary artery disease, and relative increase of heart rate during stress. Graphical Abstract.

Functional assessment of bioprosthetic mitral valves by cardiovascular magnetic resonance: An in vitro validation and comparison to Doppler echocardiography.

BACKGROUND: A comprehensive non-invasive evaluation of bioprosthetic mitral valve (BMV) function can be challenging. We describe a novel method to assess BMV effective orifice area (EOA) based on phase contrast (PC) cardiovascular magnetic resonance (CMR) data. We compare the performance of this new method to Doppler and in vitro reference standards. METHODS: Four sizes of normal BMVs (27, 29, 31, 33 mm) and 4 stenotic BMVs (27 mm and 29 mm, with mild or severe leaflet obstruction) were evaluated using a CMR- compatible flow loop. BMVs were evaluated with PC-CMR and Doppler methods under flow conditions of; 70 mL, 90 mL and 110 mL/beat (n = 24). PC-EOA was calculated as PC-CMR flow volume divided by the PC- time velocity integral (TVI). RESULTS: PC-CMR measurements of the diastolic peak velocity and TVI correlated strongly with Doppler values (r = 0.99, P < 0.001 and r = 0.99, P < 0.001, respectively). Across all conditions tested, the Doppler and PC-CMR measurement of EOA (1.4 ± 0.5 vs 1.5 ± 0.7 cm2, respectively) correlated highly (r = 0.99, P < 0.001), with a minimum bias of 0.13 cm2, and narrow limits of agreement (- 0.2 to 0.5 cm2). CONCLUSION: We describe a novel method to assess BMV function based on PC measures of transvalvular flow volume and velocity integration. PC-CMR methods can be used to accurately measure EOA for both normal and stenotic BMV's and may provide an important new parameter of BMV function when Doppler methods are unobtainable or unreliable.

Left ventricular function in patients with hypertrophic cardiomyopathy and its relation to myocardial fibrosis and exercise tolerance.

We sought to determine the relation between myocardial extracellular volume (ECV), left ventricular (LV) diastolic function, and exercise tolerance in patients with hypertrophic cardiomyopathy (HCM). Forty five HCM patients with an ejection fraction >50% and no previous septal reduction therapy underwent imaging by CMR and transthoracic echocardiography. CMR was used to quantify LV volumes, mass, EF, LA volumes, scar burden, pre and post contrast T1 relaxation times and ECV. Echocardiography was used to measure outflow tract gradients, mitral inflow and annular velocities, circumferential strain, systolic, early and late diastolic strain rates. Exercise duration and peak oxygen consumption were noted. HCM patients had increased native T1 relaxation time and ECV vs. controls [ECV controls: 24.7 (23.2-26.4) vs. HCM: 26.8 (24.6-31.3)%, P = 0.014]. Both parameters were significantly associated with LV diastolic dysfunction, circumferential strain, diastolic strain rate and peak oxygen consumption (r = -0.73, P < 0.001). Compared to controls, HCM patients have significantly longer native T1 relaxation time and higher ECV. These structural changes lead to worse LV global and segmental diastolic function and in turn reduced exercise tolerance.

Echocardiographic Evaluation of Tricuspid Prosthetic Valves: An Update.

This review focuses on the diagnostic value of novel echocardiographic techniques and the clinical application of recently described algorithms to assess tricuspid prosthetic valve function.

Functional Assessment of Bioprosthetic Aortic Valves by CMR.

OBJECTIVES: The aim of this study was to evaluate cardiac magnetic resonance (CMR) phase-contrast (PC) measures of a bioprosthetic aortic valve velocity time integral (PC-VTI) to derive the effective orifice area (PC-EOA) and to compare these findings with the clinical standard of Doppler echocardiography. BACKGROUND: Bioprosthetic aortic valve function can be assessed with CMR planimetry of the anatomic orifice area and PC measurement of peak transvalvular systolic velocity. However, bioprosthetic valves can create image artifact and data dropout, which makes planimetry measures a challenge for even experienced CMR readers. METHODS: From our institutional database, we identified 38 patients who had undergone 47 paired imaging studies (CMR and Doppler) within 46 days (median 3 days). Transvalvular forward flow volume by CMR was determined by 3 methods: ascending aorta flow, transvalvular flow, and left ventricular stroke volume. PC-EOA was derived as flow divided by PC-VTI, calculated with a semiautomated MATLAB (Mathworks, Natick, Massachusetts) application for integration of the instantaneous peak transvalvular velocity. Doppler EOA was assessed by the continuity method. RESULTS: PC-EOA by all 3 flow approaches demonstrated a strong correlation with Doppler EOA (r = 0.949, 0.947, and 0.874, respectively; all p < 0.001) and revealed good agreement (bias = 0.03, 0.03, and 0.28 cm(2), respectively). With Doppler-derived EOA as the reference standard, CMR was able to correctly characterize 24 of 26 valves as normal (EOA >1.2 cm(2)), 12 of 14 possibly stenotic valves (0.8 < EOA < 1.2 cm(2)), and 5 of 7 stenotic valves (EOA <0.8 cm(2); k = 0.826). CONCLUSIONS: We describe a new CMR-based method to derive the EOA for bioprosthetic aortic valves. This method compares favorably to traditional Doppler methods and might be an important additional parameter in the evaluation of prosthetic valves by CMR, particularly when Doppler methods are suboptimal or considered discordant with the clinical presentation.

Clinical Utility of Multidetector Computed Tomography in Redo Valve Procedures.

BACKGROUND: Transesophageal echocardiography (TEE) is recommended for diagnosis in patients suspected of prosthetic valve dysfunction, but could be limited in its ability to identify the etiology of these dysfunctions and to assess extracardiac structures. Our objective is to examine the usefulness of multidetector computed tomography (MDCT) in establishing the etiology of the dysfunctions and its clinical utility in preoperative assessment in these patients. METHODS: Twenty-two prosthetic heart valves from 20 consecutive patients who had a preoperative MDCT and underwent redo prosthetic valve procedures from December 2008 to February 2013 were examined retrospectively. Results from MDCT and TEE were compared to intraoperative findings. Extravalvular MDCT findings including coronary artery/bypass graft, high-risk features for reoperative cardiac surgery, and extracardiac findings were also assessed. RESULTS: MDCT correctly identified 15 valve regurgitation and seven valve obstructions compared to intraoperative findings. Both TEE and MDCT were able to correctly identify the etiologies in 93% (14/15) of regurgitant valves. However, MDCT was better able to identify the etiology of obstructive valves than TEE (86% [6/7] vs. 43% [3/7]) compared to intraoperative findings. In patients who had preoperative invasive angiography, MDCT correctly identified two patients with significant coronary artery disease (CAD) and ruled out 11 without significant CAD. Furthermore, MDCT detected five high-risk features for postoperative complications and eight clinically relevant extracardiac findings. CONCLUSIONS: MDCT displayed comparable or better diagnostic performance than TEE for identifying the type of dysfunction and its etiology, as well as providing additional coronary and other extravalvular evaluations useful for preoperative planning.

Comparative Assessment of Mitral Regurgitation Severity by Transthoracic Echocardiography and Cardiac Magnetic Resonance Using an Integrative and Quantitative Approach.

Although transthoracic echocardiography (TTE) and cardiac magnetic resonance (CMR) are validated in quantitation of mitral regurgitation (MR), discrepancies may occur. This study assesses the agreement between TTE and CMR in MR and evaluates characteristics and clinical outcome of patients with discrepancy. From our institutional database, 70 subjects with MR underwent both TTE and CMR within 30 days (median 3 days). MR was evaluated semiquantitatively (n = 70) using a 4-grade scale and quantitatively (n = 60) with calculation of regurgitant volume (RVol) and regurgitant fraction (RF). Of the 70 subjects, qualitative assessment by TTE yielded 30 subjects with mild MR, 17 moderate, and 23 moderately severe or severe MR. Exact concordance in MR grade was seen in 50% and increased to 91% when considering concordance within one grade of severity (κ = 0.44). A modest correlation was observed for RVol and RF between both methods (r = 0.59 and 0.54, respectively, p <0.0001). Ten patients had a significant discrepancy in quantitative MR (difference in RF >20%); the frequency of secondary MR was higher (100% vs 46%; p = 0.003) in patients with discrepancy. Although interobserver variability in RF was higher with TTE compared with CMR (-5.5 ± 15% vs 0.1 ± 7.3%), patients with discrepancy were equally distributed by severity and clinical outcome without an overestimation by either method. In conclusion, there is a modest agreement between TTE and CMR in assessing MR severity. In patients with discrepancy, there is a higher prevalence of functional MR, without a consistent overestimation of MR severity by either method.

Replicating Patient-Specific Severe Aortic Valve Stenosis With Functional 3D Modeling.

BACKGROUND: 3D stereolithographic printing can be used to convert high-resolution computed tomography images into life-size physical models. We sought to apply 3D printing technologies to develop patient-specific models of the anatomic and functional characteristics of severe aortic valve stenosis. METHODS AND RESULTS: Eight patient-specific models of severe aortic stenosis (6 tricuspid and 2 bicuspid) were created using dual-material fused 3D printing. Tissue types were identified and segmented from clinical computed tomography image data. A rigid material was used for printing calcific regions, and a rubber-like material was used for soft tissue structures of the outflow tract, aortic root, and noncalcified valve cusps. Each model was evaluated for its geometric valve orifice area, echocardiographic image quality, and aortic stenosis severity by Doppler and Gorlin methods under 7 different in vitro stroke volume conditions. Fused multimaterial 3D printed models replicated the focal calcific structures of aortic stenosis. Doppler-derived measures of peak and mean transvalvular gradient correlated well with reference standard pressure catheters across a range of flow conditions (r=0.988 and r=0.978 respectively, P<0.001). Aortic valve orifice area by Gorlin and Doppler methods correlated well (r=0.985, P<0.001). Calculated aortic valve area increased a small amount for both methods with increasing flow (P=0.002). CONCLUSIONS: By combing the technologies of high-spatial resolution computed tomography, computer-aided design software, and fused dual-material 3D printing, we demonstrate that patient-specific models can replicate both the anatomic and functional properties of severe degenerative aortic valve stenosis.

Association of Left Ventricular Diastolic Dysfunction with Subclinical Coronary Atherosclerotic Disease Burden Using Coronary Artery Calcium Scoring.

AIM: Diastolic dysfunction is a common problem in patients with obesity, hypertension, diabetes, or coronary artery disease. The purpose of this study was to evaluate the association of left ventricular diastolic dysfunction with an abnormal coronary artery calcium score (CAC score). METHODS: This study considered a cohort of patients ≥ 18 years of age with normal ejection fraction who were admitted to the hospital with chest pain. All patients underwent regadenoson myocardial perfusion stress imaging and had no evidence of ischemia or infarction. Patients then underwent cardiac CT for measurement of CAC score. Patients were excluded if they had prior history of coronary artery disease, ECG findings diagnostic of an acute coronary syndrome, an elevated troponin level, or hemodynamic instability. RESULTS: A total of 114 patients were included and 52 (45.6%) patients had echocardiographic evidence of diastolic dysfunction. Patients with diastolic dysfunction were more likely to have an abnormal calcium score (79.6% vs 20%; OR 15.10, 95% CI 5.70 to 43.85; p ＜ 0.001). In multivariable analysis, the presence of diastolic dysfunction on echocardiogram was significantly associated with an abnormal calcium score (OR 13.82, 95% CI 5.57 to 37.37; p ＜ 0.001) after adjusting for Framingham Risk Score or clinical risk factors (age, gender, diabetes mellitus, dyslipidemia, and obesity; OR 19.06,95% CI 4.66 to 107.97; p ＜ 0.001). CONCLUSIONS: Our study demonstrates that left ventricular diastolic dysfunction is associated with an abnormal CAC score even after adjusting for Framingham Risk Score or clinical risk factors. Patients without known coronary artery disease that present with chest pain and have normal perfusion imaging with evidence of abnormal diastolic function on echocardiogram may warrant more thorough evaluation for coronary atherosclerotic disease with CAC score assessment.

Echocardiographic evaluation of left ventricular diastolic function: an update.

Echocardiographic evaluation of diastolic properties and assessment of hemodynamic status of the right and the left ventricle have been traditionally applied for many years in clinical practice. Establishment of diagnosis of diastolic dysfunction, grading, and estimation of filling pressures noninvasively adds prognostic information to the clinician, which may affect treatment management. Novel methods, including left atrium strain, left ventricular diastolic strain rate, and left ventricular untwisting rate, have been imported in clinical practice attempting to provide a more comprehensive and more accurate understanding of the mechanisms and diagnosis of diastolic dysfunction.