Lauren A. Simprini

Mitral Apparatus Assessment by Delayed Enhancement CMR: Relative Impact of Infarct Distribution on Mitral Regurgitation

OBJECTIVES This study sought to assess patterns and functional consequences of mitral apparatus infarction after acute myocardial infarction (AMI). BACKGROUND The mitral apparatus contains 2 myocardial components: papillary muscles and the adjacent left ventricular (LV) wall. Delayed-enhancement cardiac magnetic resonance (DE-CMR) enables in vivo study of inter-relationships and potential contributions of LV wall and papillary muscle infarction (PMI) to mitral regurgitation (MR). METHODS Multimodality imaging was performed: CMR was used to assess mitral geometry and infarct pattern, including 3D DE-CMR for PMI. Echocardiography was used to measure MR. Imaging occurred 27 ± 8 days after AMI (CMR, echocardiography within 1 day). RESULTS A total of 153 patients with first AMI were studied; PMI was present in 30% (n = 46 [72% posteromedial, 39% anterolateral]). When stratified by angiographic culprit vessel, PMI occurred in 65% of patients with left circumflex, 48% with right coronary, and only 14% of patients with left anterior descending infarctions (p <0.001). Patients with PMI had more advanced remodeling as measured by LV size and mitral annular diameter (p <0.05). Increased extent of PMI was accompanied by a stepwise increase in mean infarct transmurality within regional LV segments underlying each papillary muscle (p <0.001). Prevalence of lateral wall infarction was 3-fold higher among patients with PMI compared to patients without PMI (65% vs. 22%, p <0.001). Infarct distribution also impacted MR, with greater MR among patients with lateral wall infarction (p = 0.002). Conversely, MR severity did not differ on the basis of presence (p = 0.19) or extent (p = 0.12) of PMI, or by angiographic culprit vessel. In multivariable analysis, lateral wall infarct size (odds ratio 1.20/% LV myocardium [95% confidence interval: 1.05 to 1.39], p = 0.01) was independently associated with substantial (moderate or greater) MR even after controlling for mitral annular (odds ratio 1.22/mm [1.04 to 1.43], p = 0.01), and LV end-diastolic diameter (odds ratio 1.11/mm [0.99 to 1.23], p = 0.056). CONCLUSIONS Papillary muscle infarction is common after AMI, affecting nearly one-third of patients. Extent of PMI parallels adjacent LV wall injury, with lateral infarction-rather than PMI-associated with increased severity of post-AMI MR.

The Right Sided Great Vessels by Cardiac Multidetector Computed Tomography: Normative Reference Values among Healthy Adults Free of Cardiopulmonary Disease, Hypertension, and Obesity

RATIONALE AND OBJECTIVES We sought to derive normative reference values for the thoracic great vessels using multidetector computed tomography (MDCT) in a healthy normotensive non-obese population free of cardiovascular disease. MATERIALS AND METHODS Non-gated axial computed tomography (CT) of the chest has traditionally been used to evaluate normal great vessel anatomy for prognosis and management. However, non-gated axial chest CT cannot account for the obliquity, systolic expansion, and non-axial motion of the great vessels during the cardiac cycle and may misclassify patients as normal or abnormal for prognostic and management purposes. To date, normative reference values for double-oblique, short-axis great vessel diameters have not been established using current generation electrocardiogram (ECG)-gated 64-detector row MDCT. A total of 103 (43% women, age 51 +/- 14 years) consecutive normotensive, non-obese adults free of cardiopulmonary or great vessel structural disease, arrhythmias, or significant coronary artery disease were studied by MDCT. Individuals underwent examination for determination of end-diastolic (ED) pulmonary artery (PA) and superior vena cava (SVC) dimensions in double-oblique short axes for comparison with the ascending aorta and the right-sided cardiac chambers. RESULTS For right sided great vessels, the 5th to 95th interval was 1.89-3.03 cm for ED PA diameter and 1.08-4.42 cm(2) for SVC cross-sectional area. The pulmonary artery to ascending aortic (PA-to-Ao) ratio was 0.66-1.13. In multivariate analysis, the PA was significantly associated with weight, whereas the PA-to-Ao ratio was inversely associated with age. Axial PA measurements were significantly higher and PA-to-Ao measurements significantly lower than corresponding short axis measurements (P = .04 and P < .001, respectively). CONCLUSIONS This study establishes ECG-gated MDCT reference values for right-sided great vessel dimensions derived from a healthy population of individuals free of cardiovascular disease, hypertension, and obesity. The traditional axial PA-to-Ao discriminant value of 1 for pulmonary hypertension is a poor diagnostic tool because it encompasses normal patients and is negatively affected by age. Thoracic great vessels should be measured by CT in ECG-gated double-oblique short-axis for accurate quantitation. These data may serve as a reference to identify right-sided great vessel pathology in individuals being referred for ECG-gated MDCT imaging.

Geometry-Independent Inclusion of Basal Myocardium Yields Improved Cardiac Magnetic Resonance Agreement with Echocardiography and Necropsy Quantified Left Ventricular Mass

Objectives: Left-ventricular mass (LVM) is widely used to guide clinical decision-making. Cardiac magnetic resonance (CMR) quantifies LVM by planimetry of contiguous short-axis images, an approach dependent on reader-selection of images to be contoured. Established methods have applied different binary cut-offs using circumferential extent of left-ventricular myocardium to define the basal left ventricle (LV), omitting images containing lesser fractions of left-ventricular myocardium. This study tested impact of basal slice variability on LVM quantification. Methods: CMR was performed in patients and laboratory animals. LVM was quantified with full inclusion of left-ventricular myocardium, and by established methods that use different cut-offs to define the left-ventricular basal-most slice: 50% circumferential myocardium at end diastole alone (ED50), 50% circumferential myocardium throughout both end diastole and end systole (EDS50). Results: One hundred and fifty patients and 10 lab animals were studied. Among patients, fully inclusive LVM (172.6 ± 42.3 g) was higher vs. ED50 (167.2 ± 41.8 g) and EDS50 (150.6 ± 41.1 g; both P < 0.001). Methodological differences yielded discrepancies regarding proportion of patients meeting established criteria for left-ventricular hypertrophy and chamber dilation (P < 0.05). Fully inclusive LVM yielded smaller differences with echocardiography (&Dgr; = 11.0 ± 28.8 g) than did ED50 (&Dgr; = 16.4 ± 29.1 g) and EDS50 (&Dgr; = 33.2 ± 28.7 g; both P < 0.001). Among lab animals, ex-vivo left-ventricular weight (69.8 ± 13.2 g) was similar to LVM calculated using fully inclusive (70.1 ± 13.5 g, P = 0.67) and ED50 (69.4 ± 13.9 g; P = 0.70) methods, whereas EDS50 differed significantly (67.9 ± 14.9 g; P = 0.04). Conclusion: Established CMR methods that discordantly define the basal-most LV produce significant differences in calculated LVM. Fully inclusive quantification, rather than binary cut-offs that omit basal left-ventricular myocardium, yields smallest CMR discrepancy with echocardiography-measured LVM and non-significant differences with necropsy-measured left-ventricular weight.

Routine cine-CMR for assessment of prosthesis-associated mitral regurgitation - a multicenter, multivendor study

Background Mitral regurgitation (MR) is clinically important for patients with prosthetic mitral valves (PMV). While CMR can quantify MR based on flow, this requires dedicated imaging. Cine-CMR (SSFP) provides an alternative approach, whereby MR can be graded based on regurgitation-associated intervoxel dephasing. As cine-CMR is a standard component of nearly all exams, it could be used to screen for patients who warrant further quantitative imaging. Diagnostic performance of cine-CMR for prosthesis-associated MR has not been evaluated. Methods Databases at 6 sites were queried for all patients with PMV in whom CMR and echocardiography were performed within 10 days. Cine-CMR images were retrieved and interpreted using a uniform protocol: MR was visually graded based solely on jet size (mild 2/3) in relation to the left atrium. MR was graded in each long axis plane (2-,3-, 4-chamber), with overall severity based on mean grade. Additional parameters included jet directionality, signal intensity (3-grade scale), and pulmonary vein flow reversal. Echocardiography (TTE, TEE) was used as a comparator for MR based on clinically reported data. Cine-CMR was interpreted blinded to patient history and TTE/TEE. Results 56 patients with PMV (70% mechanical, 30% bio) underwent cine-CMR and echo (TTE 70%, TEE 48%) within 2.5±2.6 days. Cine-CMR (1.5T, typical TR=3msec, TE=1msec, BW=977Hz/pixel) was performed using commercial scanners (Siemens 59%/GE 36%/Philips 5%). MR was present on cine-CMR in 77% of patients (mild 43%, moderate 14%, severe 20%), and varied in direction (central 88%, eccentric 12%). Patients with severe MR had higher prevalence of dense regurgitant jets (73% vs. 3%, p<0.001), more frequent pulmonary vein reversal (55% vs. 3%, p<0.001), and larger left atria (5.7±1.0cm vs. 4.7±1.4cm, p=0.03) than did those with lesser MR, but did not differ based on LVEF (53±14% vs. 49±15%, p=0.4). Compared to TEE, cine-CMR yielded excellent diagnostic accuracy (96%) for severe MR (Table); accuracy was also high (93%) when a broader TEE threshold (≥moderate MR) was applied. Among patients with TTE

Marked variability in published CMR criteria for left ventricular basal slice selection - impact of methodological discrepancies on LV mass quantification

Background Left ventricular mass (LVM) quantification by cine-CMR is typically performed by planimetry of contiguous LV short axis images. This approach relies on use of anatomic landmarks or quantitative binary cutoffs to define the basal-most aspect of the LV. Methodological discordance concerning criteria for LV basal slice selection has the potential to alter cine-CMR quantified LVM. This study assessed frequency of methodological variability in published LV basal slice definitions, as well as its impact on cine-CMR quantification of LVM.

ROUTINE CINE-CMR FOR PROSTHESIS ASSOCIATED MITRAL REGURGITATION: A MULTICENTER COMPARISON TO ECHOCARDIOGRAPHY

BACKGROUND AND AIM OF THE STUDY Mitral regurgitation (MR) is an important complication after prosthetic mitral valve (PMV) implantation. Transthoracic echocardiography is widely used to screen for native MR, but can be limited with PMV. Cine-cardiac magnetic resonance (CMR) holds the potential for the non-invasive assessment of regurgitant severity based on MR-induced inter-voxel dephasing. The study aim was to evaluate routine cine-CMR for the visual assessment of PMV-associated MR. METHODS Routine cine-CMR was performed at nine sites. A uniform protocol was used to grade MR based on jet size in relation to the left atrium (mild < 1/3, moderate 1/3-2/3, severe > 2/3). MR was graded in each long-axis orientation, with overall severity based on cumulative grade. Cine-CMR was also scored for MR density and pulmonary vein systolic flow reversal (PVSFR). Visual interpretation was compared to quantitative analysis in a single-center (derivation) cohort, and to transesophageal echocardiography (TEE) in a multicenter (validation) cohort. RESULTS The population comprised 85 PMV patients (59% mechanical valves, 41% bioprostheses). Among the derivation cohort (n = 25), quantitative indices paralleled visual scores, with stepwise increases in jet size and density in relation to visually graded MR severity (both p = 0.001). Patients with severe MR had an almost three-fold increase in quantitative jet area (p = 0.002), and a two-fold increase in density (p = 0.04) than did other patients. Among the multicenter cohort, cine-CMR and TEE (Δ =. 2 ± 3 days) demonstrated moderate agreement (κ = 0.44); 64% of discordances differed by ≤ 1 grade (Δ = 1.2 ± 0.5). Using a TEE reference, cine-CMR yielded excellent diagnostic performance for severe MR (sensitivity, negative predictive value = 100%). Patients with visually graded severe MR also had more frequent PVSFR (p < 0.001), denser jets (p < 0.001), and larger left atria (p = 0.01) on cine-CMR. CONCLUSION Cine-CMR is useful for the assessment of PMV-associated MR, which manifests concordant quantitative and qualitative changes in size and density of inter-voxel dephasing. Visual MR assessment based on jet size provides an accurate non-invasive means of screening for TEE-evidenced severe MR.

Established binary cutoffs for cine-CMR basal slice selection - an unrecognized source of CMR discordance with echocardiography and necropsy derived LV mass

Background Left ventricular mass (LVM) is widely used to guide clinical decision-making. CMR is well suited to measure LVM as it provides high-resolution delineation of myocardial contours. CMR quantification of LVM is typically performed via planimetry of contiguous short axis images, an approach fundamentally dependent on reader selection of short axis images to be contoured. Established methods have applied different binary cutoffs using circumferential extent of LV myocardium to define the basal LV, while omitting short axis images containing lesser fractions of LV myocardium. This study compared LVM, quantified using different established methods for basal slice selection, to independent references of LVM measured by echocardiography and necropsy. Methods