Age and sex corrected normal reference values of T1, T2 T2* and ECV in healthy subjects at 3T CMR

BACKGROUND

Myocardial T1, T2 and T2* imaging techniques become increasingly used in clinical practice. While normal values for T1, T2 and T2* times are well established for 1.5 Tesla (T) cardiovascular magnetic resonance (CMR), data for 3T remain scarce. Therefore we sought to determine normal reference values relative to gender and age and day to day reproducibility for native T1, T2, T2* mapping and extracellular volume (ECV) at 3T in healthy subjects.

METHODS

After careful exclusion of cardiovascular abnormality, 75 healthy subjects aged 20 to 90 years old (mean 56 ± 19 years, 47% women) underwent left-ventricular T1 (3-(3)-3-(3)-5 MOLLI)), T2 (8 echo- spin echo-imaging) and T2 * (8 echo gradient echo imaging) mapping at 3T CMR (Philips Ingenia 3T and computation of extracellular volume after administration of 0.2 mmol/kg Gadovist). Inter- and intra-observer reproducibility was estimated by intraclass correlation coefficient (ICC). Day to day reproducibility was assessed in 10 other volunteers.

RESULTS

Mean myocardial T1 at 3T was 1122 ± 57 ms, T2 52 ± 6 ms, T2* 24 ± 5 ms and ECV 26.6 ± 3.2%. T1 (1139 ± 37 vs 1109 ± 73 ms, p < 0.05) and ECV (28 ± 3 vs 25 ± 2%, p < 0.001), but not T2 (53 ± 8 vs 51 ± 4, p = NS) were significantly greater in age matched women than in men. T1 (r = 0.40, p < 0.001) and ECV (r = 0.37, p = 0.001) increased, while T2 decreased significantly (r = -0.25, p < 0.05) with increasing age. T2* was not influenced by either gender or age. Intra and inter-observer reproducibility was high (ICC ranging between 0.81-0.99), and day to day coefficient of variation was low (6.2% for T1, 7% for T2, 11% for T2* and 11.5% for ECV).

CONCLUSIONS

We provide normal myocardial T2, T2*,T1 and ECV reference values for 3T CMR which are significantly different from those reported at 1.5 Tesla CMR. Myocardial T1 and ECV values are gender and age dependent. Measurement had high inter and intra-observer reproducibility and good day-to-day reproducibility.

Assessment of aortic valve calcium load by multidetector computed tomography. Anatomical validation, impact of scanner settings and incremental diagnostic value

OBJECTIVES

To validate aortic valve calcium (AVC) load measurements by multidetector row computed tomography (MDCT), to evaluate the impact of tube potential and slice thickness on AVC scores, to examine the accuracy of AVC load in distinguishing severe from nonsevere aortic stenosis (AS) and to investigate its effectiveness as an alternative diagnosis method when echocardiography remains inconclusive.

METHODS

We prospectively studied 266 consecutive patients with moderate to severe AS who underwent MDCT to measure AVC load and a comprehensive echocardiographic examination to assess AS severity. AVC load was validated against valve weight in 57 patients undergoing aortic valve replacement. The dependence of AVC scores on tube potential and slice thickness was also tested, as well as the relationship between AVC load and echocardiographic criteria of AS severity.

RESULTS

MDCT Agatston score correlated well with valve weight (r = 0.82, p < 0.001) and hemodynamic indices of AS severity (all p < 0.001). Ex-vivo Agatston scores decreased significantly with increasing tube potential and slice thickness (repeated measures ANOVA p < 0.001). Multivariate analysis identified mean gradient, the indexed effective orifice area, male gender and left ventricular outflow tract cross-sectional area as independent correlates of the in-vivo AVC load.

CONCLUSIONS

MDCT-derived AVC load correlated well with valve weight and hemodynamic indices of AS severity. It also depends on tube potential and slice thickness, thus suggesting that these parameters should be standardized to optimize reproducibility and accuracy.

Head-to-Head Comparison of Inflammation and Neovascularization in Human Carotid Plaques: Implications for the Imaging of Vulnerable Plaques

BACKGROUND

Inflammation and intraplaque neovascularization are acknowledged to be 2 features of plaque vulnerability, although their temporal expression and their respective value in predicting clinical events are poorly understood. To determine their respective temporal associations, we conducted a comprehensive assessment of inflammation and intraplaque neovascularization in the carotid plaque of symptomatic and asymptomatic patients.

METHODS AND RESULTS

Thirty patients with severe carotid stenosis underwent ¹⁸F-fluorodeoxyglucose-positron emission tomography/computed tomographic imaging. Plaque ¹⁸F-fluorodeoxyglucose-uptake, indicative of inflammation, was measured by calculating the target:background ratio. The presence of intraplaque neovascularization during contrast-enhanced ultrasound was judged semiquantitatively; low-grade contrast enhancement (CE) suggested its absence, and high-grade CE, the presence of neovascularization. Carotid surgery was performed 1.6±1.8 days after completing both imaging modalities in all patients, and the presence of macrophages and neovessels was quantified by immunohistochemistry. We identified a significant correlation between the target:background ratio and macrophage quantification (R=0.78; P<0.001). The number of vessels was also significantly higher in carotid plaque with high-CE (P<0.001). Surprisingly, immunohistochemistry showed that high-CE and vessel number were neither associated with an elevated target:background ratio (P=0.28 and P=0.60, respectively) nor macrophage infiltration (P=0.59 and P=0.40, respectively). Finally, macrophage infiltration and target:background ratio were higher in the carotid plaque of symptomatic patients (P=0.021 and P=0.05, respectively), whereas CE grade and the presence of neovessels were not.

CONCLUSIONS

Inflammation and intraplaque neovascularization are not systematically associated in carotid plaques, suggesting a temporal separation between the 2 processes. Inflammation seems more pronounced when symptoms are present. These data highlight the challenges that face any imaging strategy designed to assess plaque vulnerability.

Impact of left ventricular outflow tract ellipticity on the grading of aortic stenosis in patients with normal ejection fraction

BACKGROUND

The pathophysiology of paradoxical low-gradient (LG) severe aortic stenosis (SAS) remains controversial. As low transvalvular flow has been implicated, we sought to investigate the impact of left ventricular outflow tract (LVOT) ellipticity on the estimation of the LV stroke volume, the calculation of the aortic valve area (AVA) by use of the continuity equation and on AS severity grading.

METHODS

We studied 190 consecutive patients (mean age: 72 ± 13 years; male: 57%) with SAS (indexed AVA < 0.6 cm2/m2) and preserved LV ejection fraction, including 120 patients with severe high gradient (HG) AS and 70 with severe paradoxical LG-AS. AS severity, LV volumes and LVOT ellipticity were assessed by 2D-Doppler echocardiography and cardiac magnetic resonance (CMR).

RESULTS

The LVOT exhibited an elliptical shape on CMR images, with a shorter anterior-posterior than median-lateral diameter (2.2 ± 0.2 vs 2.8 ± 0.3 cm, p < 0.01). Accordingly, the LVOT area measured by planimetry was larger than by 2D-echocardiography, assuming a circular orifice (4.9 ± 0.9 cm2 vs 3.7 ± 0.8 cm2, p < 0.01). Inputting the elliptical LVOT area into the continuity equation resulted in a 29% increase in the indexed AVA (from 0.41 ± 0.09 cm2 to 0.54 ± 0.10 cm2). Accordingly, 30 (43%) patients with severe paradoxical LG-SAS were reclassified as having moderate AS. Similar results were obtained when considering 3D-echo for direct planimetry of the LVOT in a subset of 75 patients.

CONCLUSIONS

Our results confirm that the LVOT is elliptical in shape and that taking this parameter into account in the calculation of the AVA results in reclassification of 43% of patients with severe paradoxical LG-AS into moderate AS.

Twenty-Year Outcome After Mitral Repair Versus Replacement for Severe Degenerative Mitral Regurgitation

Background:

Mitral valve (MV) repair is preferred over replacement in clinical guidelines and is an important determinant of the indication for surgery in degenerative mitral regurgitation. However, the level of evidence supporting current recommendations is low, and recent data cast doubts on its validity in the current era. Accordingly, the aim of the present study was to analyze very long-term outcome after MV repair and replacement for degenerative mitral regurgitation with a flail leaflet.

Methods:

MIDA (Mitral Regurgitation International Database) is a multicenter registry enrolling patients with degenerative mitral regurgitation with a flail leaflet in 6 tertiary European and US centers. We analyzed the outcome after MV repair (n=1709) and replacement (n=213) overall, by propensity score matching, and by inverse probability-of-treatment weighting.

Results:

At baseline, patients undergoing MV repair were younger, had more comorbidities, and were more likely to present with a posterior leaflet prolapse than those undergoing MV replacement. After propensity score matching and inverse probability-of-treatment weighting, the 2 treatments groups were balanced, and absolute standardized differences were usually <10%, indicating adequate match. Operative mortality (defined as a death occurring within 30 days from surgery or during the same hospitalization) was lower after MV repair than after replacement in both the entire population (1.3% versus 4.7%; P <0.001) and the propensity-matched population (0.2% versus 4.4%; P <0.001). During a mean follow-up of 9.2 years, 552 deaths were observed, of which 207 were of cardiovascular origin. Twenty-year survival was better after MV repair than after MV replacement in both the entire population (46% versus 23%; P <0.001) and the matched population (41% versus 24%; P <0.001). Similar superiority of MV repair was obtained in patient subsets on the basis of age, sex, or any stratification criteria (all P <0.001). MV repair was also associated with reduced incidence of reoperations and valve-related complications.

Conclusions:

Among patients with degenerative mitral regurgitation with a flail leaflet referred to mitral surgery, MV repair was associated with lower operative mortality, better long-term survival, and fewer valve-related complications compared with MV replacement.

αVβ3 integrin-targeted microSPECT/CT imaging of inflamed atherosclerotic plaques in mice

Background

α_Vβ₃-integrin is expressed by activated endothelial cells and macrophages in atherosclerotic plaques and may represent a valuable marker of high-risk plaques. We evaluated ^99mTc-maraciclatide, an integrin-specific tracer, for imaging vascular inflammation in atherosclerotic lesions in mice.

Methods

Apolipoprotein E-negative (ApoE^−/−) mice on a Western diet (n = 10) and normally fed adult C57BL/6 control mice (n = 4) were injected with ^99mTc-maraciclatide (51.8 ± 3.7 MBq). A blocking peptide was infused in three ApoE^−/− mice; this condition served as another control. After 90 min, the animals were imaged via single-photon emission computed tomography (SPECT). While maintained in the same position, the mice were transferred to computed tomography (CT) to obtain contrast-enhanced images of the aortic arch. Images from both modalities were fused, and signal was quantified in the aortic arch and in the vena cava for subtraction of blood-pool activity. The aorta was carefully dissected after imaging for gamma counting, autoradiography, and histology.

Results

Tracer uptake was significantly higher in ApoE^−/− mice than in both groups of control mice (1.56 ± 0.33 vs. 0.82 ± 0.24 vs. 0.98 ± 0.11, respectively; P = 0.006). Furthermore, higher tracer activity was detected via gamma counting in the aorta of hypercholesterolemic mice than in both groups of control mice (1.52 ± 0.43 vs. 0.78 ± 0.19 vs. 0.47 ± 0.31 ^99mTc-maraciclatide %ID/g, respectively; P = 0.018). Autoradiography showed significantly higher tracer uptake in the atherosclerotic aorta than in the control aorta (P = 0.026). Finally, in the atherosclerotic aorta, immunostaining indicated that the integrin signal came predominantly from macrophages and was correlated with the macrophage CD68 immunomarker (r = 0.73).

Conclusions

^99mTc-maraciclatide allows in vivo detection of inflamed atherosclerotic plaques in mice and may represent a non-invasive approach for identifying high-risk plaques in patients.

Prognostic Impact of Hypertrabeculation and Noncompaction Phenotype in Dilated Cardiomyopathy: A CMR Study

OBJECTIVES

The purpose of this study was to evaluate the impact of hypertrabeculation and left ventricular (LV) myocardial noncompaction phenotype by cardiac magnetic resonance (CMR) on outcomes of patients with nonischemic dilated cardiomyopathy (DCM).

BACKGROUND

Myocardial trabeculations and noncompaction are increasingly observed in patients with DCM, but their prognostic impact remains unknown.

METHODS

We prospectively evaluated outcomes of 162 consecutive patients (102 men; age 55 ± 15 years; ejection fraction [EF] 25 ± 8%) with DCM undergoing CMR. The amount of noncompaction was quantified as noncompacted/compacted (NC/C) length in the long-axis view and as the ratio of NC/C mass in the short-axis view and compared against 48 healthy control subjects (age 60 ± 10 years).

RESULTS

Fifty-eight DCM patients (36%) had NC/C length ≥2.3, and 71 (44%) had NC/C mass greater than the 95% confidence interval (CI) of control subjects. NC/C length and NC/C mass did not correlate with any clinical, echocardiographic, or CMR parameters. Over a 3.4-year median follow-up, 29 patients experienced major adverse cardiovascular events (MACE) (12 cardiovascular deaths, 8 heart transplantations, 4 LV assist device implantations, and 5 resuscitated cardiac arrests or appropriate device shocks). Cox univariate analysis identified smoking, New York Heart Association functional class, blood pressure, LV and right ventricular end-diastolic and end-systolic volumes, LV EF, right ventricular EF, and late gadolinium enhancement as predictors of MACE. In multivariate analysis, only LV EF and late gadolinium enhancement were independent predictors of MACE-free survival (hazard ratio: 0.922, 95% CI: 0.878 to 0.967, p = 0.001 and HR: 1.096, 95% CI: 1.004 to 1.197, p = 0.04, respectively). Neither NC/C length nor NC/C mass had significant predictive value for MACE-free survival, either unadjusted or after adjustment for baseline variables. Also, there was no difference in cardioembolic event rate between groups with high and low NC/C length or mass.

CONCLUSIONS

Cardiovascular outcomes of adult patients with nonischemic DCM do not appear to be influenced by the degree of trabeculation. This argues against a noncompaction phenotype designating a more severe form of DCM.

Histological Validation of measurement of diffuse interstitial myocardial fibrosis by myocardial extravascular volume fraction from Modified Look-Locker imaging (MOLLI) T1 mapping at 3 T

BACKGROUND

Gadolinium (Gd) Extracellular volume fraction (ECV) by Cardiovascular Magnetic Resonance (CMR) has been proposed as a non-invasive method for assessment of diffuse myocardial fibrosis. Yet only few studies used 3 T CMR to measure ECV, and the accuracy of ECV measurements at 3 T has not been established. Therefore the aims of the present study were to validate measurement of ECV by MOLLI T1 mapping by 3 T CMR against fibrosis measured by histopathology. We also evaluated the recently proposed hypothesis that native-T1 mapping without contrast injection would be sufficient to detect fibrosis.

METHODS

31 patients (age = 58 ± 17 years, 77% men) with either severe aortic stenosis (n = 12) severe aortic regurgitation (n = 9) or severe mitral regurgitation (n = 10), all free of coronary artery disease, underwent 3 T-CMR with late gadolinium enhancement (LGE) and pre- and post-contrast MOLLI T1 mapping and ECV computation, prior to valve surgery. LV biopsies were performed at the time of surgery, a median 13 [1-30] days later, and stained with picrosirius red. Pre-, and post-contrast T1 values, ECV, and amount of LGE were compared against magnitude of fibrosis by histopathology by Pearson correlation coefficients.

RESULTS

The average amount of interstitial fibrosis by picrosirius red staining in biopsy samples was 6.1 ± 4.3%. ECV computed from pre-post contrast MOLLI T1 time changes was 28.9 ± 5.5%, and correlated (r = 0.78, p < 0.001) strongly with the magnitude of histological fibrosis. By opposition, neither amount of LGE (r = 0.17, p = 0.36) nor native pre-contrast myocardial T1 time (r = -0.18, p = 0.32) correlated with fibrosis by histopathology.

CONCLUSIONS

ECV determined by 3 T CMR T1 MOLLI images closely correlates with histologically determined diffuse interstitial fibrosis, providing a non-invasive estimation for quantification of interstitial fibrosis in patients with valve diseases. By opposition, neither non-contrast T1 times nor the amount of LGE were indicative of the magnitude of diffuse interstitial fibrosis measured by histopathology.