Quantification of diffuse myocardial fibrosis using CMR extracellular volume fraction and serum biomarkers of collagen turnover with histologic quantification as standard of reference.

PURPOSE: To compare the assessment of diffuse interstitial myocardial fibrosis in valvular diseases using cardiac magnetic resonance (CMR) extracellular volume fraction (ECV) quantification and serum biomarkers of collagen turnover using results of myocardial biopsy as standard of reference. MATERIALS AND METHODS: This prospective monocentric study included consecutive patients before aortic valvular replacement. All patients underwent: i), 1.5T CMR with pre and post contrast T1 mapping sequence and ECV computation; ii), serum quantification of matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) and iii), myocardial biopsies were collected during surgery to assess collagen volume fraction (CVF). Patients with coronary artery disease were excluded. Correlation between native T1, ECV, CVF and serum biomarkers were assessed using Pearson correlation test. Agreement between basal anteroseptal ECV with global ECV was assessed using Bland-Altman test. RESULTS: Twenty-one patients, 16 with aortic stenosis and 5 with aortic regurgitation were included. There were 12 men and 9 women with a mean age of 74.1±6.8 (SD) years (range: 32-84 years). Mean global ECV value was 26.7±2.7 (SD) % (range: 23.4-32.5%) and mean CVF value was 12.4±9.7% (range: 3.2-25.7%). ECV assessed at the basal anteroseptal segment correlated moderately with CVF (r=0.6; P=0.0026). There was a strong correlation and agreement between basal anteroseptal ECV and global ECV, (r=0.8; P<0.0001; bias 5.4±6.1%) but no correlation between global ECV and CVF (r=0.5; P=0.10). Global ECV poorly correlated with serum TIMP-1 (r=0.4; P=0.037) and MMP-2 (r=0.4; P=0.047). No correlation was found between serum biomarkers and basal anteroseptal- ECV or native T1. CONCLUSION: In patients with severe aortic valvulopathy, diffuse myocardial fibrosis assessed by anterosepto-basal ECV correlates with histological myocardial fibrosis. Anteroseptobasal ECV strongly correlates with global ECV, which poorly correlates with TIMP-1 and MMP-2, serum biomarkers involved in the progression of heart failure.

Quantification of right ventricular extracellular volume in pulmonary hypertension using cardiac magnetic resonance imaging.

PURPOSE: The purpose of this prospective study was to assess the value of biventricular extracellular volume (ECV) in pre-capillary pulmonary hypertension (PH) obtained using cardiac magnetic resonance imaging (CMR) and to correlate ECV with markers of prognosis such as strain echocardiography and blood biomarkers of fibrosis. MATERIALS AND METHODS: Twelve patients with PH (6 men, 6 women; mean age=50±16 [SD] years; age range: 22-73 years) underwent the same day: (i), transthoracic echocardiography including measurement of right ventricular (RV) fractional shortening (RVfs), tricuspid annular plane systolic excursion (TAPSE), maximal tricuspid annular velocity, RV global and segmental deformation; (ii), right heart catheterization measuring pulmonary arterial pressures (inmmHg) and cardiac output (inL/min); (iii), CMR at 1.5-T measuring RV volumes and ejection fraction; (iv), native and 15min post-contrast T1 mapping using modified look-locker inversion-recovery sequence; and (v), serum quantification of two biomarkers of collagen turnover and hematocrit. Non-parametric Mann-Whitney tests were used to search for differences between categorical variables. Spearman correlation test was used for search for correlation between quantitative values. RESULTS: Global RV ECV was 34%±4.2 (SD) for our entire population. A significant correlation was found between RV ECV and RVfs (r=0.6; P=0.026), S wave velocity (r=0.7; P=0.009), TAPSE (r=0.6; P=0.040) and RV systolic ejection fraction on CMR (r=0.6; P=0.04). There were no correlations between the ECV values in the lateral wall of the RV and in the septum (r=0.4; P=0.206). A significant correlation was found between septal ECV and 2D septal strain (r=0.7; P=0.013). CONCLUSION: ECV in PH as obtained using CMR appears to correlate with known echocardiographic prognostic markers and more specifically with the markers, which assess RV systolic function.

Distribution of left ventricular trabeculation across age and gender in 140 healthy Caucasian subjects on MR imaging.

PURPOSE: The purpose of this study was to quantify the distribution of trabeculated (T) and compact (C) left ventricular (LV) myocardium masses in a healthy Caucasian population against age, gender and LV parameters, and to provide normal values for T, C and T/C. MATERIALS AND METHODS: One hundred and forty healthy subjects were prospectively recruited and underwent cardiac MRI at 1.5T with a stack of short-axis cine sequences covering the entire LV. End-diastolic volume (EDV), C and T masses were quantified using a semi-automatic method. Ejection fraction (EF) and T/C ratio were computed. RESULTS: We included 70 men and 70 women with a mean age of 44±14 (SD) years (range: 20-69 years). The mean EF was 63.7±6.3 (SD) % (range: 50.7-82.0%), the mean EDV was 75.9±16.2 (SD) mL/m2 (range: 36.4-112.2mL/m2), the mean C mass was 53.9±11.2 (SD) g/m2 (range: 26.5-93.4g/m2) and the mean T mass was 4.9±2.4 (SD) g/m2 (range: 1.1-11.4g/m2). The T/C ratio was 9.2±4.5% (range: 2.0-29.4%). Multivariate ANOVA test showed that the compact mass was influenced by EDV (P<0.0001), EF (P=0.001) and gender (P<0.0001), and the trabeculated mass depended on EDV (P<0.0001), gender (P=0.002) and age (P<0.0001), while the T/C ratio was only influenced by age (P=0.0003). Spearman test showed a correlation between EDV and C (r=0.60; P<0.0001),T (r=0.46; P<0.0001) and T/C ratio (r=0.26; P=0.0023).T and T/C ratio correlated with EF (r=-0.18, P=0.0373; r=-0.18, P=0.0321, respectively). CONCLUSION: While the compact and trabeculated myocardium masses appear to relate separately to the cardiac function, age and gender, their ratio T/C appears to only decrease with age. Furthermore, we propose here normal values for T, C and T/C in a cohort of healthy Caucasians subjects.