Geometry-independent inclusion of basalmyocardium yields improved cardiacmagnetic resonance agreement with echocardiography and necropsy quantified left-ventricular mass

Abstract

Objectives: Left-ventricular mass (LVM) is widely used to guide clinical decision-making. Cardiac magnetic resonance (CMR) quantifies LVM by planimetry of contiguous shortaxis 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 leftventricular myocardium, and by established methods that use different cut-offs to define the left-ventricular basalmost 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 (δ=11.0±28.8 g) than did ED50 (δ=16.4±29.1 g) and EDS50 (δ=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 echocardiographymeasured LVM and non-significant differences with necropsy-measured left-ventricular weight. © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins.