Cellular hypertrophy occurs before interstitial fibrosis in pressure-overload heart failure

Methods 11 mice underwent transverse aortic constriction (TAC). All mice were imaged at baseline, and a group of mice were examined early (2 weeks), intermediate (4 weeks) and late (7 weeks) post-TAC with histologic correlation. Mice were imaged at 9.8 Tesla with standard cine function sequences and T1 quantification via a Look-Locker cine experiment, pre and post gadolinium. The intra-cellular lifetime of water (τic), a-cell size dependent parameter, and the extracellular volume fraction (ECV) were determined by fitting R1 in tissue, against R1 in the blood pool, with a 2-site model for transcytolemmal water exchange. Minor (Dmin) and major (Dmaj) cell-diameters were determined by image analysis of FITC-wheat germ agglutinin stained sections.