Quantification of ventricular remodeling in the tight-skin mouse cardiomyopathy with acoustic microscopy

To determine the role of ultrasonic tissue characterization for the detection of changes in myocardial architecture associated with cardiomyopathy, acoustic microscopy was performed on the hearts of 4- to 6-month-old tight-skin mice [TSK/+, C57-B10.D2 (58B)/SN strain], a model of cardiomyopathy characterized by diffuse interstitial fibrosis. Ultrasonic backscatter was measured from excised segments of left ventricular free walls of five TSK mice and five sex- and age-matched normal controls with a 50 MHz broad band focused piezoelectric transducer operated in a saline-filled water tank at room temperature. Forty-nine radio frequency (RF) lines were digitized from each specimen at 2 ns/sample. Power spectral analysis of RF data was performed and mean integrated backscatter (IB) computed. The TSK group demonstrated greater IB (-53.6 ± 0.6 dB, n = 5) than did the control group (-56.6 ± 0.7 dB, n = 5; p < 0.02). Myocardial collagen content determined by hydroxyproline assay increased by 11% in the TSK group (2.54 ± 0.08 μg/mg dry wt, n = 5) over that in controls (2.28 ± 0.07 μg/mg dry wt, n = 5; p < 0.05). A significant linear relationship was observed between myocardial hydroxyproline concentration and IB (r = 0.74; p < 0.02). Thus, ultrasonic tissue characterization permits sensitive detection of modest changes in the extent of interstitial fibrosis that accompany tissue remodeling in the early stages of cardiomyopathy.