Development and validation of echocardiographic methods for estimating left ventricular mass in rats

1. The aim of this study was to develop non-invasive echocardiographic methods of measuring left ventricular mass (LVM) in rats, and to determine their usefulness in detecting left ventricular hypertrophy. 2. After initial studies to identify the optimum transducer and to ascertain the resolution limits of echocardiography, the repeatability of LVM estimates was studied. The average difference between two independent estimates in 86 male rats (average LVM = 674.7 mg) was 5.4 mg, and the standard deviation of the difference was 107.6 mg. 3. To determine agreement between direct and indirect methods, LVM was measured in 38 male rats by echocardiography and compared with direct measurement of the left ventricular weight at sacrifice. The mean difference between the two methods was 9.14 +/- 56.6 mg. The limits of agreement were from -122.4 to +104.1 mg. 4. Echocardiography was then used to measure LVM in eight male spontaneously hypertensive rats and eight male normotensive Donryu rats at 9 weeks of age. The mean LVM of SHR was 768.2 mg +/- 152.6, which was significantly (2P less than 0.001) greater than the LVM of DRY (435.4 mg +/- 32.2). 5. We conclude that echocardiography provides a non-invasive, repeatable and relatively accurate estimate of LVM in rats. The method is a potentially useful tool for studying the development or regression of cardiac hypertrophy in longitudinal experiments.