Gated magnetic resonance imaging of normal and hypertrophied murine hearts

Transgenic murine models are being used increasingly to explore the molecular basis of heart disease. Until recently, there were no means for noninvasive assessment of changes in mass and function of the murine heart because of its very small size and high heart rate. Transthoracic echocardiography has now been utilized to obtain noninvasive estimates of murine left ventricular (LV) wall thicknesses, internal dimension, and mass. However, this approach is based on one-dimensional (M-mode) measurements of the LV at its midwall that take no account of variations in LV chamber and wall dimensions along other minor axes and at other anatomic levels. Thus asymmetries in LV geometry, which can affect LV mass estimates, may be undetected. In this study, gated (diastolic) magnetic resonance imaging (MRI) was utilized to obtain two-dimensional images of the LV at four anatomic levels in intact, anesthetized mice. In 17 normal CD-1 mice (body mass, 18- 47 g; gravimetric LV mass, 51-135 mg), LV mass estimates produced from the MRI data correlated well (r = 0.87) with LV mass determined gravimetrically. In addition, this approach identified changes in LV mass and wall thickness- to-chamber diameter ratio in a group of seven aortic-constricted mice (body mass, 32-39 g; gravimetric LV mass, 119-198 mg) with compensated and decompensated LV hypertrophy. These findings suggest the utility of MRI for serial, noninvasive assessment of experimentally induced alterations in mass and geometry of the murine heart.