Validation of a mouse conductance system to determine LV volume: comparison to echocardiography and crystals

The application of left ventricular pressure-volume analysis to transgenic mice to characterize the cardiac phenotype has been problematic due to the small size of the mouse heart and the rapid heartbeat. Conductance technolo gy has been miniaturized for the mouse and can solve this problem. However, there has been no validation of this technique. Accordingly, we performed echocardiography followed by simultaneous ultrasonic crystals, flow probe, and conductance studies in 18 CD-1 mice. Raw conductance volumes were corre cted for an inhomogenous electrical field (a) and parallel conductance (G(p i)) yielding a stroke volume of 14.1 +/- 3.7 mu l/ beat, end-diastolic volu me of 20.8 +/- 6.5 mu l, and end-systolic volume of 9.0 +/- 5.8 mu l. The m ean conductance volumes were no different from those derived by flow probe and echocardiography but did differ from ultrasonic crystals. G(pi) was det ermined to be 14.9 +/- 8.7 mu l. However, hypertonic saline altered dimensi on and pressure in the mouse left ventricle. Although G(pi) can be determin ed by the hypertonic saline method, saline altered hemodynamics, questionin g its validity in the mouse. Although mean measures of absolute volume may be similar among different techniques, individual values did not correlate.