Development of a multifrequency conductance catheter-based system to determine LV function in mice

Transgenic mice offer a valuable way to relate gene products to phenotype, but the ability to assess the cardiovascular phenotype with pressure-volume analysis has lagged. Conductance measurement offers a method to generate a n instantaneous left ventricular (LV) volume signal in the mouse but has be en limited by the volume signal being a combination of blood and LV muscle. We hypothesized that by developing a mouse conductance system that operate s at several simultaneous frequencies, we could identify and correct for th e myocardial contribution to the instantaneous volume signal. This hypothes is is based on the assumption that mouse myocardial conductivity will vary with frequency, whereas mouse blood conductivity will not. Consistent with this hypothesis, we demonstrated that at higher excitation frequency, great er end-diastolic and end-systolic conductance are detected, as well as a sm aller difference between the two. We then empirically solved for LV blood v olume using two frequencies. We combined measured resistivity of mouse myoc ardium with an analytic approach and extracted an estimate of LV blood volu me from the raw conductance signal. Development of a multifrequency cathete r-based system to determine LV function could be a tool to assess cardiovas cular phenotype in transgenic mice.