TY - JOUR
T1 - Impact of physiological variables and genetic background on myocardial frequency-resistivity relations in the intact beating murine heart
AU - Reyes, Maricela
AU - Steinhelper, Mark E.
AU - Alvarez, Jorge A.
AU - Escobedo, Daniel
AU - Pearce, John
AU - Valvano, Jonathan W.
AU - Pollock, Brad H.
AU - Wei, Chia Ling
AU - Kottam, Anil
AU - Altman, David
AU - Bailey, Steven
AU - Thomsen, Sharon
AU - Lee, Shuko
AU - Colston, James T.
AU - Jung, Hwan Oh
AU - Freeman, Gregory L.
AU - Feldman, Marc D.
PY - 2006
Y1 - 2006
N2 - Conductance measurements for generation of an instantaneous left ventricular (LV) volume signal in the mouse are limited, because the volume signal is a combination of blood and LV muscle, and only the blood signal is desired. We have developed a conductance system that operates at two simultaneous frequencies to identify and remove the myocardial contribution to the instantaneous volume signal. This system is based on the observation that myocardial resistivity varies with frequency, whereas blood resistivity does not. For calculation of LV blood volume with the dual-frequency conductance system in mice, in vivo murine myocardial resistivity was measured and combined with an analytic approach. The goals of the present study were to identify and minimize the sources of error in the measurement of myocardial resistivity to enhance the accuracy of the dual-frequency conductance system. We extended these findings to a gene-altered mouse model to determine the impact of measured myocardial resistivity on the calculation of LV pressure-volume relations. We examined the impact of temperature, timing of the measurement during the cardiac cycle, breeding strain, anisotropy, and intrameasurement and interanimal variability on the measurement of intact murine myocardial resistivity. Applying this knowledge to diabetic and nondiabetic 11- and 20- to 24-wk-old mice, we demonstrated differences in myocardial resistivity at low frequencies, enhancement of LV systolic function at 11 wk and LV dilation at 20-24 wk, and histological and electron-microscopic studies demonstrating greater glycogen deposition in the diabetic mice. This study demonstrated the accurate technique of measuring myocardial resistivity and its impact on the determination of LV pressure-volume relations in gene-altered mice.
AB - Conductance measurements for generation of an instantaneous left ventricular (LV) volume signal in the mouse are limited, because the volume signal is a combination of blood and LV muscle, and only the blood signal is desired. We have developed a conductance system that operates at two simultaneous frequencies to identify and remove the myocardial contribution to the instantaneous volume signal. This system is based on the observation that myocardial resistivity varies with frequency, whereas blood resistivity does not. For calculation of LV blood volume with the dual-frequency conductance system in mice, in vivo murine myocardial resistivity was measured and combined with an analytic approach. The goals of the present study were to identify and minimize the sources of error in the measurement of myocardial resistivity to enhance the accuracy of the dual-frequency conductance system. We extended these findings to a gene-altered mouse model to determine the impact of measured myocardial resistivity on the calculation of LV pressure-volume relations. We examined the impact of temperature, timing of the measurement during the cardiac cycle, breeding strain, anisotropy, and intrameasurement and interanimal variability on the measurement of intact murine myocardial resistivity. Applying this knowledge to diabetic and nondiabetic 11- and 20- to 24-wk-old mice, we demonstrated differences in myocardial resistivity at low frequencies, enhancement of LV systolic function at 11 wk and LV dilation at 20-24 wk, and histological and electron-microscopic studies demonstrating greater glycogen deposition in the diabetic mice. This study demonstrated the accurate technique of measuring myocardial resistivity and its impact on the determination of LV pressure-volume relations in gene-altered mice.
KW - Diabetes
KW - Dual-frequency conductance method
KW - Gene-altered mouse
KW - Left ventricular volume
KW - Myocardial resistivity
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U2 - 10.1152/ajpheart.00609.2005
DO - 10.1152/ajpheart.00609.2005
M3 - Article
C2 - 16699072
AN - SCOPUS:33749371084
VL - 291
SP - H1659-H1669
JO - American Journal of Physiology
JF - American Journal of Physiology
SN - 0363-6135
IS - 4
ER -