Conductance catheter-based assessment of arterial input impedance, arterial function, and ventricular-vascular interaction in mice

Global assessment of both cardiac and arterial function is important for a meaningful interpretation of pathophysiological changes in animal models of cardiovascular disease. We simultaneously acquired left ventricular (LV) and aortic pressure and LV volume (V_LV) in 17 open-chest anesthetized mice (26.7 ± 3.2g) during steady-state (BL) and caval vein occlusion (VCO) using a 1.4-Fr dual-pressure conductance catheter and in a subgroup of eight animals during aortic occlusion (AOO). Aortic flow was obtained from numerical differentiation of V_LV. AOO increased input impedance (Z_in) for the first two harmonics, increased characteristic impedance (0.025 ± 0.007 to 0.040 ± 0.011 mmHg·μl ¹·s, P < 0.05), and shifted the minimum in Z_in from the third to the sixth harmonic. For all conditions, the Z_in could be well represented by a four-element windkessel model. The augmentation index increased from 116.7 ± 7.8% to 145.9 ± 19.5% (P < 0.01) as well as estimated pulse-wave velocity (3.50 ± 0.94 to 5.95 ± 1.62 m/s, P < 0.05) and arterial elastance (E_a, 4.46 ± 1.62 to 6.02 ± 1.43 mmHg/μl, P < 0.01). AOO altered the maximal slope (E_max, 3.23 ± 1.02 to 5.53 ± 1.53 mmHg/μl, P < 0.05) and intercept (-19.9 ± 8.6 to 1.62 ± 13.51 μl, P < 0.01) of the end-systolic pressure-volume relation but not E_a/E _max (1.44 ± 0.43 to 1.21 ± 0.37, not significant). We conclude that simultaneous acquisition of Z_in and arterial function parameters in the mouse, based solely on conductance catheter measurements, is feasible. We obtained an anticipated response of Z_in and arterial function parameters following VCO and AOO, demonstrating the sensitivity of the measuring technique to induced physiological alterations in murine hemodynamics.