IN-VIVO MURINE LEFT-VENTRICULAR PRESSURE-VOLUME RELATIONS BY MINIATURIZED CONDUCTANCE MICROMANOMETRY

The mouse is the species of choice for creating genetically engineered models of human disease. To study detailed systolic and diastolic lef t ventricular (LV) chamber mechanics in mice in vivo, we developed a m iniaturized conductance-manometer system. alpha-Chloralose-urethananes thetized animals were instrumented with a two-electrode pressure-volum e catheter advanced via the LV apex to the aortic root. Custom electro nics provided time-varying conductances related to cavity volume. Base line hemodynamics were similar to values in conscious animals: 634 +/- 14 beats/min, 112 +/- 4 mmHg, 5.3 +/- 0.8 mmHg, and 11,777 +/- 732 mm Hg/s for heart rate, end-systolic and end-diastolic pressures, and max imum first derivative of ventricular pressure with respect to time (dP /dt(max)), respectively. Catheter stroke volume during preload reducti on by inferior vena caval occlusion correlated with that by ultrasound aortic flow probe (r(2) = 0.98). This maneuver yielded end-systolic e lastances of 79 +/- 21 mmHg/mu l, preload-recruitable stroke work of 8 2 +/- 5.6 mmHg, and slope of dP/dt(max)-end-diastolic volume relation of 699 +/- 100 mmHg.s(-1).mu l(-1), and these relations varied predict ably with acute inotropic interventions. The control normalized time-v arying elastance curve was similar to human data, further supporting c omparable chamber mechanics between species. This novel approach shoul d greatly help assess cardiovascular function in the blood-perfused mu rine heart.