DETERMINATION OF RIGHT-VENTRICULAR STRUCTURE AND FUNCTION IN NORMOXICAND HYPOXIC MICE - A TRANSESOPHAGEAL ECHOCARDIOGRAPHIC STUDY

Background-Noninvasive cardiac evaluation is of great importance in tr ansgenic mice. Transthoracic echocardiography can visualize the left v entricle well but has not been as successful for the right ventricle ( RV). We developed a method of transesophageal echocardiography (TEE) t o evaluate murine RV size and function. Methods and Results-Normoxic a nd chronically hypoxic mice (FIO2=0.11, 3 weeks) and agarose RV casts were scanned with a rotating 3.5F/30-MHz intravascular ultrasound prob e. In vivo, the probe was inserted in the mouse esophagus and withdraw n to obtain contiguous horizontal planes at 1-mm intervals. In vitro, the probe was withdrawn along the left ventricular posterior wall of e xcised hearts. The borders of the RV were traced on each plane, allowi ng calculation of diastolic and systolic volumes, RV mass, RV ejection fraction, stroke volume, and cardiac output. RV wall thickness was me asured, Echo volumes obtained in vitro were compared with cast volumes . Echo-derived cardiac output was compared with measurements of an asc ending aortic Doppler flow probe. Echo-derived RV free wall mass was c ompared with true RV free wall weight. There was excellent agreement b etween cast and TEE volumes (y=0.82x+6.03, r=0.88, P<0.01) and flow-pr obe and echo cardiac output (y=1.00x+0.45, r=0.99, P<0.0001), Although echo-derived RV mass and wall thickness were well correlated with tru e RV weight, echo-derived RV mass underestimated true weight (y=0.53x2.29, r=0.81, P<0.0001). RV mass and wall thickness were greater in hy poxic mice than in normoxic mice (0.78+/-0.19 versus 0.51+/-0.14 mg/g, P<0.03, 0.50+/-0.03 versus 0.38+/-0.03 mm, P<0.04). Conclusions-TEE w ith an intravascular ultrasound catheter is a simple, accurate, and re producible method to study RV size and function in mice,