QUANTITATION OF VENTRICULAR SEPTAL DEFECT SHUNTING: 2D ECHO CONTRAST STUDIES IN ANIMALS; USING A STAND-ARDIZED EXPERIMENTAL ECHO CONTRAST AGENT

We tested a standardizable right heart echo contrast agent to assess contrast flow in relation to hemodynamics in an animal model with a ventricular septal defect (VSD). We produced VSDs (8-12 mm) in 4 open chest anesthetized dogs and varied pressures and shunting with aortic (AO) and pulmonary artery (PA) bands. AO and PA flows were measured with electromagnetic flow meters and right (RV) and left ventricular (LV) or AO pressures obtained. Echo 4 chamber views were recorded with an automated gain control 5 MHz scanner. Duplicate neck vein injections of 3.5cc of a solution of 1 g of SH U 454, an experimental gas producing echo contrast agent (Berliscan, Inc), yielded reproducible RV contrast filling and intensities (220-250 video units) as measured by videodensitometry. Positive contrast jets from RV to LV quantified as positive area (cm2) × contrast difference (ΔVD) between positive contrast area and control LV regions were present whenever RV systolic pressure was >30% of aortic pressure, and occurred mainly in diastole. LV to RV negative contrast jets, quantified as area × ΔVD between the negative contrast area and the surrounding opacified RV, correlated roughly with the magnitude (QP:QS) of 35 different left-to-right shunts (70 contrast injections) (r= 0.82, p<0.01). Bidirectional shunts were also observed. In this model a standardized echo contrast agent provided quantitative information about flow across VSD's.