Assessment of Left Ventricular Area at Risk by Myocardial Contrast Two-Dimensional Echocardiography: An Evaluation of a New Animal Model

BACKGROUND: New echocardiographic contrast agents are commonly tested in the dog model. However, this species has a number of drawbacks, including difficulties in experimentation, cost, and ethical considerations. The rabbit has a number of advantages due to its relative simple coronary circulation. The present study was designed to evaluate the rabbit model for determination of areas of risk (ARs) by contrast echocardiography. METHODS: Eight rabbits were intubated and mechanically ventilated after occlusion of the left coronary artery with a ligature. The transducer (operating at 7.5 MHz) was positioned on the right ventricle through a right thoracotomy. The images were obtained after intra-aortic injection of 1 ml of Albunex, followed by 3 ml of dye (Blue Uniperse) for histological analysis postmortem. The ARs were obtained after circumscription of the various echocardiographic and histological images. RESULTS: Excellent echocardiographic images were obtained, largely due to the hemodynamic stability of the rabbit to ischemia. Echocardiographic ventricular areas, absolute AR, and relative AR correlated closely with postmortem data (r = 0.86, 0.94, and 0.94, respectively). The measurements were highly reproducible with low variability. CONCLUSIONS: The rabbit model shows promise for study by contrast echocardiography of myocardium subjected to ischemia. This method for determination of ARs was validated against postmortem findings. The method also should be of value in the evaluation of reperfusion.