Multiplane Transesophageal and Intracardiac Echocardiography in Large Swine: Imaging Technique, Normal Values, and Research Applications

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Abstract
Transthoracic echocardiographic imaging has been difficult to attain in the swine model. This study: (1) compares multiplane transesophageal echocardiography (TEE) with single plane TEE and intracardiac catheter echocardiography (ICE) for imaging of the swine cardiovascular system; and (2) defines normal values using these techniques in a closed chest large swine model (n = 24, body weight 50–114 kg). Multiplane TEE increased success rate over the single plane (the variable plane array only at 0°) TEE (P < 0.01) for imaging the left ventricular (LV) long-axis view (100% vs 50%), LV outflow tract (100% vs 33%), right atrium and its appendage (79% vs 33%), ascending aorta (100% vs 58%), and aortic arch (100% vs 17%). TEE-derived normal values at end-diastole (ED) and end- systole (ES) were: LV internal diameter (ID) = 49 ± 3 mm (ED) and 33 ± 4 mm (ES); LV wall thickness = 7 ± 1 mm (ED); right ventricular (RV) ID = 24 ± 4 mm (ED); RV wall thickness = 4 ± 2 mm (ED); left atrial ID = 48 ± 6 mm (ES); aortic root ID = 26 ± 3 mm (ES); LV volume = 157 ± 49 ml (ED) and 57 ± 22 ml (ES). Baseline LV ejection fraction (64%± 6%), Doppler-derived stroke volume (86 ± 14 ml), and cardiac index (107 ml/min per kg) were determined. Basal normal values, except for an elevated cardiac index in swine, are comparable to those reported for human adults. Multiplane TEE provided better overall cardiac imaging than did single plane TEE. ICE provided higher resolution imaging of individual cardiac chambers and structures when the ultrasound catheter was introduced into the right or left heart, but whole heart imaging was limited by ultrasound penetration at 12.5 MHz. Normal indices of chamber size and function provide a reference for the physiological significance of induced pathological states in this relevant animal model.