Abstract 310: High Frequency Ultrasound Reveals Dobutamine Increases Murine Aortic Strain

Dobutamine increases heart rate and cardiac output, similar to the effects the sympathetic nervous system has on the body during exercise. This makes dobutamine an excellent surrogate for exercise, and it is often administered during stress tests. The purpose of this study was to quantify changes in arterial strain using in vivo high frequency ultrasound in order to better understand the effects of dobutamine on vascular dynamics. Here, C57BL/6 mice were infused with 40 μg/min/kg of dobutamine at a flow rate of 0.002 mL/min via a tail vein catheter (n=3; 19 weeks old, 31 ± 2.0 g). Ultrasound images of the suprarenal aorta, infrarenal aorta, iliac arteries, and carotid artery were acquired before the infusion of dobutamine (baseline) and again after the heart rate had plateaued during the infusion using B- and M-Modes images in both short and long axis. These mice showed an average heart rate increase of 76±18.7 bpm roughly 20 minutes after the start of the dobutamine infusion. Green-Lagrangian circumferential cyclic strain, calculated from arterial diameters in systole (maximum, dashed) and diastole (minimum, solid), increased throughout the vasculature after infusion. The suprarenal aorta increased from 22.5±1.3% to 41.9±2.4%, while the infrarenal aorta increased from 21.2±2.5% to 38.0±1.7%. The iliac artery increased from 22.4±2.9% to 42.0±2.7%, and the carotid artery increased from 26.0±2.3% to 43.5±5.2%. The average strain for all four locations increased from 23.0±2.1% (A) to 41.4±2.4% (B), representing a 79.6% increase from baseline. These results suggest that high frequency ultrasound is capable of capturing rapid changes in vascular dynamics due to dobutamine infusion. The effects of dobutamine on these healthy vessels can be used as a baseline for future studies that investigate murine disease models including advanced atherosclerosis and abdominal aortic aneurysms.