Micro-CT imaging assessment of dobutamine-induced cardiac stress in rats

Dobutamine (DOB) stress in animal models of heart disease has been imaged so far using echocardiography and magnetic resonance imaging. The purpose of this study was to assess normal response to DOB stress in rats using anatomical and functional data using micro-computed tomography (CT).

Ten normal adult male rats were first injected with a liposomal-based blood pool contrast agent and next infused with DOB via a tail vein catheter. Using prospective gating, 5 pairs of systole/diastole micro-CT images were acquired (a) pre-infusion baseline; (b) at heart rate plateau during infusion of 10 microg/kg/min DOB; (c) at post-DOB infusion baseline; (d) at heart rate plateau during infusion of 30 microg/kg/min DOB; and (e) after post-infusion return to baseline. Heart rate, peripheral and breathing distensions were monitored by oximetry. Micro-CT images with 88-microm isotropic voxels were segmented to obtain cardiac function based on volumetric measurements of the left ventricle.

DOB stress increased heart rate and cardiac output with both doses. Ejection fraction increased above baseline by an average of 35.9% with the first DOB dose and 18.4% with the second dose. No change was observed in the relative peripheral arterial pressures associated with the significant increases in cardiac output.

Micro-CT proved to be a robust imaging method able to provide isotropic data on cardiac morphology and function. Micro-CT has the advantage of being faster and more cost-effective than MR and is able to provide higher accuracy than echocardiography. The impact of such an enabling technology can be enormous in evaluating cardiotoxic effects of various test drugs.