Characterization of the cardiac response to a low and high dose of dobutamine in the mouse model of dilated cardiomyopathy by MRI in vivo.

Purpose: To assess the cardiac response to low (0.15-0.5 mg/kg i.p.) and high (1.5-20 mg/kg i.p.) doses of dobutamine in Tgαq*44 mice with dilated cardiomyopathy at the stage of advanced heart failure.
Materials and Methods: Inotropic, lusitropic, and chronotropic response to β(1) -adrenergic stimulation was assessed by the cine magnetic resonance imaging (MRI) protocol based on the electrocardiogram (ECG)-triggered bright-blood images of one midventricular short-axis slice.
Results: In wildtype mice increasing doses of dobutamine resulted in subsequent increase in the left ventricular function and heart rate acceleration, but significant inotropic, lusitropic, and chronotropic cardiac response was observed only after high doses of dobutamine, what is typical. In the Tgαq*44 mice low doses of dobutamine significantly increased inotropic and lusitropic cardiac performance without chronotropic changes. An increased heart rate was observed only after high doses of dobutamine, but then inotropic and lusitropic cardiac functional reserve was lost.
Conclusion: We described MRI stress test protocol based on a low and high dose of dobutamine induced response that proves useful in revealing alternation in cardiac function in mice with heart failure.
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