Comparison of Four-dimensional Echocardiographic Imaging to Cardiac Magnetic Resonance Imaging in Rats

Background: Preclinical cardiovascular research is the foundation for our understanding and broad knowledge of heart function and cardiovascular diseases. Reliable cardiac imaging modalities are the basis for applicable results. Past studies show that two-dimensional echocardiography has limitations compared with cardiac magnetic resonance imaging in rats. This study was performed to validate a completely new technology of four-dimensional echocardiography by comparing it to the gold standard of cardiac magnetic resonance imaging and the widely used method of two-dimensional echocardiography.

Methods: Assessment of heart function and left ventricular volumes was performed in 20 rats using four-dimensional echocardiography, cardiac magnetic resonance imaging and two-dimensional echocardiography. 5 rats underwent a ligation of the superior and inferior vena cava to induce low cardiac output two weeks prior to cardiac imaging.

Results: Four-dimensional echocardiography and cardiac magnetic resonance imaging measurements show a strong correlation in end-diastolic volume (r = 0.983, p ≤ 0.001), end-systolic volume (r = 0.970, p≤0.001) and left ventricular ejection fraction (r = 0.952, p < 0.001) in both groups (control and diseased). Two-dimensional echocardiography underestimates end-diastolic volume but not end-systolic volume, which leads to a significant underestimation of left ventricular ejection fraction.

Conclusion: Four-dimensional echocardiography and cardiac magnetic resonance imaging provide similar consistent results concerning left ventricular volumes and systolic function. In addition, our results confirmed that two-dimensional echocardiography is the least reliable imaging modality of the three, showing higher variance and larger standard deviation than four-dimensional echocardiography and cardiac magnetic resonance imaging.