Evaluation of cardiac structures and function in small experimental animals: Transthoracic, transesophageal, and intraventricular echocardiography to assess contractile function in rat heart

Abstract

Objectives The efficacy of three different echocardiographic techniques to assess cardiac structures and function in the rat heart was studied.

Background With increasing costs for large animal studies there is need for improved assessment of ventricular function in small animal models.

Methods Transthoracic, transesophageal, or intracavitary echocardiography was performed in 138 rats using either a pediatric or an intravascular ultrasound transducer in control, infarcted, and obese rats. Left ventricular dimensions and wall thickness were measured.

Results Transthoracic echocardiography allows qualitative and quantitative estimation of cardiac dimensions and ventricular function. End-diastolic and end-systolic diameters were 0.53±0.08 and 0.26±0.05 cm in controls, 0.63±0.08 and 0.41±0.07 cm in infarcted (p<0.001 vs controls), and 0.66±0.1 and 0.21±0.07 cm in obese rats (p<0.01 vs controls). Fractional shortening was 52±6% in controls, 36±5% in infarcted (p<0.001), and 68±9% in obese rats (p<0.001). Wall thickness was increased in obese rats. Transesophageal echocardiography allows a qualitative rather than quantitative assessment. Intracavitary ultrasound enabled visualization of the endocardium. Following coronary occlusion, fractional shortening and ejection fraction were decreased (30.8±4.5 vs 44.4±4.7%, p<0.005, and 46.7±8.5 vs 63.4±5.4%, p<0.005, respectively).

Conclusions Transthoracic echocardiography is a non-invasive technique to sufficiently provide information about cardiac structures and function, while transesophageal echocardiography allows rather a qualitative estimation of the rat heart. Intracavitary ultrasound can be used to assess the endocardium, ventricular function, and dimensions in open-chest studies in rats.