Murine Echocardiography and Ultrasound Imaging

Summary

This video demonstrates use of a rail-mounted high-frequency ultrasound probe to perform echocardiography on an anesthetized mouse. The methods describe both conventional two-dimensional and M-mode measurements of cardiac function in addition to newer, more powerful tools such as color Doppler, strain analysis, as well as general and targeted contrast imaging.

Abstract

Rodent models of cardiac pathophysiology represent a valuable research tool to investigate mechanism of disease as well as test new therapeutics.¹ Echocardiography provides a powerful, non-invasive tool to serially assess cardiac morphometry and function in a living animal.² However, using this technique on mice poses unique challenges owing to the small size and rapid heart rate of these animals.³ Until recently, few ultrasound systems were capable of performing quality echocardiography on mice, and those generally lacked the image resolution and frame rate necessary to obtain truly quantitative measurements. Newly released systems such as the VisualSonics Vevo2100 provide new tools for researchers to carefully and non-invasively investigate cardiac function in mice. This system generates high resolution images and provides analysis capabilities similar to those used with human patients. Although color Doppler has been available for over 30 years in humans, this valuable technology has only recently been possible in rodent ultrasound.^4,5 Color Doppler has broad applications for echocardiography, including the ability to quickly assess flow directionality in vessels and through valves, and to rapidly identify valve regurgitation. Strain analysis is a critical advance that is utilized to quantitatively measure regional myocardial function.⁶ This technique has the potential to detect changes in pathology, or resolution of pathology, earlier than conventional techniques. Coupled with the addition of three-dimensional image reconstruction, volumetric assessment of whole-organs is possible, including visualization and assessment of cardiac and vascular structures. Murine-compatible contrast imaging can also allow for volumetric measurements and tissue perfusion assessment.

Protocol

1. Preparation for imaging

1. Begin by securing an isoflurane anesthetized mouse to an animal-handling platform in the supine position. Place a nose cone over the animal's nose and mouth to deliver 0.5-1% isoflurane to maintain the anesthesia.
2. Secure the paws of the mouse to the electrode pads with conducting gel. Ensure appropriate ECG, body temperature at 37 °C and check respiratory rate for physiological assessment during imaging.
3. Apply depilatory cream to the chest and upper abdomen of the mouse.
4. After 2 minutes, use wet gauze remove to the cream.

2. Left parasterna....

Discussion

Serial high frequency echocardiography has emerged as a powerful tool for non-invasive, high-resolution assessment of cardiac morphology and function, particularly in murine models of heart disease. Maintaining physiological body temperature as well as comparable heart rates between mice by adjusting the anesthesia level prior to acquiring images, is critical to the success of this method. All images should be obtained using the same biomarkers (e.g. parasternal long axis imaging at the papillary muscles). Lastly, ana.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Vevo 2100 Imaging System (120V)	VisualSonics, inc.	VS-11945
Vevo 2100 Imaging Station 1	VisualSonics, inc.	SA-11982
Ultrasound Gel	Parker Laboratories Inc.	01-08
Isoflurane	Abbott Laboratories	05260-05
Vevo Compact Dual Anesthesia System	VisualSonics, inc.	SA-12055