The Progress of Advanced Ultrasonography in Assessing Aortic Stiffness and the Application Discrepancy between Humans and Rodents

Abstract

Aortic stiffening is a fundamental pathological alteration of atherosclerosis and other various aging-associated vascular diseases, and it is also an independent risk factor of cardiovascular morbidity and mortality. Ultrasonography is a critical non-invasive method widely used in assessing aortic structure, function, and hemodynamics in humans, playing a crucial role in predicting the pathogenesis and adverse outcomes of vascular diseases. However, its applications in rodent models remain relatively limited, hindering the progress of the research. Here, we summarized the progress of the advanced ultrasonographic techniques applied in evaluating aortic stiffness. With multiple illustrative images, we mainly characterized various ultrasound techniques in assessing aortic stiffness based on the alterations of aortic structure, hemodynamics, and tissue motion. We also discussed the discrepancy of their applications in humans and rodents and explored the potential optimized strategies in the experimental research with animal models. This updated information would help to better understand the nature of ultrasound techniques and provide a valuable prospect for their applications in assessing aortic stiffness in basic science research, particularly with small animals.

Keywords: aortic stiffness; atherosclerosis; cardiovascular risk factor; hemodynamics; ultrasonography.

Figure 1

The scheme of integrating applications of ultrasonography in aortic stiffness assessments. Based on the characters of each ultrasonography, aortic stiffness could be assessed through the three major measurements: aortic structure, hemodynamics, and tissue motion.

Figure 2

Representative M-mode displays of the aorta for the anterior–posterior diameter measurement. (A,B): The long-axis view of the ascending aorta (AAo) obtained in systole and diastole in human (A) and mouse (B). (C,D): The short-axis view of the descending abdominal aorta (DAAo) in systole and diastole in humans (C) and a mouse model (D).

Figure 3

The representative images of human aorta segments were obtained by B-mode. The segments of the aorta were imaged from a 20-year-old male volunteer. (A): The parasternal long-axis view of the aortic root (AoR). (B): The apical five-chamber view of the AoR. (C): The apical three-chamber view of the AoR. (D): The suprasternal view of the aortic arch (AoA). (E): The parasternal view of the descending thoracic aorta (DTAo). (F): The subcostal view of the descending abdominal aorta (DAAo). LV: left ventricle, LA: left atrium, RV: right ventricle, RA: right atrium.

Figure 4

B-mode imaged segments of a mouse aorta. (A): The parasternal long-axis view of the aortic root (AoR) and the ascending aorta (AAo). (B): The suprasternal view of the aortic arch (AoA). (C): The subcostal view of the descending abdominal aorta (DAAo). LV: left ventricle.

Figure 5

Representative Doppler signals and velocity waveforms of a human aorta. Images were obtained from a 20-year-old male volunteer representing Doppler images of the apical five-chamber view (A) and three-chamber view (B) of the aortic root (AoR) and the suprasternal view of the aortic arch (AoA) (C). (D–F): The corresponding assay of the aortic velocity of (A–C). LV: left ventricle, LA: left atrium, RV: right ventricle, RA: right atrium.

Figure 6

Color Doppler(CD) and pulsed-wave images from a mouse aorta. The representative images by CD were obtained from a healthy four-month-old C57BL/6J mouse. (A,B): CD images of the aorta arch (AoA) (A) and descending abdominal aorta (DAAo) (B). (C,D): The corresponding Inflow velocity of (A,B) using pulsed-wave Doppler imaging.

Figure 7

An illustrative example of pulse wave velocity measurement by ultrasonography. (A): The illustration of the distance and transit times assessed from signals detected at the carotid and femoral arteries in humans. (B): The illustration of the distance and transit times registered in the distal aortic arch and in the distal abdominal aorta in a mouse model.

Figure 8

Representative images of the aorta and the waveforms by tissue Doppler imaging. The segmental velocity information of the anterior wall of the aorta in human (A) and mice (B).

Figure 9

The illustration of human aortic assessments by two-dimensional (2D) speckle tracking. Intraoperative 2D speckle tracking analysis from a short-axis view of descending abdominal aorta (DAAo) in a healthy individual. The circumferential strain profile is displayed on a positively directed curve with a peak value of 18.3%.

Figure 10

Representative images of mouse aortic assessments by 2D speckle tracking. Images acquired from a four-month-old C57BL/6J mouse over one cardiac cycle. (A): B-mode image of the ascending aorta (AAo) in long-axis orientation. (B): Regional radial strain curve superimposed M-mode image of the aorta. (C): Tangential strain curve superimposed M-mode image of the aorta. (D): A B-mode image of the descending abdominal aorta (DAAo) in short-axis orientation. (E): Regional radial strain curve superimposed M-mode image of the aorta.