Analysis of Aorta
Aortic root diameter, M-mode
In M-mode, parasternal long axis view, the antero-posterior diameter of the aortic root is measured with the “leading-edge to leading-edge” method (A), synchronous with the Q wave of the EKG.
B: antero-posterior diameter of the left atrium (LA), measured at maximum atrial expansion in end-systole.
LA: left atrium; RVOT: right ventricular outflow tract.
In the example, a moderate to severe dilatation of the aortic root (54 mm).
Aortic root and sino-tubular junction diameters, 2D
In 2D mode, parasternal long axis view, the maximum antero-posterior aortic root (A, between the anterior right coronary and posterior non coronary sinus of Valsalva) and the minor sino-tubular junction (B) diameters are measured between the internal borders (intima) of the aortic walls, in end-diastole (ECG Q-wave).
LA: left atrium; LV: left ventricle; RV: right ventricle, outflow chamber.
The 2D measurement of the aortic root is smaller than the corresponding M-mode measurement (see: figure A), but it can be compared to the corresponding CAT scan measurement.
In the example, a normal exam.
Left ventricular outflow tract / aortic valve annulus diameter, 2D
In 2D mode, parasternal long axis view, the outflow tract / aortic valve annulus diameter (A) is measured in systole between the outflow tract anterior and posterior endocardiums immediately below the attachments of the anterior (right coronary) and posterior (non coronary) aortic valve leaflets.
AO: aortic root; LA: left atrium; LV: left ventricle; RV: right ventricle.
This measurement is used to calculate with the continuity equation the functional area of the native aortic valve (aortic stenosis) or of the aortic valve prosthesis.
Aortic valve diameter for the implant of a percutaneous / transapical biologic aortic valve, 2D
In 2D mode, parasternal long axis view, the annulus (A) is measured between the anterior and posterior most external borders of the native calcific (stenotic) aortic valve , in systole. For comparison purposes, the measurement of the standard LV outflow / aortic annulus (B) used in the calculation of the continuity equation (see also figure C).
AO: aortic root; LA: left atrium; LV: left ventricle.
The measure is quite demanding, and requires the differential visualization of the anterior aortic root wall and the calcific aortic valve tissue. (the arrow points at the calcific anterior right coronary aortic valve cusp).
Thoracic ascending aorta
In 2D mode, parasternal long axis view, the maximum antero-posterior diameter of the ascending thoracic aorta is measured between the inner borders (intima) of the walls (A). The measurement should be performed where the maximum diameter is visualized, noting preferably also the distance between this measurement and the aortic valve plane (B).
The ascending aorta is frequently visualized one intercostal space superior to the one utilized for the parasternal long axis view of the left ventricle. It is not necessary to visualize in the same view of the ascending aorta also the left ventricular and atrial cavities.
Aortic arch, 2D
In 2D mode, with the transducer in the suprasternal notch, the long axis of the aortic arch is visualized with a 30°-45° leftwards (clockwise) rotation of the transducer. The anonymous, left carotid and left subclavian supra-aortic branches are often visualized. The proximal (A, just before the anonymous branch), intermediate (B, after the left carotid branch), and distal (C, just distal to the left subclavian branch) diameters of the aortic arch are measured between the superior and inferior inner borders (intima) of the aortic walls.
AA: distal thoracic ascending aorta.
Aortic arch, color Doppler
In color Doppler mode, the “pseudo-angiographic” effect of color Doppler flow (caution: gain should be lowered so that the color velocities do not “overflow” over the aortic wall tissue) may facilitate the measurement of the aortic arch diameters.
In the example (arrow), the measurement of the distal aortic arch is facilitated by addition of color Doppler imaging (compare to figure B above).
AA: distal thoracic ascending aorta.
Descending thoracic aorta, 2D
In 2D mode, apical modified 2-chamber view (transducer rotated to allineate with the long axis of the descending thoracic aorta), the diameter of the aorta is measured between the anterior and posterior inner borders (intima) of the aortic walls.
AO: descending thoracic aorta; LA: left atrium; LV: left ventricle.
Ascending aorta and arch atheromas
Montgomery’s Classification of Aortic Atheromas.
Class I. Normal or mild thickening of intima.
Class II. Extensive intimal thickening.
Class III. Atheroma < 5 mm.
Class IV. Atheroma > 5 mm. Class V. Mobile lesion.
A. Class IV atheroma, ascending thoracic aorta.
2D mode, parasternal long axis view of the aortic root and ascending aorta.
The arrow points at an atheroma, located at the posterior sino-tubular junction, which protrudes more than 5 mm into the aortic lumen, and which is not mobile (Class 4).
AO: ascending aorta; LA: left atrium.
B. Class IV atheroma, aortic arch.
2D mode, jugular long axis view of the aortic arch.
Multiple atheromas (arrows) which protrude more than 5 mm into the aortic lumen from the inferior aortic wall, and which are not mobile.
AO: aortic arch; PA: left branch of the pulmonary artery.
C. Class V atheroma of the aortic arch.
Color Doppler mode, long axis view of the aortic arch.
Large, mobile atheroma originating from the superior wall of the initial segment of the aortic arch (C1: diastolic frame; C2: systolic frame). In systole the atheroma “looks” into the brachio-cephalic branch.
AO: aortic arch; Athe: atheroma; PA: left branch of the pulmonary artery.