ﺑﺎﺯﮔﺸﺖ ﺑﻪ ﺻﻔﺤﻪ ﻗﺒﻠﯽ
خرید پکیج
تعداد آیتم قابل مشاهده باقیمانده : 3 مورد
نسخه الکترونیک
medimedia.ir

Transthoracic echocardiography: Normal cardiac anatomy and tomographic views

Transthoracic echocardiography: Normal cardiac anatomy and tomographic views
Author:
Ayan R Patel, MD
Section Editor:
Warren J Manning, MD
Deputy Editor:
Susan B Yeon, MD, JD
Literature review current through: Jan 2024.
This topic last updated: Dec 08, 2022.

INTRODUCTION — Transthoracic echocardiography (TTE) is a widely available, reproducible, noninvasive ultrasound imaging modality for quantitative and qualitative evaluation of cardiac anatomy and function [1]. Two-dimensional (2D) echocardiography provides tomographic or "thin slice" imaging of cardiac structures from multiple imaging planes. Comprehensive echocardiographic examination typically involves integrating imaging of the heart from multiple "viewing" orientations in order to fully visualize cardiac structures. Doppler imaging is utilized in TTE to obtain information about cardiac hemodynamics and valvular function (see "Principles of Doppler echocardiography"). TTE is often used as a first-line cardiac imaging modality owing to its wide availability, noninvasiveness, and lack of radiation exposure. In cases where additional imaging is needed to assess cardiac structure or function, modalities such as transesophageal echocardiography, cardiovascular magnetic resonance imaging, and/or cardiac computed tomography may be utilized.

Echocardiography machines equipped with three-dimensional (3D) capability have been developed to overcome the disadvantages of 2D imaging [2-4]. These devices generally acquire a volumetric data set which can then be displayed in custom orientations. Due to the specific clinical advantages of 3D echocardiography, this modality has gained increasing clinical importance, particularly in the assessment of morphology in valvular disease. (See "Three-dimensional echocardiography".)

The nomenclature, standard protocol, and normal views associated with TTE are reviewed here. The instrumentation and physics associated with echocardiography, along with discussions of various echocardiographic techniques, are presented separately. (See "Echocardiography essentials: Physics and instrumentation" and "Principles of Doppler echocardiography" and "Tissue Doppler echocardiography".)

NOMENCLATURE — Each tomographic view is defined by the transducer position (parasternal, apical, subcostal, suprasternal) and view (eg, long-axis, short-axis, four-chamber, five-chamber, two-chamber). Transducer position is altered by placing the transducer at various locations on the thorax, while the view is manipulated by a combination of angulation and rotation. Due to limitations imposed by the thoracic skeleton and lungs, not all permutations of both variables result in clinically useful images.

Orientation — While acceptance is not universal, most labs follow the recommendations of the American Society of Echocardiography with respect to image display [5]. With this convention, the transducer position is depicted at the top of the screen, with anatomy more distant from the transducer depicted at progressively lower regions of the display, the lateral/left structures to the right, and medial/right structures to the left. A linear calibration scale is provided for all two-dimensional (2D) and M-mode measurements.

Tomographic views — Several tomographic views are commonly used (table 1A-B). Professional societies have published recommendations which have standardized myocardial segmentation and nomenclature (figure 1A-C) [5]. Modifications or angulations are used when standard imaging planes do not permit full depiction of the anatomy or pathology. Graphic depictions of the anatomy and normal echocardiographic dimensions from each view differ (table 2). In 2015, the American Society of Echocardiography published updated guidelines for chamber quantification as part of the routine echocardiographic evaluation [6].

TRANSDUCER POSITIONS — Most echocardiography laboratories follow a fairly standard protocol for transducer orientation, beginning with parasternal views and progressing to apical, subcostal, and suprasternal positions. Almost all imaging is performed with the patient in the left lateral decubitus position during quiet respiration or extended expiration. A cutout in the examination table mattress is helpful for maintaining optimal imaging position. While right-handed scanning was initially more common, left-handed scanning has been shown to be better ergonomically and to have a reduced chance of sonographer orthopedic injuries. As a result, this form of scanning now predominates.

Parasternal long-axis — With the transducer in the third or fourth left intercostal space, immediately adjacent to the sternum, a long-axis view of the heart is obtained that bisects the aortic and mitral valve (figure 2 and image 1) [5,6]. Thus, the "parasternal long-axis" (PLA) view is obtained. Proper positioning of the probe results in the ascending aorta being relatively horizontal in orientation. Lower intercostal positions may be necessary in patients with vertically oriented heart. In the PLA orientation:

The most anterior cardiac structure is the right ventricular outflow tract. Epicardial fat, sometimes mimicking an anterior pericardial effusion, can be detected.

The proximal structures of the ascending aorta (aortic root, sinotubular junction of the right and noncoronary sinuses), and the right (anterior) and noncoronary (posterior) leaflets of the aortic valve can be visualized. The aortic leaflets may be seen opening during ventricular systole with central coaptation (if tricuspid) point with ventricular diastole.

The anterior and posterior mitral leaflets are also well delineated with the anterior leaflet appearing "longer." During early ventricular diastole, the anterior leaflet extends anteriorly, towards the interventricular septum, while the posterior leaflet moves posteriorly towards the inferolateral left ventricular wall. The leaflets then "drift" closed in mid-diastole, followed by a reopening during atrial systole. Ventricular systole results in leaflet closure.

Chordae from the posterior-medial papillary muscle are commonly seen posterior to the plane of coaptation.

Posterior to the ascending aorta, and normally equal in diameter, is the left atrium. The right pulmonary artery can be seen superior to the left atrium as it crosses under the ascending aorta. The coronary sinus, usually less than 1 cm in diameter, may be seen immediately posterior to the mitral annulus. It can be distinguished from the descending thoracic aorta as the latter is external to the pericardium.

Posterior to the mid-left atrium, the descending thoracic aorta may be seen in cross-section (image 2).

The basal half of the anterior interventricular septum and inferoposterior wall of the left ventricle are seen, along with the muscular portion of the right ventricular outflow tract.

M-mode recordings — Due to its very high temporal resolution of approximately 1 millisecond, M-mode can have additive information for characterizing the motion of cardiac structures. Almost all routine M-mode measurements are made from the parasternal long- or short-axis orientation (image 3). To ensure proper alignment and reproducibility, all M-mode recordings are performed with two-dimensional (2D) guidance. 2D guided M-mode measurements of the aortic leaflets and left atrium, mitral leaflets (movie 1), and left ventricle can be obtained. The tricuspid (image 4) and pulmonic valves may also be visualized. With angulation of the transducer from the apex to the base of the heart a complete M-mode scan can be obtained. (See "Echocardiography essentials: Physics and instrumentation", section on 'M-mode'.)

Right ventricular inflow and outflow — Inferomedial angulation from the parasternal long-axis position is performed to obtain the 2D "right ventricular inflow" view, which includes the inferior vena cava, Eustachian valve, right atrium, coronary sinus, posterior and anterior leaflets of the tricuspid valve and basal right ventricle (image 5). Superior angulation of the probe permits depiction of the right ventricular outflow tract, including the pulmonic valve and main pulmonary artery.

Parasternal short-axis — From the parasternal long-axis orientation, a 70° to 110° clockwise rotation of the transducer with superior and inferior transducer manipulations permits delineation of the parasternal short-axis views at the base (aortic valve), basal left ventricular (mitral valve), mid-left ventricular (papillary muscle), and apical left ventricular levels (figure 2) [5,6]. At the basal (aortic valve) level, the atria and their interatrial septum, septal and anterior leaflets of the tricuspid valve, right ventricular free wall, right ventricular outflow tract, pulmonic valve, and main pulmonary artery can be seen "surrounding" the centrally oriented aortic valve (image 6 and image 7) [5,6]. All three leaflets of the aortic valve may be identified, forming a "Y" configuration during ventricular diastole, with the interatrial septum adjacent to the noncoronary cusp. The origins of the left and right coronary arteries may also be identified at approximately 3 o'clock and 10 o'clock, respectively (image 8).

The left atrial appendage can occasionally be visualized (movie 2).

Inferior angulation of the probe permits visualization of the left ventricle at the mitral valve level (image 9). The left ventricle appears "circular." The mitral orifice has a characteristic ovoid or "fish-mouth" appearance. A cross-section of the right ventricle is also seen.

Slightly more inferior angulation results in visualization of the contracting left ventricle at the papillary muscle level (image 10). In this orientation, the left ventricle may be divided into six segments: anterior, anterolateral, inferolateral, inferior, inferior septal, and anterior septal regions (figure 3). The posterior and lateral papillary muscles are well appreciated.

Further angulation of the transducer permits visualization of more apical segments (anterior, lateral, inferior, and septal) of the left ventricle (figure 3).

Apical four-chamber — With the patient in left lateral recumbency, the transducer is placed on the apex (figure 4 and image 11) [5,6]. In this view, all four chambers of the heart are seen simultaneously.

The left ventricle appears as a prolate ellipse, with the interventricular septum, apex, and lateral walls visualized. The lateral wall of the left ventricle is displayed to the right side of the screen. Care needs to be taken to avoid foreshortening the left ventricular cavity and exclusion of the true apex.

The basal, mid-, and apical free wall of the right ventricle are seen on the left side of the screen, with the moderator band connecting the free wall to the septum.

Inferiorly positioned on the screen are the left and right atria with intervening interatrial septum. The single-plane volume of the atria may be determined from this orientation.

The bottom of the image sector, the confluence of the pulmonary veins is seen superior to the left atrium. The longer anterior mitral leaflet appears medially, and posterior leaflet laterally. The closure point is normally apically displaced from the annulus. The septal and anterior tricuspid leaflets are also seen. The septal leaflet of the tricuspid valve is apically displaced relative to the mitral valve, and the intervening space (membranous septum) is normally less than 1.5 cm.

Slight anterior angulation allows visualization of the anterior segment of the interventricular septum and a portion of the proximal aorta. Posterior angulation permits visualization of the coronary sinus and the posterior segment of the interventricular septum.

Apical five-chamber — Anterior angulation and slight clockwise rotation of the transducer permits imaging of the left ventricular outflow tract, right and left leaflets of the aortic valve, and proximal ascending aorta (image 12).

Apical right ventricular-focused view — From the apical four-chamber view, the right ventricular-focused view can be obtained by rotating the transducer slightly counterclockwise to maximize the right ventricular area (image 13).

Apical two-chamber — Counterclockwise rotation from the apical four-chamber orientation achieves the apical two-chamber view (figure 4). In this orientation, the anterior, inferior, and apical walls of the left ventricle are visualized, along with the left atrium and its appendage. Care should be exercised to avoid foreshortening of the left ventricle and exclusion of the apex.

Apical long-axis — Further counterclockwise rotation and anterior angulation from the apical two-chamber permits acquisition of the apical long-axis view. In comparison with the apical two-chamber view, the left ventricular outflow tract, anterior septum, aortic leaflets, and proximal ascending aorta are seen (image 14).

Subcostal four-chamber — The subcostal views may be obtained with the patient supine in full inspiration to bring the heart closer to the imaging probe and with the knees bent to relax the abdominal musculature (figure 5). The transducer is positioned immediately below or to the right of the xiphoid process. This allows visualization of the basal, mid-, and apical right ventricle; the inferior interventricular septum; and anterolateral left ventricular walls (image 15). The interatrial septum is oriented nearly perpendicular to the ultrasound beam. Thus, interrogation for an atrial septal defect or an atrial septal aneurysm is best from this position.

The subcostal four-chamber view is a useful orientation for measurement of right ventricular dimensions and wall thickness as well as for visualizing anterior pericardial effusions.

Medial angulation of the transducer results in imaging of the hepatic veins and inferior vena cava as it enters the right atrium (image 16). Sliding the transducer to the left allows imaging of the abdominal aorta (image 17).

Subcostal short-axis — In cases in which parasternal views are inadequate, rotation of the probe from the subcostal four-chamber orientation will permit acquisition of a subcostal short-axis view at the base and midventricle. In this view, the inferior wall is identified by its contiguity with the liver and diaphragm.

Suprasternal notch — With the patient supine and the neck extended, the transducer is placed in the suprasternal notch to obtain an image of the distal ascending, transverse, and proximal descending aorta (image 18). The take-off of the great vessels may also be appreciated. Centrally positioned and beneath the lesser curvature of the aortic arch is a short-axis view of the right pulmonary artery (image 19).

Right parasternal — Right parasternal views may be helpful, particularly in patients with a dilated ascending aorta, and for assessment of aortic valve gradients in aortic stenosis patients. With the patient in the right decubitus position, the transducer is placed in the third or fourth intercostal space resulting in long-axis imaging of the ascending aorta.

Posterior orientations — Pleural effusion may be seen during parasternal imaging (movie 3 and image 20). In patients with large left pleural effusion, imaging from the posterolateral or posterior thorax with the patient in the upright position may permit good quality images of cardiac structures.

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

Basics topics (see "Patient education: Echocardiogram (The Basics)")

SUMMARY

Transthoracic echocardiography (TTE) is the primary noninvasive imaging modality for quantitative and qualitative evaluation of cardiac anatomy and function. Two-dimensional TTE provides tomographic or "thin slice" imaging, with each tomographic view defined by the transducer position (parasternal, apical, subcostal, suprasternal) and view (long-axis, short-axis, four-chamber, five-chamber). (See 'Nomenclature' above.)

Most echocardiography laboratories follow a standard protocol for consecutive transducer positions, beginning with parasternal long- and short-axis views and progressing to apical four-, five-, two-, and three-chamber views, followed by subcostal, and suprasternal positions. Almost all imaging is performed with the patient in the left lateral decubitus position during quiet respiration or extended expiration. The subcostal views, however, are best obtained with the patient supine in full inspiration to bring the heart closer to the imaging probe and with the knees bent to relax the abdominal musculature. (See 'Transducer positions' above.)

Topic 5319 Version 19.0

آیا می خواهید مدیلیب را به صفحه اصلی خود اضافه کنید؟