The overall goal of this tutorial is to describe how transthoracic speckle tracking echocardiography is performed in a healthy volunteer. This method can be used to quantitatively assess both segmental and global myocardial deformation. The main advantage of this technique is that it is more sensitive than conventional echocardiography, especially for the detection of subtle alterations.
Detecting subclinical dysfunction in asymptomatic patients is one example of its incremental value in myocardial imaging. Though this method is mainly utilized to measure left ventricular function, it can also be applied to assess the myocardial performance of the left atrium or the right heart. Generally, individuals new to this method might struggle because it requires impeccable image quality.
Furthermore, post-processing can be time-consuming at first. Begin by acquiring an echocardiography device featuring speckle tracking technology, or STE, equipped with an adequate sector array tissue harmonic imaging transducer. Escort the subject into the testing room and connect them to a standard three-lead electrocardiogram, or EKG.
Then plug the EKG wires directly into the echocardiography device in order to synchronize echocardiographic motion images to electromechanical activity. Unfreeze the ultrasound image to start detecting the EKG signal. Ask the patient to lie on their left side with their left arm stretched above the head, so that they are in a left lateral decubitus position.
In order to optimize image quality and guarantee accurate assessment of myocardial deformation, adjust the frame rate between 60 to 80 frames per second using the adjust frame rate option. Capture standard apical four-three-and two-chamber views by positioning the transducer at the apex of the heart near the apical impulse, in order to assess longitudinal strain and strain rate. Aim towards the right shoulder, and angulate the transducer until all anatomical structures of interest become visible.
Next, place the probe at the left parasternal border at the second or third intercostal space, and angulate until you obtain a cross-sectional, perpendicular view of the left ventricle. Finally, record images in the parasternal short axis view at the level of the mitral valve, the papillary muscles, and the apex, to detect circumferential and radial strain, and strain rate. Begin post-processing by opening the quantitative echocardiography analysis software.
Click file and open, and choose the desired echocardiographic study data. Select a patient, and pick an echocardiographic plane to analyze. Next, click the Q icon in the right, lower corner of the selected image, and press the aCMQ button on the left.
Choose the cardiac cycle of the highest image quality by using the green QRS skip keys at the bottom of the screen. Use the keyboard space bar to play and pause the loop. Select a region of interest, or ROI, to be analyzed by confirming the echocardiographic view on the left side of the screen.
In this case, the parasternal, short axis view at the level of the mitral valve. Then, have the software automatically detect the timing of end diastole, and suggest an ROI which automatically divides the myocardium into six segments. Start the speckle tracking analysis by pressing the compute button on the left side of the screen.
Click strain rate below the graphs to visualize segmental and global strain rate. Visually verify the tracking quality suggested by the software. If necessary, manually reposition the entire ROI by clicking edit on the left side of the screen.
Move each segment margin as well as the endocardial and epicardial borders individually with the cursor. Utilize a dot in the center of the ROI for orientation when moving the ROI in its entirety. In the apical four-three-and two-chamber view, have the software automatically determine a possible ROI by dividing the myocardium into seven segments.
If necessary, manually reposition the entire ROI by clicking edit on the left side of the screen. Move each segment margin as well as the endocardial and epicardial borders individually with the cursor. Utilize an orthogonal line pointing toward the apex for orientation when moving the ROI in its entirety.
Additionally, if ROI redefinition is necessary, click draw on the left, and start out tagging the endocardial border at three reference points, the two opposing insertion points of the atrioventricular valve, and the left ventricular wall, starting with the basal inferosepta part of the valve, finishing with the center of the apex. Display segmental and global strain and strain rate by clicking the preferences button at the bottom left corner of the screen. Select the desired wave form and display options from this menu.
Verify the tracking quality. If manual repositioning of the ROI is not sufficient to achieve appropriate overall speckle tracking quality, redefine the ROI, or select a different cardiac cycle, and reanalyze the data. Once optimal quality of the speckle tracking has been achieved, save and export the data for subsequent statistical analyses by clicking save at the bottom left corner of the screen.
Furthermore, export cine-loops and still frames as illustrations by clicking export at the bottom left corner of the screen, and select the desired format and file directory. Here, a correct, STE-derived longitudinal strain assessment is shown. Note that optimal image quality and adequate tissue coverage of the region of interest are essential for adequate strain analysis.
In contrast, this example demonstrates poor tissue tracking quality in the apical and mid-lateral segments, which results in the misinterpretation of myocardial deformation. Furthermore, a well-performed radial strain analysis is shown here, which reflects the systolic myocardial thickening. In contrast, incorrect tissue tracking of the anteroseptal myocardial segments results in inaccurate radial strain values in an asymptomatic, healthy patient.
While attempting this procedure, it's important to minimize artifacts, and always optimize echocardiographic image quality. Once mastered, this technique can be done within a few minutes for each echocardiogaphic plane if it's performed properly. In addition, novel echocardiographic devices provide the possibility to assess measurements instantly at the patient's bedside.
Following this procedure, speckle tracking can be combined with pharmacological or ergometer stress testing to unmask wall motion abnormalities that might remain undiscovered.
