Nesser_subbed.qxp 20/4/09 3:19 pm Page 24
Imaging
Latest Developments in Ultrasound Cardiac Imaging
Hans Joachim Nesser, MD
Head, 2nd Internal Department, Elisabethinen Teaching Hospital, Linz
Abstract
Tissue Doppler echocardiography (TDE) has been used to calculate and display myocardial velocities, strain, or strain rate in various cardiac
diseases. Unfortunately, TDE is limited due to angle of incidence dependency, noise, artifacts, tethering, and translation affecting the reproducibility
of measurements. 2D speckle tracking echocardiography (2D-STE)—a more robust, angle-independent technique—is able to overcome these
limitations and to define radial, circumferential, longitudinal, and transversal strain derived from short- and long-axis planes. 2D-STE has been
proved to disclose dyssynchrony not otherwise detected by longitudinal TDE and to offer an insight into rotational mechanics. Recently, 3D-STE
based on a pyramidal 3D data set has been introduced, improving information by avoiding loss of speckles. Left ventricular dyssynchrony,
determination of volumes, ejection fraction, and any form of myocardial disease are of clinical interest. Myocardial mechanics such as rotation,
twist, and torsion can be displayed in 3D to define early-stage myocardial dysfunction, even in patients with normal ejection fraction.
Keywords
Speckle tracking, strain imaging, 3D echocardiography, myocardial mechanics, left ventricular dyssynchrony, ischemic heart disease
Disclosure: The author has no conflicts of interest to declare.
Received: December 1, 2008 Accepted: January 16, 2009
Correspondence: Hans Joachim Nesser, MD, Director, 2nd Department of Medicine, Elisabethinen Teaching Hospital, University of Vienna and Innsbruck, A-4020 Linz, Fadingerstraße,
Austria. E:
hans-joachim.nesser@elisabethinen.or.at
Tissue Doppler-based measurements of myocardial strain are possible tissue Doppler imaging and particularly velocity imaging have been
and accurate for structures that move along the ultrasound beam, but are used widely to predict response to cardiac resynchronization therapy
underestimated in other directions and even impossible for angles close (CRT), angle dependency, noise, artifacts, tethering, and myocardial
to 90º. To overcome these limitations, the speckle tracking technique was translation are known to affect the reproducibility of these
introduced in 2004, offering a more user-friendly workflow and better measurements and may in part explain the relatively high rate of
reproducibility.
1
This echocardiographic technique is based on frame-by- non-responders to CRT among patients referred using this technique as
frame tracking of ultrasound speckles as the natural acoustic markers a criterion for referral. In contrast, the ability of 2D radial speckle
within the image. By tracking these speckles at frame rates varying from tracking to predict the increase in stroke volume after CRT has been
40 to 150 frames/s
-1
, 2D tissue velocity and displacement can be demonstrated, and this technique is accepted as a robust and highly
accurately calculated over time, irrespective of the direction of motion. sensitive and specific technique.
4
2D speckle tracking is also able to
Furthermore, myocardial strain can be determined from the displacement detect radial dyssynchrony in patients with apical dysfunction not
of speckles in relation to each other, providing an angle-independent otherwise detected by routine longitudinal tissue Doppler. The
parameter of regional myocardial function. To obtain this information, the superiority of 2D speckle tracking, particularly based on radial strain
left ventricular myocardium is first traced using the click-to-point rather than longitudinal tissue Doppler findings, may be related to a
approach on the end-systolic frame, followed by automated definition of better tracking algorithm in the short-axis view than in longitudinal
an epicardial and mid-myocardial line. Whereas apical planes are used to images obtained from apical windows.
depict longitudinal and transversal strain, the parasternal short-axis views
allow the differentiation of circumferential and radial strain. Velocity Furthermore, 2D speckle tracking has also been used to assess left atrial
vector imaging is another technique based on speckle tracking, whereby (LA) function in patients with either idiopathic or ischemic dilated
the vector length depicts the amount of strain and the direction of vectors cardiomyopathy.
5
Analysis of atrial longitudinal strain in the basal
represents the direction in which tissue is moving. segment of the LA septum, the LA lateral wall, and the LA roof showed
that peak systolic myocardial strain was significantly compromised in
Clinical applications of speckle tracking include the evaluation of patients with idiopathic dilated cardiomyopathy (DCMP) versus ischemic
ischemic heart disease and left ventricular dyssynchrony.
1–3
Although CMP in all analysed atrial segments (p<0.001).
24 © TOUCH BRIEFINGS 2009
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