2022 Volume 86 Issue 4 Pages 620-621
Echocardiography is used to assess cardiac function and hemodynamics, as well as the cause, pathophysiology, and severity of heart failure (HF). Furthermore, the JCS 2017/JHFS 2017 Guideline on diagnosis and treatment of acute and chronic heart failure recommends repeat echocardiography for the assessment of patients with a change in their clinical condition of HF as a Class I recommendation and Level C evidence.1 Thus, echocardiography can play a pivotal role in the quantification and early detection of left ventricular (LV) structural changes. Global longitudinal strain (GLS) as assessed by 2D speckle-tracking echocardiography has been recently reported to be a sensitive marker of early subtle abnormalities of LV myocardial performance. It is claimed to be helpful for the prediction of outcomes for various cardiac diseases, and superior to conventional echocardiographic indices such as LV ejection fraction, mitral inflow E and mitral e’ annular velocities ratio.2–4 Currently, GLS by means of 2D speckle-tracking is recommended for the early diagnosis of HF,1 the differentiation of cardiac amyloidosis from other causes of cardiac hypertrophy, prognostication,5 and early detection of cardiotoxicity in patients who are scheduled to undergo chemotherapy and thus prevent progression to later HF.6
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Although 2D speckle-tracking is clinically useful, it is restricted to the assessment of LV function in a single plane. Moreover, each segment must be evaluated sequentially and thus is subject to beat-to-beat variability. A more recent quantitative approach to overcoming these limitations is a newly developed 3D speckle-tracking echocardiography system. 3D speckle-tracking provides a more comprehensive evaluation of LV mechanics from pyramidal 3D datasets than was previously possible. The 3D cine loops of regional strain are color-coded and divided into 16 segments for time-strain curves, polar maps, and 3D displays.
In this issue of the Journal, Iwahashi et al7 report their investigation of the clinical significance of serial examination by 3D speckle-tracking echocardiography of 272 patients with first-time ST-elevation acute myocardial infarction (STEMI). The main findings of their study were that GLS obtained by both 2D and 3D speckle-tracking at 1-year indices proved to be a significant predictor of major adverse cardiac events using receiver operating characteristics curves and Cox hazard multivariate analysis. Moreover, they demonstrate that GLS obtained by 3D speckle-tracking at 1 year after reperfusion therapy can be the strongest predictor of the patient’s 10-year prognosis after STEMI, and GLS by means of 2D speckle-tracking was the second strongest. These findings suggest evaluation of cardiac function using serial strain imaging after the onset of STEMI, especially GLS by means of 3D speckle-tracking, is beneficial.
A major limitation of image acquisition using current 3D speckle-tracking systems is the relatively slow temporal resolution, with typical frame rates of 20–25 volumes/s. Sequential volume acquisition, which currently requires more than 4 sequential beats, is vulnerable to motion artifacts if the patient is unable to fully meet the requirements of a proper breath hold. These are practical limitations for assessment of ischemic disease and stress echocardiography, where temporal resolution and breath holding become more challenging. Furthermore, the spatial resolution and image quality of 3D images are currently not as good as those of 2D imaging because of the technological requirements for 3D imaging (Table). In addition, reproducibility of GLS obtained by 3D speckle-tracking in the study by Iwahashi et al was merely acceptable because it showed a bias of 0.110, as calculated by 2 experienced observers, with 95% limits of agreement ranging from −0.588 to −0.128.7 This is a particular concern regarding the reproducibility of parameters by means of 3D speckle-tracking. On the other hand, GLS obtained by 2D speckle-tracking echocardiography is well known to be highly reproducible.8 Despite these limitations, 3D speckle-tracking systems have exceeded expectations, because of the advantages that a 3D data set can offer. This accounts for recent revisions of both hardware and software that have resulted in marked improvements in spatial resolution and 3D image quality. Moreover, we can expect technical advances in computer technology in the near future that will likely result in further improvements in both the spatial and temporal resolution of 3D myocardial tracking systems.
| GLS by 3D speckle-tracking | GLS by 2D speckle-tracking |
|---|---|
| Advantages | |
| Simultaneous comprehensive evaluation of all left ventricular segments in a single beat |
Easy-to-use image acquisition and measurement |
| Availability of 3D cine loops with color-coding of regional strain |
Acceptable reproducibility |
| Guidelines for use in early diagnosis of heart failure, differentiation of cardiac amyloidosis from other causes of cardiac hypertrophy. Also for prognosis, and early detection of cardiotoxicity in patients scheduled to undergo chemotherapy |
|
| Disadvantages | |
| Relatively slow temporal resolution | Restricted to assessment of left ventricular segments in a single beat |
| Relatively complex image acquisition | |
| Unknown reproducibility | |
| Only available in centers with experienced personnel | |
| No guidelines for use in clinical settings | |
The emergence of new echocardiographic myocardial tracking systems utilizing 3D speckle-tracking strain has generated a great deal of excitement and enthusiastic expectations for their future clinical applications. 3D speckle-tracking GLS has provided a new insight into the potential applications of LV mechanics. As is true for many new technical advances, more time is needed to determine the precise role of 3D myocardial tracking in routine clinical practice. However, the initial experience has been sufficiently gratifying to warrant anticipation of a strong future role in patient care.
H.T. is a consultant for AstraZeneca plc and Ono Pharmaceutical Company, Limited.
