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Deformation Measurements by Echocardiography versus LE MRI in Patients with CAD


Although strain and strain rate measurements by tissue Doppler are one-dimensional and angle-dependent, they can give important pathophysiological, diagnostic and prognostic information,24,25 especially about timing, as tissue Doppler has a high frame rate and timing is an angle-independent measurement. With speckle tracking, the different deformation components can be approximated, and this has led to a search for ‘the most sensitive direction’. From basic studies in ischaemia, we know that the different myocardial layers are tightly connected. This suggests that the accuracy of the measurement is more important than the direction in which we measure.26


In a recent paper, Becker et al.16 suggested that endocardial


circumferential strain was more powerful than subepicardial measurements for predicting recovery of function after revascularisation. In a review of their experimental work with ultrasonic crystals and ischaemia, Hexeberg et al. explain why deformation in one myocardial layer can not be interpreted as representative of function in that layer.26


LV geometry can explain why


endocardial deformation is larger than epicardial deformation, and consequently that endocardial changes will be numerically larger in states of reduced function in any wall layer. In light of this, one alternative interpretation of the results from Becker et al. is that inward endocardial motion can be evaluated precisely in short-axis recordings using a speckle-tracking algorithm.


Two-dimensional deformation measurements are sensitive to image positioning, and apical foreshortening is a major source of error. Three-dimensional recordings could eliminate this and should theoretically improve reproducibility. The development of 3D echocardiography has been followed by new methods of quantifying myocardial strain in such recordings. However, as the resolution, both spatially and temporally, is significantly lower in 3D compared with 2D, the need for mathematical models and smoothing has increased, as has the gap between the developing technologist and the applying cardiologist. Furthermore, patients in which the assessment of regional function and viability might be important tend to have large left ventricles, requiring large scanning sectors. This will further reduce spatial resolution and the likelihood of adequate deformation measurements. We can expect technological improvements, but a close collaboration between technologists and cardiologists is necessary to ensure that developments are going in the right direction.


Although deformation measurements by 3D echocardiography have clear limitations, the development of scanners and probes for 3D imaging has yielded technical advances that also benefit other applications. We have recently shown that frame rate in 2D tissue Doppler imaging can approach 1,000 images/second when applying


1. Ingul CB, Malm S, Refsdal E, et al., Recovery of function after acute myocardial infarction evaluated by tissue Doppler strain and strain rate, J Am Soc Echocardiogr, 2010;23:432–8.


2. Task Force on Myocardial Revascularization of the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS), European Association for Percutaneous Cardiovascular Interventions (EAPCI), Wijns W, Kolh P, Danchin N, et al., Guidelines on myocardial revascularization, Eur Heart J, 2010;31:2501–55.


3. Heimdal A, Støylen A, Torp H, Skjaerpe T, Real-time strain rate imaging of the left ventricle by ultrasound, J Am Soc Echocardiogr, 1998;11:1013–9.


4. Ferferieva V, Van den Bergh A, Claus P, et al., The relative value of strain and strain rate for defining intrinsic myocardial function, Am J Physiol Heart Circ Physiol, 2012;302:H188–95.


5. Asbjørn Støylen, Norwegian University of Science and Technology, Strain rate imaging, Cardiac deformation imaging by ultrasound/echocardiography, Tissue Doppler and


3D scanning technology, and this might allow us to resolve myocardial deformation patterns even better.27


resulted in new tools that are highly applicable and informative in a bedside setting.28


Late Enhancement Magnetic Resonance Imaging Although the sensitivity and reproducibility of LE MRI seem superior to those of echocardiography, LE MRI has some important limitations. First, the cut-off value for prediction of viability, defined as functional response to revascularisation, is not defined. The initial landmark study by Kim et al. showed a gradual decreasing likelihood of response to revascularisation with increasing segmental infarct transmurality.20


In the large group of segments with 25–75 % infarction, the prediction of recovery was not very accurate. Second, although image quality is very good in general, the grading of segmental infarction can be challenging, especially in short-axis slices near the apex, due to partial volume effects. Assessment using both short- and long-axis images is an advantage. Third, as mentioned above, the infarct size relative to LV mass decreases with time after an infarction. This suggests that cut-off values for viability might need adjustment over time. Finally, there is no consensus on pixel intensity cut-off for defining infarction relative to normal myocardium.29


In clinical practice, LE MRI should always be evaluated in combination with the MRI cine images. Wall thickness, which is also a well-known predictor of response to revascularisation, can be accurately measured, but wall thickening can be difficult to quantify due to the effects of trabeculae that are merging in end-systole. More advanced methods for quantifying deformation, such as tagging and strain encoded MRI (SENC) have been available for quite some time and seem promising, but temporal resolution is still somewhat lower than in echocardiography.30


Future Perspectives


Echocardiography, with its versatility of methods and high applicability, will continue to be the workhorse in cardiac imaging of patients with CAD. We should be aware of the additional information we could get from deformation methods, especially due to the high temporal resolution in tissue Doppler. Deformation measurements in 3D images are still limited by the lower resolution compared with 2D but will continue to improve. The standardisation of image analysis and the collaboration within the echocardiographic community to conduct larger studies will be important tasks in the attempt to establish evidence for the new methods. LE MRI is a method with unique properties and will continue to be an important alternative in selected patients and settings, as well as an invaluable research tool. n


Speckle tracking, 2011. Available at:


http://folk.ntnu.no/stoylen/strainrate/ (accessed 2 April 2012).


6. Amundsen BH, Helle-Valle T, Edvardsen T, et al., Noninvasive myocardial strain measurement by speckle tracking echocardiography: validation against sonomicrometry and tagged magnetic resonance imaging, J Am Coll Cardiol, 2006;47:789–93.


7. Hayat D, Kloeckner M, Nahum J, et al., Comparison of real-time three-dimensional speckle tracking to magnetic resonance imaging in patients with coronary heart disease, Am J Cardiol, 2012;109:180–6.


8. Van de Werf F, Bax J, Betriu A, et al., ESC Committee for Practice Guidelines (CPG), Management of acute myocardial infarction in patients presenting with persistent ST-segment elevation: the Task Force on the Management of ST-Segment Elevation Acute Myocardial Infarction of the European Society of Cardiology, Eur Heart J, 2008;29:2909–45.


9. Stanton T, Leano R, Marwick TH, Prediction of all-cause


mortality from global longitudinal speckle strain: comparison with ejection fraction and wall motion scoring, Circ Cardiovasc Imaging, 2009;2:356–64.


10. Sveälv BG, Olofsson EL, Andersson B, Ventricular long-axis function is of major importance for long-term survival in patients with heart failure, Heart, 2008;94:284–9.


11. Vartdal T, Brunvand H, Pettersen E, et al., Early prediction of infarct size by strain Doppler echocardiography after coronary reperfusion, J Am Coll Cardiol, 2007;49:1715–21.


12. Eek C, Grenne B, Brunvand H, et al., Strain echocardiography and wall motion score index predicts final infarct size in patients with non-ST-segment-elevation myocardial infarction, Circ Cardiovasc Imaging, 2010;3:187–94.


13. Grenne B, Eek C, Sjøli B, et al., Acute coronary occlusion in non-ST-elevation acute coronary syndrome: outcome and early identification by strain echocardiography, Heart, 2010;96:1550–6.


14. Wijns W, Vatner SF, Camici PG, Hibernating myocardium, N Engl J Med, 1998;339:173–81.


EUROPEAN CARDIOLOGY 103


Additionally, miniaturisation has


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