Contrast echocardiography has been spe-cifically used for image definition and per-fusion studies. Efforts were subsequently made to quantitatively analyse regional myocardial performance. In late 1992, the first software and prototype of colour Dop-pler velocity display of the myocardial wall dynamics was developed. To date, tissue Doppler imaging is available in routine echo-lab for assessing regional systolic and diastolic function. To overcome the limitations of tissue Doppler derived myo-cardial velocities, companies have intro-duced many breakthrough quantitative ultrasound tools based on leading-edge technologies, such as speckle tracking of myocardial deformation. Advances in microprocessor technology and computa-tional power and the development of new matrix transducers using dense arrays have recently provided the potential for real-time, 3/4 D imaging. The concept of min-iaturisation has made possible to provide echocardiography anywhere or to perform echocardiograms for imaging the heart of small animals as mice and rats.

Tissue Doppler imaging and 2D speckle tracking

Evaluation of left ventricular function is an essential part of all echocardiographic examinations [2]. Tissue Doppler imaging (velocity, strain) was introduced to provide precise quantitative measurement of re-gional wall motion and function.

Tissue Doppler uses the same principles as blood flow Doppler imaging, applying standard auto-correlation processing but reversing high velocity and low amplitude filters such that the high amplitude/low velocity motion of tissue is displayed in preference to blood flow (Figure 1). Appli-cations include studies of regional systolic and diastolic function as well the timing of regional contraction. However, Doppler-only-based techniques are limited due to angle dependence of the signal [3]. As a re-sult, certain myocardial areas are excluded. To overcome such a limitation, companies have created new software that allows the analysis of myocardial deformation through tracking of “natural acoustic markers” for frame-to-frame within the cardiac cycle.

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Echocardiography: An Old Technique That Has Never Stopped Evolving

Patrizio Lancellotti, MD, PhD & Kim O’Connor, MDUniversity Hospital, CHU Sart TilmanReceived 5/3/2009, reviewed 29/3/2009, accepted 7/4/2009DOI:10.5083/ecdcip.17560993.09

ECHOCARDIOGRAPHY

CORRESPONDENCE Prof. Patrizio LancellottiDepartment of Cardiology, University Hospital,CHU Sart TilmanB - 4000 LIEGE, BELGIUM

Tel: + 32.4.366.71.94Fax: + 32.4.366.71.95

ISSN 1756-0993

INTRODUCTION

In the early 1950s, Edgler and Hertz described for the first time the use of ultrasound for assessing mitral valve movement [1]. Since this landmark event, many discoveries have been made in the field of echo-cardiography that are presently used in daily practice. M-mode echocardiography was supplemented by 2D echocardiography in the mid 1960s, with the important additions of Doppler signals (1970s) and the combination of colour Doppler (1980s) with 2D imaging. In the late 1980s, the transesophageal approach completed the armamentarium of echocardiography. With the help of engineers, transesophageal echocardiography quickly evolved from monoplane to biplane to present-day multiplane imaging. In parallel to the developments in transducer technology, image quality was consistently improved by using native second harmonic imaging and contrast agent.

EUROPEAN CARDIOVASCULAR DISEASE: CLINICAL INSIGHTS AND PRACTICE VOL I ISSUE II | SPRING 2009

Figure 1: Top, color tissue Doppler imaging. Bottom, assessment of myocardial velocities.

This approach uses common gray scale images and provides information regarding the three components of myocardial deformation (radial, longitudinal, circumferential). It is angle independent. The main limitation relates to image quality. As with MRI tagging, this technique could display bull’s-eye parametric images of the peak systolic deformation. 2D-speckle tracking is probably the most exciting development in cardiac ultrasound for the evaluation of ventricular func-tion in years (Figure 2).

It has now gained growing acceptance as a clinical tool particularly in the setting of ischaemic heart disease, stress echocardiography, diastolic function analysis, cardiomyopa-thy, and cardiac resynchronisation imaging [4-7]. It provides the unique opportunity to deeply examine the cardiac tor-sion and the twisting heart movement. 2D strain may thus be used as an alternative to MRI in the measurement of LV torsion. Efforts of engineers to miniaturise the probes has made possible to imaging small animals’ heart. New tech-nologies can also be applied in those which have opened the door of examining the effects of stem-cells therapy on regional function.

Figure 2: 2D speckle tracking analysis of regional myocardial deformation. Arrows display the time delay between the peak strain of the septal and lateral walls.

Contrast echocardiography

Ultrasound contrast agents have been used in clinical echo-cardiography since mid 1970s. Second generation of contrast agents usually consist of very small gas microspheres [8,9]. As they resonate when exposed to an ultrasound field with the appropriate acoustic pressure, they generate harmonics not shown in tissue allowing separating contrast from surround-ing tissue. This makes it easier to detect and image the con-trast agent within tissues and the cardiac chambers.

When administered from a peripheral vein, they pass the pulmonary vascular bed relatively unimpeded and appear in the left ventricular cavity resulting in enhanced visualisation of the left ventricular border. Finally, the distribution of con-trast agent in the myocardium provides an estimate of myo-cardial blood flow. It can thus be used as a marker of normal and abnormal perfusion. Currently, contrast echocardiogra-phy is used primarily for improved border delineation, shunt detection and Doppler enhancement, and in a research set-ting, for perfusion imaging of the myocardium (Figure 3).

Furthermore, new therapeutic applications using micro-bubbles and ultrasound are expected. Thus, new ultrasound technologies in combination with pharmaceutical and mo-lecular agents will create new opportunities for therapeutic ultrasound. Indeed, contrast agents could serve as vehicles for the delivery of therapeutic agents, including gene ther-apy or drugs, to patients. The ability of ultrasound to burst contrast “bubbles” will allow localised drug delivery, without significant systemic effects.

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ECHOCARDIOGRAPHY: AN OLD TECHNIQUE THAT HAS NEVER STOPPED EVOLVING

EUROPEAN CARDIOVASCULAR DISEASE: CLINICAL INSIGHTS AND PRACTICE VOL I ISSUE II | SPRING 2009

Figure 4: Assessment of left ventricular volumes by 3D echocardiography.

Indeed, 3D echocardiography makes no assumptions about the left ventricular shape and avoids foreshortened views re-sulting in a similar accuracy with cardiac MRI regarding the assessment of left ventricular mass and volumes. Thus, 3D echocardiography permits a better evaluation of the ben-eficial effects of therapy on left ventricular function [9]. This 3D technology is also particularly suited to imaging the right ventricle, a geometrically complicated chamber of the heart that has been relatively poorly evaluated with 2D methods.Another area where real-time 3D echocardiography is of in-terest is the evaluation of cardiac masses.

In mitral valve stenosis, real-time 3D echocardiography is more accurate than other non-invasive modalities in mea-suring the mitral valve area [10].The difficulty with 2D echo-cardiography is in fact to visualise epicardial border. Data obtained with 3D echocardiography are similar to those obtained with MRI. Real-time 3D echocardiography is also of great importance in visualisation of heart valves, particularly the mitral and aortic valves (Figure 5).

It can give a surgical view (en face view), providing surgeons planning to repair a valve with images very similar to what they will see at the time of surgery. In degenerative mitral regurgitation, real 3D echocardiography offers approxi-mately the same accuracy as multiplane transesophageal to diagnose which scallops are involved in the disease process. It can also precisely measure the size of the valve orifices.

In aortic stenosis, the aortic valve area is measured as precise as with the Doppler method. Real-time 3D echocar-diography also provides an accurate description of various congenital heart diseases, as well as shunts and valve pathol-ogy. Foetal 3D echocardiography is now available. Finally, 3D echocardiography is also particularly useful in the evaluation of cardiac dyssynchrony (Figure 6). Measuring the degree of LV dyssynchrony is useful in helping define which patients with heart failure will benefit from a cardiac resynchronisa-tion therapy [11].

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Figure 3: Left, Left ventricular (LV) opacification by contrast administration. Right, defect of myocardial perfusion (arrows)in the lateral wall.

Real time 3-dimensional imaging

3D echocardiography has been introduced more than 15 years ago. Over the past 2–3 years, 3D echocardiography has evolved from cumbersome reconstruction of multiple cross sectional 2D images to real-time volumetric imaging. Indeed, the newer generations of matrix-array transducers are able to capture pyramidal volumetric datasets (30° x 60°) that can be rendered immediately to provide viewing and rapid interpretation.

This approach is classically used to visualise cardiac and valve morphology. To obtain an entire volume dataset (90° x 90°), four sequential cardiac cycles are typically captured and added to create a complete volume of information. By sectioning or cropping away parts of the dataset, it is pos-sible to see inside the heart and the anatomic orientation and motion of intracardiac structures.

Real time 3D colour Doppler echocardiography has been re-cently introduced. It may lead to more precise quantification of valvular regurgitations. The recent advances in computer processing and transducer construction techniques have made that an entire 3D dataset can be acquired in one car-diac cycle. This last generation of 3/4D echocardiographic imaging brings us true real-time, full 3D volume rendering and artifact-free depictions of the entire heart. 3/4D echo-cardiography eliminates the manual cropping and cutting of conventional 3D workflow, a time consuming process.

There are already several clinical areas where the images pro-vided by real-time 3D echocardiography are already making a difference. The most important is probably the ability to quantify the function and structure of the heart in an easier, faster and more accurate way than conventional 2D echocar-diography (Figure 4).

HEALTHCARE BULLETIN | ECHOCARDIOGRAPHY

EUROPEAN CARDIOVASCULAR DISEASE: CLINICAL INSIGHTS AND PRACTICE VOL I ISSUE II | SPRING 2009

Figure 5: Assessment of mitral (top) and aortic (bottom) valve morphology by 3D echocardiography.

Figure 6: Assessment of left ventricular dyssynchrony by 3D echocardiography.

CONCLUSIONS

With more than 25 million echocardiograms performed annually worldwide, echocardiography is going to remain the leading diagnostic modality in the field of cardiology. Echocardiography has several characteristics that are unmatched by other noninvasive techniques. Indeed, this technology is harmless and combines low-cost high- technology with easy accessibility. It provides rapid quantitative information about cardiac structure and function at the bedside.

Recent technological advances have resulted in the devel-opment of sophisticated breakthrough tools that further refine the ability of echocardiography as a diagnostic modality as well as a guiding technique for various inter-ventions. Echocardiography is a still evolving technique and new transducer technologies would change the cardiolo-gist’s vision drastically. The future of this technique promises to be as productive and exciting as it has been in the previous three decades.

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Kirkpatrick JN, Lang RM. Insights into myocardial mechanics in normal and pathologic states using newer echocardiographictechniques. Curr Heart Fail Rep 2008;5:143-50.

Pavlopoulos H, Nihoyannopoulos P. Strain and strain rate deformation parameters: from tissue Doppler to 2D speckle tracking. Int J Cardiovasc Imaging 2008;24:479-91.

Serri K, Reant P, Lafitte M, Berhouet M, Le Bouffos V, Roudaut R, Lafitte S. Global and regional myocardial function quantification by two-dimensional strain: application in hypertrophic cardiomyopathy. J Am Coll Cardiol 2006;47:1175-81.

O’Connor K, Sénéchal M, Lancellotti P, Dubois M, Magne J, Champagne J, Philippon F, Pierard L, O’Hara G. Usefulness of cardiac resynchronisation therapy in patients with right bundle branch block: Is viability an important piece of the puzzle? Int J Cardiol. 2009 Jan 23. [Epub ahead of print]

Lancellotti P, Cosyns B, Zacharakis D, Attena E, Van Camp G, Gach O, Radermecker M, Piérard LA. Importance of left ventricular longitudinal function and functional reserve in patients with degenerative mitral regurgitation: assessment by two-dimensional speckle tracking. J Am Soc Echocardiogr 2008;21:1331-6.

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Dwivedi G, Janardhanan R, Hayat SA, Lim TK, Greaves K, Senior R. Relationship between myocardial perfusion with myocardial contrast echocardiography and function early after acute myocardial infarction for the prediction of late recovery of function. Int J Cardiol 2008 Dec 14. [Epub ahead of print].

Kühl HP, Schreckenberg M, Rulands D, Katoh M, Schäfer W, Schummers G, Bücker A, Hanrath P, Franke A. High-resolution transthoracic real-time three-dimensional echocardiography: quantitation of cardiac volumes and function using semi-automatic border detection and comparison with cardiac magnetic resonance imaging. J Am Coll Cardiol. 2004 Jun 2;43(11):2083-90.

Zamorano J, Cordeiro P, Sugeng L, Perez de Isla L, Weinert L, Macaya C, Rodríguez E, Lang RM. Real-time three-dimensional echocardiography for rheumatic mitral valve stenosis evaluation: an accurate and novel approach. J Am Coll Cardiol 2004;43:2091-6.

Monaghan M. Echocardiographic assessment of left ventricular dyssynchrony-is three-dimensional echocardiography just the latest kid on the block? J Am Soc Echocardiogr 2009;22:240-241.

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ECHOCARDIOGRAPHY: AN OLD TECHNIQUE THAT HAS NEVER STOPPED EVOLVING

EUROPEAN CARDIOVASCULAR DISEASE: CLINICAL INSIGHTS AND PRACTICE VOL I ISSUE II | SPRING 2009