Tissue Doppler and innovative myocardial-deformation imaging techniques for assessment of myocardial viability

PURPOSE OF REVIEW: Visual analysis of stress echocardiography allows evaluation of myocardial viability in acutely and chronically impaired left-ventricular function. Tissue Doppler and derived echocardiographic imaging techniques provide a tool for quantification of regional left-ventricular function which overcomes the limitations of subjective, experience-dependent reading of stress echocardiography. RECENT FINDINGS: Regional systolic and diastolic myocardial velocities as well as the derived myocardial-deformation parameters strain and strain rate are impaired in patients with left-ventricular dysfunction. Increase of myocardial velocities, strain and strain rate during stress stimulation are indicators of functional reserve in viable segments, while failure to increase indicates nonviability. Previous studies with very precise determination of regional myocardial deformation have shown that even analysis of resting function without evaluation of the functional reserve during stimulation allows assessment of myocardial viability. New two-dimensional echocardiography-based tissue-tracking techniques yield an angle-independent imaging modality that is likely to further improve the clinical applicability of echocardiographic imaging techniques to define regional myocardial viability. SUMMARY: This review attempts to define the role of tissue Doppler and new innovative myocardial-deformation imaging techniques for identification of myocardial viability in patients with impaired left-ventricular function.     

New echocardiographic techniques in the study of coronary artery disease: strain and strain rate]

Strain/strain rate are a new echocardiographic technique able to quantify regional myocardial deformation. Since myocardial velocity, obtained by standard tissue Doppler, is affected by global heart motion, cardiac rotation and influence from velocities in other segments, strain/strain rate have been introduced to measure regional shortening fraction and shortening rate, respectively. The present review discusses the most recent developments in the application of strain/strain rate in coronary artery disease.     

Echocardiographic assessment of myocardial strain

Echocardiographic strain imaging, also known as deformation imaging, has been developed as a means to objectively quantify regional myocardial function. First introduced as post-processing of tissue Doppler imaging velocity converted to strain and strain rate, strain imaging has more recently also been derived from digital speckle tracking analysis. Strain imaging has been used to gain greater understanding into the pathophysiology of cardiac ischemia and infarction, primary diseases of the myocardium, and the effects of valvular disease on myocardial function, and to advance our understanding of diastolic function. Strain imaging has also been used to quantify abnormalities in the timing of mechanical activation for heart failure patients undergoing cardiac resynchronization pacing therapy. Further advances, such as 3-dimensional speckle tracking strain imaging, have emerged to provide even greater insight. Strain imaging has become established as a robust research tool and has great potential to play many roles in routine clinical practice to advance the care of the cardiovascular patient. This perspective reviews the physiology of myocardial strain, the technical features of strain imaging using tissue Doppler imaging and speckle tracking, their strengths and weaknesses, and the state-of-the-art present and potential future clinical applications.     

Strain and strain rate. New and clinically relevant echo parameters of regional myocardial function

Strain (deformation) and strain rate (velocity of deformation) are parameters of regional myocardial function which can be calculated at the bedside from tissue Doppler echocardiographic data. These parameters are less image quality dependent and less subjective than visual assessment of endocardial border motion, and they track myocardial deformation with a considerably higher time resolution than magnetic resonance imaging. Thus, the technique can document short-lived subtle changes in deformation patterns, such as post-systolic shortening/thickening. The ability to detect regional myocardial ischemia and viability has been confirmed in animal experiments and clinical studies. The technique has also been used to detect early cardiomyopathy and to differentiate physiologic and pathologic myocardial hypertrophy, as well as to identify regional dyssynchrony in candidates for resynchronization therapy. Applications in heart transplantation, right ventricular disease and valvular heart disease are under evaluation. Thus, strain and strain rate data offer a new window on regional myocardial function and may, in the future, become an integral part of echocardiographic evaluation.     

Comparison of left ventricular function by tissue Doppler imaging in patients with diabetes mellitus without systemic hypertension versus diabetes mellitus with systemic hypertension

Because diabetes mellitus substantially increases the risk of development of heart failure, we sought to establish early alterations in left ventricular systolic and diastolic function in patients with diabetes mellitus with and without coexisting systemic hypertension. We studied 134 subjects using echocardiography comprising standard 2-dimensional and conventional Doppler as well as tissue Doppler imaging. Our study demonstrated the early appearance of both left ventricular systolic and diastolic dysfunction in diabetic patients at rest and the contributory effects of diabetes to myocardial impairment produced by hypertension, as well as the high usefulness of tissue Doppler imaging in detection and quantitation of myocardial dysfunction in diabetics. This method was superior to other echocardiographic techniques and plasma brain natriuretic peptide evaluation.     

Evidence of impaired left ventricular systolic function by Doppler myocardial imaging in patients with systemic amyloidosis and no evidence of cardiac involvement by standard two-dimensional and Doppler echocardiography

We examined the potential role of Doppler myocardial imaging for early detection of systolic dysfunction in patients with systemic amyloidosis (AL) but without evidence of cardiac involvement by standard echocardiography. We identified 42 patients without 2-dimensional echocardiographic or Doppler evidence of cardiac involvement. These patients had normal ventricular wall thickness and normal velocity of the medial mitral annulus. Myocardial images were obtained in these patients and in 32 age- and gender-matched healthy controls. Peak longitudinal systolic tissue velocity (sTVI), systolic strain rate (sSR), and systolic strain (sS) were determined for 16 left ventricular segments. Radial and circumferential sSR and sS were also measured. Compared with controls in this group of patients with AL, peak longitudinal sSR (-1.0 +/- 0.2 vs -1.4 +/- 0.2, p <0.001) and peak longitudinal sS (-15.6 +/- 3.3 vs -22.5 +/- 2.0 p <0.001) were significantly decreased. In conclusion, the mean sS from all 6 basal segments, or from all 16 left ventricular segments differentiated patients with AL with normal echocardiography from controls, with similar accuracy for the mean sSR from the 6 basal segments. This distinction was not apparent from peak longitudinal sTVI or from radial or circumferential sSI or sSR.     

Detection of early systolic dysfunction with strain rate imaging in a patient with light chain cardiomyopathy

Congestive heart failure (CHF) in cardiac amyloidosis has been attributed to the development of diastolic dysfunction, because severe CHF symptoms have been observed despite a normal or only mildly reduced LV ejection fraction (EF). An early impairment of longitudinal systolic function has been described by means of tissue Doppler-derived myocardial deformation imaging ('strain rate imaging', SRI).Our patient presented with signs of CHF and significantly increased brain-natriuretic peptide (BNP) levels. Conventional measures of systolic contractile function were within the normal range and mitral inflow Doppler showed only moderate diastolic dysfunction. Histopathological examination by endomyocardial biopsy revealed interstitial deposition of amyloid fibers. Quantitative assessment of myocardial velocities (TDI) and deformation properties (Strain) from the apical view demonstrated a significant impairement of systolic longitudinal myocardial function.In patients with isolated diastolic dysfunction detected by conventional Doppler echocardiography, the quantitative assessment of myocardial strain and strain rate can be helpful in the early detection of systolic dysfunction.     

Three-dimensional speckle-tracking echocardiography: methodological aspects and clinical potential

Speckle-tracking echocardiography (STE) is an advanced echocardiographic technique that allows a novel approach to the assessment of cardiac physiology through the study of myocardial mechanics. In its three-dimensional (3D) modality, it overcomes the drawbacks inherent to other echocardiographic techniques, namely two-dimensional echocardiography and tissue Doppler imaging. Several research studies and software improvements have led 3D-STE to become a promising tool for accurate evaluation of global and regional cardiac function. This article addresses the image acquisition, analytical methods, and parameters of myocardial mechanics that could be derived from 3D-STE. This systematic guidance may help to establish its usefulness in the global and regional evaluation of cardiac function, and to facilitate its clinical application.     

Right ventricular function assessed by two-dimensional strain and tissue Doppler echocardiography in patients with pulmonary arterial hypertension and effect of vasodilator therapy

Two-dimensional strain echocardiography is a new method for the assessment of regional contractility. Thirty-seven patients with pulmonary arterial hypertension (mean age 56.4 +/- 11 years) and 38 normal subjects (mean age 58.3 +/- 12 years) underwent 2-dimensional echocardiography and tissue Doppler echocardiographic evaluation of right ventricular (RV) global function and regional contractility. Patients with pulmonary arterial hypertension additionally underwent 6-minute walking distance tests and right-sided cardiac catheterization before and after (8 +/- 3 months) vasodilator therapy. Moderate or severe RV dysfunction was present in all patients (2-dimensional strain of the basal segment of the RV free wall: -8.8 +/- 4.1% systolic longitudinal deformation) compared with normal subjects (-24.3 +/- 4.7% systolic longitudinal deformation, p < 0.001) and was improved with vasodilator therapy after 6 to 11 months (-13.3 +/- 6.2% systolic longitudinal deformation, p < 0.001).     

Principles and clinical applications of strain imaging

M-Mode echocardiography, 2-D grey scale imaging and standard Doppler that constitute conventional echocardiography has been used for over many decades now. Although these modalities form the backbone in routine clinical echocardiography, its inability to objectively quantify left ventricular function at regional and global levels as well as its loading and heart rate dependency make conventional echocardiography an incomplete tool in clinical situations. Tissue Doppler imaging (which includes myocardial velocity, displacement and strain) has been successfully used in a variety of clinical situations, from investigations of diastolic function to implantation of bi-ventricular pacing for cardiac resynchronization therapy and even in preclinical diagnosis of genetic diseases such as hypertrophic cardiomyopathy. Strain imaging has been found to be superior to velocity in a variety of clinical conditions and enables us to quantify deformation as a measurable number in terms of regional myocardial deformation. Strain and strain rate have to be assessed together since they provide complementary information somewhat analogous to ejection fraction and contraction. This article has tried to simplify its principles, understand its limitations and know its utility to ensure having a better knowledge of this promising tool before one starts to actively use it. In this review, focus has been made on the physical, technical and also clinical aspects of strain imaging. In the new world of multi-modality imaging, cardiac magnetic resonance imaging (CMR) and nuclear perfusion scintigraphy (NPS) are the competitors of echocardiography, but it would be of interest to note that even these modalities are also adapting concepts of strain imaging (in CMR) and left ventricular synchronicity (in NPS). This only emphasizes the role of advanced echocardiography as a more economical and stand-alone modality visa vis the other two related technologies. The sooner we adapt to these advanced applications, stronger would be the ground to resolve technical and clinical issues. Strain imaging in its present form cannot win the game alone in this era of multi-modality imaging, but it is almost certain that with continued advancement, tissue Doppler and speckle tracking echocardiography based strain could play a pivotal role in a variety of clinical situations providing much needed incremental information.     

Stellenwert des Gewebe-Dopplers in der Ischämiediagnostik

Velocity and deformation imaging by Doppler and newer techniques based on "speckle tracking" in 2-D datasets have substantially added to the ability of echocardiography to detect myocardial ischemia. Typical parameters include tissue velocities and regional deformation ("strain") and deformation rate ("strain rate"), which with the Doppler-independent new techniques ("2-D strain", "velocity vector imaging") can be measured in several directions, largely independent of insonation angle. All of these techniques can be readily combined with stress echocardiography; so far, published results are mostly based on the combination with dobutamine echocardiography. Typical signs of myocardial ischemia include a decrease in tissue velocities, deformation rates, and deformation. Additionally, systolic deformation occurs later in systole and often still goes on after aortic valve closure (postsystolic deformation). While tissue velocities are unable to clearly identify regional ischemia because of tethering of the neighboring wall segments and a physiological variation in regional tissue velocities, deformation parameters are better suited to detect regional ischemia. The limited literature on the detection of myocardial ischemia by these techniques clearly shows a value of velocity and deformation imaging especially in those cases where qualitative visual assessment of wall motion remains ambiguous. Due to rapid evolution of these techniques, a final assessment of their potential is not possible yet.     

Aktueller Stellenwert der parametrischen Echokardiographie beim Management von Kardiomyopathien

The assessment of myocardial velocities by tissue Doppler imaging (TDI) and deformation imaging by speckle tracking echocardiography (STE) has been proposed for objective quantitative assessment of myocardial function and sophisticated analysis of cardiac mechanics in a wide range of clinical and scientific applications. These techniques are a promising new diagnostic tool for the evaluation of global and regional cardiac function in cardiomyopathies as well as detection of fibrosis, scars and ischemia. These new techniques are of increasing clinical importance but their strengths and weaknesses must be taken into account for the interpretation of the acquired data. This document describes the principles of the assessment of myocardial velocities and deformation by TDI and STE of the echocardiographic work-up in cardiomyopathies. Moreover, the growing body of evidence as well as relevant information for the clinical application of these emerging techniques for the analysis of systolic and diastolic function as well as the differentiation of restrictive cardiomyopathy from constrictive cardiomyopathy and of hypertrophic cardiomyopathy from athlete??s heart are highlighted in this article.     

Impact of newer echocardiographic modalities in the elderly

The emerging role novel echocardiographic techniques play in the practice of cardiology and how they can specifically impact care of the elderly patient are reviewed. Newer echocardiographic modalities including Doppler tissue and strain/strain rate imaging, contrast echocardiography, 3-dimensional echocardiography, and velocity vector imaging are described. Examples illustrating how these newer echocardiography modalities enhance our ability to make a variety of cardiovascular diagnoses are shown. The way in which these novel echocardiographic techniques allow for improved noninvasive estimation of left ventricular filling pressure, better diagnosis of cardiomyopathy and complications of acute myocardial infarction, better quantification of valvular heart disease, and enhance our understanding of myocardial contractile processes are reviewed. These newer echocardiographic modalities will continue to play an increasing role in the future as applications identifying ways in which they enhance cardiovascular diagnosis are discovered.     

Echocardiographic Evaluation of Cardiac Amyloid

Cardiac involvement in amyloidosis has poor prognosis and its diagnosis is challenging because of its patchy, infiltrative nature. Echocardiography plays an important role in the diagnosis, management, and prognosis in this disease process. In this article, we briefly review the utility and problems associated with traditional echocardiographic techniques and discuss the role for new echocardiographic imaging modalities such as tissue Doppler, Doppler-based strain, speckle tracking imaging, and three-dimensional imaging in the assessment of cardiac amyloid.     

Velocity vector imaging in assessing myocardial systolic function of hypertensive patients with left ventricular hypertrophy

BACKGROUND: To date, most studies about strain and strain rate (SR) are based on Doppler tissue imaging (DTI), which is dependent on the angle between ultrasonic scan line and tissue. Velocity vector imaging (VVI) is a new echocardiographic method based on two-dimensional gray scale imaging, which is angle-independent and can provide more information about cardiac function than DTI. OBJECTIVES: To assess regional myocardial SR in hypertensive patients with left ventricular hypertrophy (LVH) but normal global ejection fraction (GEF) and fractional shortening (FS) using VVI. METHODS: Using VVI, two-dimensional images were performed in 20 hypertensive patients with LVH and 20 normal control subjects. The segmental systolic peak SR (SRs) in the short-axis view and the apical SRs in the long-axis view were analyzed by offline software. RESULTS: The segmental SRs in the long-axis and short-axis views were significantly lower in the LVH group than in the corresponding segments of the control group. There was no significant difference between the circumferential SRs of different segments in the short-axis view in the LVH and control groups. The circumferential SRs decreased significantly from the endocardium to the middle layer of the myocardium in the short-axis view in the LVH group and in the control group. CONCLUSIONS: Hypertensive patients with LVH may have regional LV systolic function impairment despite having normal GEF and FS. The GEF and FS were not the decisive factors of myocardial systolic function in the present study. There was an obvious systolic gradient from the endocardium to the middle layer of myocardium in circumferential SRs in the short-axis view. VVI can be used to accurately recognize and quantify abnormalities of regional myocardial deformation.     

Analysis of myocardial deformation based on ultrasonic pixel tracking to determine transmurality in chronic myocardial infarction.

AIMS: Pixel tracking-derived myocardial deformation imaging is a new echocardiographic modality which allows quantitative analysis of segmental myocardial function on the basis of tracking of natural acoustic markers in 2D echocardiography. This study evaluated whether myocardial deformation parameters calculated from 2D echocardiography allow assessment of transmurality of myocardial infarction as defined by contrast-enhanced cardiac magnetic resonance imaging (ceMRI). Methods In 47 patients with ischaemic left ventricular dysfunction, transmurality of myocardial infarction was assessed using pixel-tracking-derived myocardial deformation imaging and ceMRI. For each left ventricular segment in a 16-segment model, peak systolic radial strain, circumferential strain, radial strain rate, and circumferential strain rate were calculated from parasternal 2D echocardiographic views using an automatic frame-by-frame tracking system of natural acoustic echocardiographic markers (EchoPAC, GE Ultrasound). Myocardial deformation parameters were related to the segmental extent of hyperenhancement by ceMRI. The relative amount of contrast-enhanced myocardial tissue per segment was used to define no infarction (0% hyperenhancement), non-transmural infarction (1-50% hyperenhancement), or transmural infarction (51-100% hyperenhancement). Results Analysis of myocardial deformation parameters was possible in 659 segments (88%). Systolic strain and strain rate parameters decreased with increasing relative hyperenhancement defined by ceMRI. Radial strain was 27.7+/-8.0, 20.5+/-9.7, and 11.6+/-8.5% for segments with no infarction (n=422), non-transmural infarction (n=106), and transmural infarction (n=131), respectively (P<0.0001). Radial strain allowed distinction of non-transmural infarction from transmural infarction with a sensitivity of 70.0% and a specificity of 71.2% (cut-off value for radial strain 16.5%). CONCLUSION: Frame-to-frame tracking of acoustic markers in 2D echocardiographic images for the analysis of myocardial deformation allows discrimination between different transmurality states of myocardial infarction.     

Tissue Doppler imaging in the evaluation of patients with cardiac amyloidosis

PURPOSE OF REVIEW: Although two-dimensional, M-mode, and Doppler echocardiography have played a major role in the assessment of amyloid deposition in the heart, diagnosis of cardiac amyloidosis (CA) based on these conventional techniques is often only possible once the disease is in a relatively advanced stage. To optimize survival, early diagnosis and institution of therapy are essential. Recently, tissue Doppler imaging (TDI) and myocardial strain rate (SR) have emerged as important clinical tools in the assessment of CA. RECENT FINDINGS: Tissue Doppler imaging-derived modalities including TDI velocities, strain, and SR are currently being used in the early diagnosis and evaluation of patients with CA. Although these new indices have been examined in relatively few patients, findings suggest an important and expanding role of TDI in amyloid infiltration of the heart. SUMMARY: This review summarizes the recent literature addressing the role of TDI velocities, strain, and SR in the diagnosis and assessment of CA.     

Non-Doppler Two Dimensional Strain Imaging for Evaluation of Coronary Artery Disease

Over the recent years, strain echocardiography has emerged as a quantitative technique for the evaluation of global and segmental cardiac function. Strain is a measure of deformation, expressed as a percent change in a segment's length compared to its predeformation length. Strain rate (SR) is the local rate of deformation or strain per unit time. Recently non-Doppler two dimensional strain imaging has been developed. This technique is based on tracking ultrasonic speckles from the two dimensional echocardiographic images. These speckles are followed over a number of successive frames, and myocardial velocity is calculated by measuring frame-to-frame changes. This technique is independent of the Doppler angle of incidence and allows measurement of several vectors of strain within myocardial tissue. Non-Doppler strain is a powerful tool, enabling detection of subtle abnormalities in myocardial function. Current evidence shows that non-Doppler strain imaging may allow identification of the early changes that occur with ischemic insult to the myocardium. It may also provide a tool for identification of scarred, non-viable myocardium, with similar accuracy to that of cardiac MRI. Non-Doppler strain imaging is likely to become a standard tool in the evaluation of patients with ischemic heart disease.     

Acute cardiac functional and morphological changes after Anthracycline infusions in children

The aim of this study was to describe the acute effects of anthracyclines on left ventricular systolic and diastolic function using different echocardiographic modalities. Thirteen children scheduled to receive anthracyclines were prospectively studied. They underwent complete 2-dimensional and Doppler echocardiographic evaluations, including tissue Doppler imaging, before the first dose and<2 hours after each of the first 3 doses of anthracyclines (dose range 30 to 75 mg/m2). After the first dose, increased end-diastolic wall thickness, decreased wall thickening, and a prolonged myocardial performance index were noted. Parameters of diastolic function changed significantly, with a lower mitral E wave, a decreased E/A ratio, and prolonged isovolumic relaxation time. Also, reduced longitudinal early diastolic myocardial velocity and myocardial velocity acceleration during isovolumic contraction as well as reduced peak longitudinal and radial systolic strain rate and strain were noted. All these parameters remained significantly lower after subsequent doses. After the second dose, significant changes in the shortening fraction and the ejection fraction compared with baseline became apparent. After the third dose, further deterioration in radial peak systolic strain was seen. In conclusion, low to moderate doses of anthracyclines acutely induce cardiac diastolic and systolic dysfunction.