Acute changes in systolic and diastolic events during clinical coronary angioplasty: a comparison of regional velocity, strain rate, and strain measurement

Influence of Power-Weighted Center of Echo Signal Within Window Function on Local Strain Rate Distribution in Left Ventricular Wall

OBJECTIVE

The deviation of the power-weighted center of the echo signal from the geometric center within the velocity estimation window for calculating strain rate (SR) causes an estimation error. This study aimed to confirm whether an erroneous multilayer pattern in the SR distribution of the left ventricular wall could be corrected by considering the power-weighted center of the echo signal.

METHODS

The SR distributions were measured locally in the transmural direction around the pre-ejection and early diastolic phases in healthy volunteers. The estimation error related to the power-weighted center of the echo signal was corrected using a previously proposed method, and the effectiveness of the correction was confirmed based on the accuracy of the estimated myocardial displacement.

RESULTS

The SR distribution in early diastole was observed as multilayers of low- and high-amplitude negative SRs. However, this multilayer pattern disappeared after correction. In the pre-ejection phase, multilayers of positive and negative SRs were observed in the SR distributions with and without correction. This correction was sufficiently effective in accurately tracking the local peak of the echo signal.

CONCLUSION

The multilayer pattern of low- and high-amplitude positive or negative SRs is caused by estimation errors related to the power-weighted center of the echo signal. The multilayer pattern of positive and negative SRs might not be caused by these errors and might relate to the actual change in myocardial thickness because the estimation errors do not convert the negative (positive) SR to positive (negative) in a homogeneous negative (positive) SR distribution.

Prediction of Significant Coronary Artery Disease Through Advanced Echocardiography: Role of Non-invasive Myocardial Work

Background: Non-invasive prediction of critical coronary artery stenosis (CAST) in patients with coronary artery disease (CAD) is challenging. Strain parameters can often capture an impairment of regional longitudinal function; however, they are load dependent. A novel non-invasive method to estimate Myocardial Work (MW) has been recently proposed, showing a strong correlation with invasive work measurements. Our aim was to investigate the ability of non-invasive MW to predict the ischaemic risk area underlying a CAST. Methods and Results: The study population comprises 80 individuals: 50 patients with CAST and 30 controls (CTRL). Echocardiography recordings were obtained before coronary angiography to measure global longitudinal strain (GLS), Myocardial Work Index (MWI), Myocardial Constructive Work (MCW), Myocardial Wasted work (MWW), Myocardial Work Efficiency (MWE). Global MWI (p = 0.048), MWE (p < 0.001), and MCW (p = 0.048) at baseline were significantly reduced in patients with CAST compared to controls (p < 0.05). Regional MWE within the myocardial segments underlying the CAST, but not LS, was significantly reduced compared to non-target segments (p < 0.001). At ROC analysis, the diagnostic performance to predict CAST for regional MWE (AUC = 0.920, p < 0.001) was higher compared to both regional post-systolic shortening index (PSI) (AUC = 0.600, p = 0.129) and regional LS (AUC = 0.546, p = 0.469). Conclusions: Non-invasive estimation of MW work indices is able to predict a CAST before invasive angiography.

[The myocardial infarction size measuring using modern methods]

An accurate quantitative assessment of myocardium necrosis area and the viable zone (stunned and hibernating) in patients with myocardial infarction is crucial for the preoperative patient selection and predicting the cardiac surgery effectiveness. Currently, researchers and clinicians are most interested in the problem of determining the viable myocardium zone. However, only the necrosis zone area directly correlates with the patients prognosis and determines the heart pathological remodeling processes. In the distant period, the data obtained can be used to predict the post-infarction period course or for analysis the relationship of the necrosis zone with arrhythmogenesis, and a number of other indicators. Thus, the necrosis zone and the viable myocardium zone are two parameters that need to be monitored in dynamics in all patients after myocardial infarction. The most accurate and reproducible method for determining the necrosis area is contrast magnetic resonance imaging of the heart, however, this technique is still inaccessible in most hospitals. In this regard, it remains relevant to estimate the necrotic myocardium area by ubiquitous non-invasive methods such as electrocardiography and echocardiography.

Estimating Regional Myocardial Contraction Using Miniature Transducers on the Epicardium

This paper describes an ultrasound system to monitor cardiac motion using miniature transducers attached directly to the epicardial surface. Our aim was to develop both a research tool for detailed studies of cardiac mechanics and a continuous, real time system for peri-operative evaluation of heart function. The system was tested on a porcine model. Two 3 mm diameter, 10 MHz ultrasound transducers were sutured to the epicardial surface. As the epicardial surface was the reference for the velocity and strain estimations, this procedure compensated for the motion of the heart. The short distance allowed for the use of high frequencies and pulse repetition rates. The system was driven in pulse-echo mode, using electronics developed for the application, and radio frequency (RF) lines were recorded at a pulse repetition rate of 2500 s^-1. The endocardial border was detected using an algorithm based on fuzzy logic with filtration to reduce noise and remove outliers, and the myocardium was divided into four layers. Inside the myocardium, radial tissue velocity as a function of depth was calculated from the recorded RF signals, and the velocity estimates were used to estimate radial strain rate and strain and to track the motion of the myocardial layers. The scope of this paper is technical, giving a detailed description of system design, hardware electronics and algorithms, with examples of processed velocity patterns and myocardial strain curves. The results from this study on a porcine model demonstrate the system's ability to estimate myocardial velocity and strain patterns and to track the motion of the myocardial layers, thereby obtaining detailed information of the regional function of the myocardium.

Myocardial Contraction during the Diastolic Isovolumetric Period: Analysis of Longitudinal Strain by Means of Speckle Tracking Echocardiography

BACKGROUND

According to the ventricular myocardial band model, the diastolic isovolumetric period is a contraction phenomenon. Our objective was to employ speckle-tracking echocardiography (STE) to analyze myocardial deformation of the left ventricle (LV) and to confirm if it supports the myocardial band model.

METHODS

This was a prospective observational study in which 90 healthy volunteers were recruited. We evaluated different types of postsystolic shortening (PSS) from an LV longitudinal strain study. Duration of latest deformation (LD) was calculated as the time from the start of the QRS complex of the ECG to the latest longitudinal deformation peak in the 18 segments of the LV.

RESULTS

The mean age of our subjects was 50.3 ± 11.1 years. PSS was observed in 48.4% of the 1620 LV segments studied (19.8%, 13.5%, and 15.1% in the basal, medial, and apical regions, respectively). PSS was more frequent in the basal, medial septal, and apical anteroseptal segments (>50%). LD peaked in the interventricular septum and in the basal segments of the LV.

CONCLUSIONS

The pattern of PSS and LD revealed by STE suggests there is contraction in the postsystolic phase of the cardiac cycle. The anatomical location of the segments in which this contraction is most frequently observed corresponds to the main path of the ascending component of the myocardial band. This contraction can be attributed to the protodiastolic untwisting of the LV.

Echocardiographic assessment of myocardial ischemia

Over the last 60 years, echocardiography has emerged as a dominant and indispensable technique for the detection and assessment of coronary heart disease (CHD). In this review, we will describe and discuss this powerful tool of cardiology, especially in the hands of an experienced user, with a focus on myocardial ischemia. Technical development is still on-going, and various new ultrasound techniques have been established in the field of echocardiography in the last several years, including tissue Doppler imaging (TDI), contrast echocardiography, three-dimensional echocardiography (3DE), and speckle tracking echocardiography (i.e., strain/strain rate-echocardiography). High-end equipment with harmonic imaging, high frame rates and the opportunity to adjust mechanical indices has improved imaging quality. Like all new techniques, these techniques must first be subjected to comprehensive scientific assessment, and appropriate training that accounts for physical and physiological limits should be provided. These limits will constantly be redefined as echocardiographic techniques continue to change, which will present new challenges for the further development of ultrasound technology.

Cardiac Imaging to Evaluate Left Ventricular Diastolic Function

Left ventricular diastolic dysfunction in clinical practice is generally diagnosed by imaging. Recognition of heart failure with preserved ejection fraction has increased interest in the detection and evaluation of this condition and prompted an improved understanding of the strengths and weaknesses of different imaging modalities for evaluating diastolic dysfunction. This review briefly provides the pathophysiological background for current clinical and experimental imaging parameters of diastolic dysfunction, discusses the merits of echocardiography relative to other imaging modalities in diagnosing and grading diastolic dysfunction, summarizes lessons from clinical trials that used parameters of diastolic function as an inclusion criterion or endpoint, and indicates current areas of research.

Present Insights on Cardiomyopathy in Diabetic Patients

The pathogenesis of diabetic cardiomyopathy (DCM) is partially understood and is likely to be multifactorial, involving metabolic disturbances, hypertension and cardiovascular autonomic neuropathy (CAN). Therefore, an important need remains to further delineate the basic mechanisms of diabetic cardiomyopathy and to apply them to daily clinical practice. We attempt to detail some of these underlying mechanisms, focusing in the clinical features and management. The novelty of this review is the role of CAN and reduction of blood pressure descent during sleep in the development of DCM. Evidence has suggested that CAN might precede left ventricular hypertrophy and diastolic dysfunction in normotensive patients with type 2 diabetes, serving as an early marker for the evaluation of preclinical cardiac abnormalities. Additionally, a prospective study demonstrated that an elevation of nocturnal systolic blood pressure and a loss of nocturnal blood pressure fall might precede the onset of abnormal albuminuria and cardiovascular events in hypertensive normoalbuminuric patients with type 2 diabetes. Therefore, existing microalbuminuria could imply the presence of myocardium abnormalities. Considering that DCM could be asymptomatic for a long period and progress to irreversible cardiac damage, early recognition and treatment of the preclinical cardiac abnormalities are essential to avoid severe cardiovascular outcomes. In this sense, we recommend that all type 2 diabetic patients, especially those with microalbuminuria, should be regularly submitted to CAN tests, Ambulatory Blood Pressure Monitoring and echocardiography, and treated for any abnormalities in these tests in the attempt of reducing cardiovascular morbidity and mortality.

Does Diabetes Have an Influence on Regional Deformation Parameters in Patients with Normal Systolic Function during Off-Pump Coronary Artery Bypass Grafting?

OBJECTIVES

The aim of this study was to assess the recovery of regional myocardial function of the left-ventricular septal wall and the septal site of the mitral valve (MV) annulus by tissue Doppler imaging (TDI).

METHODS

In 63 (32 diabetic and 31 control) patients having off-pump coronary artery bypass grafting (OPCABG), including the left internal mammary artery (LIMA) and the left anterior descending coronary artery (LAD), TDI measurements were performed before operation (baseline), 5 min after LIMA-LAD revascularization (early reperfusion) and after completion of all anastomoses (after revascularization).

RESULTS

Compared to the patients with diabetes, the controls had higher peak systolic velocities of the mid septal segments in the early reperfusion measurement (p = 0.002). After revascularization, values of peak systolic strain at the basal (-10.13 vs. -13.36%, p = 0.044) and mid septal segments (-8.25 vs. -12.69%, p = 0.009) were decreased in the diabetic patients compared to the controls. There was no difference between the groups with respect to the velocities acquired at the septal site of the MV annulus.

CONCLUSIONS

This study demonstrates an insufficient recovery of regional myocardial function in patients with type II diabetes undergoing OPCABG.

Tissue Doppler, strain and strain rate in ischemic heart disease "how I do it"

Echocardiography is the standard method for assessing myocardial function in patients with ischemic heart disease. The acquisition and interpretation of echocardiographic images, however, remains a highly specialized task which often relies entirely on the subjective visual assessment of the reader and requires therefore, particular training and expertise. Myocardial deformation imaging allows quantifying myocardial function far beyond what can be done with sole visual assessment. It can improve the interpretation of regional dysfunction and offers sensitive markers of induced ischemia which can be used for stress tests. In the following, we recapitulate shortly the pathophysiological and technical basics and explain in a practical manner how we use this technique in investigating patients with ischemic heart disease.

Characteristics of myocardial postsystolic shortening in patients with symptomatic hypertrophic obstructive cardiomyopathy before and half a year after alcohol septal ablation assessed by speckle tracking echocardiography

Objectives

Postsystolic shortening (PSS) has been proposed as a marker of myocardial dysfunction. Percutaneous transluminal septal myocardial ablation (PTSMA) is an alternative therapy for patients with hypertrophic obstructive cardiomyopathy (HOCM) that results in sustained improvements in atrial structure and function. We investigated the effects of PTSMA on PSS in HOCM patients using speckle tracking imaging.

Methods

Conventional echocardiographic and PSS parameters were obtained in 18 healthy controls and 30 HOCM patients before and half a year after PTSMA.

Results

Compared with the healthy controls, the number of segments having PSS and the average value of PSS were significantly increased in the HOCM patients. At 6 months after PTSMA, both the number of segments having PSS (10.5±2.8 vs. 13.2±2.6; P<0.001) and the average value of PSS (−1.24±0.57 vs. −1.55±0.56; P = 0.009) were significantly reduced. Moreover, the reductions in the average value of PSS correlated well with the reductions in the E-to-Ea ratio (r = 0.705, P<0.001).

Conclusions

Both the number of segments having PSS and the average value of PSS were significantly increased in the HOCM patients. PTSMA has a favourable effect on PSS, which may partly account for the persistent improvement in LV diastolic function in HOCM patients after PTSMA.

Diagnostic Value of 2D Strain Imaging In Patients with Suspected Coronary Artery Disease

Background: Strain imaging (SI) has been shown to quantify regional myocardial function in both acute ischemic myocardium and infarcted myocardium. The aim of this study is to determine the diagnostic value of SI for the detection of coronary lesions in pts with chest pain, but without apparent wall motion abnormalities. Methods: SI for advanced wall motion analysis was performed in 59 pts with suspicious stable angina (SA) and in 57 pts with suspicious unstable angina (UA), prior to coronary angiography (CAG). Longitudinal strain was measured in 3 apical views. For the identification of ischemia a magnitude parameter, being defined as a reduction of the peak systolic strain, was used. A homogenous pattern of strain was defined as relatively uniform distribution of the peak systolic strain. Heterogeneity of strain was considered abnormal; these segments were called strain (+) and the rest were called strain (-). Results: Out of the 59 SA patients, 28 had >70% stenosis (ischemic-SA) and 31 had normal coronary anatomy or 50% stenosis (normal-SA). Of the 28 patients in the ischemic-SA group, 9 patients (32%) showed a homogeneous pattern of peak systolic strain throughout the wall (strain negative) and 19 patients (67%) showed heterogeneity of strain (strain positive). 31 patients with normal coronary anatomy or <50% stenosis (normal-SA), 6 patients (19%) showed heterogeneity of strain (strain positive) and 25 patients (80%) showed a homogeneous pattern of peak systolic strain throughout the wall (strain negative). The positive predictive value of strain was 76% in the SA group. In the group of 57 UA patients, 32 had >70% stenosis (ischemic-UA), and 25 had normal coronary anatomy or 50% stenosis (normal-UA). From the 32 patients in the ischemic-UA group, 7 patients (22%) were determined to be strain negative, and 25 patients (78%) were determined to be strain positive. Out of 25 patients with normal coronary anatomy or 50% stenosis (normal-UA), 25 patients (80%) showed a homogeneous pattern of peak systolic strain throughout the wall (strain negative) and 6 patients (19%) showed heterogeneity of strain (strain positive). The positive predictive value of strain was 80.6% in the UA group. Sensitivity and specificity of 2D strain was evaluated using diagnostic test. The results were: 68% and 80.6% respectively in the stable angina group and 78% and 76% respectively in the unstable angina group.Conclusion: Ultrasound-based SI demonstrates a strong correlation with CAG and it has potential as a non-invasive diagnostic tool for detecting CAD in pts with chest pain and without wall motion abnormalities.

Alteration in the global and regional myocardial strain patterns in patients with inferior ST-elevation myocardial infarction prior to and after percutaneous coronary intervention

This study was designed to investigate the alteration on regional and global strains of left and right ventricle (LV, RV) in patients with inferior wall ST-elevation myocardial infarction (MI). Patients were examined prior to and 7 days after percutaneous coronary intervention (PCI) using speckle-tracking techniques. Fifty-nine patients (36 males and 23 females) and 60 healthy controls (40 males and 20 females) were enrolled in this study. LV strains were measured from three deformations including radial, longitudinal, and circumferential. RV strains were measured only from the longitudinal. Three types of LV global strains were significantly lower in patients than in controls, and LV global longitudinal and circumferential strains were moderately improved by PCI. The LV regional strains reduced significantly in most of the segments (87%) after inferior wall MI and over half of them (60%) were improved by PCI. The RV global longitudinal strains were significantly lower in patients than in controls, and they were moderately improved by PCI. In conclusion, the regional and global strains of LV and RV were reduced in patients with inferior wall MI, and PCI most markedly improved the global strains and regional strains of the infarct and adjacent myocardium in the apical and middle levels.

New echocardiographic findings correlate with intramyocardial inflammation in endomyocardial biopsies of patients with acute myocarditis and inflammatory cardiomyopathy

Background. The diagnosis of acute myocarditis (AMC) and inflammatory cardiomyopathy (DCMi) can be difficult. Speckle tracking echocardiography with accurate assessments of regional contractility could have an outstanding importance for the diagnosis. Methods and Results. N = 25 patients with clinically diagnosed AMC who underwent endomyocardial biopsies (EMBs) were studied prospectively. Speckle tracking imaging was examined at the beginning and during a mean follow-up period of 6.2 months. In the acute phase patients had markedly decreased left ventricular (LV) systolic function (mean LV ejection fraction (LVEF) 40.4 ± 10.3%). At follow-up in n = 8 patients, inflammation persists, correlating with a significantly reduced fractional shortening (FS, 21.5 ± 6.0%) in contrast to those without inflammation in EMB (FS 32.1 ± 7.1%, P < 0.05). All AMC patients showed a reduction in global systolic longitudinal strain (LS, −8.36 ± −3.47%) and strain rate (LSR, 0.53 ± 0.29 1/s). At follow-up, LS and LRS were significantly lower in patients with inflammation, in contrast to patients without inflammation (−9.4 ± 1.4 versus −16.8 ± 2.0%, P < 0.0001; 0.78 ± 0.4 versus 1.3 ± 0.3 1/s). LSR and LS correlate significantly with lymphocytic infiltrates (for CD3 r = 0.7, P < 0.0001, and LFA-1 r = 0.8, P < 0.0001). Conclusion. Speckle tracking echocardiography is a useful adjunctive assisting tool for evaluation over the course of intramyocardial inflammation in patients with AMC and DCMi.

Alteration of left ventricular function with dobutamine challenge in patients with myocardial bridge

BACKGROUND/AIMS

The aim of this study was to identify changes in left ventricular (LV) performance in patients with a myocardial bridge (MB) in the left anterior descending coronary artery during resting and in an inotropic state.

METHODS

Myocardial strain measurement by speckle-tracking echocardiography and conventional LV wall-motion scoring was performed in 18 patients with MB (mean age, 48.1 ± 1.7 years, eight female) during resting and intravenous dobutamine challenge (10 and 20 µg/kg/min).

RESULTS

Conventional LV wall-motion scoring was normal in all patients during resting and in an inotropic state. Peak regional circumferential strain increased dose dependently upon dobutamine challenge. Longitudinal strains of the anterior and anteroseptal segments were, however, reduced at 20 µg/kg/min and showed a dyssynchronous pattern at 20 µg/kg/min. Although there were no significant differences in radial strain and displacement of all segments at rest compared with under 10 µg/kg/min challenge, radial strain and displacement of anterior segments at 20 µg/kg/min were significantly reduced compared with posterior segments at the papillary muscle level (44.8 ± 14.9% vs. 78.4 ± 20.1% and 5.3 ± 2.3 mm vs. 8.5 ± 1.8 mm, respectively; all p < 0.001), and showed plateau (40%) or biphasic (62%) patterns.

CONCLUSIONS

Reduced LV strain of patients with MB after inotropic stimulation was identified. Speckle-tracking strain echocardiography identified a LV myocardial dyssynchrony that was not demonstrated by conventional echocardiography in patients with MB.

Detection of prolonged regional myocardial systolic dysfunction after exercise-induced myocardial ischemia by strain echocardiography with high frame rate tissue Doppler echocardiography

BACKGROUND

Strain echocardiography has enabled quantification of regional myocardial systolic function objectively and is less influenced by tethering effects and cardiac translational artifact than Doppler tissue imaging. Although strain echocardiography has been applied for the detection of inducible ischemia during dobutamine stress, it has not been fully applied to exercise stress echocardiography (ESE) because of technical difficulties. Prolonged myocardial systolic dysfunction after exercise-induced ischemia has been shown previously. Thus, we designed this study to evaluate whether the myocardial strain analysis can detect myocardial ischemia by the assessment of prolonged regional left ventricular (LV) dysfunction in ESE.

METHODS

We performed ESE with myocardial strain imaging system in 20 consecutive patients who had exercise Tl-201 single photon emission computed tomography (SPECT). Myocardial strain curves were obtained at six segments in mid LV walls from the apical approach before and 5 min after ESE. We measured the duration from the R wave in the electrocardiogram to the timing of peak systolic strain corrected by the square root of the RR interval (TPSc). We finally calculated the differences of TPSc (ΔTPSc) before ESE and 5 min after ESE. The results were compared with SPECT as a reference standard.

RESULTS

A receiver operating characteristic curve demonstrated that a ΔTPSc cutoff value of 70 ms had a sensitivity of 80% and a specificity of 84% for the detection of myocardial ischemia.

CONCLUSIONS

Prolonged regional LV systolic dysfunction assessed by ESE with strain analysis was useful for the detection of myocardial ischemia.

Peak longitudinal strain delay is superior to TDI in the selection of patients for resynchronisation therapy

BACKGROUND

Mechanical dyssynchrony has proven to be superior to QRS duration in predicting response to cardiac resynchronisation therapy (CRT). Whether time to peak longitudinal strain delay between the mid-septum and mid-lateral left ventricular wall better predicts CRT response than tissue Doppler imaging (TDI) is unclear. This study compares the value of the two methods for the assessment of mechanical dyssynchrony and prediction of CRT responders.

METHODS

66 clinical responders and 17 nonresponders to CRT with severe systolic heart failure (LVEF <35%), New York Heart Association classification III or IV and a wide QRS >130 ms with left bundle branch block were evaluated by peak longitudinal strain and TDI. Doppler echocardiograms and electromechanical time delay (EMD) intervals were acquired before and after pacemaker implantation.

RESULTS

In all responders EMD measured by peak longitudinal strain was >60 ms before implantation, compared with 76% of the patients measured by TDI. Nonresponders had EMD <60 ms measured by both techniques. Only peak longitudinal strain delay showed shortened values in every responder postimplantation and demonstrated the most significant reduction and could predict responders to CRT. However, EMD measured by TDI did not diminish in 30% of the positive clinical responders. Nonresponders showed worsening of the EMD with peak longitudinal strain, but not with TDI.

CONCLUSIONS

Responders to CRT can be excellently predicted if EMD before implantation determined by peak longitudinal strain delay is >60 ms. Peak longitudinal strain delay appears to be superior to TDI to predict the response to CRT. (Neth Heart J 2010;18:574-82.).

Pathological and physiological left ventricular hypertrophy: echocardiography for differentiation

Distinguishing physiological left ventricular hypertrophy of an athlete's heart from that of pathological left ventricular (hypertrophic cardiomyopathy) can be difficult despite the advent of new imaging techniques. Nevertheless, the final diagnosis is of utmost importance as it will have a profound impact on an individual's life. A diagnosis of hypertrophic cardiomyopathy essentially excludes an individual from sport and strenuous exertion and necessitates the need for further tests and treatment, as well as the screening of family members. Hypertrophic cardiomyopathy remains the most common cause of a pathologically hypertrophied heart in young athletes, with a prevalence of one in 500. The issue of sudden death in athletes due to pathological left ventricular hypertrophy and hypertrophic cardiomyopathy has recently gained recognition owing to the death of several word class athletes during sporting participation. What compounds this further is the fact that a proportion of athletes fall into the 'grey zone' (ventricular wall thickness of 13-16 mm) where the increase in cardiac size overlaps with the phenotypic variation of hypertrophic cardiomyopathy - making echocardiographic differentiation of the two entities challenging. This review discusses the echocardiographic differentiation of the athlete's heart, including physiological left ventricular hypertrophy from pathological left ventricular hypertrophy. Although several of the cardiomyopathies cause pathological left ventricular hypertrophy, focus will be given to hypertrophic cardiomyopathy, for reasons mentioned above. Discussion will also focus on the newer and emerging echocardiographic techniques for this purpose. The term 'hypertrophic cardiomyopathy' is used to describe the nonobstuctive form of hypertrophic cardiomyopathy as this review article focuses on distinguishing the 'mild' form of hypertrophic cardiomyopathy from an athlete's heart. When the more severe obstructive form is being described, the term 'hypertrophic obstructive cardiomyopathy' is used.

Strain measurements during adenosine triphosphate infusion before and after percutaneous coronary intervention

BACKGROUND

In regional myocardial ischemia, contractile delay develops, which can be assessed by measuring time to peak strain (TPS) on tissue Doppler imaging. The aims of the present study were to clarify the usefulness of TPS measurements during adenosine triphosphate (ATP) stress in assessing myocardial ischemia and to evaluate whether prolongation of TPS disappears immediately after percutaneous coronary intervention (PCI) or not.

METHODS AND RESULTS

A total of 26 patients underwent strain measurements before and after PCI. Corrected TPS for heart rate (TPSc) in target regions and in control regions were measured both at baseline and during ATP infusion. TPSc ratio was calculated as a ratio of TPSc during ATP stress to TPSc at baseline. TPSc in the target region significantly increased during ATP infusion before PCI, which was significantly longer than hyperemic TPSc in control regions. Accordingly, TPSc ratio in the target regions before PCI was significantly greater than that in control regions (1.22+/-0.17 vs 0.96+/-0.09, respectively, P<0.0001). Following PCI, the TPSc ratio in the target regions significantly decreased to 0.98+/-0.05 (P<0.0001). Receiver operating characteristic curve analysis provided a cut-off of 1.04 in TPSc ratio for detecting myocardial ischemia with a sensitivity of 93% and specificity of 93%.

CONCLUSIONS

TPS measurements during ATP stress differentiated target from control myocardium before PCI. The prolongation of TPSc disappeared immediately after PCI.

Global strain rate imaging for the estimation of diastolic function in HFNEF compared with pressure-volume loop analysis

AIMS

Strain rate imaging provides direct information on intrinsic myocardial function and may improve the diagnostic of diastolic dysfunction in heart failure with normal ejection fraction (HFNEF). We therefore correlated global strain with pressure-volume (PV) loop analysis and compared it with flow and tissue Doppler measurements.

METHODS AND RESULTS

Longitudinal two-dimensional strain rate and flow and tissue Doppler (TDI) indices were measured simultaneously and correlated with diastolic indices of PV relationship obtained by a conductance catheter in 21 patients with HFNEF and 12 controls. HFNEF patients showed a reduced global strain rate during isovolumetric relaxation (SR(IVR)) [0.27 (0.12-0.39) vs. 0.44 (0.29-0.56) s(-1), P = 0.028]. Global strain rate during early (SR(E)) and late (SR(L)) diastole did not defer from controls. Their ratios with early transmitral flow, E/SR(IVR) and E/SR(E), were both elevated in HFNEF [3.68 (2.57-7.52) vs. 1.73 (1.47-2.37) m, P = 0.007 and 1.13 (0.76-1.36) vs. 0.83 (0.57-1.04) m, P = 0.030]. SR(E) and SR(IVR) correlated with left ventricular (LV) relaxation τ (r = 0.40 and 0.47, P < 0.05); E/SR(IVR) and E/SR(E) with LV end-diastolic pressure (r = 0.49 and 0.57, P < 0.01) and LV stiffness constant β (r = 0.42 and 0.43, P < 0.01). Neither of the strain rate indices were significantly more accurate than TDI (area under the curve: SR(E) 0.55, SR(IVR) 0.70, E'/A' 0.72, E/SR(E) 0.75, E/SR(IVR) 0.80, and E/E' 0.83).

CONCLUSION

Strain rate imaging is accurate in detecting increased LV stiffness in HFNEF, but it is not superior to already established TDI analysis including E/E' in patients with only mild degree of disease.

Echocardiographic strain imaging and its use in the clinical setting

The use of echocardiography has grown tremendously over the past several years. It is used routinely for diagnosis, prognosis and monitoring changes of cardiac function in coronary artery disease, heart failure, pulmonary hypertension, arrhythmias, pericardial disease and valvular disease, as well as congenital conditions. In recent years, the advancing technology used to evaluate the heart by ultrasound has allowed physicians to understand the mechanics of the heart muscle and the contribution of abnormalities in myocardial movement to heart disease. This review will discuss novel echocardiographic strain imaging techniques, placing them in the context of myocardial mechanics and describing current and future applications.

Longitudinal peak strain detects a smaller risk area than visual assessment of wall motion in acute myocardial infarction

BACKGROUND

Opening of an occluded infarct related artery reduces infarct size and improves survival in acute ST-elevation myocardial infarction (STEMI). In this study we performed tissue Doppler analysis (peak strain, displacement, mitral annular movement (MAM)) and compared with visual assessment for the study of the correlation of measurements of global, regional and segmental function with final infarct size and transmurality. In addition, myocardial risk area was determined and a prediction sought for the development of infarct transmurality >or=50%.

METHODS

Twenty six patients with STEMI submitted for primary percutaneous coronary intervention (PCI) were examined with echocardiography on the catheterization table. Four to eight weeks later repeat echocardiography was performed for reassessment of function and magnetic resonance imaging for the determination of final infarct size and transmurality.

RESULTS

On a global level, wall motion score index (WMSI), ejection fraction (EF), strain, and displacement all showed significant differences (p <or= 0.001, p <or= 0.001, p <or= 0.001 and p = 0.03) between the two study visits, but MAM did not (p = 0.17). On all levels (global, regional and segmental) and both pre- and post PCI, WMSI showed a higher correlation with scar transmurality compared to strain. We found that both strain and WMSI predicted the development of scar transmurality >or=50%, but strain added no significant information to that obtained with WMSI in a logistic regression analysis.

CONCLUSIONS

In patients with acute STEMI, WMSI, EF, strain, and displacement showed significant changes between the pre- and post PCI exam. In a ROC-analysis, strain had 64% sensitivity at 80% specificity and WMSI around 90% sensitivity at 80% specificity for the detection of scar with transmurality >or=50% at follow-up.

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.

Velocity and deformation imaging for the assessment of myocardial dysfunction

Recent developments in echocardiographic imaging technology and processing enabled the quantification of myocardial motion and deformation in a clinical setting. Echocardiographic strain (-rate) imaging provides a relatively easy way to study myocardial deformation. However, although (local) deformation is clearly linked to cardiac (dys-) function, it is important to understand how this information can be used in clinical practice and how specific deformation patterns should be interpreted. This review paper first discusses which issues are important to address when assessing cardiac function and how (regional) deformation and myocardial contractility are related. The use and interpretation of deformation profiles is further illustrated for some typical cardiac pathologies. The observed deformation patterns are discussed in light of the changes in regional contractility (ischemia), timing of contractile force development (LBBB and heart failure), pressure/volume overload, and assessing diastolic function.

Optimal types of probe, and tissue Doppler frame rates, for use during tissue Doppler recording and off-line analysis of strain and strain rate in neonates at term

Measurements of strain and strain rate, obtained by tissue Doppler might provide new parameters for assessing cardiac function in neonates. The noise-to-signal ratio is high. We investigated the effect of the frequency of the probe used, and the settings for tissue Doppler frame rate, on the noise in the analyses in three series of tissue Doppler images. In the first series, we used the 5S probe, with a frequency of 2.4 MHz, and the default frame rate. We used the10S probe, with a frequency of 8.0 MHz, in the other two series, one with a low and one with the default frame rate. The noise was lower using the 5S rather than the 10S probe, and lower when using the low frame rate rather than the default rate with the 10S probe. Using the settings eligible for two segment analyses with the lowest noise for each series, the noise was from 36 to 42% higher when using the 10S probe at default frame rate, and from 13 to 14% higher when using the 10S probe at low frame rate compared to the 5S probe at default frame rate. There were no differences in peak systolic strain or strain rate between the series. We found, therefore, that use of the 5S probe with the default setting for frame rate, along with a length of 1 mm and width of 2 mm for the region of interest, and a strain length of 10 mm, provided the optimal settings for two-segment analyses in this study.

High frequency ultrasound imaging detects cardiac dyssynchrony in noninfarcted regions of the murine left ventricle late after reperfused myocardial infarction

Cardiac dyssynchrony in the left ventricles of murine hearts late (> or =28 d) after reperfused myocardial infarction (post-MI) was assessed using high frequency 30 MHz B-mode ultrasound imaging. Nine post-MI and six normal C57Bl/6 mice were studied in both short- and long-axis views. Regional time to peak displacement (T(peak_d)) and time to peak strain (T(peak_s)) were calculated in 36 sectors along the myocardial circumference; then their standard deviations (SD_T(peak_d) and SD_T(peak_s)) were computed among noninfarcted myocardial regions for each mouse and were compared between the normal and post-MI mouse groups with Student's t-test. The comparison revealed that SD_T(peak_d) and SD_T(peak_s) were significantly larger in the post-MI hearts than in the normal hearts. The displacement uniformity ratio was determined to be 0.97 +/- 0.01 and 0.85 +/- 0.07 for radial and circumferential displacements in the normal hearts, respectively; and 0.59 +/- 0.17 and 0.64 +/- 0.24 in the post-MI hearts. In conclusion, this high resolution ultrasound image tracking method provides for the detection of cardiac dyssynchrony in the noninfarcted regions in the murine left ventricles late after MI by identifying the temporal and spatial disparity of regional myocardial contraction.

Strain rate imaging pre- and post-percutaneous coronary intervention: a potential role in the objective detection of ischaemia in exercise stress echocardiography

AIMS

To determine the feasibility of strain rate imaging (SRI) in the objective detection of exercise-induced ischaemia.

METHODS AND RESULTS

Sixteen patients undergoing elective percutaneous coronary intervention (PCI) underwent treadmill exercise stress echocardiography (ESE) pre- and post-PCI. Measurement of systolic SRI parameters was attempted in all myocardial segments at baseline, peak stress, and in recovery. Segments were divided into those supplied by target (Group 1) and non-target vessels (Group 2). Percutaneous coronary intervention was successful in all patients. In Group 1, there was no significant difference in post-systolic strain rate (SRps) at baseline or at peak stress but there was significantly greater SRps pre-PCI compared with post-PCI at 30 min into recovery (-0.37 +/- 0.53 vs. -0.07 +/- 0.44 s(-1), P = 0.004). There were similar findings with the SRps index [ratio of SRps:peak systolic strain rate (SRsys)]. Group 2 segments did not demonstrate any significant differences in SRI parameters pre- and post-PCI. At peak exercise pre-PCI, Group 1 segments had significantly delayed time to SRsys compared with Group 2 (0.12 +/- 0.05 vs. 0.09 +/- 0.05 s, P = 0.013), a difference that was abolished post-PCI.

CONCLUSION

This suggests a potential role for SRI in the objective detection of exercise-induced ischaemia by echocardiography at peak stress and during recovery at the time of improved image quality.

Mechanisms of postsystolic thickening in ischemic myocardium: mathematical modelling and comparison with experimental ischemic substrates

In the setting of regional ischemia, the "at-risk" myocardium exhibits a flow-related reduction in systolic thickening with a concomitant development of abnormal thickening after aortic valve closure (postsystolic thickening [PST]). With the introduction of high time-resolution ultrasonic-based strain/strain-rate imaging, this short lived phenomenon can be measured accurately in the clinical setting. The mechanisms underlying this ischemia-related PST are poorly understood and both active and passive etiologies have been proposed. This study aims at elucidating the potential mechanisms behind PST in the intact heart. A theoretical model, describing active force development, elasticity and segment interaction has been developed to simulate radial deformation during systole and iso-volumetric relaxation. Simulation results have been compared with experimental deformation curves obtained from postero-basal segments of a pig model undergoing varying controlled ischemic challenges. Three forms of regional ischemia could be simulated by varying the model parameters of the ischemic segments: (i) chronic regional hypo-perfusion (reduced and prolonged active force development; preserved elasticity); (ii) acute short-lived ischemia-temporary vessel occlusion (no active force development; preserved elasticity); and (iii) chronic myocardial infarction (no active force development; decreased elasticity). For all ischemic substrates, the simulated curves closely correlate to the deformation measured in the corresponding porcine models without the need for active force development during the occurrence of PST. This suggests that segment interaction is the key determinant in the development of PST. Thus, in all instances, at the time of its manifestation, ischemia-related PST could be explained in a unified way as a passive phenomenon that was the result of elastic segment interaction. Its occurrence originates from the end-systolic inhomogeneous state where neighboring segments have a different wall thickness. The occurrence of these differences at end-systole depends on the presence of regional differences within the ventricle in the magnitude and duration of the developed contraction force during the first part of systole, the elasticity of the ischemic segment and the left-ventricular pressure.

Radial strain assessment of the interventricular septum wall by a new technique in healthy subjects

The aim of this study was to design a new approach for the acquisition of regional radial strain from the middle portion of the interventricular septum. We designed and wrote a program in Matlab (computer-assisted method) for use on a personal computer so that the septum thickness throughout the cardiac cycle could be measured instantaneously. Computer-assisted and conventional manual methods were used on the same 2D echocardiography image frames. Then, real-time 2D color Doppler myocardial imaging and conventional 2D imaging of the septum walls of 12 healthy participants at rest using apical four-chamber view were acquired. Wall thickness was measured using both the computerized program and velocity data used for tracking the segment and intensity line profile modification automatically. Then, the radial strain was estimated. Bland-Altman statistical analysis shows good agreement between the computer-assisted method and conventional manual method. The average of the peak and mean radial strains from the mid-septum of 12 healthy participants were 63.5 +/- 10.7 and 31.7 +/- 7.5%, respectively. We introduced a simple approach that is capable of radial strain estimation of the septum wall, which cannot be measured by current Doppler based methods in echocardiography systems.

Effect of Obesity on Left Ventricular Structure and Myocardial Systolic Function: Assesment by Tissue Doppler Imaging and Strain/Strain Rate Imaging

BACKGROUND

Obesity is associated with heart failure, cardiovascular morbidity, and mortality. A direct effect of weight on left ventricle (LV) structure and myocardial function is not well-established.

AIM

The aim of our study is to determine the effect of obesity on LV morphology and systolic function by using LV standard Doppler echocardiographic indices, myocardial Doppler imaging and strain/strain rate imaging indices.

METHODS

We studied 33 obese and 34 age, sex-adjusted control subjects who had no other pathological conditions. Standard transthoracic Doppler echocardiographical measurements, reconstructed spectral pulsed wave tissue Doppler velocities, strain and strain rate imaging of six different myocardial regions were obtained. Peak systolic velocity (SR), peak systolic strain (I), peak systolic strain rate (SR) for each region and as a global systolic longitidunal LV function mean of peak systolic strain of six myocardial regions (glsca) were compared.

RESULTS

Age, body surface area, blood pressure, and heart rate were comparable between the two groups. Obese subjects had significantly increased LV end-diastolic volume, septal wall thickness, left atrial diameter, and decreased transmitral early to late diastolic velocity ratio. In obese subjects, reconstructed spectral pulsed-wave tissue Doppler analysis showed significantly decreased basal lateral peak systolic (Sm) velocity (6.68 +/- 1.89 vs. 8.08 +/- 2.50, P < 0.05), mid lateral Sm (5.01 +/- 2.17 vs. 6.78 +/- 3.22, P < 0.05). Differences in regional strain rate (mid septal SR, 1.45 +/- 0.23 vs. 1.63 +/- 0.18, P < 0.05), regional strain (basal septum I, 19.13 +/- 3.83 vs. 22.09 +/- 4.60, P < 0.05; mid-septum I, 18.03 +/- 2.91 vs. 20.25 +/- 4.77, P < 0.05; radial I, 27.50 +/- 7.32 vs. 35.53 +/- 9.48, P < 0.05), and global strain (glsca, 19.38 +/- 1.34 vs. 21.24 +/- 2.82, P < 0.05) were identified between obese and the referent subjects.

CONCLUSIONS

Obesity is associated with morphologic alterations in left ventricle and left atrium and subclinical changes in left ventricle systolic function which can be detected by strain and strain rate imaging even without overt heart disease.

Two-dimensional strain imaging: a new echocardiographic advance with research and clinical applications

Over the past two decades the quest for quantitative evaluation of left ventricular function and regional wall motion has escalated, allowing several aspects of myocardial contractile patterns to be quantified, both during stress echocardiography and in the assessment of dyssynchrony. Most of the literature to date has used Tissue Doppler Imaging (TDI) techniques to assess essentially long-axis function due to the angle dependency of Doppler based techniques. This brief review introduces the early development, validation and potential clinical applications of a new technique of quantifying two-dimensional (radial and circumferential) strains and strain rates through tracking myocardial "speckles". In-vivo and in-vitro validation of this 2D-strain imaging technique has been undertaken and reached a point where it is considered ready for more widespread investigations into clinical utility. One important advantage over TDI techniques is that it is not limited by dependency on the angle of insonation. Several recent studies looking at ventricular function in specific groups of patients have reported practical ability to distinguish the abnormally from the normally contracting regions of ventricular walls. It provides new and complementary quantitative information about ventricular dyssynchrony and regional wall motion abnormalities. More research studies are needed to determine the sensitivity and specificity of the measurements obtained using this technique and define its strengths and limitations. In particular, whether the measured values correlate well with clinical outcomes will need to be established in longitudinal interventional studies. The clinical utilities of this technique over the coming years are likely to expand rapidly.