Giuseppe Caracciolo

Assessment of Myocardial Mechanics Using Speckle Tracking Echocardiography: Fundamentals and Clinical Applications

The authors summarize the recent developments in speckle-tracking echocardiography (STE), a relatively new technique that can be used in conjunction with two-dimensional or three-dimensional echocardiography for resolving the multidirectional components of left ventricular (LV) deformation. The tracking system is based on grayscale B-mode images and is obtained by automatic measurement of the distance between 2 pixels of an LV segment during the cardiac cycle, independent of the angle of insonation. The integration of STE with real-time cardiac ultrasound imaging overcomes some of the limitations of previous work in the field and has the potential to provide a unified framework to more accurately quantify the regional and global function of the left ventricle. STE holds promise to reduce interobserver and intraobserver variability in assessing regional LV function and to improve patient care while reducing health care costs through the early identification of subclinical disease. Following a brief overview of the approach, the authors pool the initial observations from clinical studies on the development, validation, merits, and limitations of STE.

Global Left Atrial Strain Correlates with CHADS2 Risk Score in Patients with Atrial Fibrillation

BACKGROUND The aim of this cross-sectional study was to explore the association between echocardiographic parameters and CHADS2 score in patients with nonvalvular atrial fibrillation (AF). METHODS Seventy-seven subjects (36 patients with AF, 41 control subjects) underwent standard two-dimensional, Doppler, and speckle-tracking echocardiography to compute regional and global left atrial (LA) strain. RESULTS Global longitudinal LA strain was reduced in patients with AF compared with controls (P < .001) and was a predictor of high risk for thromboembolism (CHADS2 score ≥ 2; odds ratio, 0.86; P = .02). LA strain indexes showed good interobserver and intraobserver variability. In sequential Cox models, the prediction of hospitalization and/or death was improved by addition of global LA strain and indexed LA volume to CHADS2 score (P = .003). CONCLUSIONS LA strain is a reproducible marker of dynamic LA function and a predictor of stroke risk and cardiovascular outcomes in patients with AF.

Contrast echocardiography for assessing left ventricular vortex strength in heart failure: a prospective cohort study

AIMS This study investigated the incremental role of echocardiographic-contrast particle image velocimetry (Echo-PIV) in patients with heart failure (HF) for measuring changes in left ventricular (LV) vortex strength (VS) during phases of a cardiac cycle. METHODS AND RESULTS Echo-PIV was performed in 42 patients, including 23 HF patients and 19 controls. VS was measured as a fluid-dynamic parameter that integrates blood flow rotation over a given area and correlated with non-invasively derived indices of LV mechanical performance. In comparison with early and late diastole, the VS was higher during isovolumic contraction (IC) for control and HF patients with the preserved ejection fraction (P = 0.002 and P = 0.01, respectively), but not for HF patients with the reduced ejection fraction (P = 0.41). On multivariable regression analysis, the VS during IC (VSIC) was independently related to late-diastolic VS and LV longitudinal strain (R(2)= 0.63, P < 0.001 and P = 0.003, respectively). Patients in whom diastolic VS was augmented during IC showed a higher LV stroke volume (P = 0.01), stroke work (P = 0.02), and mechanical efficiency (P = 0.008). Over a median follow-up period of 2.9 years, eight (34%) HF patients were hospitalized for decompensated HF. In comparison with the rest, these eight patients showed markedly reduced longitudinal strain (P = 0.002), and lower change in VS (P = 0.004). CONCLUSION Our preliminary data suggest that the persistence of vortex from late diastole into IC is a haemodynamic measure of coupling between diastole and systole. The change in VS is correlated with LV mechanical performance and shows association with adverse clinical outcomes seen in HF patients.

Natural history of left ventricular mechanics in transplanted hearts: relationships with clinical variables and genetic expression profiles of allograft rejection.

OBJECTIVES The aim of this study was to explore the temporal evolution of left ventricular (LV) mechanics in relation to clinical variables and genetic expression profiles implicated in cardiac allograft function. BACKGROUND Considerable uncertainty exists regarding the range and determinants of variability in LV systolic performance in transplanted hearts (TXH). METHODS Fifty-one patients (mean age 53 ± 12 years; 37 men) underwent serial assessment of echocardiograms, cardiac catheterization, gene expression profiles, and endomyocardial biopsy data within 2 weeks and at 3, 6, 12, and 24 months after transplantation. Two-dimensional speckle-tracking data were compared between patients with TXH and 37 controls (including 12 post-coronary artery bypass patients). Post-transplantation mortality and hospitalizations were recorded with a median follow-up period of 944 days. RESULTS Global longitudinal strain (LS) and radial strain remained attenuated in patients with TXH at all time points (p < 0.001 and p = 0.005), independent of clinical rejection episodes. Failure to improve global LS at 3 months (≥ 1 SD) was associated with higher incidence of death and cardiac events (hazard ratio: 5.92; 95% confidence interval: 1.96 to 17.91; p = 0.049). Multivariate analysis revealed gene expression score as the only independent predictor of global LS (R(2) = 0.53, p = 0.005), with SEMA7A gene expression having the highest correlation with global LS (r = -0.84, p < 0.001). CONCLUSIONS Speckle tracking-derived LV strains are helpful in estimating the burden of LV dysfunction in patients with TXH that evolves independent of biopsy-detected cellular rejection. Failure to improve global LS at 3 months after transplantation is associated with a higher incidence of death and cardiac events. Serial changes in LV mechanics correlate with peripheral blood gene expression profiles and may affect the clinical assessment of long-term prognosis in patients with TXH.

Relationship of contrast-enhanced magnetic resonance imaging-derived intramural scar distribution and speckle tracking echocardiography-derived left ventricular two-dimensional strains

AIMS Information is limited regarding the functional correlates of intramural scar burden in myopathic hearts. We aimed to explore the use of speckle tracking echocardiography selectively at three intramural locations, to investigate the variance in cardiac strains and their relationship to contrast-enhanced magnetic resonance imaging-derived scar distribution and global left ventricular systolic function. METHODS AND RESULTS Fifty-nine patients with evidence of myocardial fibrosis on contrast-enhanced magnetic resonance imaging and 18 healthy subjects underwent speckle tracking echocardiography for measuring subendocardial, midmyocardial, and subepicardial strains in longitudinal, circumferential, and radial directions. Patients were divided into three categories of scar distribution: Group A, endocardial and midmyocardial; Group B, midmyocardial and epicardial; and Group C, transmural. When these patients were compared with 18 healthy control subjects, longitudinal left ventricular deformation was attenuated equally for all three groups, whereas circumferential strain was relatively well preserved. On multivariate analysis, circumferential strain and scar burden were independent determinants of left ventricular ejection fraction (R(2) = 0.57; P = 0.003 for strain burden and P = 0.01 for scar burden). CONCLUSION Longitudinal strains are attenuated independent of myocardial scar location. This alteration in left ventricular deformation is associated with circumferential mechanics becoming a key determinant of global left ventricular pump function in myopathic hearts.

CRT Improves LV Filling Dynamics: Insights From Echocardiographic Particle Imaging Velocimetry

Echocardiographic particle imaging velocimetry allows blood flow visualization and characterization of diastolic vortex formation that may play a key role in filling efficiency. We hypothesized that abrupt withdrawal of cardiac resynchronization therapy (CRT) would alter the timing of left ventricular diastolic vortex formation and modify cardiac time intervals. In patients with heart failure (HF) who had chronically implanted CRT devices, the timing of the onset of the diastolic vortex (TDV) from mitral valve opening, transmitral flow, and cardiac time intervals was measured at baseline and after deactivation and reactivation of CRT. Compared with control patients with cardiovascular risk factors but structurally normal hearts, TDV was significantly delayed in patients with HF. Deactivation of CRT resulted in striking delay in TDV due to disorganized flow and reduced flow acceleration, and reactivation reversed these characteristics instantly. In addition, CRT deactivation also prolonged the isovolumic contraction interval, which closely correlated with the changes in the TDV. These data suggest that CRT plays an important role in optimization of left ventricular diastolic filling.

Myocardial deformation and rotational mechanics in revascularized single vessel disease patients 2 years after ST-elevation myocardial infarction.

Objective We sought to characterize the left ventricular strains and rotational mechanics in the infarct-related and remote regions of dilated heart following an ST-elevation myocardial infarction (STEMI) to understand the adaptive changes in global left ventricular function that develop several months after percutaneous coronary revascularization. Methods Forty-six patients with STEMI (66.6 ± 11 years, 29 men) 2 years after coronary revascularization were enrolled. Longitudinal, circumferential, radial and rotational mechanics of the left ventricle were evaluated by speckle tracking echocardiography in 39 (84.8%) of them, after excluding seven patients with multivessel coronary disease. Forty-one asymptomatic volunteers without a history of coronary artery disease (65 ± 9 years, 23 men) served as controls. Results There was no difference, between groups, regarding the prevalence of cardiovascular risk factors, whereas patients had significantly reduced left ventricular strains (P < 0.001), rotations (P < 0.001), twist (P < 0.001), torsion (P < 0.001) and untwisting rates (P < 0001) in comparison with controls. Furthermore, reduction in regional strains was observed both in infarct and remote regions of the left ventricle and correlated with the changes in ejection fraction. On logistic regression analysis, only global circumferential strain was independently related (odds ratio 4.28; 95% confidence interval 1.11–16.4; P = 0.034) with left ventricular dilation, defined as an indexed end-diastolic left ventricular volume more than 75 ml/m2. Conclusion Reduction in regional strains and rotational mechanics are detectable in both the infarct-related and remote regions of dilated left ventricle. Attenuation of global circumferential strain, rather than isolated changes in the mechanics of the infarct region might contribute to determine the extent of left ventricular dilation, independent of the presence of multiple risk factors for left ventricular dysfunction. These findings might have important clinical implications regarding novel therapeutic approaches for counteracting left ventricular remodeling.

Tissue Doppler image-derived measurements during isovolumic contraction predict exercise capacity in patients with reduced left ventricular ejection fraction.

OBJECTIVES We explored the incremental value of quantification of tissue Doppler (TD) velocity during the brief isovolumic contraction (IVC) phase of the cardiac cycle for the prediction of exercise performance in patients referred for cardiopulmonary exercise testing (CPET). BACKGROUND Experimental studies have shown that rapid left ventricular (LV) shape change during IVC is essential for optimal onset of LV ejection. However, the incremental value of measuring IVC velocities in clinical settings remains unclear. METHODS A total of 82 subjects (age 53+/-14 years, 56 men) were studied with echocardiography and CPET. Reduced LV ejection fraction (EF) (EF<50%) was present in 38 (46%) subjects. Pulsed-wave annular TD velocities were averaged from the LV lateral and septal annulus during isovolumic contraction (IVCa), ejection, isovolumic relaxation, and early and late diastole (Aa) and compared with peak oxygen consumption (VO2) and percentage of the predicted peak VO2 (% predicted peak VO2) obtained from CPET. RESULTS Patients with reduced EF had lower IVCa (6.3 vs. 4.5 cm/s, p=0.04), ejection (7.7 vs. 5.5 cm/s, p<0.001), and Aa velocities (7.9 vs. 6.6 cm/s, p=0.04). Similarly, % predicted peak VO2 was lower in patients with reduced EF (52.9% vs. 73.1%, p<0.001) and correlated with the variations in IVCa (r=0.7, p=0.001). Multivariate analysis of 2-dimensional and Doppler variables in the presence of reduced LV EF revealed only IVCa and Aa as independent predictors of % predicted peak VO2 (r2=0.612, p=0.02 for IVCa and p=0.009 for Aa). The overall performance of IVCa in the prediction of exercise capacity was good (area under the curve=0.86, p<0.001). CONCLUSIONS Assessment of TD-derived IVC and atrial stretch velocities provide independent prediction of exercise capacity in patients with reduced LV EF. Assessment of LV pre-ejectional stretch and shortening mechanics at rest may be useful for determining the myocardial functional reserve of patients with reduced EF.

Left Ventricular Rotational Mechanics before and after Exercise in Children

BACKGROUND In children, there is limited information regarding the relative contribution of left ventricular (LV) apical and basal rotation to increase LV pump function with exercise. The aim of this study was to test the hypothesis that a progressive increase in LV pump function with exercise is related to increased LV apical and basal rotation. METHODS Forty-two subjects 12 to 18 years of age with normal cardiac structure and function were recruited prospectively and imaged at rest, and in 20 subjects, imaging was repeated after moderate exercise. Conventional measures of LV systolic and diastolic performance were evaluated. Left ventricular rotation, LV twist, rotational rate, and recoil and untwist rates were measured using two-dimensional speckle-tracking echocardiography. Torsion was calculated by normalizing LV twist to LV diastolic length. Twist displacement loops were constructed from data obtained at rest and after exercise. RESULTS Apical rotation increased significantly after exercise (7.33 ± 2.8° vs 11.6 ± 4.7°, P = .0004), but basal rotation did not (-4.85 ± 1.9 vs -6.46 ± 4.81, P = .21). Similarly, peak twist, torsion, and twist rate also increased significantly after exercise. In diastole, apical recoil rate and LV untwist rate also increased significantly with exercise. The slope of the systolic limb of the twist displacement loop and the area enclosed by the loop also increased significantly with exercise. CONCLUSIONS Increases in global LV pump function during exercise in children are associated with enhanced LV apical rotation but not LV basal rotation. In addition, unique changes were seen in twist displacement loops in children before and after exercise. These data may serve as a foundation for understanding future applications of LV rotational mechanics in disease states.

Non-uniform recovery of left ventricular transmural mechanics in ST-segment elevation myocardial infarction

BackgroundAfter a transient ischemic episode, the subendocardial region is more severely injured than outer subepicardial layers and may regain a proportionately greater degree of mechanical function in the longitudinal direction. We sought to explore left ventricular (LV) transmural mechanics in patients with ST-segment elevation myocardial infarction (STEMI) for determining the mechanism underlying recovery of global LV function after primary percutaneous coronary intervention (PCI).MethodsA total of 42 patients (62 ± 11 years old, 71% male) with a first STEMI underwent serial assessments of LV longitudinal, circumferential and radial strains (LS, CS and RS) by selective tracking of subendocardial and subepicardial regions within 48 hours and a median of 5 months after PCI. LV mechanical parameters were compared with sixteen age and gender matched normal controls.ResultsIn comparison with controls, endocardial and epicardial LS were markedly attenuated at 48 hours following PCI (P < 0.001). An improvement in LV ejection fraction (EF > 5%) following PCI was seen in 24 (57%) patients and was associated with improvement in endocardial and epicardial LS (P < 0.001 and P = 0.003, respectively) and endocardial CS (P = 0.01). Radial strain and wall motion score index, however, remained persistently abnormal. The change in endocardial LS (OR 1.2, 95% CI 1.03 to 1.42, P = 0.01) and the change in epicardial LS (OR 1.2, 95% 1.03 to 1.46, P = 0.02) were significantly associated with the improvement in LVEF, independent of the location of STEMI and the presence of underlying multivessel disease.ConclusionsIn patients with STEMI treated by PCI, the recovery of LV subendocardial shortening strain seen in the longitudinal direction underlies the improvement in LV global function despite persistent abnormalities in radial mechanics and wall motion score index.