Relationship between left ventricular mechanics and low free triiodothyronine levels after myocardial infarction: a prospective study

Echocardiographic imaging is ideally suited for the evaluation of cardiac mechanics because of its intrinsically dynamic nature. Because for decades, echocardiography has been the only imaging modality that allows dynamic imaging of the heart, it is only natural that new, increasingly automated techniques for sophisticated analysis of cardiac mechanics have been driven by researchers and manufacturers of ultrasound imaging equipment.Several such technique shave emerged over the past decades to address the issue of reader's experience and inter measurement variability in interpretation.Some were widely embraced by echocardiographers around the world and became part of the clinical routine,whereas others remained limited to research and exploration of new clinical applications.Two such techniques have dominated the research arena of echocardiography: (1) Doppler based tissue velocity measurements,frequently referred to as tissue Doppler or myocardial Doppler, and (2) speckle tracking on the basis of displacement measurements.Both types of measurements lend themselves to the derivation of multiple parameters of myocardial function. The goal of this document is to focus on the currently available techniques that allow quantitative assessment of myocardial function via image-based analysis of local myocardial dynamics, including Doppler tissue imaging and speckle-tracking echocardiography, as well as integrated backscatter analysis. This document describes the current and potential clinical applications of these techniques and their strengths and weaknesses,briefly surveys a selection of the relevant published literature while highlighting normal and abnormal findings in the context of different cardiovascular pathologies, and summarizes the unresolved issues, future research priorities, and recommended indications for clinical use.

During the past several years, strain and strain rate imaging have emerged as a quantitative technique to accurately estimate myocardial function and contractility. Non-Doppler, 2-dimensional (2D) strain imaging is a new echocardiographic technique for obtaining strain and strain rate measurements. It analyzes motion by tracking speckles in the ultrasonic image in two dimensions. Current available software allows spatial and temporal image processing with recognition and selection of such elements on ultrasound image. The geometric shift of each speckle represents local tissue movement. By tracking theses speckles, 2D tissue velocity, strain, and strain rate can be calculated. Non-Doppler 2D strain imaging is simple to perform. It requires only one cardiac cycle to be acquired; further processing and interpretation can be done after image data acquisition. Because it is not based on tissue Doppler measurements, it is angle independent. Data regarding accuracy, validity, and clinical application of non-Doppler 2D strain imaging are rapidly accumulating. This technique may prove to be of significant clinical value, enabling rapid and accurate assessment of global and segmental myocardial function.

We sought to investigate the clinical prognostic value of longitudinal and circumferential strain (S) and strain rate (SR) in patients after high-risk myocardial infarction (MI). Left ventricular (LV) contractile performance after MI is an important predictor of long-term outcome. Tissue deformation imaging might more closely reflect myocardial contractility than traditional measures of systolic functions. The VALIANT (Valsartan in Acute Myocardial Infarction Trial) Echo study enrolled 603 patients with LV dysfunction, heart failure, or both 5 days after MI. We measured global peak longitudinal S and systolic SR (SRs) from apical 4- and 2-chamber views and global circumferential S and SRs from parasternal short-axis view with speckle tracking software (Velocity Vector Imaging, Siemens, Inc., Mountain View, California). We related global S and SRs to LV remodeling at 20-month follow-up and to clinical outcomes. Both longitudinal (mean: -5.1 ± 1.6 100/ms) and circumferential SRs (mean: -8.0 ± 2.8 100/ms) were predictive of death or hospital stay for heart failure (hazard ratio: 2.4, 95% confidence interval [CI]: 2.0 to 3.1, p < 0.001; hazard ratio: 1.3, 95% CI: 1.2 to 1.4, p < 0.001, respectively) after adjustment for clinical covariates by Cox proportional hazards, and longitudinal SRs further improved in predicting 18-month survivor on a model based on clinical and standard echocardiographic measures (increase in area under the receiver-operator characteristic curve: 0.13, p = 0.009). With multivariable logistic regression, circumferential SRs, but not longitudinal SRs, was strongly predictive of remodeling (odds ratio: 1.3, 95% CI: 1.1 to 1.4, p < 0.001). Both longitudinal and circumferential SRs were independent predictors of outcomes after MI, whereas only circumferential SRs was predictive of remodeling, suggesting that preserved circumferential function might serve to restrain ventricular enlargement after MI. Copyright © 2010 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.