Left ventricular dyssynchrony measured by cardiovascular magnetic resonance-feature tracking in anterior ST-elevation myocardial infarction: relationship with microvascular occlusion myocardial damage

Abstract Myocardial tissue tracking imaging techniques have been developed for a more accurate evaluation of myocardial deformation (i.e. strain), with the potential to overcome the limitations of ejection fraction (EF) and to contribute, incremental to EF, to the diagnosis and prognosis in cardiac diseases. While most of the deformation imaging techniques are based on the similar principles of detecting and tracking specific patterns within an image, there are intra- and inter-imaging modality inconsistencies limiting the wide clinical applicability of strain. In this review, we aimed to describe the particularities of the echocardiographic and cardiac magnetic resonance deformation techniques, in order to understand the discrepancies in strain measurement, focusing on the potential sources of variation: related to the software used to analyse the data, to the different physics of image acquisition and the different principles of 2D vs. 3D approaches. As strain measurements are not interchangeable, it is highly desirable to work with validated strain assessment tools, in order to derive information from evidence-based data. There is, however, a lack of solid validation of the current tissue tracking techniques, as only a few of the commercial deformation imaging softwares have been properly investigated. We have, therefore, addressed in this review the neglected issue of suboptimal validation of tissue tracking techniques, in order to advocate for this matter.

The purpose of this study was to test the hypothesis that in heart failure with normal ejection fraction (HFNEF) exercise limitation is due to combined systolic and diastolic abnormalities, particularly involving ventricular twist and deformation (strain) leading to reduced ventricular suction, delayed untwisting, and impaired early diastolic filling. A substantial proportion of patients with heart failure have a normal left ventricular ejection fraction. Currently the pathophysiology is considered to be due to abnormal myocardial stiffness and relaxation. Patients with a diagnosis of HFNEF and proven cardiac limitation by cardiopulmonary exercise testing were studied by standard, tissue Doppler, and speckle tracking echocardiography at rest and on submaximal exercise. Fifty-six patients (39 women; mean age 72 +/- 7 years) with a clinical diagnosis of HFNEF and 27 age-matched healthy control subjects (19 women; mean age 70 +/- 7 years) had rest and exercise images of sufficient quality for analysis. At rest, systolic longitudinal and radial strain, systolic mitral annular velocities, and apical rotation were lower in patients, and all failed to rise normally on exercise. Systolic longitudinal functional reserve was also significantly lower in patients (p < 0.001). In diastole, patients had reduced and delayed untwisting, reduced left ventricular suction at rest and on exercise, and higher end-diastolic pressures. Mitral annular systolic and diastolic velocities, systolic left ventricular rotation, and early diastolic untwist on exercise correlated with peak VO(2)max. In HFNEF there are widespread abnormalities of both systolic and diastolic function that become more apparent on exercise. HFNEF is not an isolated disorder of diastole.