Quantitative detection of changes in regional wall motion using real time strain-encoded cardiovascular magnetic resonance

A comprehensive cardiovascular magnetic resonance (CMR) exam includes assessment of regional wall motion, which typically involves qualitative interpretation by an experienced reader, although time-consuming quantitative measurements of myocardial wall thickening can be performed. Myocardial strain imaging offers the potential to more accurately quantify the extent and severity of regional wall motion abnormalities and has even been proposed as a mechanism to identify changes in regional contractility before they are visually evident1. Strain imaging may be particularly valuable to assess the impact of coronary artery disease on the myocardium because ischemia is known to first alter the longitudinal deformation of the subendocardial myocardial fibers prior to impacting the regional thickening in the radial direction that is required to create a visually appreciable wall motion abnormality1. In patients with chest pain, alterations in strain following the infusion of an inotrope such as dobutamine can be used to improve the detection of underlying coronary artery disease2. Myocardial strain can be measured using several different CMR-based tagging techniques, such as complementary spatial modulation of magnetization (C-SPAMM) 3 with harmonic phase encoding (HARP) post-processing 4,5, displacement encoding with stimulating echoes (DENSE) 6, cine phase contrast imaging, and strain-encoded CMR (SENC) 7–9. Additionally, it is also possible to use feature tracking algorithms to derive strain measurements from standard cine-CMR images 10,11. Each of these approaches has its advantages and limitations. Recent improvements in SENC-CMR allow for image acquisition to occur during a single heart beat in real time without sacrificing temporal resolution. Unlike the other strain imaging approaches, with SENC imaging being performed during a single heart beat, image quality is not significantly impacted by respiratory motion and arrhythmia. Previous single center studies have suggested that SENC-CMR can be used to improve the detection of coronary artery disease when compared to cine-image wall motion interpretation 12. In this multi-center study, we hypothesized that in the presence of coronary artery disease, changes in regional longitudinal and circumferential strain detected using SENC under intermediate-dose dobutamine stress CMR would precede changes in wall thickening visible on cine-CMR images.