Left ventricular endocardial and epicardial strain changes with apical myocardial ischemia in an open-chest porcine model.

Kimberly Howard‐Quijano,Aman Mahajan,Melissa Mccabe,Einat Mazor,Alexander Cheng,Kentaro Yamakawa,Wei Zhou,Jennifer C Scovotti

doi:10.14814/phy2.13042

Abstract

Early detection of acute myocardial ischemia is critical to prevent permanent myocardial damage. The impact of apical ischemia on global left ventricular (LV) function can be difficult to characterize using traditional volume‐based echocardiography measures. Myocardial strain imaging is a sensitive, quantitative marker of myocardial deformation that can measure ventricular function. Recent advances allow layer‐specific measurement of endo‐ and epicardial strain, enhancing the ability to evaluate myocardial ischemia. This study investigates the effects of apical ischemia on LV function using epi‐ and endocardial strain. We hypothesize that myocardial strain will identify changes in regional and global myocardial function associated with focal apical ischemia as compared to ejection fraction (EF), and that longitudinal strain will be a better indicator of myocardial dysfunction compared to circumferential or radial strain. In a porcine model (n = 9), acute ischemia was induced by left anterior descending coronary artery occlusion. Echocardiograms were performed at baseline, during 15‐min ischemia, and after reperfusion. Global longitudinal strain decreased with acute focal ischemia of the left ventricular apical region (baseline: −16.4% vs. ischemia: −12.2%; P = 0.010), with no change observed in global circumferential and radial strain or EF. Both endocardial and epicardial longitudinal strain decreased by 68% (P < 0.001) in the ischemic and peri‐ischemic zone, while circumferential and radial strain only decreased in endocardium of the ischemic zone. Longitudinal strain was more sensitive to ischemia, being able to detect changes in global LV function and thus may confer clinical diagnostic advantage in the evaluation of acute LV apical ischemia.

Highlights

Detection of acute myocardial ischemia is critical for prevention of irreversible myocardial damage
Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society
Major findings include: (1) Global LS was reduced with acute left ventricular (LV) apical ischemia, whereas global CS, Radial strain (RS), and ejection fraction (EF) were not; (2) In the ischemic zone, LS was reduced throughout ischemia in both the endocardium and epicardium, whereas CS and RS were reduced only transiently in the endocardium; (3) In the peri-ischemic zone, endocardial and epicardial LS were both depressed while no changes in CS or RS were observed; (4) Apical rotation was reduced transiently at 1-min ischemia and recovered

Summary

Introduction

Detection of acute myocardial ischemia is critical for prevention of irreversible myocardial damage. Subtle changes in endocardial deformation can be measured quantitatively with speckle tracking strain imaging (Mor-Avi et al 2011). Myocardial strain is a sensitive, quantitative marker of myocardial deformation (Voigt et al 2003); strain measured by speckle tracking echocardiography is angle-independent and has been validated by sonomicrometry and cardiac MRI (Korinek et al 2005; Langeland et al 2005; Amundsen et al 2006; Altiok et al 2013; Koos et al 2013). Myocardial strain has been found to improve detection of ischemia-induced regional wall motion abnormalities in stress echocardiography studies as compared to qualitative echocardiography assessment alone (Reant et al 2008).

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Discussion

Conclusion