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Technical Brief

Differential Effects of Isoproterenol on Regional Myocardial Mechanics in Rat using 3D cine DENSE Cardiovascular Magnetic Resonance

[+] Author and Article Information
Xiaoyan Zhang

Department of Mechanical Engineering, University of Kentucky, Lexington, KY, USA
xzh225@uky.edu

Zhan-Qiu Liu

Department of Mechanical Engineering, University of Kentucky, Lexington, KY, USA
Zhanqiu.Austin.Liu@uky.edu

Dara Singh

Department of Mechanical Engineering, University of Kentucky, Lexington, KY, USA
dara.singh@uky.edu

David K. Powell

Department of Anatomy and Neurobiology, University of Kentucky, Lexington, KY, USA
david.k.powell@uky.edu

Charles S. Chung

Department of Physiology, Wayne State University, Detroit, MI, USA; Department of Physiology, University of Kentucky, Lexington, KY, USA
cchung@med.wayne.edu

Kenneth S. Campbell

Department of Physiology, University of Kentucky, Lexington, KY, USA
k.s.campbell@uky.edu

Jonathan F. Wenk

Department of Surgery, University of Kentucky, Lexington, KY, USA
wenk@engr.uky.edu

1Corresponding author.

ASME doi:10.1115/1.4041042 History: Received January 13, 2018; Revised July 18, 2018

Abstract

The present study assessed the acute effects of isoproterenol on left ventricular (LV) mechanics in healthy rats with the hypothesis that ß-adrenergic stimulation influences the mechanics of different myocardial regions of the LV wall in different ways. To accomplish this, magnetic resonance images were obtained in the LV of healthy rats with or without isoproterenol infusion. The LV contours were divided into basal, mid-ventricular, and apical regions. Additionally, the mid-ventricular myocardium was divided into three transmural layers with each layer partitioned into four segments (i.e., septal, inferior, lateral, and anterior). Peak systolic strains and torsion were quantified for each region. Isoproterenol significantly increased peak systolic radial strain and circumferential-longitudinal shear strain, as well as ventricular torsion, throughout the basal, mid-ventricle, and apical regions. In the mid-ventricle, isoproterenol significantly increased peak systolic radial strain, and induced significant increases in peak systolic circumferential strain and longitudinal strain in the septum. Isoproterenol consistently increased peak systolic circumferential-longitudinal shear strain in all mid-ventricular segments. Ventricular torsion was significantly increased in nearly all segments except the inferior sub-endocardium. The effects of isoproterenol on LV systolic mechanics (i.e., 3D strains and torsion) in healthy rats depend on the region. This region-dependency is also strain component-specific. These results provide insight into the regional response of LV mechanics to ß-adrenergic stimulation in rats, and could act as a baseline for future studies on subclinical abnormalities associated with the inotropic response in heart disease.

Copyright (c) 2018 by ASME
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