Abstract
BackgroundThe purpose of this study was to quantify myocardial strain on the subendocardial and epicardial layers of the left ventricle (LV) using tagged cardiovascular magnetic resonance (CMR) and to investigate the transmural degree of contractile impairment in the chronic ischemic myocardium.Methods3T tagged CMR was performed at rest in 12 patients with severe coronary artery disease who had been scheduled for coronary artery bypass grafting. Circumferential strain (C-strain) at end-systole on subendocardial and epicardial layers was measured using the short-axis tagged images of the LV and available software (Intag; Osirix). The myocardial segment was divided into stenotic and non-stenotic segments by invasive coronary angiography, and ischemic and non-ischemic segments by stress myocardial perfusion scintigraphy. The difference in C-strain between the two groups was analyzed using the Mann-Whitney U-test. The diagnostic capability of C-strain was analyzed using receiver operating characteristics analysis.ResultsThe absolute subendocardial C-strain was significantly lower for stenotic (-7.5 ± 12.6%) than non-stenotic segment (-18.8 ± 10.2%, p < 0.0001). There was no difference in epicardial C-strain between the two groups. Use of cutoff thresholds for subendocardial C-strain differentiated stenotic segments from non-stenotic segments with a sensitivity of 77%, a specificity of 70%, and areas under the curve (AUC) of 0.76. The absolute subendocardial C-strain was significantly lower for ischemic (-6.7 ± 13.1%) than non-ischemic segments (-21.6 ± 7.0%, p < 0.0001). The absolute epicardial C-strain was also significantly lower for ischemic (-5.1 ± 7.8%) than non-ischemic segments (-9.6 ± 9.1%, p < 0.05). Use of cutoff thresholds for subendocardial C-strain differentiated ischemic segments from non-ischemic segments with sensitivities of 86%, specificities of 84%, and AUC of 0.86.ConclusionsAnalysis of tagged CMR can non-invasively demonstrate predominant impairment of subendocardial strain in the chronic ischemic myocardium at rest.
Highlights
The purpose of this study was to quantify myocardial strain on the subendocardial and epicardial layers of the left ventricle (LV) using tagged cardiovascular magnetic resonance (CMR) and to investigate the transmural degree of contractile impairment in the chronic ischemic myocardium
Seventeen patients with coronary artery stenosis, who were diagnosed as having ≥ 1 severe coronary stenosis (> 75% stenosis) using quantitative coronary artery angiography (CAG) and had been scheduled for coronary artery bypass grafting, were registered
In all patients with coronary artery disease (CAD), the absolute value of C-strain was significantly greater for the subendocardial layer (-14.3 ± 12.7%) than epicardial layer (-7.4 ± 9.5%, p < 0.0005)
Summary
The purpose of this study was to quantify myocardial strain on the subendocardial and epicardial layers of the left ventricle (LV) using tagged cardiovascular magnetic resonance (CMR) and to investigate the transmural degree of contractile impairment in the chronic ischemic myocardium. Systolic wall thickening of the left ventricle (LV) is distributed transmurally inhomogeneously. Intra-myocardial mechanisms, including wall motion strains and/or the torsion angles, can be measured when a pre-saturation tag pattern of cardiovascular magnetic resonance (CMR) is added to cine imaging. CMR-tagging has been well demonstrated in animal studies [3,4,5]. Myocardial function after infarction has been studied by CMRtagging [6,7,8] and a decrease in the transmural gradient of circumferential strain (C-strain) has been demonstrated in rats [7]
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