الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Myocardial ischemia leads to impaired ventricular relaxation and diastolic dysfunction, subsequently resulting in a decline in LV systolic function. (53) There is a series of events initiated by biochemical and metabolic changes leading to ventricular relaxation impairment and diastolic dysfunction followed by impaired systolic function. Therefore, ventricular relaxation is initially impaired before systolic function affected. (53) Even in cases when coronary collaterals are present, a majority of patients with coronary CTO arteries still experience some degree of left ventricular (LV) dysfunction. (54)
In patients with chronic total occlusions (CTOs), the distal arterioles in the CTO area maximally dilated to enhance the perfusion of the myocardium from the donor artery.(55)However, to maintain sufficient perfusion in the CTO area, the arteriolar capillary vessels and precapillary arterioles in the donor area need to constrict, thus maintaining the perfusion pressure.(56) These compensatory mechanisms may restrict the coronary blood flow to the donor area, resulting in the occurrence of early-stage ischemia or more severe ischemic conditions.(56)
Therefore, the sub-endocardium is the most susceptible area to ischemia. The longitudinal component of cardiac deformation is predominant in this part of myocardium. To assess this aspect of cardiac motion, 2D-STE longitudinal strain analysis is a sensitive technique for that purpose.(55) Impairment of longitudinal function in the left ventricle (LV) occurs at an earlier stage compared to abnormal radial contraction, as assessed by LVEF.(36) GLS is a measure of the sub-endocardial longitudinal fibers movement.(57) Therefore, in CTO patients with preserved LV function, assessing GLS using 2D-STE is an appropriate method to evaluate changes in the burden of myocardial ischemia.(43)
According to the 2014 European revascularization guidelines, chronic total occlusion percutaneous coronary intervention (CTO-PCI) is recommended when there is an anticipated reduction in myocardial ischemia