Chen-Cheng Chen, Abstract Co-Author: Nothing to Disclose

Thau-Yun Shen, Abstract Co-Author: Nothing to Disclose

Chung-Chieh Huang, Presenter: Nothing to Disclose

Wan-Chen Chen, Abstract Co-Author: Nothing to Disclose

Guang-Uei Hung, Abstract Co-Author: Nothing to Disclose

Ji Chen, Abstract Co-Author: Nothing to Disclose

Phase analysis of gated SPECT has been validated as a reliable tool to assess left-ventricular (LV) mechanical dyssynchrony. As Tl-201 SPECT acquires data shortly after stress, it can assess early post-stress LV function when stress-induced myocardial ischemia is present. The purpose of this study is to use Tl-201 SPECT to investigate whether stress-induced myocardial ischemia is associated with LV mechanical dyssynchrony.

Seventy-five patients who had dipyridamole-stress and rest Tl-201 gated SPECT were enrolled. The early post-stress scan was started at 5 minutes after Tl-201 injection, and followed by the rest scan 4 hours later. According to the quantitative assessment by the Emory Cardiac Toolbox, 25 patients (ischemia group) had significant reversible defects (summed stress score [SSS] ≥5, summed rest score [SRS] <5), 16 patients (infarct group) had significant fixed defects (SSS ≥5, SRS ≥5) and 34 patients (normal group) had no or minor defects (SSS <5, SRS <5), respectively. LV dyssynchrony parameters, phase standard deviation (PSD) and phase histogram bandwidth (PHB), were calculated by phase analysis, and compared between the stress and rest images.

LV dyssynchrony at rest was significantly larger in the infarct group than that in the normal (p <0.001 for PSD and PHB) and ischemia groups (both p <0.001), respectively. There were no significant differences in LV dyssynchrony at rest between the normal and ischemia groups. In the ischemia group, LV dyssynchrony was significantly larger at stress than that at rest (both p < 0.005). On the contrary, LV dyssynchrony was significantly smaller at stress than that at rest in the normal (both p<0.01) and infarct groups (both p<0.01), respectively.

Stress-induced myocardial ischemia caused dyssynchronous contraction in the ischemic region, and thus resulted in larger LV dyssynchrony. For normal patients, stress caused more synchronous contraction. For patients with myocardial infarction, although delayed contraction persisted in the infarct region on both stress and rest scans, stress caused more synchronous contraction in the normal region, and thus resulted in less LV global dyssynchrony. 

Comparison of LV dyssynchrony at early post-stress to that at rest using Tl-201 gated SPECT MPI can help differentiate myocardial ischemia from normal myocardium and myocardial infarction.

Chen, C, Shen, T, Huang, C, Chen, W, Hung, G, Chen, J, Stress-induced Myocardial Ischemia is Associated with Left Ventricular Mechanical Dyssynchrony as Assessed by Early Post-stress Tl-201 Gated SPECT Myocardial Perfusion Imaging.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12043414.html