Does perfusion pattern influence stress induced changes in left ventricular mechanical dyssynchrony on Thallium-201 gated myocardial perfusion SPECT?

Objectives To assess the relationship between perfusion patterns on Stress-rest Thallium-201 gated myocardial perfusion SPECT (Tl-201 MPS) and stress induced changes in left ventricular mechanical dyssynchrony (LVMD).

Methods Data of 194 patients who underwent Exercise Stress-rest Tl-201 MPS was retrospectively evaluated. Fifty patients who had normal LV perfusion and function on MPS were taken as normal group. Patients with perfusion abnormalities (n=144) were divided into 3 groups: ischemia (n=66), infarct (n=32), and mixed group (n=46; ischemia and infarct both). Summed stress score (SSS), summed rest score (SRS), LVEF, phase standard deviation (PSD), and phase histogram bandwidth (PHB) were assessed in post stress and rest images. Summed difference score (SDS), ΔPSD (Post stress PSD - Rest PSD) and ΔPHB (Post stress PHB - Rest PHB) were calculated.

Results The LV perfusion (SSS,SRS,SDS), function (LVEF) and LVMD (PSD,PHB,ΔPSD,ΔPHB) parameters obtained are given in Table. In all the groups, post stress LVMD was significantly lower as compared to LVMD at rest. However, 28/144 patients with perfusion abnormalities showed post stress worsening of LVMD. The proportion of patients showing post stress worsening of LVMD was more in group with perfusion abnormalities, than those with normal perfusion (19.4% vs. 0%; p=0.002). On sub group analysis, no difference was found in proportion of patients showing post stress worsening of LVMD between ischemia (13.6%), infarct (25%) and mixed (23.6%) groups.

Conclusions LV myocardium shows more synchronous contraction during stress as compared to rest regardless of perfusion pattern on Tl-201 MPS. While stress induced worsening of LV dyssynchrony is more common in patients with perfusion abnormalities, it does not depend on the type of perfusion abnormality.