Use of phase analysis of gated SPECT perfusion imaging to quantify dyssynchrony in patients with mild-to-moderate left ventricular dysfunction

Background: CRT has been shown to be beneficial in the majority of patients with NYHA class III-IV symptoms, prolonged QRS duration, and an EF ≤ 35%. The use of imaging modalities to quantify dyssynchrony may help identify patients who may benefit from CRT, but do not meet current selection criteria. We hypothesize that patients with mild-to-moderate LV dysfunction have significant degrees of mechanical dyssynchrony. Methods: We compared phase analysis measures of mechanical dyssynchrony from gated SPECT imaging in patients with mild-to-moderate LV dysfunction (EF 35-50%, n = 93), with patients with severe LV dysfunction (EF ≤ 35%, n = 167), and with normal controls (EF ≥ 55%, n = 75). Furthermore, we evaluated the relationships between QRS duration and dyssynchrony and determined the prevalence of dyssynchrony in patients with mild-moderate LV dysfunction. Results: Patients with mild-moderate LV dysfunction have more dyssynchrony than normal controls (phase SD 37.7° vs 8.8°, P < .001 and bandwidth 113.5° vs 28.7°, P < .001), but less dyssynchrony than patients with severe LV dysfunction (phase SD 37.7° vs 52.0°, P < .001 and bandwidth 113.5° vs 158.2°, P < .001). In the cohort of patients with LV EF 35-50%, there were only weak correlations between QRS duration and dyssynchrony (phase SD, r = 0.28 and bandwidth, r = 0.20). There were 73 patients with LVEF 35-50% and QRS duration < 120 milliseconds of which 21 (28.8%) had mechanical dyssynchrony. Overall, 37% of patients with mild-to-moderate LV dysfunction had significant degrees of mechanical dyssynchrony. Conclusions: This is the largest reported study evaluating mechanical dyssynchrony in patients with mild-moderate LV dysfunction using phase analysis of gated SPECT imaging. In this study, approximately one-third of patients with mild-to-moderate LV dysfunction had significant LV mechanical dyssynchrony. With further study, phase analysis of gated SPECT imaging may help improve patient selection for CRT.