Gated single photon emission computed tomography imaging of left ventricular mechanical dyssynchrony: Predictive value in cardiac resynchronization therapy candidates.

Cardiac resynchronization therapy (CRT) is recommended for patients with heart failure with reduced ejection fraction (HFrEF) who meet specific electrocardiographic (ECG) criteria of electrical dyssynchrony. Gated single-photon emission computed tomography (G-SPECT) is an imaging method that allows for the assessment of left ventricular mechanical dyssynchrony (LVMD); however, its predictive value for CRT response remains uncertain. This study aimed to evaluate the utility of G-SPECT in identifying LVMD and predicting CRT response in patients with HFrEF. Patients with HFrEF and a LVEF <35% were prospectively enrolled and stratified into two groups: 60 patients CRT-eligible (Group 1) and 40 CRT-ineligible (Group 2). All patients underwent ECG, echocardiography, and G-SPECT imaging at baseline and at 6-month follow-up. LVMD was assessed using G-SPECT-derived parameters: (a) histogram bandwidth (HBW), (b) phase standard deviation (PSD), and (c) phase entropy, both at rest and under stress. CRT response was evaluated based on changes in LVEF. At baseline, patients in Group 1 exhibited greater LVMD as assessed by both echocardiography and G-SPECT. All G-SPECT-derived parameters, along with septal-to-posterior wall motion delay on echocardiography, were correlated with QRS duration. After CRT, LVMD significantly improved in Group 1. Super-response, defined as EF normalization, was observed in 11.9% of patients. G-SPECT-derived LVMD parameters, particularly rest PSD and entropy measures, were significant predictors of the favorable outcome of LVEF normalization. LVMD parameters obtained from G-SPECT were significantly correlated with electrical dyssynchrony as measured by QRS duration. Following CRT implantation, LVMD improved in parallel with increases in LVEF.