Equilibrium Radionuclide Angiography in Evaluation of Left Ventricular Mechanical Dyssynchrony in Patients with Dilated Cardiomyopathy: Comparison with Electrocardiographic Parameters and Speckle-Tracking Echocardiography

Purpose of the Study: The purpose of this study was to study the role of equilibrium radionuclide angiography (ERNA) in the assessment of left ventricular (LV) mechanical dyssynchrony in patients with dilated cardiomyopathy (DCM), by correlating the findings with electrocardiographic parameters and speckle-tracking echocardiography (STE). Methods: This was a prospective observational study. A total of 55 patients with a mean age 42.5 +/- 11 years (range: 19-61 years) diagnosed with DCM underwent ERNA and echocardiography sequentially. On ERNA, phase images of LV were obtained, and standard deviation of LV mean phase angle (SD LVmPA) was derived to quantify intra-LV mechanical dyssynchrony (ILVD). Similarly, on STE, "dyssynchrony index" was calculated as the standard deviation of time-to-peak systolic circumferential strain (SDCS) of the six mid-LV segments. The cutoff values used to define mechanical dyssynchrony were SD LVmPA >13.2 degrees (or >27.1 ms) and SDCS >74 ms on ERNA and STE, respectively. The results obtained from the two modalities were then compared. Results: Speckle-tracking analysis could be done on the echocardiographic data of only 42 patients. Paired data from ERNA and STE studies of these 42 patients (26 males and 16 females) were compared, which showed no significant difference in the detection of ILVD (P = 0.125). The two modalities showed good agreement with Cohen's kappa value of 0.78 (P < 0.0001). SD LVmPA and SDCS values showed moderately strong linear correlation (rho = 0.69; P < 0.0001). No significant association of mechanical dyssynchrony on ERNA or STE was found with QRS duration and with the presence or absence of left bundle branch block. ILVD was also found to be negatively correlated with LV ejection fraction. Conclusion: ERNA is comparable to STE for the assessment of LV mechanical dyssynchrony.