Evaluation Of The Impact Of Bundle Branch Block On Left Ventricular Dyssynchrony And Function Using Phase Analysis Of Gated Myocardial Perfusion SPECT Imaging

Background Cardiac resynchronization therapy (CRT)is now an important therapy in end stage HF patients with LVEF<35%, QRS>120ms. But approximately 30%-40% of the patients who received CRT (LVEF< 35%, QRS duration > 120ms, New York Heart Association [NYHA] classⅢ/Ⅳ) do not response. The main reason for CRT no response may be that the patients with electrical dyssynchrony may not have mechanical dyssynchrony as well. How accurately measure LV mechanical dyssynchrony is the key for CRT patients selection and improving CRT response. Recently, phase analysis (SyncToolTM; Emory university, America) has developed for assessment of LV dyssynchrony from gated myocardial perfusion single-photon emission computed tomography (G-MPI) studies. This technique approximate the wall-thickening curve by Fourier harmonics over the cardiac cycle, this enable the phase analysis have enough temporal resolution for the assessment of LV dyssynchrony.Objective To evaluate the impact of left or right bundle branch block on LV dyssynchrony and LV function using phase analysis of gated myocardial perfusion SPECT imaging.Methods Thirty patients with LBBB, thirty with RBBB and thirty normal subjects were enrolled in this study. All patients have normal cardiac function and underwent gated myocardial perfusion SPECT imaging with Philips Cardio MD. End diastolic volume (EDV), end systolic volume (ESV) and LV ejection fraction (LVEF) were calculated from QGS software. The short axis of G-MPI were then submitted to SyncTool to get phase standard deviation (PSD) and phase histogram bandwidth (PHB). To identify the impaction of bundle branch block on LV dyssynchrony and function by Comparing LV dyssynchrony and function parameters between the three groups.Results Phases analysis parameters and LV function parameters of LBBB group showed statistically differences comparing to RBBB and control group, but no statistically differences between RBBB and control group. Normal values were calculated based on the control group. When PSD>12.4°is considered to be dyssynchrony, LV dyssynchrony in LBBB, RBBB and NL groups is 70%, 16.7% and 0%, respectively. When PHB>43.7°is considered to be dyssynchrony, LV dyssynchrony in LBBB, RBBB and NL groups is 63.3%, 13.3% and 3.3%, respectively.Conclusion Phase analysis with G-MPI can evaluate LV dyssynchrony caused by LBBB accurately. LBBB can lead to obvious LV dyssynchrony and dysfunction.