Gated 99mTc-MIBI myocardial perfusion SPECT in patients with right bundle branch block but without evidence of coronary artery disease

Introduction: We aimed to investigate the effect of right bundle branch block (RBBB) on perfusion and functional parameters in dipyridamole stress/rest Tc99m-MIBI gated myocardial perfusion SPECT (GSPECT) which may be helpful in interpretation of myocardial perfusion imaging. Methods: We studied 73 patients with low pre-test likelihood of coronary artery disease in two groups:  38 patients with RBBB and 35 subjects with normal ECG. Both groups underwent two-day dipyridamole stress–rest Tc99m-MIBI GSPECT. Two groups were matched. There was no significant difference in sex and age variable between two groups. Results: Visual calculated SSS and SRS in all patients were between 0 and 3. Regarding the prone images, diaphragmatic attenuation and breast attenuation, all patients GSPECT findings were within normal limits. There was no significant difference in TID ratio between two groups:  RBBB group: TID ratio= 1.02±0.16 and control group: TID ratio= 0.96±0.14 (P=0.09). There was no significant difference in left ventricular end-systolic volume, end-diastolic volume, ejection fraction, summed stress and rest motion & thickening scores between RBB patients group and control group. No regional LV wall motion abnormality was noticed in any patient in either group. Conclusion: High normality rate of the LV myocardial perfusion and functional indices in the presence of RBBB was noticed in gated Dipyridamole stress/rest Tc-99m sestamibi myocardial perfusion SPECT.  No remarkable false positive perfusion findings or abnormal LV functional indices acquired by GSPECT in this group of patients.