ABSTRACT
We aimed to investigate of effect of left bundle branch block [LBBB] on perfusion and functional parameters in dipyridamole Tc99m-MIBI gated myocardial perfusion SPECT which may be helpful in interpretation of myocardial perfusion imaging. We studied 70 patients with low pre-test probability of coronary artery disease in two groups: 35 patients with LBBB and 35 subjects with normal ECG. Both groups underwent two-day dipyridamole stress-rest Tc99m-MIBI GSPECT. From 35 patients with LBBB, 6, 12, and 3 patients had reversible, fixed and partially reversible defects respectively. In 35 patients with LBBB, 8 [22.9%], 6[17.1%] 15[42.9%] and 10 [28.6%] patients had perfusion defects in the apicoseptal, mid-anterior segments, mid-anteroseptal and mid-inferoseptal segments respectively. There was significant difference in TID ratio between two groups: LBBB group: 1.07 +/- 0.21 and control group: 0.96 +/- 0.14 [P=0.01]. There was a significant difference in end systolic volume and ejection fraction between LBBB patients group and control group, while no significant difference was noticed in end-diastolic volume. Nineteen, 14 and 2 from 35 patients with LBBB had normal LV wall motion, paradoxical septal wall motion, and septal hypokinesia, respectively. False positive septal, anterior and apicoseptal perfusion abnormalities are frequently seen on Tc99m-MIBI GSPECT, in patients with LBBB without CAD. Moreover reversible defects are frequently seen with Tc99m-MIBI. Even Tc99-MIBI and vasodilator stress do not increase diagnostic accuracy to clinically useful levels. Lower systolic performance and higher TID ratio could be seen in these patients