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

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. 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. 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 and thickening scores between RBB patients group and control group. No regional LV wall motion abnormality was noticed in any patient in either group. 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

Normal values of left ventricular functional indices in gated [99m] TC-MIBI myocardial perfusion SPECT

Although left ventricular[LV] function parameters measured by gated myocardial perfusion SPECT [GSPECT] have been validated, experimental data have revealed that the calculated the LV function parameters using GSPECT are affected by patient populations as well as particular acquisition and processing conditions. We tried to determine the normal values of GSPECT in an Iranian population. We studied 3500 Iranian patients who underwent GSPECT in an outpatient setting. To develop normal limits of LV functional indices using GSPECT, 148 patients with a low [<5%] likelihood of coronary disease and normal tomograms were selected. No one of 148 patients had known coronary artery disease, typical angina, history of hypertension, diabetes mellitus, and smoking, any abnormality in echocardiography or hyperlipidemia. They were not taking any medication known to affect LV function at least 2 days before the study. End diastolic volume [EDV], end systolic volume [ESV] and LV ejection fraction [LVEF] were calculated in rest GSPECT using iterative reconstruction and QGS [quantitative gated SPECT] software. Mean EDV, ESV and LVEF were 53.8 +/- 20.2, 14.3 +/- 10.8 and 75.0% +/- 9.6% respectively. These data showed a Gaussian distribution, so mean_2SD would show the upper or lower limits of normal for LV functional parameters. There were the marked sex differences in mean LVVs and LVEF measurements. BMI index had not effect on the measurement of the LV functional parameters. We noticed that 85.4% of our subjects had ESV<25 ml while most of them were women [112/123, 91%]. From a clinical viewpoint, each institute should use a standard protocol for the specific patient population and for the mode of SPECT acquisition and reconstruction. Normal thresholds using GSPECT, OSEM reconstruction and QGS algorithm in men and women were EDV>130, ESV>55 and LVEF<52% and EDV>77, ESV> 26 and LVEF<62% respectively