Effect of different pacing sites on ventricular synchrony evaluated by gated blood pool SPECT

Objective To compare the effect of right ventricular outflow tract (RVOT) and right ventricular apex (RVA) pacing on ventricular systolic synchrony using gated blood pool SPECT (GBPS).Methods A total of 50 patients implanted with pacemaker due to high degree or complete atria-ventricular block were enrolled in the study. Twenty-three patients were RVOT paced ( Group A, n = 23) and 27 were RVA paced (Group B, n=27). Twenty-four patients with malignancy, normal echocardiographic findings and no history of cardiac diseases were scheduled for pre-chemotherapy evaluation of cardiac structure and function and were enrolled as control group ( Group C, n = 24). All patients underwent GBPS imaging and the values of phase angle (PS), mean phase of each wall, standard deviation (SD) of mean phase of each wall, lateral-septal motion delay of left ventricle ( LV Sep-Lat Delay), septal-right ventricular (RV) delay of LV ( LV Sep-RV Delay) and LV-RV Delay were acquired. The parameters of ventricular systolic synchrony among the three groups were compared using one-way ANOVA. Results The mean phase of LV lateral wall in Groups A and B were significantly higher than that in Group C: Group A (120.50 ±40.58) ms; Group B (103.23±28.34) ms; Group C (84.63 ±22.38) ms (F=7.72, P ＜0.05). There was no significant difference between Groups A and B ( t = 1.30, P ＞ 0.05 ). The mean phase of RV in Group A was significantly larger than those in Groups B and C: Group A ( 137.05 ± 39.27) ms, Group B ( 100.85 ± 23.79) ms,Group C (59. 13 ±30.52) ms (F=35.55, P＜0.05). PS, SD and LV Sep-Lat Delay in Groups A and B were significantly higher than those in Group C: (85.73 ± 12.00)°vs (89.85 ± 15.61 )°vs (58.95 ±9.87)°, (27.68±10.66) ms vs (26.15 ±13.02) ms vs (15.63 ±8.35) ms, (25.06±34.23) ms vs (2. 62 ± 60. 31 ) ms vs ( - 23.66 ± 31.39) ms, F = 41.54,8.55,6.81, all P ＜ 0.01 ), however, there was no significant difference between Groups A and B ( t = 0. 68, 0.68, 1.30, all P ＞ 0.05 ). LV Sep-RV Delay and LV-RV Delay were significantly different among the three groups ( LV Sep-RV Delay: Group A (57.60 ±56.77) ms, Group B (6.36 ±61.88) ms, Group C ( -41.89 ±35.78) ms; LV-RV Delay:Group A (47.36 ±42.59) ms, Group B ( 3.08 ± 38.81 ) ms Group C ( - 26.50 ± 20.99 ) ms, F = 20. 32,25.38, both P ＜ 0.01 ). Conclusion Both RVA and RVOT pacing increase the segmental phases detected by GBPS, causing inter- and intra- ventricular asynchrony compared with patients without pacemakers. Key words: Cardiac pacing, artificial;  Gated blood-pool imaging;  Technetium 99m pyrophosphate