Objective To evaluate advantages and disadvantages of different pacing modes of cardiac resynchronization therapy (CRT).Methods Twelve dogs with heart failure were performed in every dog at random,and the pacing modes employed in the test included right atrium-different sites of ventricle,and ventricular sites included right ventricular bifocal (RV-Bi),biventricular (Bi-V),left ventricular (LV).The pacing frequency was 180 times per minute,and the results were measured before pacing and after 15 minutes when the pacing became stable in Color Doppler echocardiography,including left ventricular enddiastolic diameter (LVEDd),left ventricular ejection fraction (LVEF),interventricular mechanical delay (IVMD),interventricular septum and left ventricular posterior wall motion delay (SPWMD),left ventricular 12-segment peak time standard deviation (Ts-SD).Results (1)Compared with before pacing,at the RV-Bi,Bi-V,and LV pacing modes,LVEDd,IVMD,SPWMD,and Ts-SD decreased,LVEF increased,the difference was statistically significant [(42.42 ± 3.94) mm vs (34.00 ± 4.07) mm,(34.17 ± 3.95)mm,(33.75 ±4.18)mm; (28.08 ±4.01)mm vs (13.00 ±3.64) mm,(11.95 ±2.54)mm,(12.08 ±3.51) mm; (75.00 ± 10.22)mm vs (51.75 ±9.84) mm,(20.66 ±7.41) mm,(20.75 ±7.56) mm; (25.08±4.16)mm vs (14.91 ± 3.31)mm,(7.50 ±4.24) mm,(7.41 ±3.39)mm;(32.91 ±4.46)mm vs (41.50 ±4.16)mm,(42.00 ±4.63) mm,(42.41 ±4.99)mm,P ＜0.05].(2)Compared with RV-Bi pacing mode,at the Bi-V,LV pacing modes,SPWMD and Ts-SD decreased,the difference was statistically significant(P ＜ 0.05); there was no significant difference among LVEDd,IVMD,and LVEF (P ＞0.05).(3)There was no significant difference in LVEDd,IVMD,SPWMD,Ts-SD and LVEF between LV and Bi-V pacing (P ＞ 0.05).Conclusions The hemodynamic effects of RV-Bi and LV pacing modes were similar to that of Bi-V pacing,and they can be used as CRT biventricular pacing alternative modes; however,the mechanisms of improving ventricular synchronization are not identical in above pacing modes.

Objective To evaluate the ability of pleth variability index(PVI) for predicting volume responsiveness after general anesthesia induction intubation in the patients undergoing intestinal tract surgery with the velocity-time integral(VTI) of left ventricular outflow tract blood monitored by transthoracic echocardiography as the standard.Methods Twenty-five patients undergoing intestinal tract surgery were selected.After general anesthesia induction,7 mL/kg colloidal solution was infused before operation beginning,if the VTI increased percentage(△VTI％)≥10 ％,200 mL colloidal solution was infused by 50mL syringe until △VTI％＜10％;the hemodynamic indicators of MAP,CVP,HR,PI VTI and PVI were recorded before and after infusion solution.Results The PVI basic value in the patients with response was significantly higher than that in the patients without response(P＜0.05);the Pearson correlation analysis found that there was a significant linear correlation between PVI basic value and △VTI％ before infusion solution(P＜0.05);the optimal diagnostic threshold value of PVI was 13.51,its sensitivity for monitoring the volume responsiveness was 69.25％ and specificity was 70.00％.The area under the receiver operating characteristic(ROC) curve(AUC) was 0.75(95％ CI:0.63-0.88,P＜0.01).Conclusion PVI can predict the volume responsiveness in the patients undergoing intestinal tract surgery.The PVI value ＞13.51 indicates that the patient may be in hypovolemia status and needs the volume therapy.