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 investigate the relationship between low-density lipoprotein cholesterol/high-density lipoprotein cholesterol ratio (LHR) and asymptomatic carotid plaques and their stability in high-risk stroke population.Methods Between December 2012 and April 2015,a total of 39 944 permanent resident population ≥40 years were used as subjects of the survey from 11 rural communities in Haitou Town,Banzhuang Town and Tashan Town,Ganyu District,and 9 urban communities in Xinpu District and Haizhou District,Lianyungang City using epidemiological survey method of cluster sampling.Excluding those who took lipid-lowering drugs within 3 months and had a history of stroke or transient ischemic attack,6 592 people at high risk of stroke were finally screened out.Ultrasound was used to detect carotid plaques.The subjects were divided into plaque-free group and plaque group.The latter was further divided into stable plaque group and unstable plaque group.Multivariate logistic regression analysis was used to evaluate the independent risk factor for carotid plaques and their stability.The odds ratio (OR) and 95％ confidence interval (CI) were calculated.Receiver Operating Characteristic (ROC) curve was used to evaluate the prediction efficiency of LHR on carotid plaques.Results Multivariate logistic regression analysis showed that low-density lipoprotein cholesterol (LDL-C) was an independent risk factor for carotid plaques,while high-density lipoprotein cholesterol (HDL-C) was an independent protection factor of carotid plaques.Using the lowest quintile (Q1) of LHR as a reference,carotid plaque risk increased significantly with the increasing LHR (Q2:OR 1.448,95％ CI 1.082-1.937,P =0.013;Q3:OR 2.414,95％ CI 1.754-3.322,P＜0.001;Q4:OR 2.939,95％ CI 1.945-4.441,P＜0.001;Q5:OR 4.884,95％ CI 3.143-7.115,P＜0.001).ROC curve analysis showed that the area under the curve (AUC) of LHR predicting carotid plaques was 0.795 (95％ CI 0.792-0.807;P＜ 0.001),and the optimal cut-off value was 3.00 (sensitivity 68.37％,specificity 75.65％).LHR ≥3.92 (LHR in the Q4 and Q5 subgroups) was an independent risk factor for unstable carotid plaques (OR 2.915,95％ CI 2.104-4.040;P＜0.001).The AUC of the LHR predicting unstable carotid plaques was 0.658 (95％ CI 0.633-0.684;P＜0.001).Conclusions LHR was an independent predictor of carotid plaques in high-risk stroke patients.It had higher predictive value for carotid plaques,and its conversion threshold for promoting plaque formation was 3.00.When LHR was ≥3.92,there was a significant increase in the risk of unstable carotid plaques.