Molecular mechanisms of early atrial remodeling by rapid atrial pacing in rabbits

Objective: To establish a rabbit atrial fibrillation model with rapid atrial pacing (RAP) and investigate its ultrastructural changes and expressions of L-type calcium channel subunits and potassium channel Kv4. 3. Methods: Thirty-six rabbits were performed electrical stimulation through bipolar endo-cardial led by surgical technique. 600 beat per min from 0 to 48 h. Atrial ultrastructure was observed by transmission electron microscope (TEM) after different pacing times. mRNA were measured by reverse transcription-polymera.se chain reaction (RT-PCR). Results: Atrial ultrastructure had alteration after 3 hours' pacing, such as mitochondria vacuolization, myofilament lysis and glucogen aggregation. The mRNA of the Ca2+ channel β1 and α1 subunits began to decrease after pacing of 6 h. which were paralleled with the change of Kv4. 3 mRNA. But the auxiliary subunit α2 were not affected. Conclusion: Ultrastructural changes and mRNA levels of L-type calcium channel subunits and potassium channel Kv4. 3 are decreased after RAP. with a mechanism of transcriptional down-regulation of underlying ion channels due to calcium overloading after RAP.

Rapid right ventricular pacing for balloon valvuloplasty in congenital aortic stenosis:A systematic review

BACKGROUND Balloon aortic valvuloplasty(BAV)is a well-established treatment modality for congenital aortic valve stenosis.AIM To evaluate the role of rapid right ventricular pacing(RRVP)in balloon stabilization during BAV on aortic regurgitation(AR)in pediatric patients.METHODS A systematic review of the MEDLINE,Cochrane Library,and Scopus databases was conducted according to the PRISMA guidelines(end-of-search date:July 8,2020).The National Heart,Lung,and Blood Institute and Newcastle-Ottawa scales was utilized for quality assessment.RESULTS Five studies reporting on 72 patients were included.The studies investigated the use of RRVP-assisted BAV in infants(>1 mo)and older children,but not in neonates.Ten(13.9%)patients had a history of some type of aortic valve surgical or catheterization procedure.Before BAV,58(84.0%),7(10.1%),4(5.9%)patients had AR grade 0(none),1(trivial),2(mild),respectively.After BAV,34(49.3%),6(8.7%),26(37.7%),3(4.3%),patients had AR grade 0,1,2,and 3(moderate),respectively.No patient developed severe AR after RRVP.One(1.4%)developed ventricular fibrillation and was defibrillated successfully.No additional arrhythmias or complications occurred during RRVP.CONCLUSION RRVP can be safely used to achieve balloon stability during pediatric BAV,which could potentially decrease AR rates.

Autonomic mechanism for chronic atrial electrical remodeling induced by rapid atrial pacing in ambulatory danines

Objetives The mechanism for changes in the electrophysiological properties of the atria during rapid pacing induced atrial fibrillation(AF) is not well understood.We aimed to investigate the contribution of intrinsic cardiac autonomic nervous system(ICANS) in chronic atrial electrical remodeling and AF induced by rapid atrial pacing for 4 weeks. Methods Twelve adult mongrel dogs weighing 15 to 20 kg were assigned to two groups;group 1(experimental group,n= 7) and group 2(control group,n =5).All dogs were anesthetized with propofol and mechanically ventilated via endotracheal tubes.The chest was entered via bilateral mini-thoracotomy at the fourth intercostals space.Bipolar pacing electrode was sutured to the right atrial appendage.Four-electrode catheters(Biosense-Webster,Diamond Bar,CA) were secured to allow recording at the right and left atriaum.All tracings from the electrode catheters were amplified and digitally recorded using a computer-based Bard Laboratory System (CR Bard Inc,Billerica,MA).Electrograms were filtered at 50 to 500 Hz.Continuous rapid pacing(600 bpm, 2×threshold[TH]) was performed at the right atrial appendage. Ganglionated Plexi(GP) was localized by applying high frequency stimulation(HFS;20 Hz,0.1ms duration, 0.5 to 4.5 V)with a bipolar stimulation-ablation probe electrode (AtriCure,West Chester,OH).Group1 underwent ablation of bilateral GP and ligament of Marshall followed by 4-week pacing.Group 2 underwent sham operaton without ablation of GP and ligament of Marshall followed by 4-week pacing.The effective refractory period(ERP) and window of vulnerability(WOV) were measured at 2×TH before(baseline) and every week after GP ablation.WOV was defined as the difference between the longest and the shortest coupling interval of the premature stimulus that induced AF.GP consist of the anterior right ganglionated plexi(ARGP) located in the fat pad at the right superior pulmonary vein(RSPV)-atrial junction;the inferior right ganglionated plexi(IRGP) located at the inferior vena cava/right atrial junction;the superior left ganglionated plexi(SLGP) at the left superior pulmonary vein(LSPV) /left atrial junction and the inferior left ganglionated plexi(ILGP) at the left inferior pulmonary vein (LIPV)/left atrial junction.Results Immediately after ablation, the ERP in Group 1 became markedly longer and started to shorten gradually during the first 2 weeks,then stabilized at the 4th week.Compared to Group2,the ERP of Group1 was significantly longer in the first 3 weeks(P【 0.05),but no obvious difference at the 4th week in either the right or left atrium(P】0.05).In Group 1,AF could not be induced(WOV=0)in the first 3 weeks after ablation, and at the 4th week,AF was induced in 2 of 7 dogs.In Group2,WOV progressively widened during the 4-week period. AF could not be induced in 5 of 7 dogs in Group 1 and 1 of 5 dogs in Group 2 during the 4-week pacing period. Conclusions The intrinsic cardiac autonomic nervous system (ICANS) plays an important role in the early stage of atrial electrical remodeling induced by rapid atrial pacing.On the other hand,with time passing by,its effect on the formation of AF decreases gradually,which suggests that ICANS may account for a non-dominant factor in the late stage of the rapid pacing-induced chronic atrial fibrillation.

Effects of Amiodarone plus Losartan on Electrical Remodeling in Rapid Atrial Pacing in Rabbits

Objectives To investigate the electrical remodeling and the effects of amiodarone and losartan on electrical remodeling in rapid atrial pacing on rabbit model. Methods 40 normal rabbits were randomly divided into 4 groups ： the saline group （control group）, amiodarone group, losartan group, anti ＋ los group. All rabbits were raised drugs in a week. The atrial effective refractory period （AERP） was measured. Then, take a rapid atrial pacing （600 bpm） and the AERP was measured after 0.5, 1, 2, 4, 6 and 8 hours pacing and 30 minutes after the termination of rapid pacing. Results （1） In control group, after 8 hours rapid pacing, AERP200 and AERP150 were significantly shortened 16. 11% ± 3.1% （ P 〈 0. 01 ） and 9. 99 % ± 4. 2% （ P 〈 0. 01 ）. And the degree of AERP shortening induced by rapid pacing was greater at basic cycle lengths of 200 ms （BCL200） than that at BCL150. The AERP of amiodarone, losartan group and ami ＋ los group were not shortened during rapid pacing. （2） In the control group, after the termination of rapid pacing, the AERP gradually increased. The AERP at all of the BCLS examined recovered to almost the 95.78% and 96. 76% of baseline values within the first 10 minutes and recovered to almost the 99.07% and 99.39% of baseline values within the first 30 minutes. Conclusions Short-term atrial rapid pacing can induce the atrial electrical remodeling. Amiodarone and losartan can prevent the electrical remodeling.

Feasibility analysis of rapid right ventricular pacing in thoracic endovascular aortic repair under local anesthesia

Background Rapid right ventricular pacing is one of the methods for counteracting the ＂wind sock＂ effect in the thoracic endovascular aortic repair （TEVAR）. Most of the doctors are to complete this operation under general anesthesia. Now, our operation has been performed under local anesthesia. No related reports were found as to whether can the patient tolerate rapid fight ventficular pacing under local anesthesia. Methods From 2009 January to 2010 January, in our hospital all the DeBakey llI aortic dissection patients who underwent TEVAR were randomly divided into general anesthesia group （n = 50） and local anesthesia group （n = 51）. All the data were compared between two groups including the hemodynamic indexes, the graft positioning accuracy, rapid pacing duration, operation time, intraoperative discomfort and postoperative neurological understanding function changes and the complications. Results The success rate were 100% in the two groups. The duration of rapid pacing, operation time, the accuracy of graft localization and the intraoperative discomfort scores of Numerical Pain Rating Scale showed no significant difference between the two groups （P 〉 0.05）. There were no rapid fight ventricular pacing-related complications in the two groups. Conclusion During thoracic endovascular aortic repair procedure, rapid fight ventricular pacing under local anesthesia is safe and feasible. Thus it is worthy to be popularized in clinical practice.

Effect of Shen Song Yang Xin Capsule on Myocardial -lectrophysiology of Acute Atrial Fibrillation in Canine Model

Atrial fibrillation （AF） is the most common type of arrhythmia, which is reported to increase the incidence of stroke by five to seven tblds, leading to the irregular ventricular rhythm and adversely impacted life quality, and the mortality could be increased as well by AF per se. Shen Song Yang Xin （SSYX） capsule is a novel traditional Chinese medicine composed of more than a dozen Chinese medicine herbs with significant antiarrhythmic effect. In the current study, the effect of SSYX capsule has been tested in an animal study and it was also indicated by randomized double-blinded, positive drug-controlled clinical trials, However, the working mechanism of SSYX capsule as antiarrhythmic drug is not completely clear yet. This study tried to investigate the effect of SSYX capsule on the myocardial electrophysiology of acute AF dog model.