Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 1 Qingyan Zhao Congxin Huang Department of Cardiology, Renmin Hospital of Wuhan University Vagal Stimulation and Differential Densities of Three Muscarinic Acetylcholine Receptors on Atrial Fibrillation in Canine Atria

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 2  Relation of AF and ACh or Vagus nerve  Vagal nerve stimulation (VNS) initiates and maintains AF  Reentrant mechanism for AF in the presence of ACh  Lack of I KACh prevents AF Background

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 3 Background  Evidence has been provided with co-existence of the M 2, M 3 and probably also M 4 in the atrium of dog and men

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 4 Background  Effect of ACh on Atrial Myocardium Vagal nerve stimulation M 2 recepter ACh G protein I KACh outward K + current

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 5 Background  Activation of M 3 /I KM3 by ACh shortens atrial action potential duration(APD)  The role of the M 3 receptors in I KACh /I KM3 activation was found to be increased in AF

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 6 Objectives To observe the different changes of APD at atrial epicardium VNS ACh perfusion

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 7 Objectives  Distribution of M receptor subtypes in atrial myocardium was measured by western blot

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 8 Methods  Experimental Animals  Ten dogs were abdomenly anesthetized with pentobarbital sodium  Heart was exposed in a pericardial cradle after a median sternotomy

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 9 Methods Six custom-built electrode probes Right atrial appendage (RAA) High right atrium (HRA) Low right atrium (LRA) Left atrial appendage (LAA) High left atrium (HLA) Low left atrium (LLA)

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 10 Methods  Experimental Protocol Vagosympathetic trunks cut Vagosympathetic trunks cut VNS VNS ACh perfusion ACh perfusion

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 11 Methods  AF and APD Recordings  Atrial premature beats, AT, AF  APD 50  APD 90  dAPD

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 12 Methods  Groups  Control group  VNS group  ACh perfusion group

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 13 Methods  Western Blot Analysis  After electrophysiological measurement, the hearts were quickly excised and RAA, LAA, LA and RA were dissected  Distribution of M receptor subtypes in atrial myocardium were measured by western blot

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 14 Statistical Analysis  Data are expressed as x±s. Statistical comparisons were made on the basis of the variance analysis. Statistical significance was assumed if values were less than 0.05

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 15 Results  Control group: atrial premature beats in two dogs  VNS group: atrial premature beats in ten dogs, AT in 3 dogs, AF in 7 dogs  ACh perfusion group: atrial premature beats in ten dogs, AT in 4 dogs, AF in 6 dogs

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 16 Results  Changes of APD 50 APD 50 (ms) Effects of different intervention on APD 50 in atrial epicardium

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 17 Results  Changes of APD 90 APD 90 (ms) Effects of different intervention on APD90 in atrial epicardium

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 18 Results  Changes of dAPD dAPD(ms) Effects of different intervention on dAPD in atrial epicardium

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 19 LLA HLA LAA RAA HRA LRA Comparison of the figures of MAP in control group, VNS group and ACh perfusion group

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 20 Results LAA RAA LA RA (83kDa) Arbitrary Unit     P <0.05 vs RA;  P <0.05 vs LA LAA RAA LA RA

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 21 Results LAA RAA LA RA (105kDa) Arbitrary Unit   P <0.05 vs LA and RA LAA RAA LA RA  

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 22 Results LAA RAA LA RA (70kDa) Arbitrary Unit  P <0.05 vs LA and RA LAA RAA LA RA  

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 23 Discussion  Innervation heterogeneity in atria contributed to the ability of VNS in initiation of reentrant AF by increasing dispersion of refractoriness within atria  Differences may participate in the ability of the LA to act as a "driver region" for AF  Recent studies

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 24 Discussion  Our studies  The distribution of M2, M3 and M4 in atrial myocardium is nonuniform. the heterogeneity of M 2, M 3 and M 4 may be the reentrant mechanism for AF induced by VNS  APD was shortened and dAPD was increased by VNS and ACh, and AF was induced easily

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 25 Discussion  Our studies  Distribution of M 2 and M 3 receptors had higher density in LA than RA. However, there was no significant difference in APD between RA and LA  APD that we observed was in epicardium but the heterogeneity of M 2 and M 3 may be present between epicardium and endocardium

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 26 Further Investigation  The current densities of IKACh in different areas of atrium and atrial appendage  Selective IKACh blocker would be a novel antiarrhythmic drug

Renmin Hospital of Wuhan University The 16 TH Great Wall International Congress of Cardiology 27