Effect of acetylcholine on electrophysiological characteristics of human atrial myocytes from patients with atrial fibrillation

Abstract

Objective To study the changes of action potential (AP) of atrial myocytes from patients with chronic atrial fibrillation (AF) and the electrophysiological effects of acetylcholine (Ach) on AP and effective refractory period (ERP) of atrial myocytes from AF patients.Methods Right atrial appendages were obtained from 11 patients with chronic AF and 9 patients matched as controls with sinus rhythm (SR).All patients were subjected to valve replacement surgery.Rest membrane potential (RMP),50％ and 90％ action potential duration ( APD50,APD90) of human atrial myocytes were recorded before and after administration of Ach by using standard intracellular microelectrode technique.APD90 and APD50 were also measured in different pacing rate.Results Before perfusion with Ach,RMP of atrial myocytes from patients with AF was more negative than in SR patients [ (63.70 ± 3.00) mV vs.(54.70 ±2.19) mV],P＜ 0.05.APD90 and APD50 in AF patients were shorter than in SR patients [ APD90(312.60±11.92) ms vs.(406.30±14.61) ms],APD50 (177.30±14.05) ms vs.(218.50±15.10)ms,P ＜0.05 ].Ach ( 10 μmol/L) made RMP more negative [ (67.8 ±2.0) mV vs.(61.4 ± 1.8) mV]and shortened APD90 [(263.60±13.38) ms vs.(316.20±15.40) ms],APD50 [(173.60±16.82)ms vs.(217.60 ± 15.16) ms] in both groups,P＜0.05.APD50 had no significant change after perfusion with Ach,but the alterations of RMP and APD90 were more significant than those before perfusion respectively ( P ＜ 0.05).The change of APD90 in SR patients is more remarkable than that in AF patients (P ＜0.05).Conclusion Patients with atrial fibrillation has the obvious decrease of frequency adaptation and more shortened APD,which contribute to the development and maintenance of atrial fibrillation.But it is not marked that these changes have been aggravated by Ach in patients with AF.Because the effect of Ach is decreased in these patients,this is possibly a regulative mechanism against AF. Key words: Atrial fibrillation; Acetylcholine; Action potential; Frequency adaptation; Electrophysiology