Experimental Research about Etiology of Long QT Syndrome and Torsades dePointes

本研究旨在阐明先天性和获得性QT间期延长综合征(LQTS)患者QTU异常和尖端扭矩(TDP)的发生机制。用接触电极技术记录先天性LQTS患者和犬在体心脏的体表心电图(ECG)和单相动作电位(MAP)，并测定QT间期(QT)、MAP90复极时程(MAP90)和后除极早期(EAD)。临床评价：4例先天性LQTS患者(LQTS组：12个记录点)和3例病态窦房结综合征患者(对照组：9个记录点)的右、左室心内膜心内膜电信号(RV-MAP)和MAP。LQTS组在4个记录点均记录到EAD，对照组未记录到EAD。输注异丙肾上腺素后，LQTS组QT和MAP90显著延长(P<0.0 2)，同时伴有EAD扩大，而这些改变…结论：1.对照组中未发现更多的S。刺激犬锁骨下动脉前后(LAS、RAS和BAS)，记录9只成年杂种犬刺激锁骨下动脉前后的心电图、右室图和左室图。LAS和BAS后QT和MAP90显著缩短，RAS后QT和MAP90无明显缩短，刺激锁骨下动脉前后均未记录到EADS。奎尼丁诱发犬QTU异常及EADS：记录9只成年Beagle犬静注QTU前后的ECG、LV-MAP和RV-MAP，并评价BAS和维拉帕米(Ver)对EAD的影响。注气60min后，QT、LV-MAP90、RV-MAP90显著延长(P<0.01)，EADS共记录到6个记录点。EADs依赖于心动过缓，BAS后EADs增大，Ver输注后EADs减小。结论：EADs在先天性和奎尼丁诱导的LQTS患者QTU异常和尖端扭矩的发生中起重要作用。较少

The purpose of this study is to clarify the mechanisms responsible for QTU abnormality and Torsades de Pointes (Tdp) in patients with congenital and acquired long QT syndrome (LQTS). We recorded body surface electrocardiogram (ECG) and monophasic action potential (MAP) in vivo heart using the contact electrode technique, in patients with congenital LQTS and in dogs, and evaluated QT interval (QT), MAP duration at 90% repolarization (MAP90) and early after depolarization (EAD).1. Clinical evaluation : ECGs and MAPs were obtained from the right and left ventricular endocardium (RV-and LV-MAP) in 4 patients with congenital LQTS (LQTS group : 12 recording sites) and in 3 patients with sick sinus syndrome (control group : 9 recording sites). EADs were recorded in all of the LQTS group at 4 recording sites, but not in the control group. After isoproterenol (Isp) infusion QT and MAP90 were significantly prolonged (p<0.02) associated with EAD enlargement in the LQTS group, whereas these change … More s were not found in the control group.2. Effects of ansae subclaviae stimulation on ECG and MAP in dogs : We recorded ECGs, RV-MAPs and LV-MAPs in 9 adult mongrel dogs before and after left, right and bilateral ansae subclaviae stimulation (LAS,RAS and BAS). QT and MAP90 were significantly shortened after LAS and BAS, but not after RAS, EADs were not recorded before and after any types of ansae subclaviae stimulation (LAS,RAS and BAS).3. Quinidine induced QTU abnormalities and EADs in dogs : ECGs, LV-MAPs and RV-MAPs were recorded before and after quinidine (Qi) infusion in 9 adult beagle dogs, and the effect of BAS and verapamil (Ver) infusion on EAD were evaluated EADs were not recorded during control state at any MAP recording sites. 60 minutes after Qi infusion, QT,LV-MAP90 and RV-MAP90 were significantly prolonged (p<0.01), and EADs were recorded 6 recording sites. EADs were depended upon bradycardia and enlarged after BAS but diminished after Ver infusion.Conclusion : EADs play the important role in the etiologies of QTU abnormalities and Torsades de Pointes in patients with congenital and quinidine-induced LQTS. Less