Prolonged atrial action potential durations and polymorphic atrial tachyarrhythmias in patients with long QT syndrome.
Atrial APD and Polymorphic AT in LQTS.


BACKGROUND
Prolongation of the QT interval and torsades de pointes tachycardias due to altered expression or function of repolarizing ion channels are the hallmark of congenital long QT syndrome (LQTS). The same ion channels also contribute to atrial repolarization, and familial atrial fibrillation may be associated with a mutated KVLQT1 gene. We therefore assessed atrial action potential characteristics and atrial arrhythmias in LQTS patients.


RESULTS
Monophasic action potentials (MAPs) were simultaneously recorded from the right atrial appendage and the inferolateral right atrium in 10 patients with LQTS (8 with identifiable genotype) and compared to 7 control patients. Atrial arrhythmias also were compared to MAPs recorded in patients with persistent (n = 10) and induced (n = 4) atrial fibrillation. Atrial action potential durations (APD) and effective refractory periods (ERP) were prolonged in LQTS patients at cycle lengths of 300 to 500 msec (APD prolongation 30-41 msec; ERP prolongation 26-52 msec; all P < 0.05). Short episodes of polymorphic atrial tachyarrhythmias (polyAT, duration 4-175 sec) occurred spontaneously or during pauses after pacing in 5 of 10 LQTS patients, but not in controls (P < 0.05). P waves showed undulating axis during polyAT. Cycle lengths of polyAT were longer than during persistent and induced atrial fibrillation. Afterdepolarizations preceded polyAT in 2 patients. The electrical restitution curve was shifted to longer APD in LQTS patients and to even longer APD in LQTS patients with polyAT.


CONCLUSIONS
This group of LQTS patients has altered atrial electrophysiology: action potentials are prolonged, and polyAT occurs. PolyAT appears to be a specific arrhythmia of LQTS reminiscent of an atrial form of "torsades de pointes".
Kirchhof
Paulus
P
Department of Cardiology and Angiology, Hospital of the University of Münster, and Institute for Arteriosclerosis Research at the University of Münster, Münster, Germany. kirchhp@uni-muenster.de
Eckardt
Lars
L
Franz
Michael R
MR
Mönnig
Gerold
G
Loh
Peter
P
Wedekind
Horst
H
Schulze-Bahr
Eric
E
Breithardt
Günther
G
Haverkamp
Wilhelm
W
D000200:Action Potentials; D000293:Adolescent; D000328:Adult; D001281:Atrial Fibrillation / Q000175:diagnosis* / Q000235:genetics / Q000503:physiopathology*; D004562:Electrocardiography; D005260:Female; D006325:Heart Atria / Q000294:innervation / Q000503:physiopathology*; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis* / Q000235:genetics / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011110:Polymorphism, Genetic; D013612:Tachycardia, Ectopic Atrial / Q000175:diagnosis / Q000235:genetics / Q000503:physiopathology