The effect of antihistamine cetirizine on ventricular repolarization in congenital long QT syndrome.
BACKGROUND
Many drugs are known to block cardiac potassium channels, thus prolonging QT interval and predisposing to malignant arrhythmias. Patients with congenital long QT syndrome are particularly vulnerable, but usually electrophysiological effects of drugs have not been assessed in these patients at risk.


METHODS
Fifteen asymptomatic patients with type 1 (LQT1), 15 patients with type 2 (LQT2) long QT syndrome, and 15 healthy volunteers took a placebo and cetirizine 10 mg. In addition, healthy volunteers took cetirizine 50 mg. The study was single-blinded and randomized. Exercise tests were performed during stable plasma concentrations. The electrocardiogram was recorded with a body surface potential mapping system (BSPM). Data were analyzed with an automated analyze program. QT intervals to the T wave apex and T wave end and their difference (Tp-e) were determined at rest and at specified heart rates during and after exercise.


RESULTS
Cetirizine did not lengthen the QT intervals at rest or during exercise and recovery in any group. It shortened Tp-e at rest in LQT1 and LQT2 patients and during exercise test in LQT1 patients, thus slightly decreasing electrocardiographic transmural dispersion of repolarization.


CONCLUSIONS
Cetirizine does not adversely modify ventricular repolarization in types 1 and 2 long QT syndrome, suggesting that it might be used safely in these long QT syndrome patients.
Hekkala
Anna-Mari
AM
Department of Cardiology, Helsinki University Hospital, Helsinki, Finland. anna-mari.hekkala@hus.fi
Swan
Heikki
H
Väänänen
Heikki
H
Viitasalo
Matti
M
Toivonen
Lauri
L
D000328:Adult; D017332:Cetirizine / Q000494:pharmacology / Q000627:therapeutic use*; D005260:Female; D006330:Heart Defects, Congenital / Q000188:drug therapy / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006352:Heart Ventricles / Q000002:abnormalities / Q000187:drug effects; D006634:Histamine H1 Antagonists / Q000494:pharmacology / Q000627:therapeutic use*; D006801:Humans; D008133:Long QT Syndrome / Q000151:congenital* / Q000188:drug therapy* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D016037:Single-Blind Method; D016276:Ventricular Function
D006634:Histamine H1 Antagonists; D017332:Cetirizine