Electrocardiographic interventricular dispersion of repolarization during autonomic adaptation in LQT1 subtype of long QT syndrome.
OBJECTIVE
In LQT1 subtype of inherited long QT syndrome, repolarization abnormalities originating from defective I(Ks) render patients vulnerable to ventricular arrhythmia during sudden sympathetic activation. Experimental studies show lower I(Ks) density and longer action potential duration in left (LV) than in right (RV) ventricle. We studied interventricular dispersion of repolarization in patients with I(Ks) defect during autonomic tests.


METHODS
We measured interventricular (difference of QT intervals between LV and RV type leads) and transmural electrocardiographic dispersion of repolarization from 25-lead electrocardiograms in nine asymptomatic KCNQ1 mutation carriers (LQT1) and eight controls during rest, Valsalva maneuver, mental stress, sustained handgrip and supine exercise.


RESULTS
LQT1 carriers showed increased interventricular dispersion of repolarization (13+/-9 ms vs. 4+/-4 ms, p=0.03) during all tests. Valsalva strain increased the difference between the study groups. In LQT1 carriers, interventricular dispersion of repolarization correlated weakly with electrocardiographic transmural dispersion of repolarization.


CONCLUSIONS
Asymptomatic KCNQ1 mutation carriers exhibit increased and by abrupt sympathetic activation augmented interventricular difference in electrocardiographic repolarization times. Interventricular and transmural repolarization dispersion behave similarly in patients with I(Ks) defect.
Haapalahti
Petri
P
Department of Cardiology, Helsinki University Hospital, Helsinki, Finland. petri.haapalahti@hus.fi
Viitasalo
Matti
M
Perhonen
Merja
M
Mäkijärvi
Markku
M
Väänänen
Heikki
H
Oikarinen
Lasse
L
Salorinne
Yrjö
Y
Swan
Heikki
H
Toivonen
Lauri
L
D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology; D018780:Body Surface Potential Mapping; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D015444:Exercise / Q000502:physiology; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006579:Heterozygote; D006801:Humans; D051657:KCNQ1 Potassium Channel / Q000235:genetics; D008133:Long QT Syndrome / Q000235:genetics / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D013315:Stress, Psychological / Q000503:physiopathology; D014636:Valsalva Maneuver
D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human