Neural control of heart rate is an arrhythmia risk modifier in long QT syndrome.
J Am Coll Cardiol
; 51(9): 920-9, 2008 Mar 04.
Article
in En
| MEDLINE
| ID: mdl-18308161
ABSTRACT
OBJECTIVES:
The purpose of this study was to test the hypothesis that differences in autonomic responses might modify clinical severity in long QT syndrome type 1 (LQT1) patients, those with KCNQ1 mutations and reduced I(Ks), in whom the main arrhythmia trigger is sympathetic activation.BACKGROUND:
Some long QT syndrome (LQTS) patients experience life-threatening cardiac arrhythmias, whereas others remain asymptomatic throughout life. This clinical heterogeneity is currently unexplained.METHODS:
In a South African LQT1 founder population segregating KCNQ1-A341V, we correlated major cardiac events to resting heart rate (HR) and to baroreflex sensitivity (BRS) on and off beta-adrenergic blockers (BB).RESULTS:
In 56 mutation carriers (MCs), mean HR was lower among asymptomatic patients (p < 0.05). Among MCs with a QT interval corrected for heart rateCONCLUSIONS:
Lower resting HR and "relatively low" BRS are protective factors in KCNQ1-A341V carriers. A plausible underlying mechanism is that blunted autonomic responses prevent rapid HR changes, arrhythmogenic when I(Ks) is reduced. These findings help understanding phenotypic heterogeneity in LQTS and identify a physiological risk modifier, which is probably genetically determined.
Full text:
1
Database:
MEDLINE
Main subject:
Autonomic Nervous System
/
Long QT Syndrome
/
Receptors, Adrenergic
/
KCNQ1 Potassium Channel
/
Heart Rate
Type of study:
Etiology_studies
/
Prognostic_studies
/
Risk_factors_studies
Limits:
Adolescent
/
Adult
/
Aged
/
Female
/
Humans
/
Male
/
Middle aged
Language:
En
Year:
2008
Type:
Article