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. Author manuscript; available in PMC: 2009 Aug 21.
Published in final edited form as: Circ Arrhythm Electrophysiol. 2008 Jan 1;1:213–226. doi: 10.1161/CIRCEP.108.796599

Table 2.

Risk mechanisms and genotype-specific therapy based on clinical and experim ental data in LQT1, LQT2, and LQT3 forms of long QT syndrome

LQT1 LQT2 LQT3
Sensitivity to
sympathetic
stimulation
Yes To some degree No
Torsade de pointes Exercise related Startle Sleep/rest
Specific
triggers/Occurrence
Swimming Telephone, alarm
clock, postpartum
Inactivity
Risk by mutation Dominant neg.,
transmembrane
location, A341V
Pore location,
K28E
ΔKPQ
Exercise restriction +++ ++ ?
Beta-blockers +++ ++ ?
Potassium
supplement
+ ++ +
Mexiletine + + ++
Flecainide No data No data +++ (ΔKPQ,
D1790G)
Ranolazine No data No data ++ (ΔKPQ)
LCSD in high -risk
patients
++ ++ ++
ICD in high-risk
patients
+++ +++ +++

ICD = implantable cardioverter-defibrillator; LCSD = left cervicothoracic sympathetic denervation. The number of plussigns indicates the relative benefit of therapy in minimal (+), moderate (++), and marked (+++) effectiveness categories; ? = uncertain. (Reproduced and modified with permission. Table 1 from Shimizu W, et al. The long QT syndrome: therapeutic implications of a genetic diagnosis. Cardiovasc Res. 2005;67:347-356).29