|
Author
Block:
|
Mustafa
H. Hassan, MD and Elizabeth S. Kaufman, MD. Case Western Resreve University
MetroHealth Campus, Westlake, OH, Case Western Resreve University MetroHealth
Campus, Cleveland, OH
|
|
Introduction:
Grossly visible T wave alternans
has long been described as a poor prognostic sign in congenital long QT
syndrome (LQTS). Microvolt level T wave alternans (TWA), an established
marker for sudden cardiac death in patients post-myocardial infarction and
with cardiomyopathy, has been reported in LQTS, but its prevalence in this
population remains uncertain. We hypothesized that a significant subset of
LQTS subjects would demonstrate abnormal TWA.
Methods: Families were included if a proband met clinical criteria for
high probability of having LQTS and/or had a confirmed LQTS genetic mutation.
All family members willing and able to perform exercise testing were
included. Subjects underwent history, resting ECG analysis, and exercise
tests with TWA analysis. TWA studies were read by a blinded physician. All
family members were categorized as high, intermediate or low probability of
having LQTS according to the previously established Schwartz and Moss
clinical criteria. The intermediate probability group was excluded from
analysis. TWA was classified as abnormal, normal, or indeterminate according
to standard criteria. Indeterminate studies were excluded from analysis.
Results: Subjects were 182 family members from 25 families with LQTS.
Of these, 48 subjects were high probability for LQTS (age 41±18 years, 12
men), 67 were low probability (age 25±15 years, 37 men) and 67 were
intermediate probability and were excluded. TWA was present in 8 of the 48
LQTS patients (17%) and was not observed in any of the 67 normal subjects
(p<0.01 by chi-square analysis). Within the high probability LQTS group,
TWA was independent of QT duration.
Conclusion: Microvolt level TWA is observed in a substantial minority
of LQTS subjects. Its significance as a predictor of risk in this population
remains undetermined.
|