abstract

presented

at the 1999 ACC

New Orleans, LA

March 7 - 10

 

Microvolt Level T-Wave Alternans Is Prevalent in Subjects with Congenital Long QT Syndrome

 

?

Kaufman ES, Gorodeski EZ, Koide N, Verrilli LM, Rammohen G, Rosenbaum DS. Case Western Reserve University, MetroHealth Medical Center, Cleveland, Ohio

 

Background: Grossly visible T-wave alternans (TWA) is an important prognostic sign in congenital Long QT Syndrome (LQTS). Although microvolt level TWA is a marker of risk in patients with structural heart disease, its prevalence in LQTS is unknown.

Methods: 68 subjects (32M, 36F, age 36+16) with personal or family history of LQTS underwent TWA measurement during exercise on a stationary bicycle. We compared the prevalence of TWA in subjects with normal versus prolonged (>45s in males, >46s in females) QTc on the baseline ECG. Abnormal TWA (> 1.9 µ V at a threshold HR<110/min) was considered sustained if it lasted >1 min and persisted at increased HR; it was considered present (any TWA) if it lasted >0.3 min but did not necessarily meet criteria for sustained TWA. 63 subjects had diagnostic TWA tests (achieving HR>105/min with noise<1.8µV and ectopics<10%) and were included in the analysis.

Results: Both sustained (p<0.01) and any (p<0.02) TWA were found with higher prevalence among subjects with prolonged QTc.

Sustained TWA

Long QT Normal QT

6

0

21

36

Any TWA

Long QT Normal QT

21

18

6

18

Of subjects with long QTc, 78% had TWA (22% sustained). In contrast, among subjects with normal QTc, 50% had TWA (none sustained).

Conclusion: Microvolt level TWA can be detected in a substantial proportion of individuals with LQTS. TWA analysis may aid in diagnosing subjects at risk for LQTS, a potentially lethal but treatable disorder.

 

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