Published Online
on November 1, 2004

A more recent version of this article appeared on November 9, 2004

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Submitted on February 2, 2004
Revised on April 15, 2004
Accepted on April 30, 2004

Value of Electrocardiographic Parameters and Ajmaline Test in the Diagnosis of Brugada Syndrome Caused by SCN5A Mutations

Kui Hong MD, PhD, Josep Brugada MD, PhD, Antonio Oliva MD, Antonio Berruezo-Sanchez MD, Domenico Potenza MD, Guido D. Pollevick PhD, Alejandra Guerchicoff PhD, Kiyotaka Matsuo MD, PhD, Elena Burashnikov MS, Robert Dumaine PhD, Jeffrey A. Towbin MD, Vladislav Nesterenko PhD, Pedro Brugada MD, PhD, Charles Antzelevitch PhD, and Ramon Brugada MD^*

From Masonic Medical Research Laboratory, Utica, NY (K.H., A.O., G.D.P., A.G., K.M., E.B., R.D., V.N., C.A., R.B.); Arrhythmia Unit, Cardiovascular Institute, Hospital Clínic, University of Barcelona, Spain (J.B.); Cardiology Department, Hospital Universitario Puerta del Mar, Cadiz, Spain (A.B.-S.); Cardiology Department, IRCCS Casa Sollievo della Soferenza, St Giovanni Rotondo, Italy (D.P.); Pediatrics Department, Section of Cardiology, Baylor College of Medicine, Houston, Tex (J.A.T.); and Cardiovascular Research and Teaching Institute of Aalst, Belgium (P.B.).

^* To whom correspondence should be addressed. E-mail: brugada{at}mmrl.edu.

Background--The Brugada syndrome is an arrhythmogenic disease caused in part by mutations in the cardiac sodium channel gene, SCN5A. The electrocardiographic pattern characteristic of the syndrome is dynamic and is often absent in affected individuals. Sodium channel blockers are effective in unmasking carriers of the disease. However, the value of the test remains controversial.

Methods and Results--We studied 147 individuals representing 4 large families with SCN5A mutations. Of these, 104 were determined to be at possible risk for Brugada syndrome and underwent both electrocardiographic and genetic evaluation. Twenty-four individuals displayed an ECG diagnostic of Brugada syndrome at baseline. Of the remaining, 71 received intravenous ajmaline. Of the 35 genetic carriers who received ajmaline, 28 had a positive test and 7 a negative ajmaline test. The sensitivity, specificity, and positive and negative predictive values of the drug challenge were 80% (28:35), 94.4% (34:36), 93.3% (28:30), and 82.9% (34:41), respectively. Penetrance of the disease phenotype increased from 32.7% to 78.6% with the use of sodium channel blockers. In the absence of ST-segment elevation under baseline conditions, a prolonged P-R interval, but not incomplete right bundle-branch block or early repolarization patterns, indicates a high probability of an SCN5A mutation carrier.

Conclusions--In families with Brugada syndrome, the data suggest that ajmaline testing is valuable in the diagnosis of SCN5A carriers. In the absence of ST-segment elevation at baseline, family members with first-degree atrioventricular block should be suspected of carrying the mutation. An ajmaline test is often the key to making the proper diagnosis in these patients.

Key words: genetics • ajmaline • Brugada syndrome • sodium channel blockers

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