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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 i n unmasking carriers of the disease. However, the value of the test remains cont roversial. 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 ev aluation. Twenty-four individuals displayed an ECG diagnostic of Brugada syndro me at baseline. Of the remaining, 71 received intravenous ajmaline. Of the 35 ge netic carriers who received ajmaline, 28 had a positive test and 7 a negative aj maline 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-s egment elevation under baseline conditions, a prolonged P-R interval, but not i ncomplete 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 dia gnosis of SCN5A carriers. In the absence of ST-segment elevation at baseline, f amily members with first-degree atrioventricular block should be suspected of c arrying the mutation. An ajmaline test is often the key to making the proper dia gnosis in these patients.
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 However, the value of the test remains cont roversial. 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 ev Of the 35 ge netic carriers who received ajmaline, 28 had a positive test and 7 a negative a ma maline test. The twenty-four individuals were an ECG diagnostic of Brugada syndro me at baseline. Of the remaining, 71 received intravenous ajmaline. 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-s egment elevation under baseline conditions, a prolonged PR interval, but not i ncomplete 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 dia gnosis of SCN5A carriers. In the absence of ST-segment elevation at baseline, f amily members with first-degree atrioventricular block should be suspected of c arrying the mutation. An ajmaline test is often the key to making the proper dia gnosis in these patients.