Abstract 16369: Impact of New LQTS Diagnostic Criteria on Detection of Long QT Syndrome With Carrying Gene Mutations
Background: : Although the parameter of evaluation of the recovery phase of exercise was recently added to the LQTS diagnostic criteria, few data exist regarding the clinical impact of the new criteria. Therefore, we compared the Schwartz scores which were calculated by the conventional and new criteria, and performed genetic testing of the major LQTS genes.
Methods and Results: We studied 83 subjects (46 males, mean age 14
± 10 years) who were referred to our hospital because they showed prolonged QTc intervals and/or abnormal clinical history and familial findings in the cardiac screening. The Schwartz scores were determined by the conventional and the new versions of LQTS diagnostic criteria, and 6 ion channel genes were analyzed for all subjects. The clinical course was also evaluated (average follow-up 59 months per subject). Thirty six subjects showed a QTc ≥ 480 ms in the recovery phase of exercise stress test. In these subjects, KCNQ1 mutations were more frequently identified (36%) and cardiac events more frequently occurred (22%) compared with those who did not show QT prolongation after exercise (p<0.05). Interestingly, the application of the new criteria significantly increased the number of subjects with a high probability of LQTS (n=30), although 18 subjects were diagnosed as a high probability of LQTS (3.5 ≤ Schwartz score) by the conventional criteria (p<0.05). The probability of carrying mutations in subjects with a high probability by these two criteria was comparable: 16 out of 18 subjects (88%) and 25 out of 30 subjects (83%), respectively. According to the conventional criteria, 13 mutation carriers were included in subjects with an intermediate or low probability of LQTS (Schwartz score ≤ 3.0).
Conclusion: These results demonstrate that the new diagnostic criteria can identify occult LQTS subjects with gene mutations as a high probability of LQTS which cannot be identified by the conventional criteria.
- © 2013 by American Heart Association, Inc.