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. Author manuscript; available in PMC: 2012 Mar 8.
Published in final edited form as: Circulation. 2011 Mar 8;123(9):1021–1037. doi: 10.1161/CIRCULATIONAHA.109.914838

Figure 6. Genotype-Phenotype Correlations in Long QT syndrome.

Figure 6

Seventy-five percent of clinically strong LQTS is due to mutations in three genes (35% KCNQ1, 30% KCNH2, and 10% in SCN5A) encoding for ion channels that are critically responsible for the orchestration of the cardiac action potential. Genotype-phenotype correlations have been observed, including swimming/exertion and LQT1, auditory triggers/postpartum period and LQT2, and sleep/rest and LQT3. The bar graphs represent genotype-phenotype data from reference 59. Also illustrated is the relative gene-specific effectiveness in β blocker therapy where β blockers are extremely protective in LQT1 patients, moderately protective in LQT2, and may not provide sufficient protection for those with LQT3. The late sodium current blockers like mexiletine, ranolazine, and propranolol may be protective in LQT3.