ICD indicates implantable cardioverter-defibrillator; LQTS, long QT syndrome; VT, ventricular tachycardia. Figure 10. Long QT syndrome type 1. CLINICAL STATEMENTS AND GUIDELINES QT syndrome type 3 ranolazine, mexiletine, and flecainide shorten the QTc and have been used to reduce recurrent arrhythmias.S7.9.1.1-6,S7.9.1.1-7,S7.9.1.1-10 3. Mexiletine is an additional medication that can be used in patients with long QT syndrome and recurrent ICD shocks. Left cardiac sympa- thetic denervation is associated with a reduc- tion the number of appropriate ICD shocks and VA burden.S7.9.1.1-13 S7.9.1.1-16 Reduction of the QTc to <500 ms after left cardiac sympa- thetic denervation has been correlated with reduced risk of recurrent ICD shocks and fre- quency of symptomsS7.9.1.1-16,S7.9.1.1-52 ; however, SCD or SCA is reported in 3% to 10% of Although arrhythmia burden is often reduced, up to 27% of high-risk patients experience at least Patient out- comes are improved if the left cardiac sym- pathetic denervation is performed in centers with surgical expertise in this procedure. Use of additional medications is guided by long QT Figure 11. Long QT syndrome type 2. Figure 12. Long QT syndrome type 3. CLINICAL STATEMENTS AND GUIDELINES syndrome type. In long QT syndrome type 3, ranolazine, mexiletine, and flecainide shorten the QTc and have been used to reduce recurrent 4. Genetic testing for disease-causing mutations in long QT syndrome offers important diagnos- tic, prognostic, and therapeutic information in addition to the clinical evaluation, and a posi- tive test can facilitate establishing risk for family members. The yield of genetic testing in long QT syndrome phenotype-positive patients is 50% to 86%, with the higher range present in patients with marked QT prolongation or positive family history of SCD.S7.9.1.1-17,S7.9.1.1-21,S7.9.1.1-53 A negative genetic test does not exclude the diagnosis of long QT syndrome, which relies on the clinical evaluation. 