Patients with cardiac arrest in the setting of short QT syndrome are known to be at increased risk for recurrent cardiac arrest.S7.9.1.5-3 S7.9.1.5-5 Approximately 18% of the small number of reported patients with short QT and implanted ICDs have experienced appropriate ICD therapies during short-term follow-up.S7.9.1.5-3,S7.9.1.5-5,S7.9.1.5-6 Therapy with quinidine may reduce the number of ICD shocks.S7.9.1.5-3,S7.9.1.5-5,S7.9.1.5-6 3. Markedly shortened QTc values 300 ms are associated with increased risk of SCD, especially during sleep or rest, in young persons, in whom the median QTc was A clinical score including QTc duration, clinical history of documented polymor- phic VT or VF, unexplained syncope, family history of autopsy-negative SCD or sudden infant death syndrome, and positive genotype results has been proposed to identify patients at increased risk for SCD.S7.9.1.5-4,S7.9.1.5-10 Treatment with quini- dine results in lengthening of the QTc and, in selected patients, may be an alternative to ICD 4. In the setting of electrical storm with refractory VF and short QT syndrome, infusion of isoproterenol can be effective in restoring/maintaining sinus 5. Pathogenic mutations in potassium channels have been identified in approximately 10% to Recommendations for Short QT Syndrome (Continued) COR LOE Recommendations CLINICAL STATEMENTS AND GUIDELINES 20% of patients with short QT syndrome includ- Due to the rarity of the disease, genotype/phenotype correlations are unavailable, limiting the use of knowledge of genotype status. 8. VA IN THE STRUCTURALLY NORMAL HEART Recommendations for VA in the Structurally Normal Heart References that support the recommendations are summarized in Online Data Supplement 45. 