Medications With Prominent Sodium Channel Blockade Except in specific circumstances, sodium channel block- ers (Vaughn-Williams class I agents) have a limited role in the prevention of VT/SCD; this is based on a lack of survival benefit and increased mortality observed dur- ing chronic therapy in patients with ischemic heart dis- ease (see Section 10.7). Specific circumstances where sodium channel blockers have been used to treat VT/ SCA include: intravenous lidocaine for patients with re- fractory VT/cardiac arrest (especially witnessed)S5.1.5.2-3 ; oral mexiletine for congenital long QT syndromeS5.1.5.2-4 ; quinidine for patients with Brugada syndrome; and fle- cainide for patients with catecholaminergic polymor- phic ventricular tachycardia.S5.1.5.2-5 These medications could also be used in ICD patients with drug- and abla- tion-refractory VT. One newer medication of potential benefit, based on very limited data, is ranolazine. This medication, developed and FDA-approved as an antianginal agent, provides relatively specific late sodium channel current blockade in addition to less potent blockade of the phase 3 repolarizing potassium current; that is, the rap- id delayed rectifier potassium current; IKr. The potential for clinical antiarrhythmic efficacy is supported by basic studies and experimental models.S5.1.5.2-6 Clinical data are scant. In a study of 12 patients, ranolazine reduced ICD shocks in otherwise medication-resistant VT/VF in 11 In MERLIN TIMI-36 (Metabolic Efficiency With Ranolazine for Less Ischemia in Non-ST-Elevation Acute Coronary Syndromes-Thrombolysis In Myocardial Infarction 36), ranolazine did not reduce SCD but did reduce VT in the first few days after a non-ST-segment In 1 RCT, high-risk ICD patients with ischemic or NICM were randomly assigned to ra- nolazine 1000 mg twice a day versus placebo.S5.1.5.2-9 High risk was defined as: 1) having a primary prevention CLINICAL STATEMENTS AND GUIDELINES Table 7. 