Risk stratification for channelopathies is generally made on the basis of symptoms, the ECG,S4.3.2-13, exercise treadmill testing,S4.3.2-25 S4.3.2-27 and the results of genetic testing.S4.3.2-28 S4.3.2-32 The electrophysiological study (ie, programmed ventricular stimulation) does not have prognostic value for risk stratification in patients with these 5. THERAPIES FOR TREATMENT OR PREVENTION OF VA 5.1. Medication Therapy With the exception of beta blockers (eg, metoprolol succinate, carvedilol), there is no evidence from RCTs that antiarrhythmic medications for VA improve survival when given for the primary or secondary prevention of SCD. However, the use of these medications is essential in some patients to control arrhythmias and improve symptoms. Medication use for VA is discussed, and any recommendations are listed, in subsequent sec- tions. Further, medication-induced proarrhythmia is ad- dressed in Section 10.7. Antiarrhythmic medications are often categorized by the Vaughan Williams 4-level schema (class I: fast sodium channel blockers; class II: beta blockers; class III: repolarization potassium current blockers; class IV: nondihydropyridines calcium channel blockers).S5.1.5.2-1 This system does not address the complexities in antiar- rhythmic medications, since nearly every agent has mul- tiple effects. Table 7 shows uses, electrophysiological effects, pharmacological effects, and common adverse effects of antiarrhythmic medications. 5.1.1. 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). 