The signifi- cance of an abnormal blood pressure response with exercise for predicting SCD risk increases when risk modifiers are present (Table 8). 9. The ICD is recommended for the prevention of SCD in patients with HCM who have survived sustained VT or VF as antiarrhythmic medications have limited effectiveness.S7.4-31 Amiodarone has been associated with improved survival in obser- vational studies and is an option for patients for whom an ICD is not feasible due to limited expec- tation for survival or patient preference.S7.4-30,S7.4-31 10. Approximately one third of consecutive patients with HCM undergoing an electrophysiologi- cal study have polymorphic VT or VF induced by programmed ventricular stimulation, but the results of programmed stimulation do not predict SCD risk. Programmed ventricular stimulation in patients with HCM has low predictive value and a nontrivial risk of complications.S7.4-32,S7.4-33,S7.4-51 Electrophysiological studies can help to clarify the diagnosis of wide complex tachycardia or guide therapy for supraventricular tachycardia or bun- dle branch reentry. 11. SCD may cluster in certain families with HCM, and the possibility that specific sarcomere muta- tions may confer SCD risk has been hypothe- sized. However, subsequent studies of selected patients with HCMS7.4-34,S7.4-35 were unable to establish a clinically useful relation between genotype and SCD risk. 