Although sustained VT is clearly associated with SCD, the data for NSVT are less robust. Most studies do not support NSVT as an inde- pendent risk factor for SCD in patients with but the risk increases if risk modifiers are present, especially in patients <30 years of age.S7.4-27 Up to one third of patients with HCM have an abnormal blood pressure response during exercise testing (defined variably as either a 20 mm Hg decrease in blood pressure or a failure to increase systolic blood pressure by at least 20 mm Hg during effort).S7.4-28,S7.4-29 This finding has been postulated to be a risk factor for SCD; how- ever, it is unclear how this relates to the increase in dynamic LV outflow tract obstruction that occurs with exertion, a hemodynamic condition that is readily modifiable with medication or mechanical procedures. The significance of an abnormal blood pressure response with exercise predicting SCD risk increases in the presence of risk modifiers (Table 8). 8. Most studies have found that NSVT alone has a low positive predictive value for SCDS7.4-2,S7.4-26, ; therefore, use of an ICD is more appropriate if risk modifiers are also present. An abnormal blood pressure response to exercise has also been associ- ated with the risk of sudden death,S7.4-5,S7.4-28,S7.4-29 but it is unclear how this relates to the increase in dynamic LV outflow tract obstruction that occurs with effort, which is often treatable. The signifi- cance of an abnormal blood pressure response with exercise for predicting SCD risk increases when risk modifiers are present (Table 8). 9. 