A high index of suspicion for bundle- branch reentrant tachycardia is warranted in patients with myotonic dystrophy who exhibit wide QRS complex tachycardia or tachycardia- 2. In patients with Emery-Dreifuss and limb-girdle type 1B muscular dystrophies associated with Lamin A/C mutations, SCD accounts for about one third of all deaths.S7.8-4 Observational studies show a significant rate of appropriate ICD therapy in patients with cardiac conduction disorders who are gene positive for Lamin A/C mutation even if LV function is preserved.S7.8-3,S7.8-5,S7.8-17 In an obser- vational study in which 38% had isolated skeletal muscular involvement but included patients with conduction defects and other risk factors (includ- ing PR interval >240 ms, left bundle-branch block, NSVT, or bradycardia requiring a permanent pace- maker) life-threatening VAs were relatively com- mon; with 52% of patients receiving appropriate ICD therapy including approximately 40% of those patients with an LVEF 45%.S7.8-3 A study of patients who had Lamin A/C mutation, in which approximately 21% had a skeletal muscular dys- trophy phenotype, SCD and appropriate ICD ther- apy were associated with NSVT, LVEF <45%, male sex, and Lamin A/C nonmissense mutations.S7.8-4 These observational studies support the use of an ICD when a pacing indication is present and likely also when evidence of progressive cardiac involvement such as cardiac conduction defects, NSVT or reduced LVEF is present.S7.8-8 There is a paucity of data regarding the rare form of x-linked recessive Emery-Dreifuss muscular dystrophy (related to the Emerin gene mutation), but arrhythmias may be less frequent than for the Lamin A/C mutations.S7.8-15 3. Cardiac involvement can occur in a number of neuromuscular dystrophies (Table 9). To determine cardiac involvement, a 12-lead ECG and echocar- diogram are important for the initial clinical assess- ment, independent of symptom status. 