Adapted with permission from Groh, et al.S7.8 15 CLINICAL STATEMENTS AND GUIDELINES 12-lead ECG to screen for development of conduc- tion abnormalities. However, the optimal frequency of electrocardiographic screening is unknown.S7.8-18 Once cardiac involvement is present, either on the basis of conduction delay, atrial arrhythmias, or ventricular dysfunction, a low threshold for investi- gating symptoms or electrocardiographic findings by the clinician to determine the need for pace- maker implantation, invasive electrophysiological studies, or ICD implantation is optimal. 4. Up to one third of deaths in myotonic dystrophy patients are sudden.S7.8-9 Although commonly attributed to conduction block and asystole, SCD due to VT/VF has been recognized in patients with functioning permanent pacemakers, and spontane- ous VA have been documented in some.S7.8-13,S7.8-19 The risk of SCD in patients with pacemakers sug- gests that an ICD may be preferred to a pacemaker. However, these patients are also at high risk of respiratory failure as a competing cause of death. Therefore, in patients with severe skeletal muscle involvement, a pacemaker or ICD may not improve A shared decision-making approach to selecting ICD or pacing therapy is warranted. Compared with myotonic type 1 patients, myo- tonic dystrophy type 2 patients are not well studied but may also benefit from the same approach. 7.9. Cardiac Channelopathies Recommendations for Cardiac Channelopathies References that support the recommendations are summarized in Online Data Supplement 39. 