This study is enrolling participants who are already implanted with a S-ICD device ( subcutaneous ICD), and are undergoing a routine outpatient clinic follow up appointment to have their S-ICD checked. The aim of the study is to see if a feature in the device can recognize muscle movement and differentiate movement from irregular heart signals. The study involves doing some simple arm exercises while collecting device data, both with this feature turn on and then with it turned off. Participants will be randomized to either have the feature turned on or off initially then it will be programmed the alternative way and the same exercise testing will be repeated. The study will involve just one visit.

This study is enrolling participants who are already implanted with a S-ICD device ( subcutaneous ICD), and are undergoing a routine outpatient clinic follow up appointment to have their S-ICD checked. The aim of the study is to see if a feature in the device can recognize muscle movement and differentiate movement from irregular heart signals. The study involves doing some simple arm exercises while collecting device data, both with this feature turn on and then with it turned off. Participants will be randomized to either have the feature turned on or off initially, then it will be programmed the alternative way and the same exercise testing will be repeated. The study will involve just one visit. Following this visit study participation is complete.

Inclusion Criteria:

• At least 18 years of age
• Implanted EMBLEM S-ICD (Model A 209 and Model A 219, Boston Scientific, St Paul, MN, USA)

Exclusion Criteria:

• Less than 18 years of age
• Hemodynamically unstable
• Inability to preform TET due to orthopedic issues or cognitive impairment