Clinical Research Directory

Inclusion Criteria: 1. Subject has an active CromeTM or CobaltTM ICD or CRT-D MRI SureScanTM system which has been implanted for at least 30 days and which has not yet reached the Recommended Replacement Time (RRT) 2. Subject is implanted with one of the following models of a true bipolar right ventricular lead manufactured by Medtronic: * Model 6946M * Model 6947 * Model 6947M * Model 6935 * Model 6935M 3. Subject is ≥ 18 years of age 4. Subject (or subject's legally authorized representative) is willing and able to provide written informed consent 5. Subject is willing and able to comply with study procedures Exclusion Criteria: 1. Subject has existing condition that necessitates the use of supplemental oxygen 2. Subject has active acute respiratory infection or respiratory disorder that may affect ability to perform breathing or exercise activities, as assessed by the investigator 3. Any concomitant condition that might endanger the subject through participation in the study or interfere with study procedures, as assessed by the investigator 4. Subject has an active or suspected lead integrity issue, in the opinion of the investigator 5. Subject is enrolled in another study that could confound the results of this study 6. Subject has NYHA Class IV heart failure