Placement of a pacemaker for control of rhythm Patients with a pacemaker or defibrillator Symptomatic bradycardia in the absence of a pacemaker. Patients with a permanent pacemaker Patients with a pacemaker Placement of a pacemaker for control of rhythm. Inability to undergo MRI or SRS (e.g. due to safety reasons such as presence of a pacemaker) Patients who are pacemaker or defibrillator-dependent Inability to undergo MRI (e.g., due to safety reasons, such as presence of a pacemaker) Presence of pacemaker or intracranial aneurysm clip Cardiac pacemaker. Patients with pacemaker, defibrillator, or documented significant arrhythmia, are not allowed Presence of a pacemaker Placement of a pacemaker for control of rhythm Subject is pacemaker dependent Placement of a pacemaker for control of rhythm; Presence of a cardiac pacemaker Subject with intra-cardiac defibrillators or pacemaker Patients with a permanent pacemaker Has a heart pacemaker or other electronic device implants Pacemaker/defibrillator Patients who are pacemaker or defibrillator-dependent Patient is pacemaker dependent Inability to undergo MRI (e.g., due to safety reasons, such as presence of a pacemaker) Obligate need for a cardiac pacemaker; Patients with a pacemaker Participant has a pacemaker Have a cardiac pacemaker Pacemaker Presence of permanent pacemaker or implantable medical device\r\n* Artificial joint prostheses and venous filters are allowed Cardiac pacemaker Cardiac pacemaker Subject has a pacemaker present in the field of radiation or quadrant of the breast cancer Subject has a permanent cardiac pacemaker. Have a pacemaker Patients who have cardiac pacemaker or other electronic or metal implant Pacemaker pacemaker, Presence of a pacemaker or defibrillator Have a cardiac pacemaker or defibrillator device Patients with metal implant or a cardiac pacemaker Presence of a pacemaker or defibrillator Has a pacemaker or other internal medical device, or reports being pregnant (PCS study) Use of a ventricular-paced pacemaker