The purpose of this research study is to test the function of a subjects implantable cardioverter defibrillator (ICD) function throughout the duration of their heart surgery. ICD function can be altered during some types of heart surgery such as those when a pump (ventricular assist device - VAD) is implanted. The investigators would like to study the mechanism of device and ICD malfunction.

ICD function is typically measured prior to and after surgery. For the study, the investigators will measure ICD lead function multiple times throughout the surgery as well, to determine if and when device malfunction occurs. ICD lead function is measured noninvasively through a specialized computer the same way it is checked in the clinic. In addition, the investigators will test ICD function as they usually do following surgery.

Inclusion Criteria:

• Patients ages 18 and older
• Have a wireless implantable cardioverter defibrillator (ICD) and are undergoing VAD implantation or other cardiothoracic surgery.

Exclusion Criteria:

• Patients who are pacemaker dependent
• children, human fetuses, neonates
• prisoners will not be included
• Pregnant women will not be included

Patients with wireless ICDs undergoing VAD implantation (study group) or other cardiothoracic surgery (control group) will be included.