OptiVol Fluid Status Monitoring is an exclusive Medtronic feature that allows clinicians to monitor heart failure in patients with an implantable cardioverter defibrillator (ICD) or cardiac resynchronization therapy device (CRT-D).1-4
OptiVol monitoring to predict worsening heart failure is not intended to replace assessments which are part of standard clinical practice.
Ref:
http://optivol.medtronic.com/what-is-optivol/index.htm