OptiVol Fluid Index (Medtronic CRT-D) Calculator

OptiVol Fluid Index (Medtronic CRT-D): explanation and clinical context The OptiVol Fluid Index is a device-derived metric based on changes in intrathoracic impedance measured by Medtronic CRT/ICD systems; it represents the cumulative difference between a device reference impedance and the measured daily intrathoracic impedance over time. A falling daily impedance (daily < reference) produces a positive deviation; when these deviations accumulate, the Fluid Index rises and has been associated with an increased short-term risk of heart-failure events and hospitalisation. Multiple studies and Medtronic technical documents commonly report a nominal alert threshold near 60 Ω·days, though performance and thresholds can vary by cohort and firmware version; OptiVol 2.0 introduces refinements to account for individual variation and to reduce false alerts.

Clinicians should interpret OptiVol trends alongside clinical data (symptoms, weight, natriuretic peptides, exam) and other device diagnostics to guide management.