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OptiVol Fluid Index (Medtronic CRT-D) Calculator

  • Reference Impedance (Ω)
  • Daily Intrathoracic Impedance Values (Ω) — comma separated (oldest → newest) Example: 68.2,67.9,67.4,66.7
  • Algorithm variant
  • Threshold for Alert (Ω·days) Nominal literature threshold often used: 60 Ω·days
  • 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.

    Reference:
    Medtronic OptiVol™ 2.0 product/technical information and performance summary.
    Yang XW et al., systematic analyses of OptiVol performance and limitations (PMC review).
    Circulation commentary and device-impedance explanation (Circulation 2011 overview on OptiVol mechanics and interpretation).
    Comparative/algorithm refinement literature (PARTNERS HF / refined detection algorithm analyses).

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