What it is
Cardiac index is cardiac output divided by body surface area.[1]
Why it matters
The same cardiac output can mean different things in a small or large body, so cardiac index puts pump flow on a body-size-adjusted scale.[1,2]
Root causes of abnormal values
- Normalization relation: Cardiac index rises when cardiac output is high for body surface area and falls when pump flow is low relative to body size.[1]
- Typical scale: A healthy adult example is often near 3 L/min/m² at rest, but clinical interpretation depends on method, body surface area, and illness context.[2,1]
What it affects
- It links cardiac output, body size, perfusion, shock context, and heart-failure assessment.[1]
Interpretation traps
- Cardiac index is not a consumer-facing screening value and should not be inferred from wearable data alone.[1]