Cardiac index

Cardiac index (CI) is a haemodynamic parameter that relates the cardiac output (CO) from left ventricle in one minute to body surface area (BSA),^[1] thus relating heart performance to the size of the individual. The unit of measurement is litres per minute per square metre (L/min/m²).

Calculation

The index is usually calculated using the following formula:

$\text{CI} = \frac{\text{CO}}{\text{BSA}} = \frac{\text{SV}\times\text{HR}}{\text{BSA}}$

where

CI 

Cardiac index

BSA 

Body surface area

SV 

Stroke volume

HR 

Heart rate

CO 

Cardiac output

Clinical significance

The normal range of cardiac index in rest is 2.6–4.2 L/min/m².

The cardiac index is frequently measured and used in both intensive care medicine and cardiac intensive care. The CI is a useful marker of how well the heart is functioning as a pump by directly correlating the volume of blood pumped by the heart with an individual's body surface area.

If the CI falls below 2.2 L/min/m², the patient may be in cardiogenic shock.

References

1. "Cardiac Catheterization: Cardiovascular Tests and Procedures: Merck Manual Professional". Retrieved 2009-03-06.