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

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

Physiology of the cardiovascular system

Heart

Cardiac output	Cardiac cycle Cardiac output Heart rate Stroke volume Stroke volume End-diastolic volume End-systolic volume Afterload Preload Frank–Starling law of the heart Cardiac function curve Venous return curve Wiggers diagram Pressure volume diagram

Ultrasound	Fractional shortening = (End-diastolic dimension End-systolic dimension) / End-diastolic dimension Aortic valve area calculation Ejection fraction Cardiac index

Heart rate	Cardiac pacemaker Chronotropic (Heart rate) Dromotropic (Conduction velocity) Inotropic (Contractility) Bathmotropic (Excitability) Lusitropic (Relaxation)

Conduction	Conduction system Cardiac electrophysiology Action potential cardiac atrial ventricular Effective refractory period Pacemaker potential Electrocardiography P wave PR interval QRS complex QT interval ST segment T wave U wave Hexaxial reference system

Chamber pressure	Central venous Right atrial ventricular pulmonary artery wedge Left atrial ventricular Aortic

Other	Ventricular remodeling

Vascular system/
Hemodynamics

Blood flow	Compliance Vascular resistance Pulse Perfusion

Blood pressure	Pulse pressure Systolic Diastolic Mean arterial pressure Jugular venous pressure Portal venous pressure

Regulation of BP	Baroreflex Kinin–kallikrein system Renin–angiotensin system Vasoconstrictors Vasodilators Autoregulation Myogenic mechanism Tubuloglomerular feedback Cerebral autoregulation Paraganglia Aortic body Carotid body Glomus cell

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