Cardiac index is defined as:
**Core Concept**
Cardiac index is a measure of cardiac output that is adjusted for body size, allowing for a more accurate comparison of cardiac function in individuals of different sizes. It is calculated as the cardiac output divided by the body surface area. This concept is essential in evaluating the cardiac function of patients with various cardiovascular diseases.
**Why the Correct Answer is Right**
The cardiac index is a vital parameter in clinical practice, as it helps in assessing the cardiac function in patients with heart failure, cardiomyopathy, or other cardiovascular conditions. The cardiac output is determined by the product of the heart rate and stroke volume, and when this value is divided by the body surface area, it gives the cardiac index. This index is particularly useful in patients with a large body mass index (BMI), as it provides a more accurate estimate of cardiac function.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not take into account the body surface area, which is essential for comparing cardiac function in individuals of different sizes.
**Option B:** This option is incorrect because it is not the correct formula for calculating the cardiac index.
**Option C:** This option is incorrect because it does not include the heart rate in the calculation of the cardiac index.
**Clinical Pearl / High-Yield Fact**
Cardiac index is an essential parameter in evaluating cardiac function in patients with various cardiovascular diseases. It is particularly useful in patients with a large BMI, as it provides a more accurate estimate of cardiac function.
**Correct Answer:** C. Cardiac index is defined as the cardiac output divided by the body surface area.