What is a Cardiac Output Formula?
Cardiac output, often called CO, is a crucial measure of heart function. It represents the blood pumped by the left ventricle into the aorta per minute (Martini et al., 2017, 680-681). This is typically measured in liters of blood per minute. Another way to think of it is the volume of blood circulating through the body's systemic circuit in a minute.
While there are analytical methods like Fick’s principle to measure cardiac output, a simple way to express it is by considering its two main components: stroke volume and heart rate.
As a reminder, stroke volume is the amount of blood pumped with each heartbeat, and heart rate is the number of beats per minute. If we multiply these two parameters, we get the blood pumped per minute—cardiac output!
So, we can express cardiac output as the product of heart rate and stroke volume:
Cardiac Output = Heart Rate x Stroke Volume.
You might also see it written as:
CO = HR x SV.
It may seem straightforward, but there's a bit more to it. Thankfully, our cardiac output formula template can help you understand all the factors affecting heart rate, stroke volume, and cardiac output.
How Does it Work?
Our Cardiac Output Formula can be completed digitally, printed, and filled in by hand. Let's walk through the steps to ensure you calculate cardiac output accurately each time.
Step 1: Input End-Diastolic Volume (EDV)
If you already have the stroke volume value, feel free to skip ahead to Step 3. Otherwise, enter the end-diastolic volume (in milliliters) into the designated EDV box.
Step 2: Provide End-Systolic Volume (ESV)
Next, input the end-systolic volume (in milliliters) into the ESV box.
Step 3: Calculate Stroke Volume
If you already know the exact value for stroke volume, just put it in the SV box in Equation 2. If not, subtract ESV from EDV in Equation 1, resulting in your stroke volume in milliliters. Enter this value, changed into liters, into the SV box.
Step 4: Insert Heart Rate
Enter the heart rate in beats per minute (bpm) into the HR box.
Step 5: Compute Cardiac Output
In this final step, multiply the stroke volume and heart rate values (or those in the SV and HR boxes). This will give you the cardiac output in liters per minute.
That's it! You're all set to calculate cardiac output accurately.
Cardiac Output Formula Example (Sample)
In a real-life scenario, let's explore how to calculate cardiac output using the end-systolic volume (ESV), end-diastolic volume (EDV), and heart rate. Take Marie, for instance, with an end-systolic volume of 45mL, end-diastolic volume of 120mL, and a heart rate of 80 bpm.
We've prepared a downloadable PDF of the cardiac output formula template to guide you through this calculation. Feel free to download it here and work through the example to enhance your understanding.
When Would You Use This Cardiac Output Formula?
When to apply this formula? Cardiac output estimation can be approached through various methods like echocardiography, thermodilution techniques, Fick techniques, or angiography.
This Cardiac Output Formula is versatile and can be employed with any technique that enables quantitative measurement of left ventricular volume at different phases of the cardiac cycle. Whether you're utilizing cardiac MRI, echocardiography, or angiography, this formula will prove helpful.
While Fick techniques are known for their precision and are considered the gold standard, imaging-based techniques offer an efficient estimate. This is particularly valuable for monitoring changes in relative cardiac output over time (Maleki et al., 2017, 183-184).
Practitioners who might benefit from having this Cardiac Output Formula on hand include:
- Medical or nursing students
- Trainee cardiologists, physiologists, or medical research scientists
- Imaging scientists or radiologists.
What do the Results Mean?
Remembering that a single number can't capture all the factors affecting a patient's cardiac health is crucial. Cardiac output is exceptionally variable and can be influenced by factors like exercise, hormones, or body temperature. Consequently, each patient will have a unique baseline for their heart function, and normal values for cardiac output can vary widely.
For a healthy adult, stroke volume is often cited around 70mL, and when combined with a typical resting heart rate of 60-80 bpm, a specific cardiac output is usually given as 5 L/min.
Suppose a patient's cardiac output falls below the expected value for a healthy individual. In that case, it might indicate a heart condition like congestive heart failure, cardiomyopathy, or another underlying issue leading to heart failure.
Conversely, a higher-than-expected cardiac output can result from hyperthyroidism, stress, or vigorous exercise. This underscores the importance of interpreting a single cardiac output value in context to determine whether it indicates an underlying pathology. Understanding the broader picture is critical in assessing cardiac health.
Research & Evidence
The cardiac output formula we're diving into here has a rich history, developed and enhanced by numerous scientists and cardiologists over the past century. It's universally accepted as the foundational formula for a theoretical cardiac output (Young, 2010).
The evidence for this formula for cardiac output dates back to the work of Otto Frank and Ernest Starling in the early 1900s, following the development of the Frank-Starling law of the heart. Subsequently, many physiologists and cardiologists have contributed to developing and validating this formula.
Despite its longevity and widespread nature, this equation does not encompass all the factors that can impact cardiac output and is a more simplified representation of cardiac output.
Recognizing the need for refinement, various methods have been created, including normalizing with a body surface area estimate (Maleki et al., 2017, 184). Factors impacting cardiac output include preload, vessel contractility, certain hormones, and body temperature (Martini et al., 2017). However, we focus on the basic formula in many beginner or undergraduate resources to build a solid foundation. Our approach ensures a clear understanding of the fundamentals before delving into more intricate calculations.
Why Use Carepatron as Your Cardiac Output Formula App?
Cardiovascular diseases represent a considerable proportion of the global disease burden, creating a substantial workload for healthcare professionals who deal with test orders, image interpretations, result sharing, and treatment decisions. Fortunately, the advent of automation and electronic health records has significantly reduced the burden of these routine tasks. If you're seeking a solution to streamline your medical billing, scheduling, and electronic patient records processes, look no further than Carepatron.
Carepatron is a comprehensive software suite designed to enhance efficiency in medical and healthcare practices. With smart practice management solutions, you can provide patients with their patient portal software for booking appointments, accessing results, or engaging in telehealth appointments.
Use our AI-powered smart dictation software and a library of useful templates, including the cardiac output formula, to optimize your workflow and save valuable time. Carepatron is your ally in delivering efficient and patient-centric healthcare services.
Maleki, M., Alizadehasl, A., & Haghjoo, M. (Eds.). (2017). Practical Cardiology. Elsevier.
Martini, F., Ober, W., Nath, J., Bartholomew, E., & Petti, K. (2017). Visual Anatomy and Physiology. Pearson.
Young, D. B. (2010). Control of Cardiac Output. Morgan & Claypool Life Sciences.