Content

• Steps
• Method 1 of 3: Determining your heart rate
• Method 2 of 3: Determining Stroke Volume
• Method 3 of 3: Factors Affecting Cardiac Output

Cardiac output, or circulation per minute, is the amount of blood that the heart pumps per minute (measured in liters per minute). It shows how efficiently the heart delivers oxygen and nutrients to the body, and how well it functions compared to the rest of the cardiovascular system. To measure cardiac output, it is necessary to measure stroke volume and heart rate. This can only be done by a doctor using an echocardiogram.

Steps

Method 1 of 3: Determining your heart rate

1. 1 Take a stopwatch or watch. Heart rate is the number of heartbeats per unit of time. It is usually measured in one minute. This is very easy to do, but you will need a device that will accurately count the seconds.
   • You can try to count the beats and seconds mentally, but this will be inaccurate, since you will be focused on the pulse, and not on the inner sense of time.
   • Better to set a timer so you can concentrate only on counting beats. The timer is in your smartphone.
2. 2 Find your pulse. While there are many points on your body where you can feel your pulse, the easiest way to find it is on the inside of your wrist. Another location is on the side of the throat, where the jugular vein is located. When you feel for a pulse and you can clearly feel its beat, place the index and middle fingers of your other hand in place of the beat.
   • Usually, the pulse is best felt from the inside of the wrist, on a line mentally drawn from the index finger through the wrist and about 5 cm above the first crease on it.
   • You may need to move your fingers back and forth a little to find where the pulse will be heard most clearly.
   • You can lightly press on your wrist with your fingers to feel the pulse. However, if you have to push too hard, you have chosen the wrong place. Try moving your fingers to a different point.
3. 3 Start counting the number of beats. When you find your pulse, turn on the stopwatch or look at the watch with the second hand, wait until it reaches 12 and start counting beats. Count the number of beats in one minute (until the second hand returns to 12). This number is your heart rate.
   • If you find it difficult to count the beats for a whole minute, you can count 30 seconds (until the second hand is at 6) and then multiply that result by two.
   • You can also count the hits in 15 seconds and multiply by 4.

Method 2 of 3: Determining Stroke Volume

1. 1 Get an echocardiogram. Heart rate is simply the number of times the heart beats per minute, and stroke volume is the volume of blood pumped by the left ventricle of the heart with each beat. It is measured in milliliters and is much more difficult to determine. For this, a special study is carried out called echocardiography (echo).
   • When taking an echocardiogram, radio waves are used. With their help, a picture of the heart is created and the volume of blood passing through it can be measured.
   • An echocardiogram provides the measurements needed to calculate stroke volume.
   • Having the results of the echocardiogram, you can make the necessary calculations.
2. 2 Calculate the area of ​​the left ventricular outlet (LVOT). The outlet of the left ventricle is the area of ​​the heart through which blood enters the arteries. To calculate the stroke volume, you need to know the left ventricular outlet area (LVOT) and the integral of the left ventricular outlet flow (LVEF).
   • These calculations need to be done with a professional echocardiogram reading. The specialist can calculate the area of ​​the left ventricular outlet using the following formula.
   • Area = 3.14 x (LVOT diameter / 2) ^ 2.
   • Nowadays, this method of calculation is gradually beginning to be replaced by more modern imaging technologies.
3. 3 Determine the integral of the blood flow velocity. The blood flow integral is the integral of the speed at which blood flow passes through a vessel or valve over time. To calculate the VOLVI, the specialist will measure the flow using Doppler echocardiography. To do this, he uses a special function of the echocardiograph.
   • To determine the VOLVI, the area under the aortic curve is calculated using a pulse-wave Doppler. The specialist can take multiple measurements to infer how efficiently your heart is working.
4. 4 Calculate the stroke volume. To determine the stroke volume of blood, subtract the volume of blood in the ventricle before the stroke (end diastolic volume, EDV) from the volume of blood in the ventricle at the end of the stroke (end systolic volume, ESV). Stroke volume = BWW - KCO. Stroke volume is usually associated with the left ventricle, but it can also be associated with the right ventricle. Usually the stroke volume of both ventricles is the same.
   • To determine the stroke index, divide the integral of blood flow velocity (the volume of blood that passes through the heart in one stroke) by the surface area of ​​the left ventricle (in square meters).
   • This formula allows you to analyze the stroke volume of the heart of a patient of any size.
5. 5 Determine cardiac output. Finally, to calculate cardiac output, multiply heart rate by stroke volume. This is a fairly simple calculation that tells you how much blood your heart pumps in one minute. The formula is: Heart rate x Stroke volume = Cardiac output. For example, if your heart rate is 60 beats per minute and your stroke volume is 70 ml, you get:
   • 60 beats per minute x 70 ml = 4200 ml / min., Or 4.2 liters per minute.

Method 3 of 3: Factors Affecting Cardiac Output

1. 1 Understand what heart rate means. You will better understand what cardiac output is if you know what affects it. The most immediate factor is heart rate (pulse), which is the number of heartbeats per minute. The faster the pulse, the more blood is pumped throughout the body.A normal heart rate is 60-100 beats per minute. If the heart beats too slowly, it is called bradycardia, a condition in which the heart pumps too little blood into the circulation.
   • If your heart beats very quickly, it can cause tachycardia (heart rate above normal) or, in severe cases, arrhythmias (abnormal heart rate or rhythm).
   • You might think that the faster the heart beats, the more blood circulates, but in reality, with each beat, the heart throws out less blood.
2. 2 Learn what contractility means. If you are interested in how the body's physical condition affects cardiac output, familiarize yourself with the concept of contractility. Contractility is the ability of a muscle to contract. The heart is made up of muscles that contract in a specific way to pump blood. When the heart muscle contracts, such as during exercise, it boosts cardiac output.
   • The more the heart contracts, the more blood is pumped through it.
   • This ability is impaired when part of the heart muscle dies and the heart starts pumping less blood.
3. 3 Learn about the importance of preload. This term refers to the length of the heart muscle before contraction begins. According to Starling's Law, the force of contraction depends on the length of the heart muscle in the stretched state. Thus, the greater the preload, the greater the force of contraction, and, consequently, the volume of blood driven through the heart.
4. 4 Learn about afterload. The last factor that affects cardiac output and is associated with heart condition is afterload. It refers to the force that the heart needs to overcome in order to push blood out, and it is highly dependent on the state of blood vessels and blood pressure. Less afterload can increase cardiac output, especially in cases where the contractility of the heart is impaired, which is often the case with heart disease.
   • If the heart muscle is damaged, improving the condition of the arteries and lowering blood pressure can help increase cardiac output.