Hemodynamics

What is hemodynamics?

Hemodynamics is how your blood flows through your arteries and veins and the forces that affect your blood flow.

Normally, your blood flows in a laminar (streamlined) pattern. It flows fastest in the middle of a blood vessel, where there’s no friction with blood vessel walls.

However, the flow is turbulent in your ventricles (lower heart chambers) and in places where a vessel branches off or changes in diameter. You’ll need to use more energy to move blood that has a turbulent flow because it’s not moving efficiently.

Your aorta and its branches deliver a constant flow of blood, oxygen and nutrients to your body through smaller and smaller blood vessels. Once your organs extract the oxygen, the blood then returns to your heart via veins. Your heart then pumps the blood to your lungs to get oxygen and restart the cycle.

As blood travels through your blood vessels, it may have to flow over a type of “speed bump” when you have a collection of cholesterol that makes up plaque in an artery. These plaques can rupture and block an artery.

In addition, a blood clot can create an obstacle, too.

Your heart may be too weak to send your tissues as much blood and oxygen as they need.

Any of these issues makes it difficult for your circulatory system to do its job successfully and efficiently. That job is to send blood (which contains oxygen and nutrients) to all of your body’s cells, tissues and organs.

Why are hemodynamics important?

Hemodynamics are important because understanding the factors that affect your blood flow can help you understand your cardiovascular condition. For example, when you know that high blood pressure makes it harder for your heart to pump blood, it makes sense to take medicine that relaxes your blood vessels. Giving your blood more room to get through brings your blood pressure down.

Your provider can use hemodynamics to make a diagnosis and/or prognosis. They can see if your heart valve is leaking, which means all of the blood isn’t getting where it’s supposed to go. They can check to see if the surgery you had or medication you started taking has improved your blood flow.

Is hemodynamics blood pressure?

No. Blood pressure is only part of what your provider considers when looking at your hemodynamics. Many other factors affect how your blood moves through your body.

What are hemodynamic factors?

Hemodynamic factors are things that affect how well your blood flows. They can make it easier or harder for your blood to get to your organs and tissues. Your body makes constant adjustments to give your cells what they need.

Hemodynamic factors include:

• The size (diameter) of a blood vessel. It’s easier for your blood to move through a larger or more open vessel. It’s harder for blood to flow through an artery that’s become narrow because of a plaque deposit containing cholesterol.
• The amount of friction your blood must overcome to keep moving. The friction of blood flowing against a blood vessel wall slows it down. Blood closer to your artery wall moves more slowly because of this friction. Blood in the middle of your artery moves faster.
• Blood vessel expansion and contraction in response to blood pressure changes. Your blood vessels have the ability to become wider or narrower to control blood flow and keep it consistent.
• Pressure differences between how forcefully your heart pumps and how much resistance your blood vessels provide. The blood your heart pumps has to push against your blood vessels’ force. This is why having high blood pressure makes your heart work harder.
• Cardiac output. Your heart can pump out more or less blood with each heartbeat depending on what you’re doing at the time. When you exercise, your heart sends more blood to your cells because they need more oxygen than when they’re resting.
• Heart rate. Your heart can beat more times per minute when you’re exercising than when you’re resting. This helps your body get the increased amount of oxygen it needs for exercise.
• How well your heart’s ventricles are working. If you have a heart condition that makes your ventricles unable to pump blood well, this affects how much blood they can send to your body.

What is hemodynamic instability?

Hemodynamic instability means your body can’t get enough blood flow. This is known as shock. There are several types, depending on the cause.

Types of shock

• Cardiogenic.
• Hypovolemic.
• Obstructive.
• Distributive.
• Neurogenic.

How are hemodynamics measured?

Your provider can use various tests to measure your hemodynamics.

They may:

• Use cardiac catheterization to check for heart valve issues by measuring the pressure on either side of your valve.
• Check central venous pressure using ultrasound or by placing a catheter in a vein.
• Check pulmonary artery pressure with a catheter.
• Measure cardiac output using a pulmonary artery catheter and/or transthoracic echocardiogram.
• Use an electrocardiogram (EKG) to check for an abnormal heart rhythm.
• Use a catheter to do invasive blood pressure monitoring in an artery.
• Use a regular blood pressure cuff to measure blood pressure.
• Do an echocardiogram to see if your lower chambers are pumping well.
• Do a head-up tilt table test to evaluate fainting.

What are the common conditions and disorders that affect hemodynamics?

Any cardiovascular condition that affects how well your blood flows affects your hemodynamics. Conditions that affect your hemodynamics include:

• Atherosclerosis.
• High blood pressure (hypertension).
• Low blood pressure (hypotension).
• Heart valve issues.
• Heart failure.
• Peripheral artery disease.
• Deep vein thrombosis.
• Heart attack.

Common signs or symptoms of hemodynamics issues

Problems with your hemodynamics will create symptoms, such as:

• Shortness of breath.
• Fainting.
• Dizziness.
• Tiredness.
• Pale skin.
• Cool skin.
• Confusion.
• Abnormal heart rhythm.

A note from Cleveland Clinic

When you hear your healthcare provider talk about hemodynamics, they’re talking about your blood flow. If you have an issue with your heart or blood vessels, your blood may not be flowing well through your body. Your provider can evaluate you and give you a treatment that improves your blood flow. This may be medicine or surgery, depending on what’s wrong. Treating the issue is important so you can improve your cardiovascular system’s ability to send a constant supply of fresh oxygen to your body.