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Cardiovascular Autonomic Reflex Test

What is autonomic reflex testing?

Autonomic reflex testing, along with plethysmography, is used to evaluate the integrity of the autonomic nervous system, which controls the heart and blood circulation. This is the nervous system that does not involve voluntary control. Your body’s response to different stimuli, shown by changes in blood pressure and heart rate, will help your doctor understand how your autonomic nervous system is working.

Why is this test recommended?

The autonomic reflex testing and plethysmography results will help your referring doctor determine possible causes of your dizziness/fainting and develop a successful plan of care for your treatment. The test results will help determine whether the cause of the problem is a drop in your blood pressure while you’re upright, abnormal function of the autonomic nervous system, or another cause.

What is syncope?

Syncope (pronounced “sin ko pea”) is the brief loss of consciousness and posture caused by a temporary decrease in blood flow to the brain. Syncope may be associated with a sudden fall in blood pressure, a decrease in heart rate or changes in blood volume or distribution. The person usually regains consciousness and becomes alert right away, but may experience a brief period of confusion.

Syncope is often the result of an underlying medical condition that could be related to your heart, nervous system or blood flow to the brain.

Scheduling the autonomic reflex test

The scheduling secretary will help make your appointment and will give you a printed reminder so you will know when to come in for the testing. Please call to schedule an appointment by phone, and your appointment information will be mailed to you.

How long does the test last?

The test takes about 1 ½ to 2 hours to complete. Plan on being at the hospital for 2 to 2 ½ hours.

Should I take my medications?

Take all prescribed medications with water at their scheduled time(s), except diuretics or laxatives. If you have any questions or need help adjusting your medications, please call or talk with your referring physician. Do not stop taking any medication without first talking to your healthcare provider.

Can I eat before the test?

Yes, unless you are having another test or procedure on the same day that requires you to fast.

What should I wear?

Wear comfortable, loose-fitting clothing. Please do not wear tight jeans or dress clothes. During the testing, one pant leg will need to be raised above the knee.

What should I bring?

Please bring the following to your appointment:

  • Recent medical history and physical exam report
  • Medical records related to your health condition (if available)
  • List of your current medications and dosing information
  • List of allergies (including medications, food and environmental)
  • Your insurance card

Where do I go for my appointment?

  • Please check in at the desk at least 10 minutes before your scheduled appointment time.
  • Before going to the testing area, your height and weight will be recorded.
  • You will have an opportunity to use the restroom before the test.

The autonomic technician or nurse will explain the procedure in detail and answer any questions you may have. You will be asked to lie on your back during testing. If you are uncomfortable, tell the nurse or technician so they can help you find a more comfortable position.

An intravenous (IV) line will be placed in a vein of one arm. This IV will be used during the third part of the test to give you a dose of a short-acting medication.

EKG Monitoring: Small, sticky patches called electrodes will be placed on your chest. The electrodes are connected to an electrocardiograph (EKG) monitor that records the electrical activity of your heart as a graph, or series of lines, on a moving strip of paper. The EKG shows your heart rate and rhythm during the test.

Blood Pressure Monitoring: A blood pressure cuff will be placed on one arm. This cuff is attached to a monitor so your blood pressure can be measured throughout the test. Your blood pressure will also be checked using a small cuff that will be placed on one of your fingers. This cuff will squeeze your finger from time to time throughout the test. Some patients say the finger cuff feels funny, but not painful.

Respiration Monitoring: A small belt will be placed around the lower part of your chest to monitor your breathing.

Plethysmography Monitoring: A monitoring cuff made of latex and two pressure cuffs will be placed on one of your legs. You will be asked about latex allergies prior to the cuff placement. The monitoring cuff is placed at mid-calf level. A larger cuff is placed over the knee. This is a low-pressure cuff and should not cause pain to the knee. A small cuff will be placed near the ankle. This is a high-pressure cuff that will be very tight, but not painful. The plethysmography measures small pressure changes in the arteries, which carry blood from the heart.

There are four parts to the test:

Part One

During the first activity of the test, you will be asked to strain by blowing air into a small tube against resistance (Valsalva test). Each blow into the tube is usually 15 seconds, but the technician will tell you when to stop. You may become a little lightheaded during straining, but this usually goes away quickly right after you stop blowing/straining.

Part Two

During the second part of the test, one of your hands will be placed into iced water for about two minutes (Cold Pressor Test). Iced water can be uncomfortable or painful to the hand; you may stop the test early if you need to. Just tell the technician that you need to take your hand out of the water.

PLEASE NOTE: The plethysmography monitoring will be done during the Valsalva and Cold Pressor testing.

Part Three

During the third portion of the test, you will receive a short-acting medication through the IV placed in your arm at the beginning of the test. Your heart rate and blood pressure will be monitored and recorded while you receive this medication, and the results will be analyzed.

Part Four

During the fourth and final part of the test, you will inhale a medication through your nose using a sniffing fashion. Your heart rate and blood pressure will again be monitored and recorded, and the results will be analyzed.

PLEASE NOTE: The Medications given during these procedures are very short-acting and have no long-term residual effects. At the end of the test, you should feel similar to the way you felt before the testing was done.


As with any procedure, there are risks involved with the autonomic reflex test. Your healthcare provider will discuss the risks and benefits of the procedure with you before the test is ordered. If necessary, due to pre-existing conditions, the test may be modified to minimize any potential risks.

Risks to be considered include:

  • Latex allergy. The plethysmography uses a pressure cuff that contains latex. If you are allergic to latex, plethysmography cannot be performed.
  • Plethysmography involves the use of a blood pressure cuff on your ankle or wrist. If you cannot tolerate the amount of pressure used during the test, the plethysmography part of the test cannot be done.
  • You may feel lightheaded during the Valsalva procedure when straining/blowing. If this happens, you may be asked to strain for a shorter period of time than the typical 15 seconds. The lightheadedness usually goes away right after the procedure.
  • You may feel hand “cold” or “pain” during the Cold Pressor Test. If you cannot tolerate this sensation, the length of this test can be shortened. The sensation usually goes away quickly by wrapping your hand in towels after the procedure.
  • Temporary reactions to medications used during testing. You may get a headache when you receive phenylephrine to increase your blood pressure during the test. You may become lightheaded when you receive amyl nitrite to lower your blood pressure during the test. These are very short-acting medications, and usually the symptoms go away quickly after the use of the medications is complete.
  • You may feel a stinging sensation when you receive the IV used to administer phenylephrine, and some patients experience bruising when the IV is removed, which may not appear until the next day.

If you have swelling, redness or free bleeding at the site of the removed IV cannula, you must call the Syncope Department immediately. Please talk to the staff prior to going home if you have any concerns or questions concerning your IV site.

Going home after the test

After the test is over, you will be able to return home right away. If you desire, you may stay in the lab area an additional 15 to 20 minutes or until all of the symptoms you may have experienced during the test have resolved.

If you have any discomfort during the testing, we recommend you have a responsible adult drive you home after the test.

If you experience severe symptoms during the testing, the test will be stopped early.

When will I get the test results?

The Autonomic Reflex test is usually ordered by your doctor along with other tests, such as tilt table testing and blood volume/hemodynamics testing. A full report that includes all of your test results will be sent to you and your referring physician or primary care physician within 10 to 14 business days. Your
physician(s) will talk to you about recommended changes to your medications and/or treatment plan, if necessary.

Reviewed: 09/13

This information is about testing and procedures and may include instructions specific to Cleveland Clinic.
Please consult your physician for information pertaining to your testing.

Talk to a Nurse: Mon. - Fri., 8:30 a.m. - 4 p.m. (ET)

Call a Heart & Vascular Nurse locally 216.445.9288 or toll-free 866.289.6911.

Schedule an Appointment

Toll-free 800.659.7822

This information is provided by Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition.

© Copyright 2015 Cleveland Clinic. All rights reserved.

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