How is PoTS Diagnosed?
Detailed questioning of the patient is the key to accurate diagnosis. Physical examination and appropriate investigations are also important. Other causes of symptoms need to be considered and identified.
Patients are usually diagnosed by a cardiologist, neurologist or medicine for the elderly consultant.
To be given a diagnosis of PoTS, a person needs to have:
- A sustained increase in heart rate of greater than 30 beats per minute within 10 minutes of standing
- Those aged 12-19 years require an increase of at least 40 beats per minute
- These criteria may not apply to those with a low heart rate when resting
- There is usually no drop in blood pressure on standing
It may be necessary for patients to have some or all of the tests below
An ECG is performed to rule out any heart problems that may cause symptoms similar to those found in PoTS.
The Active Stand Test
The active stand test can be used to diagnose PoTS. Under careful supervision, heart rate and blood pressure are measured after resting lying down, then immediately upon standing and after 2, 5 and 10 minutes. This test may bring on symptoms of PoTS and some people may faint.
Head-Up Tilt Table Test
This involves lying on a table that can be tilted to an angle of 60 to 70 degrees in a quiet, dimly lit, temperature controlled room. Blood pressure and heart rate are recorded in a continuous manner. After a period of 5 to 20 minutes of lying flat, the table is tilted. Although a diagnosis of PoTS should be made by an increase in heart rate of 30 bpm within the first 10 minutes, this upright position can last between 10 and 45 minutes. The patient will be asked how they are feeling during the test, so symptoms can be matched with heart rate and blood pressure. The test will end if your blood pressure becomes too low, satisfactory results have been obtained, or the maximum time has elapsed.
If facilities are available, some patients are tilted after a carbohydrate drink (liquid meal challenge), exercise or heat.
24 hour ambulatory blood pressure and heart rate monitor
Sticky patches are applied to the chest and are linked to a little box which is attached by a belt your waist. It monitors heart rate over a 24 hour period. A blood pressure cuff on your arm will intermittently check your blood pressure. The patient is asked to go about their usual daily activities, trying to reproduce events that seem to cause the symptoms. A diary stating the time and activity performed at the moment when the symptoms started should be kept. Doctors look to see if there is a fast heart rate or drop in blood pressure at the time of symptoms.
Echocardiogram (Heart Ultrasound)
This test is to check if the heart’s structure is normal. In this test a technician will apply some jelly on the chest and will roll an ultrasound probe in many directions to create a 3 dimensional image of the heart. It is a painless and harmless test that similar to the ultrasound scan used routinely during pregnancy to look at the unborn baby.
24-hour Urine Collection
Individuals with PoTS often have low urinary sodium levels of less than 150 millimole per 24 hours.
Another 24 hour urine collection may be carried out to test for high levels of noradrenaline and epinephrine to rule out pheochromocytoma (a growth on the adrenal gland) as a possible cause of symptoms.
Bloods are taken to rule out other conditions. These may include:
- Kidney function
- Blood count including ferritin
- Liver tests
- Thyroid tests
- Calcium levels
Blood can also be taken for norepinephrine whilst lying and then standing (or when upright on the tilt table); if levels exceed 600 picogram/millilitre, it may suggest hyperadrenergic PoTS.
Other tests which may be carried out
- Autonomic function screening tests
- Sweat testing
Written by: PoTS UK Team
Medically approved by: Dr John Purvis and Dr Satish Raj
review date: 1/2/18