Screening for a PFO
Updated: Jan 22, 2020
PFO can be very difficult to detect even when we are looking specifically for it. A standard cardiac ultrasound or echocardiogram through the chest wall is not sensitive enough to pick up a PFO, nor can a PFO be heard through a stethoscope.
The current ‘gold standard’ test to confirm a PFO is a Trans-Oesophageal Echocardiogram (TOE). This procedure requires day admission to a hospital and a light anaesthetic so an ultrasound probe can be placed down the food pipe (oesophagus) to look at the heart in detail. TOE is an invasive procedure and should not be performed without good reason.
Through our specialised neuro-cardiac clinic, Cardio Remedy, we do not use the TOE to screen for PFO. We have discovered a better screening tool that is faster, safer and more accurate.
Instead, we are the first in Australia to use a Transcranial Doppler (cTCD) ultrasound with contrast.
Why a Transcranial Doppler?
1. It’s faster - the whole procedure takes around 15 minutes, and you can go back to work straight away.
2. It’s safer – the non-invasive procedure is done in our rooms without the need for any anaesthetic, involving your own blood and a small amount of salt solution.
3. It’s more accurate – the invasive TOE test misses up to 15% of PFOs – 25% of which are large. The cTCD is 100% accurate in detecting a potential abnormal connection in the heart.
Talk me through it
At our specialised clinic, Cardio Remedy, we use Doppler ultrasound via two small probes placed over the temples to listen to and measure the blood flow in the main cerebral arteries. Once the probes are positioned and a stable recording of the blood flow can be maintained, a small intra-venous cannula or drip will be inserted into a vein in the arm, near the elbow.
We then mix sterile salt water, known as saline, with a small amount of your own blood in the syringe, and a small volume of air. The solution is mixed together to create a foam or micro bubble solution to which the ultrasound is highly sensitive, but it is not harmful to you. Your doctor may refer to this test as a 'bubble study'.
When the solution is injected back into the vein it passes into the right atrium of the heart, where all blood flow returns. If there is a hole in your heart, then some of the micro bubbles will travel through it. This will then be pumped through the chambers on the left side of your heart, before being distributed throughout your normal arterial circulation.
We then listen to the blood flow in your brain for the presence of these micro bubbles, which will give a strong audible sound and signal on the Doppler display. You will also be asked to perform a ‘Valsalva’ or straining manoeuvre to improve the sensitivity of the test. The technician will talk you through how to do this.
The test will find out if there is a hole that allows blood to flow from the right to the left side of your heart, and how significant it is. The stronger the level of this test indicates how significant your hole is likely to be in terms of function.
Are there risks?
Transcranial Doppler (cTCD) with saline contrast is a very safe procedure that has been used in medicine for over 20 years. It is the most accurate and non-invasive test specifically looking for a hole in the heart or lungs.
We have had no reports of serious complications using this method, which we’ve performed on over 5,000 cases. A small number of patients that suffer from frequent and severe migraine with aura have reported experiencing a migraine at some stage after this test. In most cases this occurs some hours after. If you think you may be affected in this way, it is advisable to arrange for alternate transport or to take the rest of the day off. If you do develop a migraine, just treat it the same way you do normally. Please bring your normal medications with you.
What happens after the test?
If the test is normal, the results will be sent back to the referring doctor for them to discuss with you. If the test is strongly positive, you will see Dr Sharpe who will go through the results of the test and your clinical situation in greater detail.
I think I have a PFO, what do I do?
If you are experiencing any or a combination of the symptoms visit your GP for a referral to our neuro-cardiac clinic, Cardio Remedy.
We have a very structured, proven and efficient process to rapidly and accurately assess for PFO, allowing our team to deliver effective treatment strategies quickly.
Eligible patients may be invited to join one of our many research projects that are conducted through the PFO Research Foundation, a registered charitable organisation dedicated to advancing the science, and to educate the general public and medical community about PFO-related disease.