Introduction
Patent foramen ovale (PFO) is a common abnormality, with an occurrence of 20-34% in the adult population. Most of the time, a PFO does not pose a high medical risk and can be a benign incidental finding. However, in some patients, PFO may open widely, causing paradoxical embolus (blood clots that break off from the venous circulation) to enter into the arterial circulation. This is known to be associated with cryptogenic stroke and systemic embolisation, with PFO being the most common cause of cryptogenic stroke in patients younger than 55 years old.
Percutaneous closure of PFO, a minimally invasive procedure to close the PFO using a device can help patients with cryptogenic stroke to reduce the risk of recurrent stroke. Other potential indications for closure include systemic embolisation, decompression sickness, platypnoea-orthodeoxia syndrome, amaurosis fugax, and migraine with aura.
What is a PFO?
In short, a PFO is a small hole in the heart. In the majority of the infants, closure of the foramen ovale occurs naturally after birth as negative intrathoracic pressure caused by the infants’ first breaths will cause the PFO to close. In some cases, the primum and secundum atrial septa fail to fuse completely, causing the foramen ovale to remain patent, enabling a continuous communication between the left and right heart.
Many times, a PFO may remain undetected throughout a person’s lifespan. However, when a blood clot breaks off and travels from the venous to arterial circulation (from right to left heart) through the PFO, it may start to cause serious medical conditions such as (cryptogenic) stroke, as well as decompression sickness in divers.
How to assess a PFO?
The first method of imaging to detect the presence of PFO is a transthoracic echocardiogram (TTE), or cardiac ultrasound. It is a non-invasive and safe method to see the heart. Using an ultrasound technique called color flow doppler, computerized colorization of these signals can help to identify if there is any blood flow communication between the right and left heart.
Agitated saline contrast (bubble) study is also performed to assess for a PFO. A sterile salt solution is shaken until tiny bubbles are formed which is then injected into a vein. Combined with a technique called the Valsalva maneuver to transiently increase the pressure in the right atrium, a positive bubble study whereby bubbles appear on the left side of the heart will indicate the presence of PFO.
The findings can subsequently be confirmed via transoesophageal echocardiography (TEE). The cardiologist inserts a probe through the mouth into the oesophagus (gut) to see the heart using ultrasound. A TEE is able to visualize the heart better and clearer as the distance of the TEE probe to the heart is nearer. A patient undergoing the TEE procedure has to fast (strictly no food, no water) for at least 6 hours before.
Percutaneous Minimally Invasive PFO Device Closure
The PFO device closure is performed in a catheterization laboratory with fluoroscopic (live X-ray) and TEE guidance. It is a minimally invasive procedure whereby the cardiologist implants the device across the PFO, through a catheter (plastic tube), inserted via the leg vein in the groin. The device acts like a double-sided umbrella that opens on each side of the heart between the top chambers, thereby sealing up the hole. It can be performed with mild sedation, within an hour, and with one night’s day in the hospital.
View this video published by Abbott Cardiovascular to learn more about the PFO Occluder:
To read up more on decompression sickness in divers, read the follow article:
Device closure in Scuba Divers
References:
https://onlinelibrary.wiley.com/doi/full/10.1111/joim.13143
https://my.clevelandclinic.org/health/diseases/17326-patent-foramen-ovale-pfo
https://www.graphicnews.com/en/pages/18720/science-fixing-a-hole-in-the-heart
