Patent foramen ovale: a review of associated conditions and the impact of physiological size

Abstract

Patent foramen ovale (PFO) is implicated in platypnea-orthodeoxia, stroke and decompression sickness (DCS) in divers and astronauts. However, PFO size in relation to clinical illness is largely unknown since few studies evaluate PFO, either functionally or anatomically. The autopsy incidence of PFO is approximately 27% and 6% for a large defect (0.6 cm to 1.0 cm). A PFO is often associated with atrial septal aneurysm and Chiari network, although these anatomic variations are uncommon. Methodologies for diagnosis and anatomic and functional sizing of a PFO include transthoracic echocardiography (TTE), transesophageal echocardiography (TEE) and transcranial Doppler (TCD), with saline contrast. Saline injection via the right femoral vein appears to have a higher diagnostic yield for PFO than via the right antecubital vein. Saline contrast with TTE using native tissue harmonics or transmitral pulsed wave Doppler have quantitated PFO functional size, while TEE is presently the reference standard. The platypnea-orthodeoxia syndrome is associated with a large resting PFO shunt. Transthoracic echocardiography, TEE and TCD have been used in an attempt to quantitate PFO in patients with cryptogenic stroke. The larger PFOs (approximately > or =4 mm size) or those with significant resting shunts appear to be clinically significant. Approximately two-thirds of divers with unexplained DCS have a PFO that may be responsible and may be related to PFO size. Limited data are available on the incidence of PFO in high altitude aviators with DCS, but there appears to be a relationship. A large decompression stress is associated with extra vehicular activity (EVA) from spacecraft. After four cases of serious DCS in EVA simulations, a resting PFO was detected by contrast TTE in three cases. Patent foramen ovales vary in both anatomical and functional size, and the clinical impact of a particular PFO in various situations (platypnea-orthodeoxia, thromboembolism, DCS in underwater divers, DCS in high-altitude aviators and astronauts) may be different.

Percutaneous Transcatheter Closure of Patent Foramen Ovale in Patients With Paradoxical Embolism

“…Frequent forms of presentation of paradoxical embolism include cryptogenic stroke, [1][2][3][4] peripheral embolism, 3,5 brain abscess, 6 and decompression sickness in underwater divers. 4,7,8 Although the underlying mechanism whereby PFO accounts for this phenomenon is unknown, it is thought to involve the passage of emboli from the right-to the left-sided cardiac chambers through the PFO. 9,10 Patients with PFO and paradoxical embolism are at increased risk of recurrent systemic thromboembolic events, ranging from 3.2% to 3.8% per year.…”

Is the patent foramen ovale closure the best option?

“…The flap of the foramen ovale (septum primum) closes against the atrial septum (septum secundum) and normally fuses within the first two years of life. If the septum secundum covers the oval foramen, but does not seal to the septum primum, then a probable PFO exists that can be "opened" by the Valsalva or other maneuvers that increase right atrial pressure 1,2 . Prevalence of incomplete fusion is approximately 25-27% 1,3 and is associated with atrial septum aneurysm (ASA) in 50-80% patients in a global population 3 .…”

“…If the septum secundum covers the oval foramen, but does not seal to the septum primum, then a probable PFO exists that can be "opened" by the Valsalva or other maneuvers that increase right atrial pressure 1,2 . Prevalence of incomplete fusion is approximately 25-27% 1,3 and is associated with atrial septum aneurysm (ASA) in 50-80% patients in a global population 3 . The opening between the left and right atria can introduce venous blood or venous thrombus to the arterial system by crossing into the left heart through a right-to-left shunt (RLS) [1][2][3][4][5] .…”

“…Prevalence of incomplete fusion is approximately 25-27% 1,3 and is associated with atrial septum aneurysm (ASA) in 50-80% patients in a global population 3 . The opening between the left and right atria can introduce venous blood or venous thrombus to the arterial system by crossing into the left heart through a right-to-left shunt (RLS) [1][2][3][4][5] . Studies have demonstrated that RLS emboli and PFO are significantly associated with cryptogenic ischemic stroke, transient ischemic attack (TIA) and migraine with aura in young adults (below 55 years of age) [2][3][4][5] .…”

Semper aliquid haeret: A paradoxical embolus lodged in patent foramen ovale

“…The fetal, physiologically apert foramen ovale closes within the first 2 years of life, with the flap of the foramen ovale (septum primum) closing against the atrial septum (septum secundum), with incomplete fusion in about 25% of people, consequently resulting in defect. A patent foramen ovale (PFO) is usually an incidental find in a certain percentage (10 -30 %) [2,3] of all performed autopsies, usually with no significance, this due to the fact that a PFO is usually somewhat obliterated due to the physiological left-right shunt, as caused by the high left-sided pressure. Any transient increase of the right-sided pressure, as seen in the obstruction of the pulmonary arteries due to pulmonary embolism or severe pulmonary hypertension can, however, lay grounds for the passing of thrombotic material from the venous to the arterial system.…”