Patent foramen ovale: Unanswered questions

Abstract

The foramen ovale is a remnant of the fetal circulation that remains patent in 20-25% of the adult population. Although long overlooked as a potential pathway that could produce pathologic conditions, the presence of a patent foramen ovale (PFO) has been associated with a higher than expected frequency in a variety of clinical syndromes including cryptogenic stroke, migraines, sleep apnea, platypnea-orthodeoxia, deep sea diving associated decompression illness, and high altitude pulmonary edema. A unifying hypothesis is that a chemical or particulate matter from the venous circulation crosses the PFO conduit between the right and left atria to produce a variety of clinical syndromes. Although observational studies suggest a therapeutic benefit of PFO closure compared to medical therapy alone in patients with cryptogenic stroke, 3 randomized controlled trials (RCTs) did not confirm the superiority of PFO closure for the secondary prevention of stroke. However, meta-analyses of these RCTs demonstrate a significant benefit of PFO closure over medical therapy alone. Similarly, observational studies provide support for PFO closure for symptomatic relief of migraines. But one controversial randomized study failed to replicate the results of the observational studies while another two demonstrated a partial benefit. The goal of this review is to discuss the clinical conditions associated with PFO and provide internists and primary care physicians with current data on PFO trials, and clinical insight to help guide their patients who are found to have a PFO on echocardiographic testing. Embryology and anatomySince fetal lungs in utero are incapable of oxygenating blood, the fetus is dependent on the maternal circulation for oxygen delivery via the placenta. Oxygenated blood returning to the right atrium via the umbilical vein needs to be delivered to the brain and vital organs before further loss of oxygen occurs. To facilitate this rapid transit, an inter-atrial communication evolved in all mammals, known as the foramen ovale [1].After birth, the foramen ovale flap (the septum primum) physiologically closes against the septum secundum when pulmonary vascular resistance and right atrial pressure decrease. An atrial septal aneurysm (ASA), a saccular deformity of the atrial septum that protrudes 15 mm in the direction of either atria, is associated with 15% of PFOs and is often seen with the largest size PFO [3] and [4]. PFO imagingThe most accurate test for determining the presence of a PFO is a right heart catheterization with documentation of a guidewire crossing the atrial septum. The standard non-invasive method for diagnosing a PFO is transesophageal echocardiography (TEE) using agitated saline contrast [5]. Transcranial Doppler (TCD) is a more sensitive and less uncomfortable method for diagnosing PFO with a sensitivity of 97% and specificity of 93% [6]. Transthoracic echocardiogram (TTE) with bubble study is a less expensive, non-invasive test compared to TEE with comparable specificity [7] and [8]. Howeve...

LMA Gastro Airway Seen Through the Eyes of a Cardiac Anesthesiologist

“…6 We report the successful insertion of a TEE probe in the channel for esophageal intubation of the LMA Gastro in 9 patients undergoing percutaneous patent foramen ovale (PFO) closures, a short procedure done with increasing relevance and frequency. [7][8][9][10][11][12] Written informed consent was obtained from patients.…”

Patent Foramen Ovale and Diving

“…Fusion, which begins with contact, is completed irreversibly, in the first two years of life. Foramen ovale remains patent in 25% of the population (1,2). The patent foramen ovale (PFO) was drawn and depicted by Leonardo Da Vinci in the form of a "channel" centuries after the physiological closure was defined by Galen.…”

“…However, daily activities such as lifting, coughing, vomiting, and pushing which increase intrathoracic (ITP) and intraabdominal pressure may reverse the interatrial pressure gradient, creating a temporary right-to-left shunt. One of the most effective methods is an extended and forced Valsalva maneuver (VM) (1,2,5). The maneuver, originally described in 1704 by Mario Antonio Valsalva in detail in his work "De Aure Humana Tractatus" (Treatise on the Human Ear), is simply an effort of forced expiration against a closed airway.…”

“…However, during echocardiographic studies with contrast agents, for safety reasons, oxygen should be available and the diver should not have dived within the last 24 hours (6). It has been shown that TCD has similar sensitivity to shunt detection, but it fails to differentiate cardiac and pulmonary localizations (2,9,10).…”

Percutaneous patent foramen ovale closure for cryptogenic stroke: learning from clinical trial and error

“…In addition, inclusion of patients with TIA and other peripheral embolism was not reflective of the study population included in most observational studies. Lack of blinding may also have potentiated the use of off-label PFO occluding devices in patients included in the medical therapy arm (9,10). Although the RESPECT trial did not demonstrate superiority of closure using the Amplatzer device in an intention-to-treat analysis (7), the extended follow-up data (median 5.9 years) showed superiority of PFO closure with a 62% relative risk reduction in recurrent cryptogenic stroke; the benefit of closure was enhanced in those with a large shunt or atrial septal aneurysm.…”