Introduction of Review of Data and Discussion - Who Should Undergo Patent Foramen Ovale Closure in 2014?

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Overview

Summary

The foramen ovale is an integral component of the fetal circulation, responsible for facilitating the flow of placental pre-xygenated venous blood from the right atrium to the left, thereby circumventing the quiescent developing lungs. Physiological closure is usually achieved after birth when pulmonary vascular resistance and right heart pressures reduce, resulting in the left atrial pressure exceeding that of the right. The ‘flap valve’ is pressed up to the secundum septum and seals over; often in the early postnatal period, and this is usually completed within the first year of life. However, it has long been known that patency of the foramen ovale frequently persists into adulthood. Although not always shunting at rest, increases in right atrial pressure (as occurs during sneezing or a Valsalva manoeuvre) can cause short periods of significant passage of deoxygenated blood at the atrial level.

A patent foramen ovale (PFO) is usually asymptomatic; however, its presence has been implicated in a number of conditions including, but not limited to, paradoxical embolism (causing a stroke, peripheral arterial occlusion or myocardial infarction with normal coronary arteries), migraine (particularly those occurring with aura), decompression illness and the more rare and underdiagnosed platypnoea-orthodeoxia syndrome (POS). In addition, it may increase risk in large-scale orthopaedic surgery and neurosurgery performed in the seated position.

It is hypothesised that bloodborne material from the venous circulation, normally excluded from the systemic side during passage through lung vasculature, bypasses this through the PFO. Such materials could include thrombus, air, vasoactive substances or even fragments of bone and fat in the context of fractures and surgery.

As a result, ever since the first report in 19881 of temporary closure of a PFO with a Swan-Ganz catheter to facilitate surgery, abolishing this shunt when found in specific circumstances has been attractive, particularly with modern day low-risk transcatheter techniques.

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