PFO

Images Genevieve Carbonatto and Tina Cullen. Text Genevieve Carbonatto

A 35 year old lady presents to the Emergency Department with chest pain. She has had a recent admission for drainage of a pericardial effusion (non malignant) and is concerned that it may have reaccumulated. An point of care ECHO was performed .There was no evidence of pericardial effusion. However, her apical 4 chamber view showed a hypermobile atrial septum.

This is her Apical 4 chamber view

Note the hypermobile atrial septum which seems to balloon into one atrium and the other with the cardiac cycle.

 

There is an association between a hypermobile interatrial septum and a patent foramen ovale (PFO). To further investigate this a subcostal view will have the interatrial septum at right angles with the probe and will be visualised more clearly. Interrogation with colour Doppler of the interatrial septum to look for a PFO will also be better as the flow of blood from one atria to the other will be in line with the probe. Below is her subcostal view without colour Doppler.

There is a suggestion of a PFO.

 

With colour Doppler, a “flame” of colour is visible at the point of the PFO and at some point during the cardiac cycle, blood flow is clearly visible going from the right atrium to the left atrium.

“Flame” of colour signal at the point of the PFO

Flow of blood visible with colour Doppler though IAS (interatrial septum)

Discussion

The identification of a PFO in the Emergency Department is clearly not a core skill, however it may be an incidental finding as in this case, and may be relevant  in the context of a young person presenting with possible paradoxical emboli. During fetal circulation, a portion of blood flow passes from the right atrium to the left atrium bypassing the lung. As pulmonary blood flow increases during the neonatal period, the left atrial pressures increase causing compression of the septum primum against the septum secundum, functionally closing the PFO. Anatomic closure occurs later in infancy, however autopsy studies have shown that up to 25% of the adult population retain a PFO. It is therefore a normal variant rather than a pathological finding in the absence of paradoxical embolism. (2) In general there is a trivial shunting of blood from right to left, but release of a Valsalva manoevre transiently reverses the normal  left-to-right pressure gradient and causes an exaggerated transient leftward shift of the free edge of the septum primum with apparent enlargement of the orifice of the PFO. Increases in  right atrial pressures will increase the right to left shunt.

Some features associated with PFO’s include (7)

  • An increase prevalence of cryptogenic (no cause found) stroke. 40% of adults with cryptogenic strokes are under 55, 46% of which have been found in one study to have a PFO. The brain, the eyes, the heart and the kidneys are most affected by emboli. It is though that a PFO is essentially a “tunnel” across the IAS and that this is favourable to thrombus formation.
  • Increase in prevalence of migraine and migraine like symptoms
  • Increase incidence of neurologic decompression sickness
  • Can increase in severe PAH

The origin of paradoxical emboli (2)

PFO’s are not always associated with hypermobile IAS. Septal hypermobility is inaccurately referred to as an atrial septal aneurysm (ASA). Inaccurate because it is not an aneurysm as such. It is defined as a mobile protrusion of the septum primum tissue into the atrium measuring at least 10 to 15 mm or a phasic septal excursion of at least 15 mm occurring at some point during the cardiorespiratory cycle (1).

Atrial septal aneurysms (hypermobile IAS)  are

  • Often associated with PFO’s but not always.
  • Predicts the degree of right to left shunt across a PFO
  • It’s association with stroke recurrence is debatable

Management of PFO’s

Since PFOs are so ubiquitous, there is no need for any special treatment or management except in the patient with recurrent TIA’s or strokes. In this case closing of the shunt may be necessary if anticoagulation  is contraindicated or ineffective.

Teaching point: PFO’s are very common in the general population and usually cause no symptoms. There is however an increase likelihood of paradoxical emboli due to  PFO’s causing ischaemic strokes in patients under 55. This should be kept in mind when a patient presents with a TIA or ischaemic stroke in this age group.

References

  1. Am Heart J 2003 Apr;145(4):730-6. Interatrial septal mobility predicts larger shunts across patent foramen ovales: an analysis with transmitral Doppler scanning.
    Fox ER1, Picard MH, Chow CM, Levine RA, Schwamm L, Kerr AJ.
  2.  J Am Coll Cardiol. 2012;59(19):1665-1671. Review article Patent Foramen OvaleThe Known and the To Be KnownShelby Kutty, MD; Partho P. Sengupta, MD, DM; Bijoy K. Khandheria, MD
  3. J Am Coll Cardiol Vol. 46, No. 9, 2005Cardio EXPEDITED REVIEW State-of-the-Art PaperPatent Foramen Ovale: CurrentPathology, Pathophysiology, and Clinical StatusHidehiko Hara, MD,* Renu Virmani, MD,† Elena Ladich, MD,† Shannon Mackey-Bojack, MD,‡Jack Titus, MD,‡ Mark Reisman, MD,§ William Gray, MD,§ Masato Nakamura, MD,Michael Mooney, MD,* Anil Poulose, MD,* Robert S. Schwartz, MD*Minneapolis and St. Paul, Minnesota; Gaithersburg, Maryland; Seattle, Washington; and Tokyo, Japan
  4. Medscape Paradoxical EmbolismUpdated: Jun 10, 2016 Author: Igor A Laskowski, MD; Chief Editor: Vincent Lopez Rowe, MD
  5. Postgrad Med J 2007 Mar; 83(977): 173–177. Patent foramen ovale and atrial septal aneurysm in cryptogenic stroke Sujoy Ghosh, Arjun Kumar Ghosh, and Sandip Kumar Ghosh
  6. Circulation  Atrial Septal Aneurysm in Adult Patients A Multicenter Study Using Transthoracic and Transesophageal Echocardiography  Andreas Mügge, Werner G. Daniel, Christiane Angermann, Christoph Spes, Bijoy K. Khandheria, Itzhak Kronzon, Robin S. Freedberg, Andre Keren, Karl Dennig, Rolf Engberding, George R. Sutherland, Zvi Vered, Raimund Erbel, Cees A. Visser, Oliver Lindert, Dirk Hausmann, Paul Wenzlaff
  7. Up to date : Patent Foramen Ovale: practice essentials, background, pathophysiology

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