Patient foramen ovale

Kent DM, Thaler DE.  Is Patent foramen ovale a modifiable risk factor for stroke recurrence?Stroke 2010: 41 (supplement 1) S 26-S30.

Authors make statistical arguments about PFO management.  Facts that form a basis:

1.  PFO occurs in 25 % of autopsies.
2.  PFO occurs in a higher rate in cryptogenic stroke, but in at least 33 % of strokes with PFO the PFO is incidental.
3.  PFO in Cryptogenic Stroke Study (PICSS) shows near identical stroke recurrence risk in patients with cryptogenic stroke whether or not they have a PFO.  Further, small PFO's had a higher recurrence rate than large ones.  This simply indicates, however, that PICSS included patients who were eventually given a TEE , even if they had a different defined mechanism for their stroke.  Other occult mechanisms such as occult afib or subthreshold aortic atherothrombotic disease may have a higher recurrence rate.
4.  Consistently, studies show that patients with cryptogenic stroke and PFO have less conventional stroke risk factors than patients without PFO.  Since recurrence risk of stroke is about equal in PFO + and - patients, PFO singlehandedly compensates for lack of other risk factors.  Therefore, PFO IS a risk factor for stroke.  Younger patients without DM or HTN are much more likely to have a PFO. 
5.  When a PFO is found in setting with an atrial septal aneurysm, the PFO is rarely incidental to the stroke.
6.  "PFO propensity" is likelihood based on age or other factors that a CS patient has a PFO.  A higher PFO propensity correlates with a lower chance of incidental PFO.  A younger patient without other risk factors may have a very high PFO propensity and therefore probability of nonincidental PFO. 
7.  The margin of benefit in PFO closure is narrow.  Even a low rate of procedure complications could nullify benefit.  "Testing the procedure (closure) in a population in which many incidental PFOs occur may falsely suggest the procedure is of no benefit."