Evaluation of the severity of right-to-left shunt in patent foramen ovale patients after systemic embolism (MEASURE-PFO study).

BACKGROUND

Patent foramen ovale (PFO) is the most common inherited cardiac abnormality, with intermittent right-to-left (R-L) shunt of variable size.

AIMS: To study the quantification of R-L shunt (shunt) in PFO patients using an original thermodilution method in relationship to the morphology of the interatrial septum, measured by echocardiography and cardiopulmonary exercise tests before and after the occlusion of a PFO.

METHODS

A multicenter study enrolled a population of 151 patients, eligible for PFO closure in secondary prevention, who underwent transthoracic echocardiography, contrast transesophageal echocardiography, and cardiopulmonary exercise tests before and 6 months after the closure. The size of the shunt was measured by catheterization using the thermodilution Inntherm® system.

RESULTS

Shunt was detected in 133 (90%) patients. Size of shunt >20% was present in 41 (28%) patients, 10%-20% in 33 (22%), and <10% in 49 (40%) patients. Shunt size >10% was associated with greater atrial septal separation during the Valsalva (P = 0.03) and respiration (P = 0.04), amplitude of septal displacement (P = 0.009), amount of contrast media in the left atrium (P = 0.03), and hypermobility of septum (P = 0.03). After PFO closure, work (W) capacity increased in patients with shunt ≥20% (Δ +6.8; standard deviation [SD] 16.9 [W]) compared with those with <10% (Δ -2.1; SD 24.5 [W]; P = 0.02). Migraine occurrence decreased in 8 patients (62%) (P = 0.008). A decrease in saturation on exercise occurred in 12 cases (9%), after the PFO closure saturation normalized from 90.5% to 95.0% (P = 0.009), with no effect on exercise.

CONCLUSIONS

We proved safe use of thermodilution for R-L shunt measurement. The main cause of inducible shunt severity is atrial septal mobility. A severe PFO shunt impacts work capacity.