Residual Shunt Following PFO Closure Triples Risk of Recurrent Stroke

New research is shedding light on the long-term impact of residual shunt after a patent foramen oval (PFO) closure on incidence of recurrent stroke.

Results of the prospective cohort study, which included more than 1000 patients, indicated presence of a PFO closure was associated with 3 times greater risk of experiencing a recurrent stroke or transient ischemic attack (TIA).

Present in up to 25% of patients after PFO closure, investigators from Massachusetts General Hospital and Harvard Medical School designed the current study to assess potential associations of residual PFO closure with incidence of recurrent stroke or TIA. Using data from consecutive patients admitted to Massachusetts General Hospital between January 1995 and November 2017.

Investigators assessed residual shunt through trans thoracic echocardiography with saline contrast. Shunt size was determined by the maximum number of bubbles appearing the left atrium within 3 cardiac cycles—0 bubbles indicating no shunt, 1-10 indicating a small shunt, 10-30 indicating a moderate shunt, and more than 30 indicating a large shunt.

The primary endpoint of the investigators' analysis was a composite of first recurrent ischemic stroke or TIA after PFO closure. Investigators determined the etiology or cause of stroke through evaluation by 2 independent vascular neurologists using TOAST criteria—this pair of neurologists were blinded to shunt status and not involved in the analysis of data.

In total, investigators identified 1078 patients for inclusion in the study. The mean age of the population was 49.3 (13.7) years and had a mean follow-up duration of 3.7 years. Of note, individuals were followed for up to 11 years and a total of 3988 patient-years were included in the analysis.

Investigators pointed out effective closure, defined as a no or small residual shunt was achieved in 91.4% of the patient population. No shunt was observed in 835 (77.5%). Of the 243 patients with residual shunt, 150 patients were classified as having a small shunt, and 93 had a moderate or large shunt.

Upon analysis, the total observation period among patients in the shunt group included 775 patient-years and the no-shunt group contained 3213 patient-years of data. The primary endpoint of the study occurred run 18 patients in the shunt group compared to 24 patients in the no-shunt group—yielding rates of 2.32 events per 100 patient-years and 0.75 events per 100 patient-years for the groups, respectively.

Based on these results, investigators calculated patients with residual shunt were at a 3.05 (95% CI, 1.65-5.62) times greater risk of recurrent stroke or TIA than patients without residual shunt. Furthermore, investigators determined the cumulative probability of recurrent stroke or TIA 5 years after PFO closure was 9.3% among patients with residual shunt and 2.5% for patients without residual shunt.

Even after adjustment for factors including age, study period, device, presence of hypertension, hyperlipidemia, diabetes, and other potential covariates, results still indicated a 3-fold increase in risk of recurrent stroke or TIA (HR, 3.01; 95% CI, 1.59-5.69; P <.001).

Additionally, an analysis examining associations with shunt size indicated moderate or large shunts (HR, 4.50; 95% CI, 2.20-9.20; P <.001) were associated with a greater riskier stroke or TIA recurrence than those with residual shunts (HR, 2.02; 95% CI, 0.87-4.69; P=.102).

This study, “Residual Shunt After Patent Foramen Ovale Closure and Long-Term Stroke Recurrence A Prospective Cohort Study,” was published in the Annals of Internal Medicine.