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Having a residual shunt after percutaneous patent foramen ovale (PFO) closure was associated with an elevated risk of stroke or transient ischemic attack (TIA) recurrence years after the procedure, researchers found in a prospective cohort study.

The incidence of these events reached 2.32 per 100 patient-years with a shunt on transthoracic echocardiography (TTE) compared with 0.75 per 100 patient-years with a complete seal. The elevated risk persisted after adjustment for other factors (adjusted HR 3.01, 95% CI 1.59-5.69).

Whereas small residual shunts were not significantly linked to increased risk (HR 2.02, 95% CI 0.87-4.69), moderate or large residual shunts were (HR 4.50, 95% CI 2.20-9.20), reported MingMing Ning, MD, MMSc, of Massachusetts General Hospital and Harvard Medical School, and colleagues. Their findings were published online in the .

Noting that stroke and TIA recurrence most often occurred within the first few years after PFO closure, Ning's team suggested that patients with moderate or large residual shunts undergo long-term follow-up of at least 5 years with a multidisciplinary team, with TTE with bubbles performed every 3 to 6 months during the first year and every 6 to 12 months thereafter to evaluate shunt size.

And because shunts can be expected to diminish over time as the closure device gets further epithelialized, stepping up antithrombotic treatment is reasonable until the shunt stabilizes, they added.

"It would seem reasonable pending longer-term follow-up data to extend oral anticoagulation, as they suggest, hoping that the shunt will eventually diminish along with the attendant risk for further neurologic events," agreed Annals associate editor William Kussmaul, III, MD, a retired cardiologist in Media, Pennsylvania.

Some skeptics of percutaneous PFO closure may have changed their minds after the publication of positive trial data and meta-analyses in 2017 and 2018, according to his .

"More information is still emerging regarding new randomized controlled trial results, long-term outcomes data, cost-effectiveness of PFO closure, and the relationship between PFO and migraine and pulmonary embolism. Technologic advances are inevitable," Kussmaul noted.

"Yet for many patients with PFO who have a stroke, closing the hole already makes sense. Perhaps further along on the learning curve -- with newer, simpler techniques and less bulky implants -- the risk-benefit equation in this group of patients can be tilted even further toward permanent stroke prevention," he said.

The American Academy of Neurology recently started recommending the procedure for some stroke survivors.

The FDA approved the Amplatzer PFO Occluder in 2016 and granted the Cardioform Septal Occluder an expanded indication for PFO occlusion for recurrent stroke prevention in 2018.

Ning's study included 1,078 consecutive patients (mean age 49.3 years) who had had a PFO-related cryptogenic stroke and underwent percutaneous PFO closure at Massachusetts General Hospital in 1995-2017 to prevent future strokes. At discharge, all patients were on aspirin and/or clopidogrel (Plavix). Patients were followed for 3.7 years on average.

Residual shunts were observed on TTE with agitated saline microbubbles in 22.5% of people. Most of those found were small shunts.

People with moderate or large shunts were older (52.2 vs 47.1 years with small shunt, P=0.009) and had higher rates of atrial septal aneurysm, hypertension, hyperlipidemia, and diabetes. After adjustment for these factors, larger shunt size was still associated with more stroke or TIA recurrence.

There were 37 deaths over follow-up, none of which were said to be related to recurrent events.

"Some points in the report by Deng and colleagues are puzzling. For one, a remarkable 44% of their patients had a hypercoagulable state, whereas the diagnostic yield of thrombophilia testing in unselected stroke patients is very low," Kussmaul noted.

"This may represent a reasonable institutional tendency to refer for PFO closure these patients who are at particularly high risk for recurrent embolic events. But does this affect generalizability to stroke patients without hypercoagulable status? How many outcomes were observed in that group of patients, who are probably more representative of the stroke population in most hospitals?" the editorialist wrote.

Ning's group acknowledged that the single-center, observational study could have been biased by patient selection. Also, it was possible that operators did not always conduct the "gold standard" TTE bubble test with absolute accuracy, so shunt size could have been misclassified.

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