Percutaneous PFO closure has been established as a first-line therapy for preventing recurrent strokes in selected patients. The devices used for the specific purpose contain and release nickel, which is considered as the most allergen metal in nature. Skin patch tests are considered as gold-standard for documenting nickel allergy. While the allergic contact dermatitis induced by nickel is well described, literature is inadequate on explaining the effect of nickel release on the clinical manifestations of patients implanted with such devices.

Our prospective, randomized, blinded trial will try to investigate the above by performing nickel skin patch tests to all patients, 14 days before and 90 days after the implantation. During follow-up, clinical manifestations and transthoracic echocardiographic findings will be evaluated and associated with patch skin tests.

Percutaneous PFO closure has been established as a first-line therapy for preventing recurrent strokes, after embolic stroke of unknown source (ESUS) and a patent foramen ovale. The PFO closure is achieved by the implantation of suitable devices, which occlude the shunt between the two atria and prevent the creation and detachment of thrombi. Until today, there are two devices approved by FDA for the specific purpose; Amplatzer PFO Occluder and Gore Cardioform Septal Occluder. Despite the architectonic differences between these devices, the main material of both is nitinol, an alloy of nickel and titanium. While titanium is an extremely rare allergen, nickel is considered as one of the most common allergens and the most frequent metal allergen in nature, with a prevalence about 20%. The main clinical expression of nickel hypersensitivity is allergic contact dermatitis, but cases with systemic allergic reaction have been described as well. It has been observed that nickel is released by the implanted devices and circulates through bloodstream, having the potential to cause systemic clinical picture. Device syndrome includes signs and symptoms (i.e. palpitations, dyspnea, chest pain, rash, etc.), which are appeared after the device placement and are associated with hypersensitivity reaction. The existing literature is considered as inadequate for explaining the effect of nickel release in the patients implanted with an occluder.

The aim of our study is to evaluate whether patients with nickel hypersensitivity have an increased risk of adverse events following PFO closure, to assess the potential influence of device selection, and to evaluate potential sensitization or desensitization in patients without or with pre-existing nickel allergy, respectively.

Nickel hypersensitivity was assessed using skin patch testing prior to the procedure. The primary endpoint was device syndrome, a composite of patient-reported symptoms (chest pain, palpitations, migraines, dyspnea, and rash). Secondary endpoints included arrhythmias, bleeding, stroke, and all-cause mortality.

Inclusion Criteria:

• Age: at least 14 years old
• Well-documented indication for percutaneous PFO closure

Exclusion Criteria:

• Corticosteroid treatment
• Patient's refusal to participation

The dermatologist will be blinded regarding the device implanted in the patients. The interventional cardiologist will be blinded regarding the results of skin tests. The outcomes assessor will be blinded for both skin patch tests and the implanted device of each participant.