Determinants of in-hospital death in patients with a thrombus straddling a patent foramen ovale: protocol of a systematic review

Background: Thrombi identified on echocardiography at the time of straddling a patent foramen ovale (PFO) constitute a medical emergency with an associated imminent risk of death. Ischemic stroke (IS) and myocardial infarction (MI) occurring in patients with a thrombus straddling a PFO (TSPFO) may be associated with increased risk of in-hospital death. Variables associated with increased risk of death in women and men may be different. We will perform a systematic review of case reports and cases series of patients with a TSPFO to assess if IS and MI are associated with increased risk of in-hospital death and we will further stratify analyses by sex. Methods: This systematic review will include all case reports and case series of adult patients (18-year-old or older) with echocardiographic or pathological (e.g. at autopsy for older reports) evidence of a TSPFO published between inception and June 30, 2020, in any language. We will search in PubMed and Embase databases. Two reviewers will independently screen titles and abstracts, retrieve full texts, and extract the data in a predesigned form. We will apply a multivariable logistic regression analysis to estimate the association of IS and MI with in-hospital mortality. We will stratify analyses by sex. Discussion: IS and MI in patients with TSPFO could potentially be associated with worse outcomes if they are not timely identified or left untreated. Both acute IS and MI require specific treatment (e.g. thrombolysis, primary coronary intervention, or mechanical thrombectomy) that may be influenced by the therapy instituted for the TSPFO. Knowing the incidence of acute IS and MI among patients diagnosed with TSPFO and whether they are associated with an increased risk of death would help to improve the management of this medical emergency. Protocol registration: CRD42020216118, PROSPERO.