Validation of intracardiac shunt using thoracic bioimpedance and inert gas rebreathing in adults before and after percutaneous closure of atrial septal defect in a cardiology research unit: study protocol

INTRODUCTION: Intrathoracic shunt quantification is a major factor for appropriate clinical management of heart and pulmonary diseases. Intracardiac shunts quantified by pulmonary to systemic output ratio (Qp/Qs) are generally assessed by Doppler echocardiography, MRI or catheterisation. Recently, some authors have suggested the concomitant use of thoracic bioimpedance (TB) and inert gas rebreathing (IGR) techniques for shunt quantification. The purpose of this study is to validate the use of this approach under conditions where shunt fraction is directly quantified such as in patients with isolated atrial septal defect (ASD). METHODS AND ANALYSIS: This trial is a prospective, observational single-centre, non-blinded study of adults seen for percutaneous closure of ASD. Qp/Qs ratio will be directly measured by Doppler echocardiography and direct Fick. IGR and TB will be used simultaneously to measure the cardiac output before and after closure: the ratio of outputs measured by IGR and TB reflecting the shunt fraction. The primary outcome will be the comparison of shunt values measured by TB-IGR and Doppler echocardiography. ETHICS AND DISSEMINATION: The study has been approved by an independent Research Ethics Committee (2017-A03149-44 Fr) and registered as an official clinical trial. The results will be published in a peer-reviewed journal. TRIAL REGISTRATION NUMBER: NCT03437148; Pre-results.