Non-Invasive Shunt Quantification in Interatrial Communication

Plain-language summary

Shunt quantification in atrial septal defect (ASD) is estimated by Echocardiography-Doppler, with the pulmonary-to-systemic blood flow ratio: Qp/Qs. Higher is the ratio, more important is the shunt, and the consequence on right ventricular function. A value higher than 1.5 is one of the criteria for percutaneous closure of Secundum ASD. Maatouk and al. have demonstrated that a shunt fraction (Qp/Qs) over 3 is a predictive factor of an incomplete reversibility of the right ventricular remodeling \[1\]. Even if the accuracy of Doppler echocardiography is admitted for Qp/Qs measurement, there is still some technical difficulties. Thus, the right cardiac catheterization for O2 consumption measurement by the direct Fick method is used. The major inconvenient is the potential risk of adverse effects. Non-invasive methods have been developed using physical properties (as the thoracic bioimpedance) or inert gas rebreathing technique. Thoracic Bioimpedance (TB) and inert gas rebreathing (IGR) techniques have been studies on healthy individual and different respiratory or cardiac diseases to evaluate the cardiac output (CO). TB and IGR measure the systemic and pulmonary blood flow respectively. Without shunt the pulmonary blood flow is equal to the systemic blood flow. Thus, Investigator suppose that combine the two techniques in disease with shunt, will allow a quantification of the shunt fraction Qp/Qs as accurate as with the gold standard technique (Fick method and Echocardiography Doppler). The purpose of the study is to evaluate the feasibility and the accuracy of the non-invasive measurement of the Qp/Qs ratio in secundum ASD using the IGR technique and the TB versus the two gold standard techniques: the Fick method and the Echocardiography-Doppler. The study hypothesizes that the values of Qp et Qs determined by IGR et TB respectively are in the same range of values that the one determined by gold standard techniques.

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