Bubble stream reveals functionality of the right-to-left shunt: detection of a potential source for air embolism

The existence of a right-to-left shunt may increase the likelihood of micro-embolism by allowing a flux of bubbles under hyperbaric conditions. The aim of the study was to measure the relationship between these shunts and bubbles in 10 consecutive subjects using trans-thoracic and trans-esophageal echocardiography. In video frames, all cardiac chambers were segmented and bubbles were analyzed by our proposed method and two other methods. The relationship with bubbles and shunts was divided into three classes: no bubbles, 1-20 bubbles, >20 bubbles and measured over 2160 frames. Our sensitivity was 100% and our specificity was between 90.1% and 96.4%. There were 4.32-23.78 bubbles/frame in the left atrium according to our method. After the automatic analysis, shunts were graded double-blinded by two cardiologists. Consequently, we noted that aperture size does not necessarily reflect how active the right-to-left shunt is. Instead, our proposed decay curves constitute a better tool for determining functionality.