Optimal Transducer Level for Atrial and Pulmonary Arterial Pressure Measurement in Patients with Functional Single Ventricle.

This study aimed to investigate the optimal transducer level for accurate measurement of atrial and pulmonary arterial pressures in the supine position for patients with functional single ventricle. Contrast-enhanced chest computed tomographic images of 108 patients who underwent either the bidirectional cavopulmonary shunt (BCPS) placement or the Fontan procedure were reviewed. Vertical distances from the skin of the back to the uppermost levels of fluid in the single atrium or the pulmonary artery confluence and their ratios to the greatest anteroposterior (AP) diameter of the thoracic cage were determined. In patients who underwent BCPS, the ratios of the uppermost levels of blood in the atrium and pulmonary artery confluence to the greatest AP diameter of the thorax were 76.0 ± 8.1 and 56.3 ± 5.5 %, respectively. The distance (mm) between these two levels was calculated as 24.2 + 0.31 × age (years) (r  = 0.08, P < 0.03). In patients who underwent the Fontan procedure, the ratios were 79.3 ± 10.0 and 58.3 ± 5.8 %, respectively. The distance (mm) between these two levels was calculated as 31.1 + 0.44 × age (years) (r  = 0.05, P < 0.11). The optimal transducer levels for measuring atrial and pulmonary arterial pressures in the supine position are 75-80 and 55-60 % of the AP diameter of the thorax, respectively, in patients with functional single ventricle. We should consider the difference of the pressure when atrial and pulmonary arterial pressures were measured with the same level of transducers.