Editor,—We read with great interest the article by Kaulitz et al where Doppler measurements of various venous flows were performed with simultaneous respiratory and venous pressure recordings.1 The main findings were: venous flow and pressure are dependent on respiration in total cavopulmonary connection (TCPC); and venous flow and pressures are cardiac dependent in atriopulmonary connection (APC).

While the authors should be commended for monitoring simultaneous flow and pressure data along with respiratory and cardiac monitoring, there were no new insights. Venous …