Background and aim: The curvilinearity of the atrial pressure-volume curve implies that atrial compliance decreases progressively with increasing left atrial pressure (LAP). We predict that reduced left atrial (LA) compliance leads to more rapid deceleration of systolic pulmonary venous flow. With this rationale we investigate if the deceleration time (t_dec) of pulmonary venous (PV) systolic flow velocity reflects mean LAP. Methods: In 8 patients during coronary surgery, before extracorporeal circulation, PV flow by ultrasonic transit time, and invasive LAP were recorded during stepwise volume loading. The t_dec was calculated using two methods: By drawing a tangent through peak deceleration, and by drawing a line from peak systolic flow through the nadir between the systolic and early- diastolic flow waves. LA compliance was calculated as the systolic PV flow integral divided by LAP increment. Results: Volume loading increased mean LAP from 11 ± 3 to 20 ± 5 mm Hg (p < 0.001) (n = 40), reduced LA compliance from 1.16 ± 0.42 to 0.72 ± 0.40 ml/mm Hg (p < 0.004) (n = 40), and reduced t_dec from 320 ± 50 to 170 ± 40 ms (p < 0.0005) (n = 40). Mean LAP correlated well with t_dec ( r = 0.84, p < 0.0005) (n = 40) and with LA compliance (r = 0.79, p < 0.0005) (n = 40). Conclusion: Elevated LAP caused a decrease in LA compliance and therefore more rapid deceleration of systolic pulmonary venous flow. The t_dec has potential to become a semiquantitative marker of left atrial pressure and an index of left atrial passive elastic properties.