Left atrial and pulmonary capillary wedge pressure tracings

The left atrial pressure, obtained directly via a transseptal catheter, and the pulmonary capillary wedge (PCW) pressure, obtained through a balloon-tipped pulmonary artery catheter, are recorded simultaneously and are nearly identical in waveform. However, normal LA pressure wave timing precedes PCW pressure by 40 to 120 msec and often has a slightly higher pressure compared to the PCW pressure due to transmission of pressure backward through the pulmonary capillaries.