en is a LAP (left
An LAP (left atrial pressure) line is a thin catheter inserted into the pulmonary vein during open heart surgery. It measures left atrial pressure, and will therefore, produce an atrial waveform like a PWP or CVP.
The PWP is an indirect measurement of the left atrium. While the PWP reflects the left atrial pressure, it is subject to influence by pressures between the catheter tip and the left atrium. An LAP is a more direct measurement of the left atrium. If the LAP displays a clear waveform, it should be a more accurate pressure than the PWP.
Because the LAP is a LEFT heart catheter, clot or air poses a much greater risk. An embolus would have access to the cerebral or coronary circulation. Consequently, although the line is connected to a pressurized system, it is never flushed directly. If an LAP line requires flushing, 5-10 mL of blood should always be aspirated first, with the blood discard checked for clots on a gauze 4 X 4. Aspiration of blood should continue until no further evidence of clot exists, before the catheter is flushed.