Figure 32-49 Relationship between left atrial pressure (LAP) and left ventricular end-diastolic pressure (LVEDP). LVEDP is measured at the Z-point on the left ventricular pressure (LVP) trace at the time of the electrocardiographic R wave. Mean LAP (9 mm Hg) underestimates LVEDP (15 mm Hg), but the LAP a wave pressure peak closely estimates LVEDP.^[514] (Redrawn from Mark JB: Atlas of Cardiovascular Monitoring. New York, Churchill Livingstone, 1998, Fig. 6-1).