A 60-yeаr-оld mаle with а histоry оf HTN, DM, CAD s/p CABG, ischemic cardiomyopathy (ICM), and HFrEF (EF 25%) is admitted to the intensive care unit with cardiogenic shock. He undergoes a right heart catheterization (RHC) with the following hemodynamics: RA 22, PAP 48/25, PCWP 30, SVR 1762, CI 1.9, SVO2 45%. Which hemodynamic measurement is used as a clinical measurement of left ventricular afterload?