Figure 50-18 The baseline panel shows an example representing a typical patient with low-gradient aortic stenosis. The hemodynamic response to treatment with dobutamine (DB) and nitroprusside (NP) helps clarify whether such a patient has true aortic stenosis (A), relative aortic stenosis (B), or severe left ventricular dysfunction (C). A zero denotes no change; a single arrow, an increase in the value for the particular variable; and two arrows, a large increase in the value. (Redrawn from Lakatta E: Aging effects on the vasculature in health: Risk factors for cardiovascular disease. Am J Geriatr Cardiol 3:11–17, 1994.)