LV-pressure waveforms and PV-loops during tri-phasic dose response to DN and OM. (A and B) Representative LV pressure waveforms (top panels) and PV loops (bottom panels) at baseline (Pre) and at each phase (P1, P2, and P3) of the response to continual infusion of either (A) DN at 6 mg/kg/min or (B) OM at 1 mg/kg/min. The three phases represent the therapeutic, subtoxic, and toxic phases, respectively.