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Figure 2 Regression line of the relation between end-systolic wall stress and velocity of circumferential fiber shortening (VcFc) for vagotomized adult pigs after afterload manipulation from baseline to a sodium nitroprusside infusion rate up to 5 µg/kg/min. This relation seems linear, but represents merely a segment of the nonlinear curve as found in Figure 1, in which values at lower afterload obtained during infusion of sodium nitroprusside at a rate of 10 µg/kg/min are included.