Developed pressure data may provide misinformation when used alone to evaluate systolic function in isovolumetric left ventricle preparations

We report data showing that developed pressure (DPmax) may lead to opposite conclusion with respect to maximal developed circumferential wall stress ( sigma(max)) when used to assess contractile function in left ventricle isov olumic preparations. Isovolumetric left ventricle preparations of rats with cardiac hypertrophy (H; N = 10) induced by isoproterenol administration sh owed higher DPmax (174 +/- 14 mmHg) than control (C; N = 8) animals (155 +/ - 12 mmHg) or rats with regression (R; N = 8) of hypertrophy (144 +/- 11 mm Hg). In contrast, the estimated sigma(max) for C (145 +/- 26 kdynes/cm(2)) and R (133 +/- 17 kdynes/cm(2)) was higher than for H (110 +/- 13 kdynes/cm (2)). According to Laplace's law, the opposite results of DPmax and sigma(m ax) may depend on the increased mass/volume left ventricle ratio of the hyp ertrophied hearts, which favored pressure generation. These results clearly show that DPmax should be used with caution to analyze systolic function.