We report data showing that developed pressure (DPmax) may lead to opposite conclusion with respect to maximal developed circumferential wall stress (<FONT FACE="Symbol">s</FONT>max) when used to assess contractile function in left ventricle isovolumic preparations. Isovolumetric left ventricle preparations of rats with cardiac hypertrophy (H; N = 10) induced by isoproterenol administration showed 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 mmHg). In contrast, the estimated <FONT FACE="Symbol">s</FONT>max for C (145 ± 26 kdynes/cm2) and R (133 ± 17 kdynes/cm2) was higher than for H (110 ± 13 kdynes/cm2). According to Laplace's law, the opposite results of DPmax and <FONT FACE="Symbol">s</FONT>max may depend on the increased mass/volume left ventricle ratio of the hypertrophied hearts, which favored pressure generation. These results clearly show that DPmax should be used with caution to analyze systolic function.
contractile function; developed pressure; wall stress; cardiac hypertrophy; Laplace's law
