myocardial mechanics of 56 rat papillary muscles were investigated in various inotropic states , i.e. , early postpartum ( 1st day , 1st mo ) and , in adult , by altering external calcium concentration , [ ca2+ ] 0 , stimulation frequency ( f ) , and initial muscle length ( l ) .
C0027061
myocardial
C0030352
papillary muscles