1 effects of various frequencies ( 0.25 , 0.5 , 1.0 , 1.5 or 2.0 hz ) of stimulation for various durations ( 2 , 5 , 10 or 15 min ) on the contractile force of trabecular or papillary muscles of dog myocardium were investigated .
C0030352
papillary muscles
C0027061
myocardium