Inotropic and lusitropic dysfunction in myocardium from patients with dilated cardiomyopathy

Abstract Isometric force of contraction (DT), peak rate of tension increase (+T), peak rate of tension decrease (−T), time to peak tension (TPT), and time to half-relaxation ( T 1 2 T ) were measured in electrically driven human papillary muscle strips (New York Heart Association [NYHA] class IV heart transplants, dilated cardiomyopathy; nonfailing (NF) donor hearts, brain dead) (1 Hz, 37° C) under basal conditions (1.8 mmol/L Ca 2+ ) and after stimulation with isoprenaline, ouabain, and Ca 2+ . There was no difference in the isometric contraction (+T, −T, TPT, and T 1 2 T ) between NYHA IV hearts and NF hearts under basal conditions. Inotropic stimulation above 300% of basal DT increased −T significantly more in NF hearts ( p 2+ to increase DT was not significantly changed in NYHA IV hearts compared with NF hearts. The isoprenaline-mediated increase in DT was reduced ( p p 2+ handling.