Failing human myocardium exhibited reduced SR Ca2+ ATPase activity compared to non-failing myocardium, contributing to impaired systolic and diastolic function.
Observational (n=17)
A reduction in SR Ca2+ ATPase activity contributes to the impairment in both systolic and diastolic function of failing human hearts.
Two of the most significant characteristics of failing human myocardium are an increased diastolic Ca2+i and a prolonged diastolic relaxation. These abnormalities are more pronounced at higher frequencies of stimulation and may be caused by an altered Ca2+ resequestration into the sarcoplasmic reticulum (SR). The force-frequency relationship was determined in multicellular preparations obtained from non-failing (n=6) and failing human myocardium (n=11). The active force in non-failing tissue increased as a function of the frequency of stimulation. In failing myocardium, an increase in frequency of stimulation (>1 Hz) was accompanied by a decrease in active force. Changes in the frequency of stimulation and active force were also associated with changes in intracellular calcium concentrations. The diastolic force in failing myocardium was augmented following an increase in frequency of stimulation, whereas in non-failing tissue, no increase in diastolic force was observed. Associated with the increase in diastolic force was an increase in intracellular diastolic calcium concentrations. The SR Ca2+ ATPase activity was reduced in failing compared to non-failing myocardium. SR Ca2+ ATPase was positively correlated with diastolic force in non-failing myocardium. The relationship between Ca2+ ATPase activity at 1 micromol/l Ca2+ and active force between 0.5 and 2.0 Hz was different between failing and non-failing myocardium. The diastolic force demonstrate an inverse relationship with the SR Ca2+ ATPase activity in failing myocardium. These data suggest that a reduction in SR Ca2+ ATPase activity contributes to the impairment in both systolic and diastolic function of failing human hearts.
Schmidt et al. (1998) conducted an observational in Heart Failure (n=17). Heart failure vs. Non-failing myocardium was evaluated on Sarcoplasmic reticulum Ca2+ ATPase activity and active/diastolic force. Failing human myocardium exhibited reduced SR Ca2+ ATPase activity compared to non-failing myocardium, contributing to impaired systolic and diastolic function.