High-energy phosphates, myocardial contractile function and material properties after short periods of oxygen deficiency

To investigate myocardial performance and diastolic properties after repeated periods of oxygen deficiency auxotonic and isovolumic measurements were performed after three periods of asphyxia in Wistar rats. Additionally, the response of the peak isovolumic left ventricular pressure to postextrasystolic potentation was measured. The hemodynamic results were compared to the levels of high-energy phosphates. Our results demonstrated normal postasphyctic basal hemodynamics and material properties. Thus, the energy supply was sufficient to maintain steady state conditions - in spite of decreased overall adenine - nucleotide levels. Isovolumic measurements and postextrasystolic potentation tests, however, indicated that the contractile performance of the postischemic myocardium was still reduced. This functional limitation cannot be exlained by altered material properties and is probably not causally related to the decreased overall ATP content.