Frequency-dependence of myocardial energetics in failing @entity1 myocardium as quantified by a new method for the measurement of XXXX consumption in muscle strip preparations.

@entity1 @entity26 @entity15480 @entity67 @entity1054
@entity67 at high heart rates may be associated with increased myocardial energy consumption. Frequency-dependent changes of isometric force and @entity26 consumption (MVO2) were investigated in strip preparations from endstage failing @entity1 hearts exhibiting various degrees of @entity67 . MVO2 was determined by a new method which was validated. When stimulation rate was increased from 40 to 200 min-1 (n=7), developed force decreased from 16.5+/-4.3 to 7.9+/-2.9 mN/mm2 (P<0.01), diastolic force increased from 15.9+/-3.2 to 22.0+/-3.0 mN/mm2 (P<0.01), and total MVO2 increased from 2.6+/-0.6 to 4.7+/-0.9 ml/min/100 g (P<0.025). Resting MVO2 and resting force were 1.8+/-0.4 ml/min/100 g and 15.9+/-3.0 mN/mm2, respectively. After addition of 30 mm @entity15480 (BDM) to inhibit crossbridges, resting MVO2 and resting force decreased by 46% (P<0.05) and 15% (P<0.01), respectively, indicating the presence of active force generation in unstimulated failing @entity1 myocardium. In each muscle preparation, there was a significant correlation between @entity1054 ( @entity1054 ) and total MVO2 (r=0.96+/-0.01). The strength of these correlations did not vary with the contribution of diastolic @entity1054 to total @entity1054 . The ratio of activity related MVO2 to developed @entity1054 , an inverse index of the economy of contraction, increased depending on the rise of diastolic @entity1054 at higher stimulation rates. In conclusion, in failing @entity1 myocardium, diastolic force development is occurring at the same energy expenditure as systolic force generation. Therefore, in muscle preparations with disturbed diastolic function economy of contraction decreases with higher stimulation rates, depending on the rise of diastolic force.
