Depressed contractile state and increased myocardial consumption for non-mechanical work in patients with heart failure due to old myocardial infarction

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Abstract
Objective: The aim was to characterise the impaired myocardial mechanoenergetics in patients with heart failure due to old myocardial infarction by using the oxygen consumption versus left ventricular pressure – volume area (PVA) relationship. Methods: The o2-PVA relationship was assessed in 15 patients: group N consisted of seven patients with vasospastic angina pectoris whose left ventricular ejection fractions were normal [72(SD 8)%], and group F consisted of eight patients with old myocardial infarction whose left ventricular ejection fractions were reduced [45(11)%]. Left ventricular volume and pressure were measured by the conductance catheter method. o2was measured by thermodilution. Results: Linear o2-PVA relationships with dextran infusions were obtained in both groups (median r = 0.92 v 0.90). There was no difference in the slope between the two groups. There was a positive correlation between Emax and V̇o2 at median PVA (V̇o2.PVAO.8) in group N. Emax an index of left ventricular contractility, was significantly smaller in group F than in group N, at 5.1(2.1) v 3.2(1.1) mm Hg·ml−1·m2 p 2 intercept in group F was comparable to that in group N, at 0.71(0.63) v 0.40(0.29) J·beat−1·100 g LV−1; NS). In addition, the ratio of V̇o2,PVA0.8 to Emax was significantly larger in group F than in group N: 0.55(0.14) v 0.89(0.37) J·beat−1·100 g LV−1·mm Hg−1ml·m−2 (p Conclusions: These results suggest that the V̇o2 for non-mechanical work in group F is disproportionately high relative to the reduced contractility. An abnormality of excitation-contraction coupling rather than of crossbridge cycling may be responsible for the impaired mechanoenergetics in patients with heart failure due to old myocardial infarction. Cardiovascular Research 1994;28:1251-1257

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