Improvement of myocardial mitochondrial function after hemodynamic support with left ventricular assist devices in patients with heart failure

Abstract

Objectives: Mitochondrial abnormalities have been described in cardiac tissue of patients with heart failure. These changes may result from chronic hypoxia. Our goal was to determine whether mitochondrial functional capacity can be improved in patients with heart failure by means of long-term left ventricular assist device therapy, which improves myocardial oxygen supply by decreasing myocardial work. Methods: Mitochondria were isolated from myocardial tissue obtained from 13 patients with heart failure without a left ventricular assist device (HF group) and seven patients with heart failure treated with a left ventricular assist device (LVAD-HF group). Mitochondrial respiratory rates (State 2, State 3, and State 4) were measured by means of polarographic techniques with reduced nicotinamide adenine dinucleotide–dependent (pyruvate/malate, α-ketoglutarate, glutamate) and –independent (succinate) substrates. The respiratory control index of Chance (State 3/State 4) and Lardy (State 3/State 2) and phosphorus to oxygen ratios were determined. Results: The respiratory control index of Chance was higher in LVAD-HF than in HF when using NADH-dependent substrates pyruvate/malate and α-ketoglutarate (pyruvate/malate HF: 4.9 ± 1.0; LVAD-HF: 6.5 ± 1.5; α-ketoglutarate HF: 8.5 ± 2.4; LVAD-HF: 11.8 ± 2.9; both p = 0.04). Similarly, the respiratory control index of Lardy was greater in the LVAD-HF than the HF group when α-ketoglutarate and glutamate were used as substrates (α-ketoglutarate HF: 7.8 ± 1.7; LVAD-HF: 9.9 ± 1.5; glutamate HF: 7.6 ± 2.2; LVAD-HF: 10.7 ± 2.1; both p = 0.04). The phosphorus to oxygen ratio was comparable for both groups using all substrates. No change in mitochondrial respiration was observed after left ventricular assist device therapy with the NADH-independent substrate, succinate. Conclusion: Cardiomyocyte mitochondrial function is improved by long-term therapy with a left ventricular assist device. This improvement suggests that cardiomyocyte metabolic dysfunction in heart failure may be reversed with left ventricular assist device support. (J Thorac Cardiovasc Surg 1998;116:344-9)