We report a high incidence of reduced respiratory Complex III activity in heart muscle concomitant with the presence of a specific mutation in cytochrome b (cytb) in patients with ischemic cardiomyopathy. This C → A mutation at nt 15452 converts the 236th residue of cytb from a leucine to isoleucine, is heteroplasmic and was observed in only 2 of 43 controls. Complex III activity is reduced (> 50%) in 5 of 6 patients with the C → A15452 mutation suggesting that the cytb mutation is responsible for decreased Complex III activity and may play a role in the pathophysiology of ischemic cardiomyopathy.
- Mitochondrial DNA
- Myocardial ischemia