Free radical levels are increased in venous blood in dilated cardiomyopathy

Evidence supporting the concept of increased oxidative stress in chronic heart failure (CHF) has been based either on animal models or relied on indirect measures of oxidative stress. In addition, human studies have included patients with coronary disease, itself a cause of enhanced oxidative stress. Our study aimed to measure free radical levels directly in CHF patients with dilated cardiomyopathy (DCM) employing electron paramagnetic resonance (EPR) spectroscopy. Methods: We studied 15 DCM patents with NYHA class II-IV symptoms of CHF, LV ejection fractions <35% on optimal medical therapy with no other recognised risk factors for enhanced oxidative stress and 15 healthy controls (C). Morning venous blood samples were taken in preprepared spin trap (α-phenyl N-tert-butyl nitrone (PBN))-containing tubes and analysed immediately for free radical levels by a process involving toluene extraction of the PBN adduct and EPR spectroscopy employing a Varian E104 spectrometer. Results: The DCM patients and controls were well matched for age and sex. The mean magnitude of EPR spectra obtained from the DCM group was significantly greater [(mean ± SD) DCM = 0.48 ± .22 vs. C = 0.26 ± 0.12, p< 0.0005]. Conclusion: This study has demonstrated that free radical levels in venous blood are elevated in DCM patients with CHF. Our findings support previous work based either on animal studies or by indirect markers of free radical injury suggesting enhanced oxidative stress in CHF. Further studies are now needed to establish the main source of free radicals in this condition, the pathophysiological mechanisms underlying this process and the potential therapeutic role of antioxidants.