Figure 4. Myocardial iron overload was linked with greater mitochondrial DNA (mtDNA) damage.

(A) The association between cardiac MRI T2* in subjects on transfusions > 6 years and the 4977-bp mitochondrial DNA deletion (ΔmtDNA⁴⁹⁷⁷) was significant (n = 29, Pearson r = –0.43, P = 0.019). All subjects with current or history of iron-induced cardiac dysfunction (solid symbols) had > 20 ΔmtDNA⁴⁹⁷⁷ per 1 × 10⁷ mtDNA copies. (B) The proportion of patients with MRI T2* < 20 milliseconds significantly increased with a higher frequency of ΔmtDNA⁴⁹⁷⁷ when the 3 groups were compared using χ² test for trend (n = 29, P = 0.025).