18. PET for Diagnosis of Mytochondrial Cardiomyopathy in Children

Purpose: To study the capability of positron emission tomography for mitochondrial dysfunction diagnosis on basis of oxidative metabolism evaluation.

Methods: PET studies were carried out in 13 patients (pts.) aged from 2 to 13 years (7,5+3,1) with CMP: hypertopic (HCMP) – 4, dilated (DCMP) – 9.The dynamic study with [C-11]-acetate was performed for evaluation of Krebs cycle activity. Rate constant (k_mono) and [C-11]-activity clearance half-time (t_1/2) were calculated using myocardial time-activity curve (from 3 to 10 min.). Myocardial perfusion was assessed with [N-13]-ammonia, glucose metabolism - with [F-18]-fluorodeoxylucose (FDG).

Results: Perfusion was normal in hypertohic parts of left ventricle (LV) in patients with HCMP. Krebs cycle activity was reduced (k_mono = 0,077 ± 0,013 min⁻¹). Glucose utilisation was increased in comparison with norm. Thus, Krebs cycle activity reduction (mitochondrial dysfunction) was compensated by increasing glycolysis activity. Perfusion was normal in all children with DCMP. Krebs cycle activity was reduced in LV in 6 pts. (k_mono = 0,065 ± 0,029 min⁻¹), normal - in 3 (k_mono = 0,104 ± 0,010 min⁻¹). All children had normal oxidative metabolism in right ventricle (k_mono = 0,129 ± 0,203 min⁻¹).Focal perfusion defects were noted in 2 pts. with CMP. In this region the Krebs cycle activity was decreased more then another LV parts. It means that ischemic injuries were. Glucose utilisation reduction in this field means that injuries were irreversible.

Conclusion: PET study showed Krebs cycle activity reduction in children with cardiomyopathy was noted despite in normal perfusion (mitochondrial dysfunction) vs. ischemic injuries of myocardium.