Aims: To determine the frequency of cardiomyopathy in children with mitochondrial disease and describe their clinical course, prognosis and cardiological manifestations.
Methods and results: Of 301 children with CNS and neuromuscular disease referred to our institution in 1984 to 1999, 101 had mitochondrial disease. Seventeen patients had cardiomyopathy, diagnosed by echo-Doppler investigations, all of the hypertrophic, non-obstructive type. The onset of symptomatic mitochondrial disease ranged from birth to 10 years of age. Eight children had cytochrome-c oxidase deficiency, while the remaining nine had various defects. Cardiomyopathy was diagnosed from birth to 27 years. Left ventricular posterior wall and septal thickness were both increased: z-scores +4.6+/-2.6 and +4.3+/-1.6 (mean+/-SD), respectively. The left ventricular diastolic diameter z-score, +1.3+/-3.4, and fractional shortening, 24+/-13%, displayed marked variations. Nine patients developed heart failure. Eleven patients with cardiomyopathy died, including all eight with cytochrome-c oxidase deficiency, and one patient underwent a heart transplantation. Mortality in children with mitochondrial disease was higher in those with cardiomyopathy (71%) than those without (26%) (P<0.001).
Conclusions: In children with mitochondrial disease, cardiomyopathy was common (17%) and was associated with increased mortality. The prognosis for children with cytochrome-c oxidase deficiency and cardiomyopathy appeared to be particularly unfavorable.