Serum versus Imaging Biomarkers in Friedreich Ataxia to Indicate Left Ventricular Remodeling and Outcomes

Abstract

Patients with Friedreich ataxia typically die of cardiomyopathy, marked by myocardial fibrosis and abnormal left ventricular (LV) geometry. We measured procollagen I carboxyterminal propeptide (PICP), a serum biomarker of collagen production, and characterized genotypes, phenotypes, and outcomes in these patients. Twenty-nine patients with Friedreich ataxia (mean age, 34.2 ± 2.2 yr) and 29 healthy subjects (mean age, 32.5 ± 1.1 yr) underwent serum PICP measurements. Patients underwent cardiac magnetic resonance imaging and outcome evaluations at baseline and 12 months. Baseline PICP values were significantly higher in the patients than in the control group (1,048 ± 77 vs 614 ± 23 ng/mL; P <0.001); severity of genetic abnormality did not indicate severity of PICP elevation. Higher PICP levels corresponded to greater LV concentric remodeling only at baseline (r=0.37, P <0.05). Higher baseline PICP strongly indicated subsequent increases in LV end-diastolic volume (r=0.52, P=0.02). The PICP levels did not distinguish between 14 patients with evident myocardial fibrosis identified through positive late gadolinium enhancement and 15 who had no enhancement (1,067 ± 125 vs 1,030 ± 98 ng/mL; P=0.82). At 12 months, cardiac events had occurred in 3 of 14 fibrosis-positive and none of 15 fibrosis-negative patients (P=0.1); their baseline PICP levels were similar. We conclude that PICP, a serum marker of collagen synthesis, is elevated in Friedreich ataxia and indicates baseline abnormal LV geometry and subsequent dilation. Cardiac magnetic resonance and PICP warrant consideration as complementary biomarkers in therapeutic trials of Friedreich ataxia cardiomyopathy.