Circulating biomarkers and right ventricular function in adolescents and young adults with congenital heart disease

Abstract

The population of adolescent and adults with congenital heart disease (CHD) has grown rapidly. Right ventricular (RV) dysfunction remains an important issue of concern in the long-term follow up of these patients. While circulating biomarkers have shown promise in the assessment and monitoring of adult patients with left heart diseases, little is known of the role of biomarkers in reflecting RV performance in CHD patients. Emerging circulating biomarkers that reflect underlying pathophysiologic processes have gained increasing attention. These include inflammatory cytokines namely tumour necrosis factor (TNF)-α, a biomarker of apoptosis annexin A5 (AnxA5), carboxy-terminal propeptide of type I procollagen (PICP) and amino-terminal propeptide of type III procollagen (PIIINP) that reflects collagen synthesis and turnover, low circulating levels of cardiac troponin T as detected by highly sensitive assay (hs-cTnT) that may reflect subclinical myocardial injury, and microRNAs found to be involved in cardiac remodeling. The studies in this thesis aimed to test the hypothesis that circulating biomarkers may be altered in patients with volume-overloaded right ventricles after repair of tetralogy (TOF) and pressure-overloaded right ventricles after atrial switch operation for complete transposition of the great arteries (TGA), and are related to indices of RV function.

In patients after TOF repair, increased circulating PICP and PIIINP levels were associated with worse subpulmonary RV and left ventricular (LV) function. In particular, these propeptides correlated positively with LV mechanical dyssynchrony, implicating a possible role of increased collagen synthesis in its pathogenesis. Increased plasma levels of hs-cTnT were further found in 30% of female, but not male patients. Female patients with elevated hs-cTnT levels compared to those without had greater RV volumes and LV mechanical dyssynchrony. Independent correlates of hs-cTnT in patients as determined from multivariate analysis were sex and RV ejection fraction. MicroRNA profiling following validation confirmed alteration of circulating levels of miR-99b and miR-766 in repaired TOF patients, a pattern distinct from that reported for left heart diseases. The miRNA expression was, however, not related to the cardiac functional indices.

Patients after atrial repair for TGA had significantly higher circulating AnxA5 and TNF-αlevels, but similar PICP, PIIINP levels, compared with controls. Elevated AnxA5 level was associated with impaired systemic RV myocardial deformation, increased subpulmonary ventricular eccentricity, and increased TNF-αlevel. Elevation of hs-cTnT is found in 39% of the patients. The positive correlation between hs-cTnT level and systemic RV volume may suggest a role of hs-cTnT in reflecting RV remodeling. Circulating microRNA expression profiling and further validation identified 11 upregulated microRNAs (miR-16, miR-106a, miR-144*, miR-18a, miR-25, miR-451, miR-486-3p, miR-486-5p, miR-505*, let-7e and miR-93). Among them, miR-18a and miR-486-5p correlated negatively with systemic ventricular myocardial acceleration during isovolumic contraction, a relatively-load independent measure of systemic RV contractility.

To conclude, these biomarkers reflect in varying extent the structural, functional, biological alteration of the subpulmonary and systemic right ventricles of the CHD patients late after surgical repair. These data may provide new perspectives in the understanding of progressive RV dysfunction in the adult CHD population and hopefully shed more lights on novel therapeutic interventions.