RV pressure overload: from hypertrophy to failure.

In pulmonary arterial hypertension (PAH), right ventricular (RV) adaptation is essential to overcome the chronic increases in RV pressure overload. Ultimately, RV compensatory mechanisms are not sufficient and patients succumb to RV failure. The processes underlying the transition of RV adaptation to RV failure are not well understood. In this review, we propose that important insights in RV adaptation processes can be obtained by comparing different etiologies of PAH, namely patients with PAH secondary to Eisenmenger syndrome, patients with PAH secondary to systemic sclerosis and patients where no cause is identified: idiopathic PAH. Although the amount of RV afterload does not differ between these patient groups, their prognosis is distinctly different. We will show that an adaptive RV phenotype, as is observed in Eisenmenger patients, coincides with RV hypertrophy, increased RV contractility, low RV fibrosis and low RV diastolic stiffness. Whereas a phenotype of RV failure, as is observed in patients with PAH-secondary to systemic sclerosis, is characterized by impaired contractile reserve, RV fibrosis and RV diastolic stiffness.