KDR and pulmonary arterial hypertension: However, no statistically significant enrichment of (likely) pathogenic variants has yet been identified to prove a causal role of KDR. Recently, pLoF variants in KDR were associated with pulmonary arterial hypertension in a large cohort [71] and in two families [72] and with a congenital heart defect called tetralogy of Fallot [73].