Résumé : Imaging studies have shown that pulmonary hypertension (PH) is associated with inhomogenous right ventricular (RV) regional contraction, or dyssynchrony, and that this is of prognostic relevance. This study aimed at the identification and functional significance of RV dyssynchrony in borderline PH defined by a mean pulmonary artery pressure between (mPAP) 20 and 25 mmHg. RV dyssynchrony was measured by 2-dimensional speckle tracking echocardiography in 17 patients with pulmonary arterial hypertension (PAH), 13 patients with borderline PH and 14 controls. Dyssynchrony was defined as the R-R interval-corrected standard deviation of the times to peak-systolic strain for the basal and medium segments of the RV. All the PH patients underwent a right heart catheterization. RV dyssynchrony amounted to 69 ± 34 ms in PAH, 47 ± 23 ms in borderline PH and 8 ± 6 ms in controls, all different from each other (p < 0.05). RV dyssynchrony in borderline PH was the only parameter of RV systolic dysfunction in 11 of 13 (85%) of the patients. RV dyssynchrony was accompanied by postsystolic shortening and correlated to RV fractional area change, not to mPAP or pulmonary vascular resistance. RV dyssynchrony occurs in borderline PH and may reflect early RV-arterial uncoupling.