Impaired left ventricular mechanics in pulmonary arterial hypertension: identification of a cohort at high risk

Abstract

Background: Pulmonary arterial hypertension (PAH) is characterized by pulmonary vascular remodeling and right heart failure. The right (RV) and left ventricles (LV) do not function in isolation, sharing a common pericardial sac and interventricular septum. We sought to define the clinical and prognostic significance of ventricular interdependence in PAH and its association with LV filling patterns through speckle-tracking strain echocardiography.

Methods and results: Echocardiography was performed in 71 adults with a new diagnosis of PAH. To analyze LV and RV function separately, we measured peak systolic longitudinal and circumferential strain of the LV and RV. Survival was assessed >2 years. Patients had dilated right-sided chambers (right atrial volume index, 44 ± 19 mL/m(2); RV end-diastolic area, 34 ± 9 cm(2)), and reduced RV function (RV fractional area change, 28 ± 12%). Speckle-tracking echocardiography revealed significant reductions in RV free wall peak systolic strain (-15 ± 3%). Despite normal LV size and normal conventional measures of LV systolic function (end-diastolic dimension, 42 ± 6 mm; ejection fraction, 65 ± 8%; cardiac index, 2.6 ± 0.8 L/min per m(2)), patients had reduced LV free wall systolic strain (-15 ± 3%). Decreased LV free wall systolic strain was associated with a delayed relaxation mitral inflow Doppler pattern, P=0.0002. During 2-year follow-up, 19 patients (27%) died. LV strain was associated with increased mortality (unadjusted hazard ratio, 2.40 per 5% decrease in LV free wall strain, 1.22-4.68), which remained significant when adjusted for age, sex, World Health Organization functional class, and PAH pathogenesis (hazard ratio, 3.11, 1.38-7.20).

Conclusions: The pressure loading in PAH results in geometric alterations and functional decline of the RV, with marked reduction in RV systolic strain. Despite preservation of LV ejection fraction, LV systolic strain was also reduced and associated with early mortality, highlighting the significance of ventricular interdependence in PAH.

Keywords: diastolic function; echocardiography; heart ventricles; hypertension, pulmonary; risk prediction; strain rate.