Impact of Severe Pulmonary Arterial Hypertension on the Left Heart and Prognostic Implications

Background: Severe pulmonary arterial hypertension (sPAH) results in a dilated and dysfunctional right ventricle (RV) together with a small left ventricle (LV) with preserved systolic function. RV size and function parameters have an established association with poor prognosis in sPAH. We sought to determine the impact of RV geometry and function on LV mechanics and its relationship with mortality. Methods: We studied 114 patients (54 +/- 13 years) with sPAH, normal LV ejection fraction (LVEF), and complete two-dimensional transthoracic echocardiograms (TTE) and compared them with 70 normal controls of similar age and gender distribution. TTE measurements of atrial sizes, ventricular volumes and function, tricuspid and mitral regurgitation (TR, MR), and LV diastolic function were performed. Speckle-tracking strain was measured in all four chambers, including LV global longitudinal strain (GLS). Cox proportional hazards regression with forward selection was performed to determine the associations between measured indices and mortality over a 20-month follow-up period. Kaplan-Meier curves were generated for variables most associated with death. Results: Compared with controls, sPAH patients had greater TR severity and right-chamber size with worse function. Of note, LVEF was normal in both groups. Left atrial peak strain and LV GLS were reduced in sPAH, with greater reductions in nonsurvivors. In multivariate analysis, right atrial volume index (hazard ratio [HR] = 1.02 [CI, 1.01-1.04], P < .01), RV free-wall strain (HR = 1.08; CI [1.01-1.15]; P = .03), and LV GLS (HR = 1.11 [CI, 1.01-1.22]; P = .04) were independently associated with mortality. Conclusions: Although PAH is predominantly a right heart disease, in our cohort of sPAH with normal LVEF, LV GLS was independently associated with death in addition to RV and right atrial abnormalities. These findings indicate that the role of left heart dysfunction in sPAH may be underappreciated in clinical practice.