Right ventricular mass/volume in PAH: A double edged sword?

Abstract

A high right ventricular (RV) mass-to-volume (M/V) ratio is used as a measure of the structural adaptation in pulmonary arterial hypertension. However, low M/V ratio can indicate either a normal or dilated RV. The aim of the study was to investigate the association between RV structure (M/V) and RV function (RVCR) in PAH patients utilizing serial measurements on PAH therapy. Prospectively followed Group I PAH patients (N = 38) underwent catheterization and cardiac MRI after 3 months (3mo) of parenteral treprostinil and again on combination therapy (COMB). A subset of patients underwent exercise catheterization (3mo: n = 27 and COMB: n = 24). RVCR was defined as the difference between exercise peak cardiac index (CI) and resting CI. Analysis were stratified by median M/V and resting systolic PAP (sPAP) at 3 mo. On 3mo of therapy, RV mass, end-diastolic volume, and M/V did not significantly associate with sPAP(Figure 1A). RVCR was higher in the low M/V (1.0±0.2) versus high M/V groups (0.6±0.2, p=0.03). After 332 (98-1260) days of follow-up on COMB, M/V did not change (p = 0.9) but RVCR increased from 0.8±0.6 to 1.2±0.6 (p=0.05) and sPAP dropped (74±16 to 66±15, p The heterogenous association between M/V and afterload in this PAH population suggests that the improvement in RVCR with combination therapy is not due to high M/V of the RV.