Objectives: External cardiac work performed is represented by the area within the ejection loop (P-V) and correlates poorly with the heart’s total energy demands until the internal work component is added. Further, the ratio of the arterial elastance (Ea) to the ventricular end-systolic elastance (Emax) is a measure of ventriculo-arterial coupling. We investigated the impact of both indices of right ventricular (RV) performance on outcome in patients with pulmonary hypertension (PH).

Methods: Cardiac magnetic resonance (CMR) studies of a retrospective consecutive cohort of 115 PH pts (61±14 yrs) were examined for RV volumetrics, functional indices and the presence of RV late gadolinium enhancement (LGE) from 2008-2014. Right heart cath (RHC) parameters were included in the analysis (performed within 1±1.5 mo of CMR) as was 3D RV mass and RVEF. The Ea/Emax ratio was derived in part as RV end-systolic volume (ESV)/RV stroke volume. Internal mechanical work was estimated as RVESV*(RV-ES pressure- RV-ED pressure). Patients were followed up to 5 yrs.

Results: During follow-up, 42/115 (37%) pts had a MACE. On a multivariable logistic regression analysis, the strongest predictor of MACE was the internal RV mechanical work followed in order by Ea/Emax versus mean pulmonary artery pressure, RV mass, RV EF, and RV LGE. The strongest predictors of time to MACE were the RV internal mechanical work (χ2=10.8) and Ea/Emax ratio (χ2=9.2). Kaplan-Meier analysis of time to MACE for quartiles of RV internal mechanical work and Ea/Emax are shown in Figure 1A & B.

Conclusions: Higher RV internal mechanical work and Ea/Emax are both markers for worsening prognosis in PH patients; Ea/Emax having the added advantage of being an entirely non-invasive CMR derivation and statistically equivalent. Both metrics were superior to standard clinical metrics including RV LGE, RVEF, PA pressure and RV mass and for the first time address integrated cardio-pulmonary physiology as early markers for MACE.