Introduction: Measurements of RV function, such as RVEF and RV-measured ventricular-vascular coupling (VVC), maybe important in predicting survival in PAH, but are dependent on load and mathematical assumptions. However, independent measures, such as flow efficiency (FEI) within the main PA may be better predictors. FEI is dependent on the natural ratio between MPA area to pulsatile blood wavelength (λ), where λ is proportional to the product of λ velocity and the pulse time, but is difficult to measure directly. Hypothesis: We hypothesize pulmonary FEI will correlate with the VVC and RVEF. Methods: CMR was performed on 18 pts with PAH to assess RV function. Eight pts additionally underwent RV CMR during physiologic stressors: 1) inhaled NO 2) dobutamine (20μ/kg/min) and 3) volume challenge (500ml NaCl). MPA flow was measured via phase velocity mapping (PVM). The RVEF, VVC ratio and ejection time (ET) were calculated from CMR. The MPA area was measured from the PVM images along with avg velocity (Vel avg . Pulmonary FEI = (average Vel avg x ET) / MPA area. Results: A total of 38 unique measures of RVEF (52±12%), VVC (0.89±.3) and MPA flow conditions were measured: Vel avg (49±15cm/s), MPA area (51±11mm 2 ) and ET (295±61ms). The FEI correlated with RVEF and VVC via log term: RVEF = 11.5 log nat (FEI) + 37.2; and VVC = 0.34 log nat (FEI) + 1.17.Bland-Altman analysis of the measured RVEF vs. the FEI modeled RVEF (Fig 1) has an offset bias of 0, a four SD range of ±14.4; r=0. 0.8, while the measured VVC vs. modeled has a bias of 0 and a 4 SD range of ± 0.45; r = 0.74. Conclusions: The linear combination of average pulmonary blood velocity, ejection time and MPA area combine to form a pulmonary FEI that strongly correlates with RVEF and VVC. Importantly, it is devoid of the afterload/preload assumptions of RVEF and the multitude of assumptions of V 0 and RVEDP in VVC. As such, this index may provide additional clinical value since it reflects the directly measured intrinsic efficiency of integrated RV-PA conditions.
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 (E a ) to the ventricular end-systolic elastance (E max ) 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 E a /E max 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 E a /E max 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 (χ 2 =10.8) and E a /E max ratio (χ 2 =9.2). Kaplan-Meier analysis of time to MACE for quartiles of RV internal mechanical work and E a /E max are shown in Figure 1A & B. Conclusions: Higher RV internal mechanical work and E a /E max are both markers for worsening prognosis in PH patients; E a /E max 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.
