In individuals with pulmonary hypertension, oncoming right ventricular failure can be detected by right ventricular-pulmonary arterial coupling, defined as the ratio of end-systolic to arterial elastances (Ees/Ea). Normal values range from below 0.8 to between 1.5 and 2. This research was recently published in Circulation: Heart Failure.
This study included 42 individuals with pulmonary hypertension, all of whom received cardiac magnetic resonance imaging less than 1 day after invasive right ventricular pressure-volume loops measurement via right heart catheterization. Transformations were applied to all non-normally distributed variables, which were then examined via linear regression. Tertiles and quartiles were used to examine a potential cutoff value for Ees/Ea that would predict impending right ventricular-pulmonary arterial uncoupling.
End-systolic elastance had a median value of 0.49 mm Hg/mL (interquartile range [IQR], 0.35-0.74) and arterial elastance was 0.74 mm Hg/mL (IQR, 0.45-1.04), with an Ees/Ea value of 0.73 (IQR, 0.47-1.07) and an end-diastolic elastance measure of 0.14 mm Hg/mL (IQR, 0.06-0.24). Participants had a right ventricular ejection fraction of 39%±13%, with the ratio of end-systolic and end-diastolic volumes to body surface area of 62 mL/m² (IQR, 45-101) and 104 mL/m² (83-143), respectively. An Ees/Ea cutoff of 0.805 correlated with pending right ventricular failure. There were inverse associations between Ees/Ea and other measures, including increasing ratios of right ventricular end-diastolic volume and mass to body surface area, increasing pulmonary arterial stiffness, and decreasing ejection fraction. This indicated great reserve in Ees/Ea values, which decreased from a median of 0.89 to 1.09 among those with early maladaptation to 0.56 to 0.61 among those with acute maladaptation. There was a positive association between rising end-diastolic elastance and rising ratios of end-diastolic volume and right ventricular mass to body surface area, decreasing ejection fraction, and rising T1 mapping.
Limitations to this study included small sample size, estimates of Ees and Ea confined to the single-beat method, and individual variation in right ventricular-pulmonary arterial preservation among those with acute pulmonary hypertension.
The study researchers concluded that “our analysis of [cardiac magnetic resonance], hemodynamic, and single-beat pressure-volume loop data in 42 consecutive patients with [pulmonary hypertension] shows that [right ventricular-pulmonary arterial] coupling defined by Ees/Ea has considerable reserve and is associated with parameters reflecting [right ventricular] maladaptation. [Stroke volume/end-systolic volume] might be at least as useful as Ees/Ea in detecting pending [right ventricular] failure in [pulmonary hypertension].”
This study received funding from the Excellence Cluster Cardio-Pulmonary System and the Collaborative Research Center. Several authors report financial associations with pharmaceutical companies. For a full list of disclosures, see the reference.
Tello K, Dalmer A, Axmann J, et al. Reserve of right ventricular-arterial coupling in the setting of chronic overload [published online January 8, 2019]. Circ Heart Fail. doi: 10.1161/CIRCHEARTFAILURE.118.005512