Ea indicates arterial stiffness and is measured by RV afterload. In the evaluation of Ea made among patients with pulmonary hypertension due to left heart disease, high Ea could predict mortality over pulmonary vascular resistance and the transpulmonary gradient,2) and be correlated with exercise intolerance.3)

Marked histologic abnormalities of the pulmonary artery in postoperative TOF patients are demonstrated, and Ea as a potential outcome predictor was also suggested by several studies.4)5)6) High Ea was related to reduced RV ejection and RV enlargement in Inuzuka et al.’s study.5) It is consistent regarding RV volume and function as the poor outcome predictors. Egbe et al.6) also reported high Ea in the postoperative TOF group and the effect on exercise intolerance. In this study, TOF patients had higher Ea compared to normal control, and it was negatively associated with peak oxygen consumption suggesting pulmonary vascular dysfunction may contribute to exercise intolerance in this disease group.

Kim et al.1) also evaluated the significance of Ea in postoperative TOF patients. They classified TOF patients according to the level of Ea and compared pre-and postoperative hemodynamic data. High Ea group had low exercise capacity, similar to Egbe et al.’s study,6) but had less pulmonary regurgitation and both ventricular volumes, contrary to Inuzuka et al.’s study.5) In addition, Ea could not predict the optimal surgical outcome. However, compared to Egbe et al.’s study,6) Ea of TOF patients in Kim et al.’s study1) was relatively lower (low Ea group 0.3±0.1, high Ea group 0.5±0.2 mmHg/mL/m² in Kim et al.’s study1) vs. TOF group 0.64±0.12, normal group 0.48±0.08 mmHg/mL/m² in Egbe et al.’s study6)). In addition, age was younger (not appeared, age at PVR 21.9 [19.4–27.5], vs. 33±13 year), and fewer patients had prior palliative shunt (0.04% vs. 41%), which may contribute to the difference of results.

On the other hand, RV-PA coupling on RV function in postoperative TOF patients has also been under evaluation. In addition to RV dysfunction caused by residual pulmonary valve regurgitation leading to ventricular dilation and ventricular failure, a highly compliant low-pressure pulmonary artery known as RV-PA coupling has emerged as a significant contributing factor to the outcome. RV-PA coupling is defined as Ea/RV end-systolic elastance ratio (Ea/Emax). Typically, Ea/Emax ratio is around 0.5, and above 1.0, known as uncoupling, is considered ineffective mechanical work production.7) Sandeep et al.8)9) reported two third of postoperative and 80% of transannular patch-repaired patients had RV-PA uncoupling. The increased Ea/Emax ratio could be a marker to identify the progress of RV dysfunction and the optimal timing of PVR in postoperative TOF patients. Panaioli et al.10) also reported worse RV-PA coupling could be an indicator for PVR despite normal RV systolic function.

In Kim’s study,1) RV-PA coupling was not different between low and high Ea groups. However, it was one of the risk factors for suboptimal outcomes along with preoperative RV end-diastolic and systolic volumes in the univariate analysis, even though it was not significant in the multivariate analysis.

Based on these findings, Ea and RV-PA coupling as predictors of postoperative risk factors in postoperative TOF patients are still controversial but of practical value. Further evaluation in a large number of patients and long-term evaluation are needed.