Data availability.

Introduction
Right heart catheterization (RHC) is the diagnostic standard for establishing residual pulmonary hypertension (PH) after pulmonary endarterectomy (PEA) in patients with chronic thromboembolic pulmonary hypertension (CTEPH). A potential non-invasive alternative diagnostic test could be electrocardiography (ECG)-derived ventricular gradient optimized for right ventricular pressure overload (VG-RVPO).
Methods
We studied 66 CTEPH patients who underwent PEA. A subgroup of 20 patients also had a cardiac MRI before and after PEA. The diagnostic performance of the VG-RVPO for the detection of residual PH as well as the potential to replace RHC were assessed. Different cut-off values to define a normal VG-RVPO were evaluated. Also, we evaluated the association between mean pulmonary artery pressure (mPAP) and CMR derived indexed right ventricular (RV) mass and the VG-RVPO.
Results
During follow-up, 28 patients had residual PH (42%). A decrease in VG-RVPO after PEA was associated with decrease in mPAP or indexed RV mass post PEA (r = 0.55, p < 0.05 and r = 0.64, p < 0.05, respectively). If a normal VG-RVPO would exclude residual PH, the need for RHC would be reduced with 15–48%, but up to 36% of the CTEPH patients with residual PH would have been missed as they had a normal VG-RVPO.
Conclusion
Although there was an association between the change in VG-RPVO and changes in mPAP or indexed RV mass, our study demonstrated that VG-RPVO has limited value in excluding the presence of residual PH post-PEA as up to 36% of the CTEPH patients with residual PH would have been missed if residual PH would have been excluded based on a normal VG-RVPO.