Estimating pulmonary haemodynamics and vascular resistance in CTEPH from pre- and post-endarterectomy CTPA

Pulmonary endarterectomy (PEA) is a suitable treatment for some patients with chronic thromboembolic pulmonary hypertension (CTEPH). The patient outcome depends on the extent and architecture of small vessel remodelling, which is considered irreversible and cannot be directly assessed. We aim to determine whether personalised biophysical models fitted to pre-PEA hemodynamics are predictive of post-PEA function. Computed tomography pulmonary angiography (CTPA) and hemodynamic data from six CTEPH patients were used. A structure-based model of pulmonary arterial anatomy, including obstructed vessels, was derived for each patient. The vascular remodelling extent was fitted to best match patient pre-PEA data. Obstructions were removed to estimate post-PEA mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance (PVR) and compared to post-PEA hemodynamics. Predicted pre-PEA PVR and mPAP for all patients were 7.0±0.7 WU and 36.3±9.0 mmHg, respectively. The model predicted post-PEA reduction in PVR (3.2±3.1 WU) and mPAP (12.7±11.1 mmHg), with differences between estimated and measured values of 0.7±0.7 WU and 3.3±8.9 mmHg, respectively. Predicted mPAP was strongly influenced by two patients with relatively low pre-PEA PVR (3 and 4 WU) and for whom mPAP returned to <15 mmHg post-PEA. In the other four patients, PVR and mPAP difference was 0.3±0.6 WU and -2.1±4.9 mmHg, respectively. This initial study demonstrates the feasibility of using patient-specific models to estimate post-surgical outcomes in CTEPH. Simplified assumptions were initially used for this complex process, a more advanced approach is likely to provide better predictive accuracy in this diverse disease.