Visualization of Intimal Proliferation in the Pulmonary Arteries by Optical Coherence Tomography

Objectives: Optical coherence tomography (OCT) is well established and increasingly used for visualization of plaques and intimal proliferation in coronary arteries. It is rarely applied in patients with pulmonary arterial hypertension (PAH), where it can be helpful in documenting regression of vascular remodelling after medical treatment. We sought to assess the potential role of OCT for evaluation of pulmonary artery (PA) wall alterations in different congenital heart defects (CHD).

Methods: OCT of the PAs was performed analogue to its application within the coronary arteries in 25 patients (age: 3–49 years; median: 14.5 years). Diagnoses were: 5 post HTx, 5 Fontan palliations, 5 with pulmonary stenosis/TOF, 7 with ASD/PFO/PDA, 1 with thrombotic PA occlusion and 2 patients with PAH. Wall (intimal) thickness (WT) was measured and correlated to PA blood flow pattern on angiography, mean pulmonary arterial pressure (mPAP) and pulmonary vascular resistance (PVR) where applicable.

Results: Patients with minor CHD (ASD/PFO/PDA) and normal PAP showed unimpaired vascular architecture with a normal range of WT, similar in both pulmonary arteries (LPA 0.07–0.22 mm; RPA 0.07–0.20 mm). An increase in WT was detected in patients with PAH (LPA 0.11–0.31; RPA 0.15–0.39 mm), correlating with elevated mPAP and PVR (mPAP 34–69 mm Hg; PVR (i) 11.8–17.0 WE). Patients with Fontan circulation showed also an increased WT, especially on the left side (LPA 0.12–0.32 mm; RPA 0.12–0.26 mm) and especially if IVC blood drained to a hypoplastic LPA. Similar aspects were found in a patient with TOF, who showed a noticeable difference of WT in both PAs (LPA 0.1–0.2 mm; RPA 0.08–0.15 mm) and macroscopic intimal hyperplasia in the less perfused and hypoplastic LPA compared with the other side. Patients post-HTx showed near to normal WT on both sides (LPA 0.05–0.23; RPA 0.07–0.2 mm), consistent with normal mPAP and PVR in the selected group. In one patient with intravascular thrombi, these wall adherent formations could be located with OCT and were resolved by balloon angioplasty.

Conclusion: This proof-of-concept study shows the feasibility of OCT to detect intimal changes within the PAs. We saw a tendency to an increase in WT if elevated pulmonary pressures or wall-shear stress were present. Further studies are warranted to confirm these results and assess the diagnostic value of OCT in the PAs.