Optical Coherence Tomography as a Novel Diagnostic Tool for Distal Type Chronic Thromboembolic Pulmonary Hypertension

he new classification of pulmonary hypertension (PH) has been recently updated, 1 in which 5 major categories of the disorder have been classified.Among them, pulmonary arterial hypertension (PAH, class 1) and chronic thromboembolic (CTEPH, class 4) are characterized as having similar hemodynamic pulmonary circulation despite their different pathological vascular structures.Optical coherence tomography (OCT) is an interferometerbased optical imaging modality that produces a 2-dimensional image of optical scattering from internal tissue micro-structures with a high resolution of approximately 10-20 μm, 10-fold higher than that of intravascular ultrasound. 2-4Here, we report the potential usefulness of OCT as a novel diagnostic tool for the differential diagnosis of distal type CTEPH from PAH.The Ethics Committees of Tohoku University Hospital approved the study protocol and all patients provided written informed consent.We prospectively enrolled 31 consecutive patients with PH, including PAH (n=17), CTEPH (n=9), and normal hemodynamic subjects (control, n=5), who were