Imaging characteristics relevant to pulmonary perfusion improvement after balloon pulmonary angioplasty in chronic thromboembolic pulmonary hypertension

Purpose Balloon pulmonary angioplasty (BPA) has been proven to be an effective alternative treatment for inoperable chronic thromboembolic pulmonary hypertension (CTEPH). However, the segmental lung perfusion (LP) improvement after BPA may be inapparent. Therefore, this study aimed to explore the characteristics of BPA-targeted vessels related to segmental perfusion improvement after BPA. Methods Twenty-seven patients with CTEPH who underwent ≥ 4 BPA sessions and had both pre- and post-BPA LP single-photon emission computed tomography (SPECT) were retrospectively analyzed. The baseline perfusion defect score (PDs), location, and angiographic characteristics of BPA-targeted vessels were collected to evaluate their correlations with the efficacy of BPA assessed by LP-SPECT. Results The percentage of overall PDs improvement correlated with the percentage of mean pulmonary artery pressure (mPAP) improvement after BPA (r values of 0.479, P = 0.012). Lesions in the upper lobe had the lowest perfusion improvement rate (upper lobe vs middle or lingual lobe, P < 0.001; upper lobe vs lower lobe, P < 0.001). Moreover, lesions with baseline PDs ≥ 0.5 had a lower perfusion improvement rate than those with PDs < 0.5 (all P < 0.05). Nevertheless, angiographic characteristics of target vessels had no association with the perfusion improvement rate. Based on these results, a 3-point scale was constructed for predicting segmental perfusion improvement after BPA. The perfusion improvement rates of vessels with scores of 0, 1, and 2 were 76.5%, 62.3%, and 8.3%, respectively (all P < 0.05). Conclusions This study demonstrates that LP-SPECT can effectively evaluate the efficacy of BPA in patients with CTEPH. Lesions located in the upper lobe with mild perfusion injury are unsuitable for BPA.