Retrograde Balloon Pulmonary Angioplasty for Otherwise Uncrossable Lesions in Chronic Thromboembolic Pulmonary Hypertension

BACKGROUND: Balloon pulmonary angioplasty (BPA) is an established treatment for chronic thromboembolic pulmonary hypertension (CTEPH). However, some totally occlusive lesions remain uncrossable with conventional antegrade BPA because the proximal entry of the occlusion cannot be identified angiographically. AIMS: To evaluate the outcomes of transcollateral retrograde BPA for lesions that are not amenable to antegrade recanalization. METHODS: We retrospectively investigated the procedural outcomes of 30 lesions in 19 patients treated with transcollateral retrograde BPA at our institution between April 2016 and December 2025. All lesions were either uncrossable with a guidewire despite antegrade attempts or had an indistinct proximal end of the occlusion, precluding identification of a safe antegrade entry point despite angiographic and intravascular imaging assessment. Procedural success was defined as successful balloon dilation restoring antegrade flow. Procedure-related complications were defined as hemoptysis, respiratory deterioration requiring positive-pressure ventilation, or procedure-related death. RESULTS: Procedural success was achieved in 15 of 30 lesions (50%). When divided into three sequential groups of 10 lesions each, success rates were 50%, 30%, and 70%, respectively. Mild hemoptysis occurred in 3 cases (10%), whereas severe complications or death did not occur. Causes of procedural failure included inability to cross the collateral channel (12 cases) and failure to penetrate the occlusion (3 cases). Difficult collateral channels were characterized by severe tortuosity, small vessel diameter, and capillary-like connections. CONCLUSIONS: Transcollateral retrograde BPA may enable recanalization of otherwise untreatable occlusive pulmonary artery lesions with an acceptable safety profile.