Abstract
Chronic thromboembolic pulmonary hypertension (CTEPH) results from an obstruction of pulmonary arteries (PAs) by organized thrombi. The stenosed PAs are targeted during balloon pulmonary angioplasty (BPA). We aimed to evaluate the mechanism of BPA in inoperable patients with CTEPH. We analyzed stenosed PAs with intravascular grey-scale ultrasound (IVUS) to determine the cross-sectional area (CSA) of arterial lumen and of organized thrombi. The composition of organized thrombi was assessed using virtual histology. We distinguished two mechanisms of BPA: Type A with dominant vessel stretching, and type B with dominant thrombus compression. PAs were assessed before (n = 159) and after (n = 98) BPA in 20 consecutive patients. Organized thrombi were composed of dark-green (57.1 (48.0–64.0)%), light-green (34.0 (21.4–46.4)%), red (6.4 (2.9–11.7)%;) and white (0.2 (0.0–0.9)%) components. The mechanism type depended on vessel diameter (OR = 1.09(1.01–1.17); p = 0.03). In type B mechanism, decrease in the amount of light-green component positively correlated with an increase in lumen area after BPA (r = 0.50; p = 0.001). The mechanism of BPA depends on the diameter of the vessel. Dilation of more proximal PAs depends mainly on stretching of the vessel wall while dilation of smaller PAs depends on compression of the organized thrombi. The composition of the organized thrombi contributes to the effect of BPA.
Highlights
Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare and progressive disease caused by obstruction of pulmonary arteries (PAs) by organized thrombi with accompanying precapillary arteriopathy [1,2]
As organized thrombi are not removed during balloon pulmonary angioplasty (BPA), investigation of its mechanisms is limited by a lack of tissue material
Twelve (60%) patients had been treated with stable doses of targeted medications before starting the first BPA session, including subcutaneous treprostinil (n = 5; 25%), riociguat (n = 4; 20%), or sildenafil (n = 1; 5%), or a combination of subcutaneous treprostinil and riociguat (n = 2; 10%)
Summary
Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare and progressive disease caused by obstruction of pulmonary arteries (PAs) by organized thrombi with accompanying precapillary arteriopathy [1,2]. Pulmonary endarterectomy (PEA) remains the treatment of choice for most patients with CTEPH [5]. This procedure enables direct visualization of the organized thromboembolic material and provides tissue for additional microscopic and biochemical examination which contributes to prognostic stratification of operated patients [6]. The role of compression of organized thrombi has not been fully explored. It has not been investigated whether the composition of organized thrombi affects the results of BPA [12,13]
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