Bronchial artery embolization

It is said that hemoptysis is caused by the formation of anomalous anastomosis (bronchial artery-pulmonary artery shunt) between the bronchial artery and the pulmonary artery, and if the bronchial artery is embolized, hemorrhage will cease. Although it is termed bronchial artery embolization, various systemic arteries other than the bronchial artery (non-bronchial arteries) also form a shunt with the pulmonary artery and cause hemoptysis. Therefore, it is common to embolize such non-bronchial arteries, but the expression of bronchial artery embolization, BAE, rather than the universal expression "arterial embolization" is more common. The therapeutic outcomes are improving, due to the combined approach such as spreading the treatment target to non-bronchial arteries, development of 3D-CT angiography following the development of MDCT, the advancement of devices such as coils and micro-catheters, and the evolution of therapeutic strategies. BAE has become the gold standard for hemoptysis for its dramatic improvement. In addition, direct hemorrhage from the pulmonary artery is rare (less than 5%), which requires embolization of the pulmonary artery. == Treatment indications ==

BAE is effective for hemoptysis in most underlying diseases such as bronchiectasis, nontuberculous mycobacterial disease (NTM), cryptogenic hemoptysis, pulmonary aspergillosis, and pulmonary tuberculosis sequelae. As for lung cancer, hemoptysis is caused mostly by bleeding from the tumor itself, and not by the bronchial-pulmonary artery shunt mechanism; embolism of the feeding vessels for the tumor causes necrosis of the cancer which may evoke massive hemoptysis. In addition, subsequent chemotherapy and endovascular treatment cannot be performed if the route of anticancer drugs is permanently obstructed. Lung cancer needs a different strategy. Seki et al. reported the usefulness of endovascular treatment for lung cancer hemoptysis. Kichang et al. reported BAE for hemoptysis in 84 lung cancer patients, and demonstrated that massive hemoptysis and cavity formation were significantly poor prognosis factors; re-hemoptysis rate was 23.8% in their follow-up period. Even though BAE is currently considered the gold standard treatment for hemoptysis, Ishikawa et al. found that only 9065 patients (8.4%) out of 107,389 patients hospitalized for hemoptysis between 2010 and 2018 in Japan were treated with BAE. According to Ishikawa basically, all patients with hemoptysis who are admitted to the hospital are eligible for BAE, and the reason why BAE has been performed only in such a small number of patients is that there are still few facilities that can perform BAE, Besides, among the 660 hospitals that performed BAE, half of them (334 centers) experienced less than one case per year. Centralization of hemoptysis treatment facilities will be necessary to increase the performance rate of BAE and to improve the quality of BAE. == Treatment technique details ==

A catheter with a diameter of less than 2 mm is inserted at the base of the foot (femoral artery) or the artery in the wrist (radial artery). The tip of the catheter is inserted into the orifice of the bronchial artery (normally smaller than 1 mm) or other non-bronchial hemoptysis-related arteries. Contrast agent is injected through the catheter, and when abnormal findings are observed, such as systemic–pulmonary shunts, proliferations of the capillary vessels, or extravasation of the contrast medium to the lung tissues, they were super selectively embolized using the 3 Fr microcatheter system. A thinner microcatheter (about 0.8 mm) is passed through the catheter into the blood vessel, and then, embolic material is injected into the appropriate site. Thus, hemostasis is performed by ceasing or reducing the pressure applied to a bronchial (or non-bronchial)-pulmonary shunt (abnormal anastomosis). BAE is performed under local anesthesia, and the required time is about 1 hour to 3 hours. == Effectiveness ==

In the past, BAE was mostly considered a palliative or a bridge therapy to surgical operation owing to the high rate of re-hemoptysis with BAE. But with the improvement in treatment strategy and devices, it is regarded as a permanent therapy for hemoptysis nowadays. but in recent years, specialized high volume centers where a trained pulmonologist performs BAE are emerging. which is equivalent to the results of the article by Ishikawa. It is considered to reflect the progressive nature of the disease. Below are the treatment results summarized according to underlying diseases based on peer-reviewed papers published by Eishinkai Kishiwada Rehabilitation Hospital Hemoptysis and Pulmonary Circulation Center (EHPC), and The National Hospital Organization Tokyo Hospital Pulmonary Circulation and Hemoptysis Center (Tokyo Hp) ; the top two representatives of high-volume centers in Japan. In cases of recurrence, re-BAE is possible to perform several times. Furthermore, Takeda et al. showed that the 1, 2, 3, and 5-year hemostatic rates of bronchiectasis (without nontuberculous mycobacteriosis or pulmonary aspergillosis) were 91.3, 84.2, 81.5, and 78.9%, respectively. This paper is valuable for its long-term results of 5 years. == Embolic material ==

These include polyvinyl alcohol (PVA), n-butyl-2-cyanoacrylate (NBCA), gelatin sponge, metallic coil, etc. NBCA - This is a kind of medical instant adhesive. Generally, there are many complications such as non-target blood vessel embolization and adhesion of catheter and vessel wall. However, in the article by Woo et al., major complication rate was 0%. Metallic coil There are three kinds of platinum vascular embolic coil. One is a detachable coil, which is expensive, but can be deployed repetitively until electric detach. This enables safest and fully controlled embolization. The second one is pushable coil, which is affordable, and allows for only one deployment. The third one is mechanical detachable coil; it has a moderate price range, and repetitive deployment is feasible. Ishikawa termed BAE with metallic coil as ssBACE, and published the world's largest number of cases of ssBACE long-term results in 2017. == Re-hemoptysis mechanism ==

Ryuge classified the re-hemoptysis mechanism after ssBACE into four as shown below. They also demonstrated that for the improvement of the long-term results in ssBACE in the future, suppressing recanalization is necessary. Some readers misunderstand that 45.2% of the embolized coils recanalized. This, in fact, is the ratio of re-hemoptysis mechanism occurring in 9.6% cases in 1 year, and in 14.1% of those in 2 years. Recanalization was the main cause of re-hemoptysis, and the suppression of new hemoptysis-related vessels, which is the second cause, cannot be controlled by the BAE procedure itself. It was shown that suppression of the recanalization was the key to improvement in ssBACE result in future. == Complications ==

Chest pain is the most common complication for who had undergone BAE, ranging from 24 to 91%. However, the symptom is temporary due to accidental embolisation of coronary artery supplying the heart. In the past, paraplegia caused by spinal cord ischemia due to erroneous embolization of the anterior spinal artery was well known as a rare, but serious complication. Super selective BAE using microcatheter reduced the incidence of the spinal ischemia. However, according to Ishikawa et al., spinal cord infarction still occurs, with an incidence of 0.19% (16/8563). They also compared it between three embolic agents (GS, NBCA, Coil) and demonstrated that the incidence of spinal cord infarction was significantly lower in coils: 0.06% (1/1577) compared with GS 0.18% (12/6561) and NBCA 0.71% (3/425) (p=0,04). Major complications reported by Ishikawa et al. are presented below. Mediastinal hematoma occurs by injury of hemoptysis-related vessel, mainly by wire, and can easily bail out by proximal coil embolization. == Improvement in mortality and quality of life ==

The majority of research on BAE was the single-center retrospective observational studies. Descriptive epidemiological studies using French medical big data is precious in that aspect. From the fall of 2020 to January 2021, a collaborative study led by the Yasunaga Laboratory of the University of Tokyo published two landmark papers using the Japanese medical database. == Main evidence for BAE ==

• Bronchial artery embolization to control hemoptysis: comparison of N-butyl-2-cyanoacrylate and polyvinyl alcohol particles An important paper with long-term results from Seoul National University encompassing 406 cases (293 PVA cases, 113 NBCA cases). The non-hemoptysis survival rates at 1, 3, and 5 years for PVA were 77%, 68%, and 66% respectively, and 88%, 85%, and 83% for NBCA, higher in the NBCA group (P = .01). NBCA was associated with fewer complications and better outcomes than previously reported for PVA. Woo S, Yoon CJ, Chung JW, et al. Radiology. 2013 Nov;269(2):594-602. PMID 23801773. • Haemoptysis in adults: a 5-year study using the French nationwide hospital administrative database An epidemiological study on hemoptysis using the French insurance healthcare database (2008–2012). Approximately 15,000 hospital admissions for hemoptysis occur annually, making up 0.2% of all admissions. 50% of hemoptysis causes were idiopathic, followed by respiratory infections (22%), lung cancer (17.4%), bronchiectasis (6.8%), pulmonary edema (4.2%), anticoagulants (3.5%), tuberculosis (2.7%), pulmonary embolism (2.6%), and aspergillosis (1.1%). Mortality rates were 9.2% during the initial admission, 21.6% at 1 year, and 27% at 3 years. Abdulmalak C, Cottenet J, Beltramo G, et al. Eur Respir J. 2015 Aug;46(2):503-11. PMID 26022949. • Bronchial artery embolization in hemoptysis: a systematic review The first systematic review for BAE, covering papers from 1976 to 2016, including 22 studies with at least 50 cases each. Recurrence rates for BAE were found to be high, between 10% and 57%. The presence of non-bronchial systemic arteries, bronchopulmonary shunts, aspergillosis, recurrent tuberculosis, and multi-drug resistant TB significantly increased the risk of recurrence (P https://doi.org/10.58585/respend.2023-0035 == References ==