Adequate, high-resolution digital subtraction angiography (DSA) is a prerequisite.
Sheath and Catheter
For access via the right common femoral artery, a long 5-Fr. introducer sheath (45 cm) is preferred in patients with tortuous arteries to negotiate the effect of the curves on catheter manipulations . Transbrachial or transradial access can be used as well and may be required to catheterise aberrant vessels from the subclavian artery or the inner curve of the aortic arch [4, 24].
The selection of guidewire and diagnostic catheter (DC) depends on the anatomy (Table 6). End hole-only design is essential and 4-Fr. or 5-Fr. Sidewinder or Mikaelsson catheters allow a more stable ostial position than forward facing cobra-curved catheters. A diameter of 4 Fr. carries a lower risk of damaging the BA ostium.
A braided, hydrophilic low-profile 1.9–2.8 Fr. microcatheter (MC), with internal diameter of 0.0165–0.027 inch is preferred as coaxial “tapered” extension of the diagnostic catheter for super-selective catheterisation . Continuous flushing of the DC by a drip infusion using a haemostatic valve may be advantageous.
Non-ionic contrast agents will minimise the risk of transverse myelitis .
Non-spherical, PVA particles, 355–500 µm in diameter were most commonly used [6, 14, 21, 26, 27]. Due to their non-uniform shape, PVA particles can aggregate and form plugs that result in premature embolisation proximal to the intended level . Occlusion is completed by thrombus formation and moderate perivascular inflammatory change .
Alternatively, any calibrated microsphere particles (300–900 μm) can be used [6, 30]. These particles are more uniform in size and in penetration characteristics than PVA, and their smooth hydrophilic coated surface is less prone to clumping within catheters [27, 29, 30].
When large pulmonary arterial or venous shunts are present, larger sized tris-acryl microspheres (700–900 μm) or coil embolisation may help avoid complications [14, 31, 32] such as pulmonary, myocardial, or systemic infarcts [13, 32]; the presence of spinal cord feeders arising from the bronchial artery also seems to be less critical when using larger sized (700–900 μm) particles [19, 27].
However, microparticles with a larger diameter may occlude the index bronchial artery more proximally than preferred, which could lead to recurrent haemoptysis from systemic collaterals. This risk can be diminished by placing the tip of the MC to a location as close as possible to the abnormal vasculature .
Smaller particles (< 300 μm) may occlude regular blood supply of the bronchi, oesophagus, vasa vasorum of the pulmonary artery or the aorta, with increased risk of excessive tissue ischaemia and necrosis and therefore may not be used in BAE .
Occasionally small quantities of gelatine in the form of a pledge or thick slurry can be placed after particulate agents to complete the embolisation, but its use as a sole agent is not as durable, and thus not recommended [13, 22].
N-butyl cyanoacrylate (NBCA) glue mixed with iodised oil for both opacity and modification of the polymerisation rate has shown a better haemoptysis control rate than PVA [13, 28]. A variable degree of vessel penetration is controlled by the injection rate and the dilution ratio at the time of preparation, which is typically 1:2 to 1:4 NBCA to lipiodol . Inexperience with NBCA may potentially lead to a variety of pitfalls, including premature polymerisation, non-target embolisation, or attachment of the MC tip to the glue cast. NBCA is not recommended for the treatment of haemoptysis until the provider has gained significant familiarity with its behaviour in other settings .
Non-adhesive, high-viscous polymers dissolved in dimethyl sulfoxide (DMSO) include tantalum powder or iodine component to enhance visibility and contrast [1, 34] in cases of refractory massive haemoptysis in patients with CF where conventional particle embolisation has failed . However, similar to NBCA, application of liquid polymers requires experience, and aggregation of the polymer may block the MC as well.
The prevailing view of using microcoils for BAE is that coil embolisation would prevent future BAE for recurrent haemoptysis due to proximal embolisation and the development of challenging collateral vessels [14, 22, 36]. However, high-packing-density coil deployment, using hydrogel-polymer-coated or high thrombogenic coils may be still used in recurrent haemoptysis  to protect spinal supply  and distal circulation, to occlude actively bleeding vessels as in pseudoaneurysms, or to occlude large bronchial-to-pulmonary shunts [3, 5].
Self-expanding microplugs (diameter 5.0–6.5 mm) loaded within a 0.027″ microcatheter can occlude blood flow within BAs 1.5–5 mm in diameter . To our knowledge, only one study reported a vascular microplug system to treat paediatric haemoptysis; however, the procedure had to be repeated up to 4 times to stop haemoptysis .
For further information about current available microcatheter and embolic agents, one may consult the European Device Guide website .
Procedural Features and Variations of the Technique(s)
In the absence of a preceding contrast-enhanced MDCT, a flush aortogram can be obtained to identify bronchial and non-bronchial systemic collaterals [5, 6]. A shallow left anterior oblique angulation may help to visualise the origins of bronchial arteries. The field of view should extend several centimetres superior to the lung apices to avoid exclusion of important apical collateral vessels.
Angiography of the subclavian arteries should be considered, to determine the origin of ectopic BA supplied by internal thoracic arteries or thyrocervical trunks, in apical-predominant disease . When the origin of the BA has been documented by the preprocedural CT, the procedure will start with the selective catheterisation of the BA. After careful control of the DC stability, selective angiogram of the BA will be performed–hand injection will suffice for adequate opacification in most cases .
The DC is then gently advanced 1–2 cm through the ostium of the BA, avoiding complete occlusion of the lumen. Rigorous verification of absence of any branches supplying critical structures, such as the spinal cord, is mandatory before commencing BAE. These branches may arise directly from intercostal bronchial trunks, or may be in close communication via short collateral vessels.
The MC should not be advanced too far in the target vessel, in order to preserve free flow around its distal tip. Any “aggressive” manipulation of the guidewire may induce spasm, dissection, or rupture of the BA .
Immediately before embolisation, a hand injection of contrast through the MC using a small size Luer-lock syringe should be performed, at a rate determined not to cause reflux . Note that this rate will change during embolisation, as downstream flow resistance increases.
At all times embolisation is performed with a small (1 ml) Luer-lock syringe under active fluoroscopy to ensure any sign of reflux is picked up as early as possible. Careful pulsatile injection of minute amounts of the embolic agent may be slowly continued when there is no resistance to the blood flow. When the resistance builds up or a limited reflux appears, a new manual contrast injection has to be carried out after carefully flushing residual embolic material through the catheter. Vigilant attention to newly appeared collateral vessels, to bronchial-to-pulmonary shunts or reverse flow to branches supplying the spinal cord, or other vital structures is mandatory.
When flow is sluggish, stop embolisation and carefully flush the remaining embolic material within the MC with saline. If flow has already stopped, flushing the MC should be avoided and aspiration of embolic agents within the MC lumen is necessary until free-flowing blood is obtained. If unsuccessful, removal of the MC during aspiration and flushing outside the patient is recommended.
When bronchial branches originate from the aortic arch, mammary or subclavian arteries, careful consideration should be given during embolisation, since tiny amounts of reflux can cause cerebral emboli.
For good haemoptysis management, all pathological arteries must be embolised . In malignant disease, the aim is to obtain permanent occlusion of the abnormal circulation distally. In chronic inflammatory disease such as CF, reduction of blood flow will sufficiently reduce the vascular pressure, thus lowering the risk of recurrent haemoptysis .
Do not inject intercostals at the vessel origin as this increases the chance of radiculomedullary branch embolisation. Rather advance the MC a few centimetres into the vessel (at least beyond the pedicle) to avoid particle reflux .
Where clinical or imaging lateralisation of the bleeding site is uncertain, treat any enlarged bronchial arteries at the first session. If no bronchial supply or abnormality is detected, consider MDCT to exclude bleeding sources such as pulmonary artery aneurysms, PAVMs and fistulas [1, 3, 41]. When the culprit lesion is not identified, or if there is any abnormal circulation on both sides, bilateral BAE is required.
An angiogram of lower thoracic and abdominal aorta may help to detect the origin of vessels arising from phrenic arteries or other abdominal branches (in cases involving the lower lobes).
Open surgical options must be undertaken urgently in cases in which haemorrhage of the pulmonary arteries is caused by a destructive pulmonary process (lung cancer, necrotising pneumonia, pulmonary mycetoma)  or if other methods fail .