Balloon pulmonary angioplasty for chronic thromboembolic pulmonary hypertension: State of the art

Table 1 Types of organized thrombus assessed by different imaging modalities

Imaging modalities	Types	Description
Pulmonary angiography	Ring-like stenosis lesion (band lesion)	Localized lesions with concentric stenosis, as if a ring were put on the vessel
	Web lesion	Slit, hazy, or abrupt narrowing opacity of the vessel
	Subtotal occlusion lesion	Tapered and almost completely occluded, but with subtle and slow flow distal to the obstruction
	Total occlusion lesion (pouch defect)	Concaved obstructions with invisible distal vessel
	Tortuous lesion	Highly tortuous small vessels distal to subsegmental arteries
Cone beam computed tomography	Webs	Thrombi frequently observed at the bifurcation of branches appear in diverse forms of fenestrated membranes or thick eccentrically situated branching mass
	Web and slits	Concurrence of proximal web at a bifurcation of branches and distal intravascular fibrous septa (flap-like thin membrane)
	Slits	Intravascular fibrous septa alone
	Narrowing or complete occlusion	Narrowing or complete occlusion
Optical coherence tomography	Septum	Vessel lumen is separated by a partition into less than 4 components
	Multi-hole with thin wall	Vessel lumen is separated into more than 5 channels by thin mesh-like flaps
	Multi-hole with thick wall	Occupied thrombus with more than 5 channels and thick partition walls
	Mono-hole	Occupied thrombus with a single small channel in the lumen
Angioscopy	Mesh thrombus	Organized white thrombus
	Slit thrombus	Filamentous thrombi
	Flap thrombus	Thrombi that almost completely occupy the vessel lumen and block blood flow
	Mass-like thrombus	Thrombi that form a solid mass

Table 2 A proposed classification of balloon pulmonary angioplasty complications in the 6^th World Symposium on Pulmonary Hypertension

During the procedure	After the procedure
Vascular injury with/without hemoptysis	Lung injury (radiographic opacity with/without hemoptysis, with/without hypoxemia)
Wire perforation	Renal dysfunction
Balloon over-dilatation	Access site problems
High-pressure contrast injection
Vascular dissection
Allergic reaction to contrast
Adverse reaction to conscious sedation/local anesthesia

Signs of vascular injury: Extravasation of contrast, hypoxemia, cough, tachycardia, increased pulmonary arterial pressure; Causes of lung injury: Vascular injury much greater than reperfusion lung injury.