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Andò et al. Vessel Plus 2023;7:15 https://dx.doi.org/10.20517/2574-1209.2023.26 Page 13 of 22

calcified lesions but remains the only option when the lesion cannot be crossed -even with a micro-catheter-
to allow placement of a RA guidewire. In a small study of 58 uncrossable/undilatable lesions with
conventional balloons, very satisfactory results were obtained with ELCA, with even better efficacy if the use
[98]
of the laser was followed by RA .

Chronic total occlusion (CTO) may typically be treated with the ELCA. Even after the passage of the
guidewire through a CTO, the angioplasty procedure cannot sometimes be ultimately performed because of
the impossibility of crossing the lesion with either a micro-catheter or a balloon . ELCA is a valuable
[99]
option in such circumstances because, differently than with RA, the laser catheter can be used over standard
guidewires; it creates a channel through the CTO and allows other devices to ultimately cross the lesion .
[100]

[101]
ELCA can be used for in-stent restenosis due to neointimal hyperplasia and in calcified non-expandable
in-stent restenosis , especially when the latter is a consequence of stent under-expansion at time of
[102]
original implantation . A recent OCT study showed the superiority of ELCA over high pressure POBA in
[89]
the treatment of non-dilatable intrastent restenosis and confirmed the action of ELCA in breaking the
calcium behind the stent struts, especially during the administration of contrast agent, which allows for
generating larger bubbles with a higher photomechanical effect [103,104] .

Intra-vascular lithotripsy
General principles
Intra-Vascular Lithotripsy (IVL) is the most recent technique that has been developed to treat calcific
atherosclerotic lesions. IVL operation mode is based on pulsatile mechanical energy delivered by
miniaturized emitters positioned along a rapid exchange semi-compliant balloon (Rx Shockwave,
Shockwave Medical, Santa Clara, California) and transmitted to the vessel by means of the inflated balloon
inside the vessel. These emitters produce circumferential sound pressure waves that traverse the soft tissue
and fracture the calcium of the tunica intima and especially of the tunica media within the vessel wall.
Microfractures in calcium increase vessel compliance, allowing adequate dilatation of calcific lesions or
passage of larger devices. Barotrauma on the vessel walls is minimized by the low inflation pressure of the
semi-compliant balloon (4-6 atmospheres). Such a preferential effect on deep calcium is the great advantage
of lithotripsy over plaque ablation techniques. Its use was first described in the treatment of calcified lesions
of peripheral arteries and subsequently extended to the treatment of calcified coronary artery disease.
[105]
Technical and procedural considerations
The coronary IVL system consists of a disposable catheter, connector cable, and pulse generator. The
catheter does not differ in concept from a conventional balloon catheter, even though it has a larger profile
and much more stiffness. The size of the IVL balloon is chosen according to the reference vessel diameter is
chosen, with a ratio ≥ 1 being considered appropriate . Once the lesion has been reached, the 12 mm long
[106]
IVL catheter balloon is inflated to 4 atmospheres to allow contact with the vessel wall and optimization of
sonic pulse wave energy delivery. Treatment cycles include one pulse per second for 10 s. After each cycle,
the balloon is brought to 6 atmospheres. This helps to compress the fractured calcium before a new
treatment cycle. A maximum of 8 treatment cycles (80 pulses) can be delivered for a single IVL catheter. For
lesions longer than 12 mm, the catheter must therefore be repositioned to treat the lesion along its entire
length. In the event that the IVL catheter is unable to initially cross a calcified lesion, it is possible to
perform predilatation with low-profile angioplasty balloons or even a rotational atherectomy, which will
facilitate positioning of the IVL catheter (Rota-Shock technique). However, coronary IVL remains a
[107]
balloon-based technique and therefore, a relatively simple technique with a short learning curve. These
considerations, combined with the accruing efficacy and safety evidence, place IVL in the foreground