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Zivelonghi et al. Vessel Plus 2019;3:30 I http://dx.doi.org/10.20517/2574-1209.2019.06 Page 3 of 11

Figure 2. Illustrative representation of the hybrid algorithm. It is important to highlight the possibility to switch from one technique to the
other if the previous technique is in failure mode. ADR: antegrade dissection and re-entry; RDR: retrograde dissection and re-entry

positioned in the subintimal space thorough the antegrade guidewire. Then the balloon is inflated to
expand the subintimal space and to facilitate the transition of a retrograde guidewire from the subintimal
space connected with the proximal true lumen.

[6]
The hybrid algorithm [Figure 2] was first described by Brilakis and colleagues in 2012, in contrast to
the Japanese School that traditionally favors true lumen-to-true lumen techniques. Given this variety of
new techniques and increasingly dedicated materials, the aim of the hybrid algorithm was to optimize
not only success but also time and procedural steps by suggesting an easy switch among techniques to
select the “right technique for the right CTO”. Theoretical additional advantage of such approach is also
that of allowing reduction in exposure times for the operator and the patient. The hybrid approach indeed
includes all available CTO techniques. It starts mandatorily with dual-injection angiography. In order to
select the best strategies, the operator focuses on 4 main anatomic characteristics of the lesion: (1) proximal
[7]
cap ambiguity; (2) distal target vessel; (3) interventional collateral; and (4) lesion length . After careful
angiographic evaluation, bailout and consecutive strategies are determined upfront. It is recommended to
change strategy after not more than 5-10 min without any progression.

Despite the excellent results of this algorithm in the USA and Europe, in the Asian regions this is rarely
applied. The Asian Pacific CTO club has therefore introduced a new type of algorithm since 2017. There
are three characteristics that guide the operator in choosing the primary strategy and if it has to be
anterograde or retrograde. The three features are: proximal cap ambiguity, the quality of the vessel distally
and if there are good caliber collateral branches. Unlike the Hybrid approach, the length of the lesion alone
is not enough to determine whether a wire escalation or re-entry dissection technique should be more
advisable .
[8]