Chronic total occlusion

CHRONIC TOTAL OCCLUSION
Dr Virbhan Balai
Interventional Cardiology Fellow
MSSH, New Delhi

DEFINITION
 CTO -: defined as (1) obstruction of coronary artery with no
luminal continuity, (2) TIMI flow grade 0 and (3) duration of
occlusion >3 months.
 Functional or subtotal occlusions - : Lesions with trace antegrade
luminal flow (TIMI grade 1).
 Pseudo-occlusions-: Lesions with a residual lumen but without
antegrade flow bcz of competing collateral flow.
 Functional and pseudo-occlusions overlap in practice and may be
difficult to distinguish from a true CTO unless imaged with dual-
catheter angiography or probed with a guidewire.
 Spontaneously recanalized CTO - long, tortuous microchannel exists
within the presumed architecture of a previous occlusion.

Challenge of CTO PCI
1) Initial traversing of the lesion with a guide
wire.
2) Length of the occlusion.
3) Presence of calcification.
4) Suture line fibrosis after graft failure.

Current coronary CT angiography has limited
spatial resolution and does not capture the
temporal information required to determine
flow rate or directionality.
Can not distinguish CTO from a functional or
pseudo-occlusion or even reliably from a high-
grade stenosis with preserved flow.

PREVALENCE OF CTO
Prevalence of CTOs vary widely depending on
the cohort studied.
Retrospective study from U.S. Veterans
Administration center extracted pt`s with at least
one 70% stenosis (by visual estimate), no prior
CABG, and no MI within 3 months from 8004
consecutive pt`s undergoing cardiac
catheterization b/w 1990 and 2000. Within the
derived cohort of 3087 patients, 52% (1612) had a
CTO.
– Am J Cardiol. 2005;95:1088–1091.

In a prospective study, Fefer and colleagues
reported data on more than 14,000 pt`s
undergoing non emergent angiography at three
tertiary Canadian centers in 2008 and 2009.
They found nonacute coronary occlusions
present in 14.7%.
– J Am Coll Cardiol. 2012;59:991–997.

Swedish registry of non acute general
angiography and PCI found a similar CTO
prevalence of 16% in over 91,000 pt`s with
significant CAD.
Like the Canadian registry, this prevalence
was calculated after exclusion of those with
prior CABG.

PATHOLOGY OF CTO
 Post necropsy CTOs demonstrate preservation of vessel
architecture; a multilayered structure in which the intima
and neointima (including atherosclerotic plaque) is
distinguishable from the muscularis and adventitia.
 The external elastic lamina remains intact.
 This preservation of architecture is a fundamental feature
enabling percutaneous recanalization.
 Tapered tip occlusions contain - microchannels and loosely
packed fibrous tissue. Such occlusions tend to be shorter.
 Blunt cap occlusion are composed of densely packed
fibrous material and fibro calcific intimal plaque and tend to
be longer.

A twofold excess in history of prior MI was observed
among CTO pts in both Canadian and Swedish
registries (40% vs. 23% and 37% vs. 17%, respectively,
P < .01 in both).
Half of the pts in the Canadian registry had LVEF
<50%, but sig Q-waves were present in only 32% of
RCAs, 13% of LAD coronary arteries, and 26% of
LCX artery occlusions.
In the VA registry, chronic CAD pts with CTO had a
lower LVEF than those without a CTO (LVEF 53% vs.
60%, P < .0001) but also had sig more multivessel
CAD (66% vs. 42%, P < .0001).

Pts with a CTO detected at Pri PCI had
significantly worse prognosis than pts with
SVD (infarct vessel only) or those with
multivessel CAD without a CTO.

INDICATIONS FOR
REVASCULARIZATION
Indications for CTO revas. largely same as the
indications for revas. in otherwise obstructive
non occlusive stable CAD.
Primary indication for CTO PCI in the setting
of SVD is the relief of ischemic symptoms that
persist despite anti ischemic medical therapy.

Neither American nor European guidelines
distinguish b/w CTOs and obstructive non
occlusive lesions with respect to the threshold for
undertaking revas, whether by PCI or CABG.
Ad hoc CTO PCI (coincident with diagnostic
cath.) is discouraged.
ACC/AHA/ SCAI guidelines state that “CTO PCI
in pts with appropriate clinical indications and
suitable anatomy is reasonable when performed
by operators with appropriate expertise” (class
IIa, LOE B).

Current Guidelines
 2011 ACC/AHA/SCAI Guideline for PCI recommended CTO-PCI in pts
with clinical indications and suitable anatomy when performed by
operators with appropriate expertise (Class IIa, [LOE] B).
 2014 ESC/EACTS guidelines on MI recommend CTO-PCI to be
considered in pts with expected ischemia reduction in a corresponding
myocardial territory and/or angina relief (Class IIa, LOE B).
 ACC/AATS/AHA/ASE/ASNC/SCAI/SCCT/STS 2017 -: Appropriate Use
Criteria for Coronary Revas in Pts With Stable IHD have eliminated the
separate criteria for CTO lesions as was the case in the 2012 guidelines.
 Currently, indications for revas. in SIHD are determined irrespective of
whether the lesion is a CTO.
 The indication for revascularization of a coronary artery lesion, whether
CTO or severe stenosis, is based on symptoms, the extent of antianginal
medications, and the risk of ischemia.

Indication of PCI for CTO includes
(1) medically refractory angina, (2) large area of
ischemia by noninvasive study, and (3) favorable
angiographic morphologies.
Favorable angiographic morphologies included
tapered proximal stump, functional occlusion, no
side branch at occlusion site, and absence of
bridging collaterals.
Non-favorable ones included blunted proximal
stump, total occlusion, side branch at occlusion
site, and presence of bridging collaterals.

2017 Appropriate Use Criteria for Coronary
Revas.in Pts With Stable IHD from the American
Societies no longer distinguish b/w appropriate
indications for CTO PCI and PCI of obstructive
non occlusive lesions.
Asymptomatic pts are classified as
“inappropriate” in many scenarios, but may be
appropriate in the setting of high risk findings on
noninvasive testing, including severe LV
dysfunction.

ISCHEMIAAND LV FUNCTION
Ischemia burden in a territory supplied by a CTO
is determined by the LV mass supplied by the
occluded segment, the degree of infarction in that
zone, the degree of collateralization, and the
severity of coronary obstruction, in vessels that
supply those collaterals.
Relationship b/w CTO, ischemia, regional and
global LV dysfunction, and post-PCI LV recovery
is complex and incompletely understood.

Pts undergoing pri PCI for STEMI who are found to hv
CTO in a non infarct related vessel are sig. more likely
to hv mod or sev LV impairment (28% vs. 17%, P <
.01) and are more than twice as likely to suffer
progressive LV impairment at f/u (39% vs. 17%, P <
.01) compared with pts who do not hv CTO.
Total Occlusion Study of Canada (TOSCA), 244 pts
had paired baseline and 6-month core laboratory
evaluated LV angiograms, and 106 of these (43%) had
an impaired EF at baseline (EF <60%, mean 46% ±
9%).

COLLATERAL CIRCULATION
Collateral vessels can be assessed for:
a. Size (CC classification)
b. Tortuosity
c. Angle of connection

 Hemodynamic quantification of collateral function most
commonly done collateral pressure index (CPI).
 CPI = ([Pw − CVP]/[Pa − CVP]).
 (Pw) = mean pressure of collateral circulation
 (Pa) = mean aortic pressure
 (CVP)= central venous pressure
 Both wedge and direct measurements of collateral pressure
have been described.
 CPI values >0.3 are considered adequate to prevent
ischemia at rest but have not been rigorously validated.

Optimal Views for Visualizing Collaterals
1. Septal collaterals
a. RAO cranial - best for determining the origin of the collateral.
b. RAO caudal - best for visualizing the part of the collateral closer
to PDA.
c. LAO view - helpful during wiring attempts.
2. Epicardial collaterals in the lateral wall (Diagonal-OM
vessels)
a. LAO cranial
b. RAO cranial
3. Epicardial collaterals b/w the prox LCX and RCA
a. AP caudal
b. RAO

Rentrop et al. described four collateral grades:
Grade (0)-: No visible filling of any collateral
channels
Grade (1)-: Filling of side branches of the
occluded artery.
Grade (2) -: Partial filling of the recipient main
vessel.
Grade (3)-: Complete filling of the epicardial
vessel.

Werner collateral connection grade
CC0 -No angiographic continuous connection
CC1 -Threadlike like connection (<0.4mm)
CC2 -Side branch like connection (>0.4 mm)
CC3 - >1 mm diameter of direct connection (not
included in the original description)

Collateral pathways and their
interventional suitability
SVG GRAFT> SEPTAL COLLATERAL>EPICARDIAL COLLATERAL

Types of preferred wire according to
patient type of collateral channel

PREPARATION FOR CTO PCI
Femoral or radial approach
 Dual angiography to visualize collateral flow &
length of the occlusion.
Larger sheath/guide sizes (femoral) can be
weighed against the reduction in vascular
complications and improved pt comfort (radial).
When femoral access is used, long (45 cm)
sheaths can overcome iliac tortuosity and increase
guide support.
Good passive support with coaxial alignment is
crucial, esp. in complex CTO procedures.

Guide with optimal backup support
Radial - active guide manipulation to augment
the support, balloon anchoring, mother-and-
child guide extension tech to improve support.

Comparisons of the size of guide catheters,
IVUS catheters, and microcatheters

Guide catheters chosen usually in
coronary intervention

Guide Support
1) Passive Support - coaxial alignment, Long-tipped and bigger-sized
(7 F, 8 F) catheters.
2) Active Support - by operators’ skills, deep-seating tech or by
molding the catheter in the coronary sinus.
3) Buddy Wire Tech- lessens the angle of the coronary artery, can
hold guide catheters tightly.
4) Anchor Balloon Tech - anchoring a SB using balloon, balloon is
equal to or larger than 0.25 mm in diameter compared to the SB.
Minimal inflation pressure that does not move the balloon
catheter when pulled is needed.
5) Mother-Child Catheter Tech- engaging a large (mother) catheter
for passive support in the target vessel and inserting a small
(daughter) catheter into it for active support.

Buddy wire/Anchor Balloon Tech

Projection angle according to the CTO
segment

 When the distal vessel is filled by ipsilateral collaterals, flow may be impaired after
wire and catheter advancement, resulting in a collateral or preferential collateral
shift to the retrograde collaterals during the procedure.
 Therefore, to achieve the best diagnostic angiography (i.e., to fill the entire
collateral bed), contralateral injection should be performed at the start of the
procedure if any visible contralateral collaterals are present.
 Operators from the EuroCTO Club have used contralateral injection in 62% of their
cases, whereas dual injection was used in 78% of cases in a more recent North
American series.
 Dual-injection collateral analysis is best performed using low magnification, so that
the entire coronary tree is visualized without panning.
 Careful study of the collaterals not only provides important information in choosing
the most appropriate collateral, but will also alert the operator to the risk of
ischemia and hemodynamic or electrical instability if the wired collateral becomes
occluded.
 Three typical collateral pathways are demonstrated.

Anticoagulation with UFH bcz it allows for
titration of the anticoagulant effect, ACT of
>350 sec is recommended retrograde CTO PCI
to minimize the risk of donor vessel and guide
thrombosis.
As with all PCI, preloading with a P2Y12 ADP
receptor inhibitor and aspirin is important to
reduce the risk of acute stent thrombosis and
peri procedural MI.

Scoring Systems to Stratify Difficulty
of CTO PCI
J-CTO score- developed to determine
likelihood of successful wire crossing within
30 minutes.
J-CTO score correlated well with the
probability of successful guidewire crossing
within 30 min (87.7%, 67.1%, 42.4%, and
10.0%, resp.).

Anatomical classification of CTO lesion

PROGRESS CTO Score -: predict technical
success of CTO PCI performed using the hybrid
approach.
It involves assigning one point to each of four
variables:
1) Proximal cap ambiguity
2) Absence of interventional collaterals
3) Mod-sev tortuosity with 2 bends >70 degrees or 1
bend >90 degrees.
4) Circumflex CTO.

Coronary CT angiography-based
scoring system for CTO PCI

Comparison of CTO Scoring for PCI

Transapical Epicardial Collateral

Guidewires
1. Penetrability - Penetrability is the ability to puncture a lesion, the
stiffer the lesion the more penetrability is required;
-Penetrability depends on: (1) Tip load (2) Tapered tip (3) Wire
support (micro-catheter/OTW Balloon, anchoring tech, child-in-
mother catheter) (4) Lateral support of the wire
2. Pushability - Pushability is the amount of force needed to advance
the wire.
-Pushability depends on (a) the characteristic of the tissue a wire has
to traverse as well as the (b) length of the tissue to be traversed along
the CTO. This feature is determined by the lateral support provided
by the wire.
3. Trackability - Trackabilty is the ability of the device to track over a
guidewire during insertion especially around bends. This feature is
deter-mined by the lateral support provided by the wire.
4. Torquabilty 1:1 transmission of bend.

Torquability is the response of the wire to turning
by the operator when navigating vessels (the ability
to transmit torque from the proximal end to the distal
end of the wire).
This property is important in drilling strategy where
wire is rotated in a controlled manner to search for
path of least resistance.
It depends on:
1. Single core wire – force transmission is not
dampened by the terminal coil.
2. Lateral support provided by the wire.
3. Specially designed wires capable of torque transmission (wires
with dual or composite core)

6. Steerability- Steerability is the ability and responsiveness of the
wire tip to navigate vessels.
7. Bending - Ability to bend if required to circumvent a very stiff
tissue e.g. calcium. Coil structure at the end of the wire allows for
this property (while single core wire resists it).
8. Lubricity - Resistance is encountered while moving the wire in a
vessel or through any lesion. Lubricity is the ease of this passage.
 The resistance encountered depends on-
1. The tissue encountered: vessel lumen << micro-channel< lipid
plaque < proteoglycan < collagen/elastin.
2. Bends (tortuous lesions)
3. Length of the lesion
In general resistance offered is as follows: Polymer coat <
hydrophilic < hydrophobic < non coated.

Sequence of GW selection in CTO

Current algorithm for wire selection

Recommendations of preferred wires
for each CTO technique

Description of Coronary Guidewires
Commonly Utilized in CTO PCI

Basic structure and characteristics of
current Gaia

If Wire Crosses into the Distal True Lumen
1. Advance the microcatheter/over-the-wire into
the distal true lumen.
2. Remove the CTO crossing guidewire and
exchange it for a workhorse guidewire.
3. Remove the microcatheter (using the trapping
technique to minimize wire motion and use of
fluoroscopy).
4. Proceed with standard balloon angioplasty and
stenting.

MICROCATHETER
Role of Microcatheter during CTO PCI
1. Strong backup support during wiring
2. Reinforce torque transmission
3. Easy wire exchange
4. Selective angiography
5. Support double lumen for parallel wire technique
6. Septal channel dilator during retrograde
approach

Corsair
 ASAHI Corsair - originally developed as a septal channel dilator, to
ease retrograde approaches for CTO PCI.
 Can be used both as a microcatheter and as a support catheter.
 135 cm device made for anterograde support, and 150 cm device
made for retrograde support.
 Different from other microcatheters, unique spiral structure
(SHINKA Shaft) effectively transmits rotational torque to the distal
tip.
 This rotation gives ASAHI Corsair its high crossing performance
through tortuous channels.
 Tapered soft tip provides superior tip flexibility which enables
smooth advancement through narrow tortuous vessels, such as septal
channels or other microchannels.
 Radiopaque marker is located closer to distal tip which enhances the
visibility and safety of Corsair.

When rotating the catheter, do not rotate >10
times in the same direction which can cause
catheter damage. After rotating 7–8 times in
one direction, rotate in the opposite direction.
Do not use in a very severely calcified lesion
(Corsair may be stuck in the lesion).

FineCross
FineCross - Composed of fully stainless steel
braided shaft, which supports strong guidewire
backup, and tapered inner and outer lumen.
This microcatheter has the lowest profile among
microcatheters, but pushability is minimum.
Bcz FineCross has the lowest profile, it can pass
narrow CTO space smoothly.
Distal 13 cm is consisted of ultra-flexible material
to support optimal trackability at tight and
tortuous anatomy.

Bcz the inner layer is coated by PTFE, optimal
guidewire manipulation is possible.
Proximal lumen’s size (2.6 Fr/0.87 mm) is
enough which facilitates buddy wire technique in 6
Fr guiding catheter, and distal lumen (1.8
Fr/0.60 mm) is enough for proper guidewire
handling and contrast injection.
The floppy distal segment is manufactured to be
atraumatic and offers a best balance b/w trackability
and safety while navigating through the tortuous
anatomy.

Crusade
Most unique feature is that it consists of dual
lumen.
One is over the wire lumen, while other is rapid
exchange lumen.
Facilitated efficient wiring of difficult branches
and wiring through stent struts.
Also useful in antegrade parallel wire technique.
Crusade has durable shaft and low profile tapered
flexible tip.

Features of microcatheter Crusade

Caravel
 Multipotent microcatheter that completes the simple lesion and
simplifies the complex lesion.
 Provide support to facilitate the placement of guidewires in the
coronary and peripheral vasculatures and can be used to exchange
from one guidewire to another.
 It has an excellent crossing profile of 0.62 mm (1.9 Fr), and braided
wires maintain lumen diameter and guidewire performance.
 Lower profile support catheter in anterograde approach
 It navigates very narrow and tortuous lesion in retrograde approach.
 Bcz of its lower outer profile, 6 Fr guiding catheter can house two
Caravel microcatheters, as well as 7 Fr catheter with one Caravel
and IVUS catheter

CrossBoss
• CrossBoss device has a 1 mm atraumatic tip.
• It can be utilized as an initial strategy when the
proximal cap is “tapered.”
• Initial penetration is performed with a penetrative wire
and a microcatheter. This is followed by knuckling a
wire such as Fielder XT or Mongo wire (Asahi Intecc).
• A knuckle can be utilized safely in combination with
CrossBoss.
• CrossBoss should not be utilized with a penetrative
wire since it will weaponize the penetrative wire,
resulting in a possible perforation.

Stingray catheter
Stingray catheter is a dedicated balloon
catheter with the purpose of achieving targeted
reentry at the landing zone.
The Stingray balloon is 2.5 mm wide when
inflated and 10 mm in length and has a flat
shape with two-side exit ports. Upon low-
pressure (2-4 atm) inflation, it orients one exit
port automatically toward the true lumen.

Snares
Needed for gathering the retrograde guidewire
into the antegrade guide catheter.
 Three-loop (tulip) snares, such as the Ensnare
(Merit Medical) and the Atrieve (Angiotech),
are more effective in capturing the guidewire
compared with the single-loop snares, such as
the Amplatz Gooseneck snare (Covidien).

Guide Catheter Extensions
Two guide catheter extensions are currently
available.
Guideliner V2 catheter (Vascular Solutions) and
Guidezilla (Boston Scientific).
Guideliner V2 catheter is a rapid exchange,
“mother and child” guide catheter extension and
is manufactured in four sizes (5.5, 6, 7, and 8 Fr).
It is 145-cm-long and has a 25-cm single lumen
cylinder that enters the coronary vessel.
It has a radiopaque marker 2.66 mm from the
catheter tip.

• Guidezilla catheter is also a rapid exchange,
“mother and child” guide catheter extension
that was approved by the FDA in March 2013
and is manufactured in one size (6 Fr) that fits
though a 6-Fr guide catheter.

Through four questions, we decide whether to
use antegrade, retrograde, dissection, or
reentry.
1. Is the proximal cap clearly visible on angiography
or IVUS?
2. Is the lesion 20 mm or more in length?
3. Is the distal target clear?
4. Is collateral channel appropriate for the
procedure?

ANTEGRADE APPROACH
ANTEGRADE WIRE ESCALATION
Most common approach worldwide.
Microcatheter catheter is delivered to the prox.
cap on a workhorse wire, and then CTO-
specific tech`s and wire shaping are applied.

Modern step-up/step-down
techniques
Start with soft, tapered, polymer/hydrophilic
wires  stiff, spring-coil tapered wires to
overcome any hard, calcified, or fibrotic seg.
of the occlusion soft, polymer/hydrophilic
wires to continue tracking along the occluded
segment and complete the crossing of the
CTO.

Balloons or catheters should never be advanced over a
wire unless it is certain that the wire is in the
architecture of the vessel (within the boundary of EEL)
bcz small diameter wire perforations that occur within
the occluded segment are usually benign but can
become catastrophic if larger equipment is advanced
outside the vessel, thereby enlarging the size of the
perforation.
Once wire is crossed, the relatively stiff CTO-crossing
wires should be exchanged for safer workhorse wires to
avoid distal plaque disruption/ dissection, and in
particular to prevent inadvertent distal perforation of
small vessels, causing delayed tamponade.

1. Antegrade wire escalation: clear proximal cap, short
lesion less than 20 mm, good target, interventional
collateral irrelevant.
2. Antegrade dissection re-entry: clear proximal cap, long
lesion, good target, interventional collateral irrelevant.
3. Retrograde wire escalation: ambiguous proximal cap,
short lesion, good or poor target, suitable interventional
collaterals.
4. Retrograde dissection and re-entry: ambiguous
proximal cap, long lesion, good or poor target, suitable
interventional collaterals.

Antegrade Dissection/Reentry
Primary mode of failure when recanalizing a
chronically occluded vessel using wire-based
techniques is failure of the wire to enter the distal true
lumen and to instead reside within plaque or within the
subintimal plane.
Reentering the true lumen from these positions can be
extremely challenging with wire-based techniques
alone.
CrossBoss catheter, Stingray balloon, and Stingray
reentry guidewire (Boston Scientific, Natick, MA) used
for successfully gaining reentry into the coronary
lumen.

Stingray dedicated antegrade
dissection and reentry

 Using fluoroscopy and collateral angiography, operators can
select the lumen port with the dedicated Stingray reentry
wire or other stiff, tapered wires to puncture into the distal
true lumen and achieve control by either advancing the stiff
wire into the distal vessel (stick-and go technique) or
switching for a soft, tapered, polymer/hydrophilic wire
(stick-and-swap technique).
 Occasionally, subintimal wire manipulation can cause
significant subintimal hematoma that can compress the
distal true lumen and can thus require decompression
through aspiration.
 Stingray balloon or other microcatheters can be used for this
purpose with a subintimal transcatheter withdrawal
(STRAW) technique.

Retrograde Approach
 In 2005, Katoh and colleagues pioneered the modern era of
retrograde CTO recanalization by introducing new
techniques such as targeted septal or epicardial collateral
crossing, retrograde lesion crossing, and management of the
subintimal space through the use of balloon dilation for
connecting antegrade and retrograde channels.
 Currently, retrograde procedures account for 15% to 34% of
specialist CTO PCI procedures recorded in dedicated
European and U.S. registries.
 These methods require access to the vessel distal to the
CTO from a collateral or occasionally a bypass graft vessel
with successful placement of a support catheter into the
distal target vessel.

Retrograde Wire Escalation
Retrograde wire crossing refers to successful
lesion crossing in the retrograde direction from
true lumen in the distal vesselto true lumen in
the proximal vessel; it is successful in less than
30% of retrograde procedures.

 Standard approach after successful retrograde wire manipulation
includes placing the retrograde wire and then the microcatheter into
the antegrade guide catheter and then exchanging those for a long
wire to be externalized from the antegrade guide.
 Externalized wire—such as the R350 (Vascular Solutions,
Minneapolis, MN), RG3 (Asahi Intecc, Nagoya, Japan), or Viper
Wire Advance (CSI, St. Paul, MN)—is then used as the
interventional platform to complete the PCI procedure.
 It is important for the portion of the retrograde guidewire that is
traversing fine collaterals to remain covered by a microcatheter to
protect the collateral vessel from laceration and perforation.
 Equally important is careful attention to retrograde guide movement
to prevent guide-induced donor vessel injury.

Retrograde Dissection and Reentry
Techniques
 CART -: Controlled antegrade and retrograde subintimal tracking
with intentional dissection followed by reentry has become the
dominant retrograde technique for successful crossing of CTOs.
 The principle of this technique is to create a limited subintimal
dissection space at the CTO segment that is connected with the
proximal and distal true lumen, thereby facilitating antegrade or
retrograde wire crossing.
 The current evolution of this technique, termed reverse CART, uses
retrograde delivery of a microcatheter within the CTO segment
either with traditional wire or knuckle-wire techniques. An
antegrade wire is then advanced distal to the retrograde equipment,
followed by dilation of the occlusion segment with a balloon
delivered over the antegrade wire.

 CART (Controlled antegrade and retrograde subintimal
tracking).
a) An antegrade wire is advanced from the proximal true
lumen into the subintimal space and the retrograde wire is
delivered into distal true lumen and then into the CTO
subintimal space.
b) The balloon is advanced through the retrograde wire and
dilated.
c) Balloon makes a large dissection in subintimal space of
distal lumen.
d) An antegrade wire in proximal lumens is advanced into
distal dissection space and connects proximal and distal
true lumen.

 This tears (dissects) together the two spaces occupied by antegrade and
retrograde equipment to create a single, common subintimal space that is in
continuity with the lumen. The retrograde wire can then be advanced into
the proximal vessel true lumen.
 Ultrasound observations suggest this maneuver is easiest when both the
antegrade and retrograde guidewires are on the same side of the internal
elastic lamina, either both within the subintimal space or both within the
original true lumen.
 The most common reason for failure of this technique is use of undersized
balloons, a problem overcome with experience and use of IVUS for
optimal balloon sizing and positioning.
 After the retrograde wire is advanced into the antegrade guide,
externalization of the retrograde wire is performed as described previously.
 The use of an antegrade mother-child guide extension catheter positioned
immediately proximal to the reverse-CART segment can expedite
retrograde wire capture and externalization.

Reverse CART -: It is similar to the CART technique
except that a balloon is advanced over the antegrade
guidewire to the proximal part of the occlusion and the
retrograde wire crosses into the proximal true lumen.
a) The anterograde guidewire is advanced into
subintimal space;
b) Antegrade balloon is delivery through anterograde
guidewire and is ballooned in subintimal space;
c) Balloon makes a large dissection space.
d) The retrograde guidewire is advanced into proximal
true lumen through large dissection space.

STRUCTURED ALGORITHMS
FOR CTO PCI
Hybrid Algorithm
The “hybrid method” for CTO PCI is an effort
to standardize initial and provisional tech
selection based on pt anatomy.
The implementation of the hybrid method
requires skill-set development in all
techniques—optimal wire manipulation,
dissection/ reentry, and retrograde techniques.

Asia-Pacific Algorithm
 Similar to the hybrid algorithm, it recommends a systematic
approach to determine whether the primary strategy should
be antegrade or retrograde.
 However, unlike the hybrid algorithm, occlusion length
alone does not determine the choice of either a wire
escalation strategy or a dissection reentry strategy. Rather, a
combination of factors, including ambiguity of the vessel
course, severe calcification, tortuosity, length, and previous
failure, are used to determine this.
 It includes the use of IVUS–guided puncture to overcome
proximal cap ambiguity, the parallel wire technique, IVUS-
guided wiring, and limited subintimal tracking and reentry.

Asia Pacific CTO club (APCTO club) algorithm
for retrograde crossing approaches

Asia Pacific CTO club (APCTO club)
algorithm for IVUS guided r-CART

What if the Proximal Cap Is Non-
Penetrable?
 Techniques or maneuvers enhancing support to the penetrating wire,
such as side branch anchoring and guiding catheter extension, may
help solving the first scenario.
 If all failed, operator can apply the so-called scratch and go
technique to enter sub-intimal space intentionally proximal to the
cap.
 There are also situations that the cap tissue is too resistant for device
delivery despite all maneuvers to enhance support. In this condition,
balloon-assisted micro-dissection may be helpful to “shake loose”
the cap tissue for later device delivery.
 Alternatives also include the use of rotational atherectomy on a cut
Rotawire advanced via antegrade MC in exchange of the penetrating
wire, or Excimer laser ablation, if the devices and expertise are
available.

When to Abort
The rule of 3-4-5 proposed by the APCTO
Club algorithm is a reasonable and practical.
The intervention should be terminated, unless
well progressed, if the procedure time is
already 3 h, or the contrast volume exceeds 3.7
times of patient eGFR, or radiation exposure
exceeds AirKERMA 5Gy.

National Heart, Lung, and Blood Institute
classification system for coronary dissection

Classification according to coronary
perforation severity grade

Perforation management algorithm

Covered Stents: Tips and Tricks
 In general:
a) The Graftmaster consists of two stainless steel stents with a middle layer of
ePTFE.
b) It is bulky and difficult to deliver, hence excellent guide catheter support is
important.
c) The Graftmaster may be difficult to advance through previously deployed stents,
necessitating techniques such as distal anchor and use of guide catheter
extensions such as the Guideliner catheter (Vascular Solutions, Minneapolis, MN)
(ideally the larger 8 Fr Guideliner).
d) Minimum inflation pressure is 15 atm, but even higher pressures (and use of
IVUS) are preferred to ensure adequate stent expansion.
e) After expansion the stent may shorten up to 1.6 mm on each side (for a total of
3.2 mm at nominal pressure—15 atm). Hence, adequate overlap of stents is
important to cover long areas of perforation.
f) Use of a dual catheter (“ping-pong guide”) technique is often required to
minimize bleeding into the pericardium while preparing for covered stent delivery
and deployment.

Rapid exchange system (Graftmaster Rx):
a. Is available in diameters of 2.8- 4.8 mm and lengths
between 16 and 26 mm.
b. Requires a 6-Fr guide catheter for the 2.8-4.0 mm
stents and a 7-Fr guide catheter for the 4.5 and 4.8 mm
stents.
Over-the-wire system (Jostent Graftmaster):
a. Is available in diameters of 3.0- 5.0 mm and lengths
between 9 and 26 mm.
b. Requires a 300-cm-long wire for delivery.
c. Its use will likely decline now that a rapid exchange
covered stent (Graftmaster Rx) is available.

 Coils -Coils should be available for use in case of distal branch or collateral
vessel perforation. Metallic coils are permanent embolic agents that can be
deployed through large microcatheters.28 Coils are usually made of
stainless steel or platinum alloys with synthetic wool or Dacron fibers
attached along the length of the wire to increase thrombogenicity. Once
advanced into the target vessel, the coils assume a preformed shape, sealing
the perforation .
 Coils: Tips and Tricks: a. Given that coils are used very infrequently in
cardiac catheterization laboratories, it is important for each operator to be
familiar with the principles underlying their use and with 12 specific coil
types that can be delivered rapidly in case of perforation. b. Coils cannot be
delivered through the usual microcatheters used during CTO PCI (such as
the Finecross or Corsair catheter) but require larger microcatheters, such as
the Progreat Renegade, and Transit microcatheters.
 Pericardiocentesis Tray - Pericardiocentesis can be performed using a
standard 0.018 needle, a J-tip 0.035 in. guidewire, and a standard pigtail
catheter

Risk factors of coronary perforation

1. Device Entrapment, Dislodge (Loss), or
Migration
2. Balloon Catheter Break and Entrapment
3. Guidewire Entrapment or Fracture
4. Donor Artery Thrombosis
5. Transient Myocardial Ischemia
6. Collateral Channel Damages
7. Retrograde LM and Aortic Dissection
8. Chronic Aneurysm Formation and Late Stent
Malapposition

RADIATION SAFETY
 ALARA PRINCIPLE: As low as reasonably achievable (ALARA)
radiation has become the governing principle for the use of radiation to
reduce both deterministic and stochastic effects.
 Even applying this principle, the radiation dose for cardiac catheterization
is in the range of 1 - 10 milli sieverts, typically 3- 5 mSv, which is
equivalent to 2 to 3 years of natural background radiation.
 DETERMINISTIC EFFECTS- are dose related, increasing in severity with
increasing dose, typically once a threshold is exceeded.
 Cataracts and hair loss are examples, but skin injury is the most common
deterministic effect, ranging from skin erythema, which can develop in
hours, to desquamation and skin necrosis, developing over days to weeks.
 A reference point for the dose at the patient's skin level has thus been
defined, termed the interventional reference point, when isocentric
interventional equipment is used, and is located 15 cm (6 inches) from the
x-ray tube on the central axis of the x-ray beam.

STOCHASTIC EFFECTS- such as neoplasms and
genetic defects are related to probability and not
dose, although the likelihood increases with
increasing exposure.
An approximation of the total x-ray energy
delivered to the patient therefore serves as a
measure of the risk for stochastic effects.
This is expressed as the dose-area product, which
is the absorbed dose to air (air kerma) multiplied
by the cross-sectional area of the x-ray beam at
the point of measurement.

 Best practices to minimize radiation exposure include minimization
of fluoroscopic beam time, use of beam collimation, application of
the least magnification possible, and optimal positioning of the x-ray
tube-image receiver unit with avoidance of extreme angles and
rotation of the radiographic projection during long procedures.
 The estimated patient dose is continuously recorded, and warnings
can be issued when certain levels are reached. State regulations vary
but may state that procedures with an air kerma of 6000 milligray
(mGy) or higher require reporting to an institutional radiation safety
committee with documented patient follow-up.
 Similarly, all laboratory personnel exposed to radiation are required
to record their exposure. It is recommended that at least two film
badges be worn: one on the outside of the apron at the neck and the
other under the apron at the waist.
 The latter monitors the effectiveness of the lead apron.

The maximum allowable whole-body radiation dose per
year for those working with radiation is 5
roentgenequivalents- man (rem = 50 mSv), or a
maximum of 50 rem in a lifetime.
Exposure reduction is accomplished by maximizing the
distance from the x-ray source and scatter using
appropriate shielding, lead aprons, thyroid collars, lead
eyeglasses, and movable leaded barriers.
Avoiding severely angulated views decreases radiation
exposure to the operator as well by reducing scatter.
The highest-risk angulation in this regard is the LAO
projection.

Threshold of radiation hazard for
deterministic and stochastic effect to skin

CIN risk score (Mehran risk score)

OBSERVATIONAL DATA FOR
CTO PCI
 British Columbia Cardiac Registries; PCI success among
approximately 1400 CTO PCI procedures was associated
with a 9% absolute survival advantage at 6-year follow-up
(adjusted HR 0.44; 95% CI 0.30 to 0.64; P < .0001), with a
nearly 20% absolute reduction in early and late coronary
bypass.
 U.K. National Institute for Cardiovascular Outcomes
Research examined the data from nearly 15,000 pts who
underwent elective PCI b/w 2005 and 2009 to target one or
more CTOs.
 After adjustment for recorded baseline characteristics, PCI
success was significantly associated with lower all-cause
mortality at mean follow-up of 2.7 years (HR 0.71; 95% CI
0.62 to 0.82; P < .001; Fig. 26.9).

In the National Cardiovascular Data Registry
Cath PCI database, success rate of CTO PCI was
only 59% compared with 96% in non-CTO PCI,
with twice the incidence of MACE at 1.6% vs
0.8%.
The Canadian multicenter registry reported a
procedural success rate of 70% in CTO PCI,
while the European RECHARGE registry
reported an overall success rate of 74% using the
hybrid algorithm.

 Procedural MACE in CTO PCI with experienced providers has
previously been reported at 1.8%.
 Coronary perforation and MI were the most common adverse events
in a meta-analysis of more than 18,000 pts undergoing CTO PCI.
 Coronary perforation leading to tamponade, emergency CABG, and
death were reported at <1%, each with tamponade occurring more
frequently in retrograde cases.
 In a meta-analysis of six CTO studies that reported symptoms using
various methodologies and follow-up, PCI success was associated
with a much higher likelihood of freedom from residual or recurrent
angina (n = 1601, HR 2.2; 95% CI 1.5 to 3.3; P = .0001).
 Use of early and late CABG decreased after successful CTO PCI.

 In the largest contemporary dataset of CTO PCI from the
PROGRESS CTO registry, outcomes of CTO PCI using
the hybrid algorithm were examined in 3055 pts at 20
centers in the US, Europe, and Russia.
 The overall technical success rate was 87%, and the rate of
in-hospital major complications was 3.0%.
 The final successful crossing strategy was AWE in 52.0%,
retrograde in 27.1%, and antegrade dissection reentry
(ADR) in 20.9%, with >1 crossing strategy required in
40.9%.
 Median contrast volume was 270 mL (IQR: 200 to 360 mL),
air kerma radiation dose was 2.9 Gy (IQR: 1.7 to 4.7 Gy),
and procedure time was 123 min (IQR: 81 to 188 min).

In a prospective study from the Flow Cardia’s
Approach to Chronic Total Occlusion
Recanalization (FACTOR) trial, the benefit of
CTO PCI on health status was evaluated.
Successful CTO PCI was independently
associated with improvements in angina
frequency, physical limitations, and enhanced
quality of life at 1 month follow-up as assessed
by the Seattle Angina Questionnaire (SAQ).

Differences in Mortality b/w Failed
Vs Successful CTO PCI

OPEN CTO registry.
This is an adjudicated, prospective cohort of more
than 1000 consecutive CTO pts who underwent
PCI at 14 high-volume centers in the US with 30-
day, 6-month, and 1-year pt follow-up.
Success rates have been reported at 86% with
0.9% in-hospital and 1.3% 1 month mortality.
Perforations requiring treatment occurred in 4.8%.
This registry includes post- CABG, as well as
inoperable pts.

Randomized Controlled Trials
 Three randomized trials evaluating CTO PCI vs OMT.
 EXPLORE trial - evaluated 304 pts from 14 centers in Canada and
Europe with STEMI and concurrent CTO in a non infarct-related
artery.
 Shortly after, primary PCI pts were randomized to CTO PCI or
conservative Tt without CTO PCI.
 There was no significant difference b/w groups in the primary
outcomes of LVEF & LV end diastolic volume on cardiac MRI or
MACE after 4 months.
 However, subgroup analysis revealed that pts with CTO located in
the LAD coronary artery who were randomized to the CTO PCI
strategy had significantly higher LVEF compared with pts without
CTO PCI (47.2 ± 12.3% vs. 40.4 ± 11.9%; P = .02).

 DECISION-CTO trial from Korea planned to enroll 1284 pts but
was stopped early bcz of slow enrollment, after randomizing 834 pts
with coronary CTOs to CTO PCI vs OMT alone.
 CTO PCI was performed with a high success rate (91%).
 Concurrent non occlusive lesions were revascularized following
randomization in many pts in both groups (77% and 79% for the
OMT and CTO PCI groups, respectively).
 Nearly 20% of the OMT group crossed over to CTO PCI.
 At 3 years, the primary end point of death, MI, stroke, or repeated
revascularization occurred in 19.6% of the OMT versus 20.6% of
the CTO PCI group, suggesting noninferiority of OMT.
 Measures of quality of life (QoL; SAQ) were similar b/w study
groups.

 Limitations DECISION-CTO trial
1. High prevalence of non-CTO lesions that were treated
after enrollment in both study groups without knowledge
of the presence of ischemia or symptoms after non-CTO
lesion revascularization;
2. High rates of crossover from OMT to CTO PCI.
3. Mild baseline symptoms
4. Hard clinical primary end points including death and MI
rather than symptom improvement which would be the
expected benefit of CTO PCI;
5. Noninferiority design as opposed to superiority in order
for CTO PCI to replace the less invasive OMT.
6. Low power.

EuroCTO trial - first randomized controlled trial
of CTO PCI to look at QoL outcomes.
407 pts were randomized 2:1 to CTO PCI vs
OMT
Primary efficacy end point was health status at 12
and 36 months.
Pts with non-CTO lesions were enrolled only after
such lesions were successfully revascularized and
if pts continued to experience anginal symptoms.

Study showed significant improvement in angina
frequency with CTO PCI over OMT (P = .009) as well
as greater improvements in CCS angina scores with
PCI over OMT (P < .001).
Improvements in physical limitation, QoL, angina
stability, and Tt satisfaction were numerically higher in
the PCI-treated pts.
MACCE at 12 months was similar b/w the PCI and
OMT arms (5.2% vs. 6.7%; P = .52).
In CTO PCI- most symptomatic pts are likely the ones
to derive the most benefit from CTO PCI. Therefore,
the effect of CTO PCI is likely underestimated RCTs.

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