Introduction

CTO are present in about 20% of patients with relevant CAD,

History of remote myocardial infarction (MI) could be found in 42−68% of CTOs.

Many patients with single or multivessel disease is referred for CABG becauseextremely difficult and time-consuming task of addressing CTO by PCI.

Thanks to specific wires and sophisticated techniques continuously evolvingsince the early 1990s but, even more importantly, owing to a few strenuouslyenthusiastic CTO PCI advocates like O Katoh, H Tamai and T Suzuki, who arepioneers in the field of CTO intervention.

Also, there is a shift in long-term patency from less than 50% to more than 90%due to DES.

“Every interventionist dreams of expertise in

CTO intervention which is last niche in the field of

interventional cardiology”

Definition

CTO is defined as a complete occlusion of a coronary arterywith TIMI 0 flow, for more than 3 months duration.

The arbitrary duration of 3 months is used due to thechanges that ensue in the occluded segment during thisperiod (fibrosis, calcification, development of micro-channels and bridging collaterals).

These changes directly influence the success rate of PCI ofthese lesions.

Functional CTO unlike true chronic CTO shows antegradecontrast filling of distal vessel in the absence of bridgingcollaterals and without visible intraluminal contrast fillingof the occluded segment (TIMI I flow).

Pathology of CTO lesions

CTO characterized by heavy atherosclerotic plaque- and thrombus .

A tough, fibrous cap is often present at the proximal and distal margins ofthe CTO.

The density of the proximal fibrous cap is higher than that of the distal cap.These obstructions are thus more likely to deflect guidewires into thesubintimal area, creating dissection planes.

Hard plaques are more prevalent with increasing CTO age (>1-year-old). Theextent and severity of calcification increase with occlusion duration.

Autopsy studies demonstrated neovascularmicrochannels within CTO lesions—someextending from the proximal to the distal lumen,but others, leading to small side branches or vasavasorum in the vessel wall.

WHY TO OPEN UP A CTO ?

Significant clinical problem (JACC intvn 2009;2:489 –97)

Similar risk to non CTO PCI (JACC intvn 2009;2:489 –97)

Angina relief (FACTOR TRIAL-2010)

Improved L V function JACC 2006;47:721–5

Improved tolerance of a future ACS JACC intvn 2009;2:1128 –34

Potentially better survival with successful PCIAmHeart J 2010;160:179-87

Avoidance of CABG AmHeart J 2010;160:179-87

Presentation

Most patients p/w stable angina, a change in anginalstatus, silent ischemia or heart failure of ischemic origin.

More than 50% of patients with CTOs have well-preserved LV function and more than 80% have no Q-waves in the CTO territory, suggesting that thedependent myocardium is viable.

CTOs are one of the commonest reasons for referral forCABG and many are left untreated because ofuncertainty regarding the procedural success and long-term benefit.

Expertise and Financial burden

Broader access to operators performing CTO PCI is needed—thesafety and effectiveness of the more complex strategies are relatedto operator volume and the ascension of a learning curve.Adequate training programs and CMEs will need to continue tobe developed to broaden the pool of CTO operators.

Very few health-care and reimbursement systems value the timeand resource use that can be required for a successful CTO PCIprogram.The financial burden of performing CTO intervention is

high, particularly in our country where reimbursementfor CTO is equaled as simple angioplasty. CTOintervention requires multiple devices with a chance offailure. This situation creates problems when there is afailure of recanalization of CTO.

Japanese-CTO investigators have improvised thetechniques and innovations which lead to the safetyand effectiveness of CTO PCI.

On the basis of the collective emerging data, it seemsthat success rates of 80–90% with the contemporarystrategies and techniques are consistently achievablein experienced hands with a safety profile comparableto standard risk-adjusted PCI.

J-CTO Score

The most common failure mode of CTO interventionsremains the inability to successfully cross theocclusion with a guidewire.

The retrograde approach through collateral channelshas been introduced to cross complex CTOs.

Older occlusions, greater CTO length, a non-tapered stump, the origin of a side branch ofthe occlusion site, and calcification negativelyaffect the ability to successfully cross a CTO.

Preprocedural planning

Spend time examining diagnostic films & decide on

Approach ,vascular access, guide shape & sizededicated equipment availability

Discourage routine adhoc CTO PCI

Occluded & contralateral vessel reviewed in multiple projection frame by frame to

understand complete anatomyidentify proximal & distal capvessel course & side branch calcification

details of collateral circulation

EURO CTO club;2012 consensus

Role of dual injection

Critical for performing CTO PCI–in all case of contralateral collateral

Allows for optimal visualization of CTO vessel

Crucial for determining lesion length, size & location of distaltarget vessel

To asses any bifurcation at distal cap

Assess presence, size & tortuosity of collateral vessel

Best performed At low magnification ,prolonged imaging exposure

No table panning - allows for optimal delineation of CTO segmentcollateral vessel location & course

JACC intrvn2012;5:367-79

First inject donor – then occluded vessel – minimize radiation

Septal collaterals best visualized –RAO cranial OR straight RAO

LAO & RAO cranial – Best to image distal lateral wall collaterals(OM-PLV, diagonal to OM connections)

JACC intrvn2012;5:367-79

Repeat procedures – when to stop

Repeat procedures – More common with CTO

failure of a specific recanalization strategy

Parameters to consider before repeat procedure

First attempt complete ?

contemporary technique & materials properly employed

reason for failure recognized ?clear alternative strategy for reattempt ?

General rule- two attempts at a CTO

Know when to stop key issue in CTO PCIdissection of distal lumen – Better to abandon procedure

Access route

Depend on individual patient situations

Operator preference & experience

Femoral artery - usual and preferred accessin most labs(90% - Europe)

Trans radial PCI for CTO - increased

Anticoagulation

UFH – ease of use & available antidote

Avoid bivaluridin &gp 2b 3a inhibitor

Brilakis et al,2012Korean Circ J 2010;40:209-215

Hardware for CTO

Guide catheter selection

For effective guide wire manipulation :coaxial orientation of guide catheter importantstability& back up force

Guide catheter stability insufficient or unable to achieve

May use Anchor technique for guide catheter stabilization

First key to success

RCA - AL1Prox RCA lesion - JR ( avoid ostial damage)LCA - Extraback up (XB,EBU,BL)LCX (short leftmain) - AL1 or2 (better support & co-axial)

Korean Circ J 2010;40:209-215

Guide wires

Crossing the lesion with GW – very important step in CTO PCI

Floppy wire- initial choice

Exchange to a stiffer dedicated guide wire

Polymer coated wires – poor tactile feedback, lack of resistancemore chance of subintimal passage

Majority favour – step up approach – moderately increased stiffness(miracle-3) – switch to greater stiffness &penetration ability, taperd (conquest pro wires)

Some believe –use of stiffer wires initially to cross hard occlusion cap Rationale: risk of initial dissection minimized,

procedure shortened & simplified with this approach

Kcj 2010

Most common reason for failed CTO PCI- failure of GW to cross

Microcatheters

Low profile,trackable OTW microcath - indispensable tool for CTO PCI

Allow ease of wire exchange

Facilitates transmission of torque to tip & improve feedback

Modulates tip stiffness of guide wire

Dedicated microcatheters – better tip flexibility > OTW balloonsUseful for CTO immediately distal to a bend

Larger inner lumen – reduces friction during wire manipulation

Finecross microcath

terumois.com

Penetration Catheter

Corsair microcatheter:

This is a 2.7-F catheter with a lubricious outercoating, a bidirectional wire braiding for torquetransmission, and an inner polymer lumen with asoft tip for optimal wire control

Penetration catheter

Guideliner(Guidezilla)

Known as guide extension catheter

A GuideLinerTM catheter (mother and child technique):

The “mother and child” technique is a powerfultechnique used to provide additional backup force toconventional guiding catheters.

After crossing the lesion with a conventional guidewire,the GuideLinerTM is used as an inner catheter andinserted inside the 6 Fr.

Guiding catheters, creating a “mother and child” system,and can be used to intubate the coronary artery.

STRATEGIES AND WIRING TECHNIQUES

Wire tip shaped as short as possible <45º

Second milder curve - improve maneuverability of wire

Exception - a sharp (>60º) angle with 1 to 2 mm bend based on lumen size, to navigate the wire from subintimal space back to true lumen( Parallel wire technique or IVUS guided wiring)

Confianza Pro or Pilot 200 - best suited to this purpose

EuroInterv.2006;2:375-381Korean Circ J 2010;40:209-215

Simultaneous rotation & probing of lesion

High chance of entering to subintimal space ( tactile response - nil )

SLIDING

Relatively recent occlusion with predominance of microchannels

Extremly low friction wires for picking microchannels used

Recent total, subtotal occlusion ,ISR attempted with this strategy

Long duration – Microchannels replaced by fibrotic tissue

Indian Heart J. 2009; 61:275-280

BEWARE bridging collaterals masquerading as microchannel

Polymer sleeved wires NOT forced against resistance, small tip bend, probing with mild rotation

Soft wires with polymer sleeve – Fielder series/ Whisper/ PT II

Drilling Strategy

If discrete entry point present

Techniqueshort curve(2mm) @45-60º to distal tip

sometimes a secondary curve given proximally

wire advanced with rapid rotational tip and gentle probing

start with MOD stiffness – progressive increase in stifness

Entry to false lumen judged by tactile feel on pulling stiff wire

Reserved for the most skilled and experienced operator

Ineffective with Blunt entry ,heavily calcific & resistant lesions

Indian Heart J. 2009; 61:275-280

Penetration

TechniquePushing stiff wire slowly& gradually – minimum rotation to target direction

Tapered tip wires Softer tip intially progressively stiffer wires Route determined – various angio or CT findings not by tactile feel

Useful for blunt ,heavily calcific or resistant lesions

Not for CTO with tortuous angulated or bridging collaterals because of higher chance of perforation

Drilling & penetration – guide support & tipload important

Tip load - success - chance of perforation

Penetration power = tip load/tip area

May use to redirect in conjunction with parallel wire technique

Approaches for CTO PCI

ALGORITHM FOR CROSSING CHRONIC TOTAL OCCLUSIONS

After the dual coronary injection is performed, four angiographies parameters are assessed:

1. Clear understanding of the location of the proximal cap usingangiography or IVUS.

2. Lesion length: Lesions more than 20 mm in length tends to havelower success rates and longer procedure times.

3. Presence of branches, as well as size and quality of the target vesselat the distal cap.

4. Suitability of collaterals for retrograde techniques: Optimalcollateral vessels for retrograde CTO PCI is sourced from a healthy(or repaired) donor vessel.

GUIDEWIRE SELECTION AND UTILIZATION

There are four important features regarding CTO wires:1. Polymer covers: Plastic sleeves of flexible but solid material

that are applied directly over the core or over spring coils covering the tip of the wire.

2. Wire coatings: There are two types, hydrophilic and hydrophobic. There is an inverse relationship between lubricity and tactile feedback related to the presence or absence of coatings over coils and polymers at wire tips.

3. Core materials and tapering: The majority of CTO wires has a stainless steel core.

4. Tip stiffness: This range from 0.5 g to 20 g. Tip tapering strongly affects penetration power as the force is applied over a smaller cross-sectional area in tapered wires.

Four-Wire Strategy

Hydrophilic and/or polymer-jacket 0.014 inch guidewire, lowgram-force, with tapered 0.009 inch tip, for antegrademicrochannel or soft tissue probing—Fielder XT

Nontapered, polymer-jacket hydrophilic 0.014 inch guidewirefor collateral channel crossing in retrograde procedures—Fielder FC/Pilot 50

Moderately high gram-force (4‒6g), polymer-jacket, non-tapered 0.014 inch guidewire for complex lesion crossing, longlesions—Pilot 200

High gram-force 0.014 inch guidewire, with a tapered 0.009inch nonjacketed tip for penetration techniques, cappuncture—Confianza Pro 12 wires.

Antegrade Approach

most used approach with success rates of 60–80% during the last 20 years.

Tapered guidewires are first choice for this approach, including the Fielder XT.

Recently, new tapered wires, such as the Gaia 1st have been developed and aregaining acceptance. These tapered guidewires are not intended for intentionalcrossing of the CTO by wiring and are designed for microchannel tracking,Theyare not used to treat a CTO without microchannels and are unlikely to passthrough tortuous or kinked microchannels

If the affected artery is tortuous, a tapered guidewire should be switched to animmediate type of wire. The Miracle 3g, 4.5g, and 6g guidewires arerepresentative wires for this purpose.

The Gaia 2nd guidewire (0.011 inch, Lifeline) was developed recently and it hasattracted the attention of leading interventional cardiologists. Because of itsexcellent torque transmission, the Gaia 2nd is particularly efficient at passingalong tortuous arteries and entering fine channels.

To rationalize a CTO in a relatively straight artery, a stiff wire can beused to begin with. The Conquest Pro is a representative stiff guidewirewith better penetration than the other guidewires in this class.

Increased risk of coronary artery injury, so the operator must make allpossible efforts to keep the guidewire within the vessel lumen and shouldnot choose this wire if the course of the vessel is difficult to visualize orpredict

If the CTO is too dense to cross, the guidewire should be exchanged forone with a stiffer tip such as a Conquest Pro 12 g or 20 g23

The operator should not rotate the guidewire excessively as this mayenlarge the subintimal space. If a guidewire enters a subintimal space,the wire will feel ‘‘trapped’’ and this can be confirmed by frequentlyperforming alternating withdrawal/advancement

The operator should not forget to check multiple views of the CTO whileattempting to cross the lesion. It is important to check the CTO in twoviews so as to keep the guidewire within the intimal space

Advance wiring techniques for Antegrade approach

In case of failure of the guidewire to enter the CTOsegment; many advanced techniques can be used.

These should be used by either experiencedoperators or under their supervision.

These techniques include -

(1) parallel wire technique,

(2) antegrade subintimal dissection and reentry

(3) antegrade intentional intimal plaque tracking

Retrograde Chronic Total Occlusion

Retrograde wiring is performed with a dedicated,microcatheter-supported slippery guidewire from thecollateral-supplying vessel through the collaterals intothe distal vessel.

Important modifications of the retrograde techniquehave occurred since earlier descriptions, notably theadvent of the channel dilator (Corsair). Then, theretrograde guidewire is steered proximally through theCTO to the antegrade guiding catheter (retrograde wirecrossing technique).

If the retrograde guidewire enters a false lumen,controlled antegrade and retrograde subintimaltracking (CART) technique can be used.

Stepwise approach for the retrograde recanalization for CTO:

Retrograde collateral channel access and crossing: Nontortuous septal collaterals are preferentially used for the retrograde approach, whereas epicardial and/or tortuous collaterals are at higher risk of procedure-related vessel trauma

Crossing the CTO: Successful channel crossing of the catheter was achieved in 96.8%, and the channel dilator successfully advanced into the occlusion reversely during retrograde wiring in 94.4%.

Wiring the antegrade guide, snaring, and externalization: Of the several available retrograde wiring techniques, the reverse CART technique has become the most commonly used technique in the Corsair era because retrograde balloon access is not required

ADVANCE WIRING TECHNIQUES FOR

RETROGRADE APPROACH

However, still retrograde approach is not considered as first-line approach and is reserved for prior failed attempts of antegrade approach.

Three possible routes to reach distal cap of a CTO:

(1) through arterial or venous grafts anastomosed to the distal vessel;

(2) through epicardial collaterals and

(3) through septal collateral channels.

Septal collaterals are the preferred collaterals owing to their shorter, less tortuous route and feasibility of balloon dilation for facilitating device passage without significant risk of perforation and tamponade.

Hydrophilic soft-tipped floppy guidewires are ideal for negotiating these collateral channels.

Use of microcatheter is mandatory to provide support to these floppy guidewires and allow preciseguidewire control by preventing flexion, kinking and prolapse.

Various microcatheters such as Terumo FineCross ,however, the recently introduced Corsairmicrocatheter (ASAHI Intecc Co. Ltd, Aichi, Japan) is more widely in use.

Corsair microcatheter is a hydrophilic OTW system composed of eight thin wires wound along twolarge wires. The narrow flexible tip and extreme lubricity of this microcatheter supported by astrong metal shaft allows for gradual advancement along with simultaneous dilation of the septalchannel, obviating the need of balloon predilation.

This microcatheter allows for rapid wire exchanges so that various guidewires can be tried, crucialfor procedural success.

Corsair is slowly “screwed” through the collateral channel under the fluoroscopic guidance to reachthe distal bed of occluded vessel.

Once the distal coronary bed is reached, the soft-tipped hydrophilic guidewire can be exchangedfor a stiffer guidewire to attempt penetration of distal fibrous cap.

Retrograde strategies can be classified into four major types :

1. Retrograde wire cross

2. Kissing wire cross

3. Controlled Antegrade and RetrogradeTracking(CART)

4. Reverse CART.

Retrograde wire cross:

Direct penetration of the distal fibrous cap may be easier than penetrating the more resistant proximal cap .

Once the microcatheter reaches the distal coronary bed, its tip is positioned as close to the distal cap as possible.

The choice of guidewire for penetrating distal cap is similar to that in the antegradeapproach. Initially a soft tapered wire (Fielder XT®, Runthrough NS® tapered) is tried, if unsuccessful then dedicated recanalization wires like Miracle series with gradual increase in tip stiffness can be tried.

Due to the long course followed by the retrograde wire via a tortuous collateral channel, its maneuverability is poor, and it is difficult to lead it through the CTO lesion.

As such the success rate of direct retrograde wire cross is relatively low and this technique has been largely discontinued.

Kissing wire cross:

Also known as marker wire technique,

utilizes simultaneous combined use of the antegrade and retrograde approaches .

The retrograde guidewire in the distal vessel serves as a marker of the distal CTO location and aids in maneuvering of the antegrade guidewire until both meet (kiss) each other.

The retrograde guidewire can also help in antegrade wire cross by creating intraluminal channel in the distal CTO portion. As the distal wire acts as an effective marker, no additional contrast injection is needed during the manipulation of antegrade wire; as such this technique is suited for patients with renal dysfunction in whom contrast dose is limited.

However currently this technique has fallen out of favor against the now preferred CART technique, and is used only when CART cannot be performed due to failure of bringing an OTW balloon catheter through the intercoronary channel.

Controlled antegrade and retrograde tracking(CART):

combines the simultaneous use of both antegrade and retrograde approaches.

A guidewire is advanced antegradely from the proximal lumen into the subintimal space at the CTO site.

After successfully crossing the collateral channels retrogradely, the OTW balloon or the microcatheter is placed in distal true lumen.

A selective contrast injection is made in distal lumen to define anatomy of the distal cap. Depending on the anatomy of the distal cap, either the same polymer-coated wire which was used to negotiate the collateral channel or a stiffer wire is used to penetrate into the distal CTO subintimal space.

A balloon is advanced in retrograde fashion into the CTO subintimalspace and inflated to enlarge the subintimal space. The antegradewire is maneuvered ahead to seek this enlarged subintimal space and subsequently cross to the distal true lumen .

Over this antegrade wire the lesion is dilated and stented to complete the revascularization procedure. Inability to negotiate OTW balloons across the long and tortuous collateral channel is main reason for procedural failure of this approach.

Serial dilations of collateral channel or recently the use of Corsair dilation catheter have obviated this problem to a certain extent. In cases when there is inability to pass OTW balloons retrogradelyeven after dilating the collateral channel, reverse CART technique is utilized

Reverse CART:

This technique is similar to the CART procedure, except that the balloon dilation is done over antegrade wire to increase subintimal space at proximal CTO site.

The retrograde wire is then negotiated subintimally to seek the proximally created subintimal space and thus cross to the proximal lumen.

Unlike CART procedure where subsequent balloon and stents are delivered over the antegrade wire, this is not possible in reverse-CART because of long and tedious course taken by the retrograde wire.

As such this technique involves an additional step of wire externalization, so as to pass balloons and stents antegradely.

Intravascular ultrasound (IVUS) guided reverse CART:

Use of IVUS guidance can increase success of reverse CART procedure. After dilating the balloon over the antegrade wire in proximal CTO subintimal space, an IVUS catheter is advanced antegradely in the subintimalspace. This IVUS catheter is used to assess the subintimalspace, visualize the connecting channel and aid the guided crossing of retrograde wire into the proximal true lumen.

Confluent balloon technique: In confluent balloon technique, balloon dilation is simultaneously performed over both antegrade and retrograde wires to create a common subintimal space, which facilitates easy wire crossing to the true lumen.