Chronic Total Occlusion.

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CTO are prevalent in the right coronary artery and least common in the circumflex artery.

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How to treat a CTO

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Who can do a CTO

CTO are quite complicated lesions that must be treated by experienced interventional cardiologists. It is advised to do a minimum of 50 CTOs per year to maintain competence to treat them. This translates into a model where only a limited number of operators and centers should be allowed to perform CTO treatment.

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Factors for the success of a CTO recanalization

The factors for a successful intervention are depending on the patients’ characteristics and the training of the operator. The operator is able to evaluate the chances of a CTO recanalization looking at different factors evaluated in the J-CTO score table:

[pic 6]

- The shape of the proximal cap

- Calcification of the lesion

- Tortuosity of the vessel

- Length of the occluded segment

If one of the characteristics is present it will count as one point. A CTO with 4 points is the most difficult one.

However other factors are also relevant:

- Longer occlusion duration

- Previous failed attempt of CTO

- Patient tolerance and comorbidities such as renal failure and muscular-skeletal pain.

- Inability to see the distal part of the vessel.

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Steps for CTO recanalization

CTO are complex lesions with totally blocked blood flow. So the doctor treating them should be very prepared. Before starting, he usually will decide what strategy to adopt to recanalize the artery. He should have different strategies in case his plan A might fail.

In order to treat a CTO optimally, there are steps to respect to decide if the doctor should treat it.

- Assess a risk/benefits analysis to see if a CTO recanalization is required. The important factors to consider are:

- Age

- Symptoms

- Ischemic burden

- Renal function

- Ability to take dual antiplatelet therapy

- Previous radiation exposure

- Suitability for dual access sites

- The J-CTO score of the lesion

- The doctor should consider the maximal consumption of contrast possible in regard to the patient’s age and other factors like renal function. Too much contrast can provoke renal failure.

- He will decide after that the vascular access, femoral or radial, depending on his and the patient preferences.

- He will decide which material to use.

- At the end of the intervention, the patient should be treated with dual anti-platelet therapy: Clopidogrel and oral aspirin in order to inhibit blood clots in the coronary artery.

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Techniques of revascularization

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Antegrade approach

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The antegrade approach is the technique used most frequently by the operators. It is the one needing the less training of the operators. It means that you take the direct path to the occlusion. The guiding catheter is first inserted until the beginning of the coronary artery, at the end of the aorta. Then the guidewire is advanced to cross the lesion. It can be followed with a microcatheter or an OTW balloon for a better support of the guidewire. Once the lesion is crossed, a non-compliant balloon is inserted to dilate the CTO. A stent is placed afterwards.

CTOs are complicated techniques because usually there is no open way to cross the lesion. So you need to perforate the lesion with the guidewire. Sometimes there is a calcified plaque in the lesion that easily derivate the guidewire in the subintimal, preventing to cross the lesion.

To advance the catheter in the arteries, an operator will do a combination of movements. He will push and pull or drill the catheter inside the lesion. The drilling technique will be useful when there is no clear visualization as the push and pull is a strategy used when there is a fibrocalcific lesion. The push and pull technique is better used with a tapered wires

Different techniques exist in order to cross the lesion when a single guidewire won’t cross the lesion by itself.

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Retrograde approach

Indication of retrograde approach as a primary approach should be performed in case antegrade wiring seems very difficult in terms of anatomical factors”[3]. In the retrograde technique, the operator approaches the lesion by getting around the CTO with a collateral artery. “Characteristics of the proximal and distal cup are the main reason why retrograde approach has been developed and gained successful application for percutaneous CTO revascularization. In summary, if the antegrade crossing of the lesion is too difficult, the operator may try a retrograde approach. But before starting this approach, the operator will estimate the difficulty of a retrograde approach by evaluating different criteria:

- Well visible collateral

- Non-tortuous collateral,

- Proximal septal collateral collateral, preferably from LAD to RCA and blood flow originating not exclusively from collateral vessels used for retrograde approach.

Below you can find Alfredo Galassi table (to verify) to assess a CTO recanalization.

Indication of retrograde approach as a primary procedure

Antegrade