Chronic total occlusion (CTO) PCI
A completely blocked heart artery is not always a dead end. What a chronic total occlusion is, when opening it can help, what the procedure involves, and how risk is kept as low as possible.
What it is
- A heart artery completely blocked for three months or longer.
Common symptoms
- Chest tightness or breathlessness on effort. Some people have none.
Why treat it
- To relieve symptoms that continue despite medication.
How often it works
- About 85 to 90 in every 100 CTOs are opened in experienced centres.
Understanding CTO
A blocked artery, with a natural detour.
Your heart muscle is supplied by three main coronary arteries. A chronic total occlusion (CTO) is when one of them has been 100% blocked for at least three months. The blockage is usually old and firm, and often hardened with calcium.
When an artery closes slowly, the body often grows small natural bypass channels, called collaterals, from the neighbouring arteries. They keep the heart muscle alive, which is why many people never have a large heart attack from a CTO. During exercise, though, collaterals often cannot supply enough blood, and that is when symptoms appear.
CTOs are common. They are found in about 1 in 5 people with significant coronary artery disease who have an angiogram.
The anatomy
What a CTO looks like.
- 1The artery before the blockage, with normal blood flow.
- 2The blockage: old, firm and often calcified.
- 3Collaterals: small natural bypass channels from a neighbouring artery.
- 4The artery beyond the blockage, supplied only by the collaterals.
Symptoms
What a CTO can feel like.
- Chest tightness on effort. Pressure or heaviness when walking, climbing stairs or carrying things, which settles with rest (angina).
- Breathlessness. Running out of breath on a hill or stairs that used to be easy.
- Gradually doing less. Giving up walks, sport or tasks because they have become hard work.
- No symptoms. Some people feel well. If the collaterals are working well, the blockage can often be left alone.
Symptoms, not just the appearance of the blockage on a scan, usually guide the decision to treat.
Treatment options
Three options, one shared decision.
The right choice depends on your symptoms, the rest of your arteries, how well your heart pumps, your other health conditions and what matters to you. Complex decisions are discussed with a cardiac surgeon where appropriate (the Heart Team).
Medication
The foundation for everyone. Often enough when symptoms are mild or well controlled.
CTO PCI
Opening the blocked artery with fine wires, balloons and stents, through the wrist or groin. Considered when symptoms continue despite medication.
Bypass surgery
Often preferred when several arteries are severely diseased, particularly with diabetes or a weakened heart.
The evidence
Feeling better is the goal.
In EuroCTO, people who had their CTO opened had less angina and better quality of life than with medication alone. DECISION-CTO found no clear difference, partly because many patients switched groups. In 2026, the first placebo-controlled trial (ORBITA-CTO), a small trial of 50 people, found a moderate reduction in angina in carefully selected patients.
The evidence does not show that routinely opening a CTO helps people live longer or prevents heart attacks. CTO PCI is therefore a planned procedure to help you feel and do more, not an emergency, and leaving the artery alone is always one of the options discussed.
Training
Trained in complex and high-risk PCI.
After advanced coronary training at Royal Perth Hospital, Dr Ng was selected as the only overseas fellow to train at the University of Washington Medical Center in Seattle, under Dr Bill Lombardi, Dr Kate Kearney and Dr Lorenzo Azzalini: interventional cardiologists who have helped develop and teach many of the CTO techniques now used internationally.
The training centred on a safety-first way of working: planning each case in detail, protecting the kidneys, limiting radiation, and stopping when the risk of continuing outweighs the likely benefit.
More about Dr Ng- FellowshipComplex and High-Risk Indicated PCI (CHIP), University of Washington Medical Center, Seattle
- TechniquesForward (antegrade) and retrograde CTO PCI, guided by intravascular imaging
- ResearchFirst-author papers describing new CTO techniques, including SLASH and retrograde approaches
- AppointmentInterventional Cardiologist and Co-Lead, Complex Coronary Therapeutics Program, Royal Perth Hospital
Safety
Your safety, at every step.
A CTO procedure can be longer and more complex than a routine stent. These principles guide every procedure Dr Ng performs.
Planned in advance
Your angiogram, and often a cardiac CT, are studied before the day, so the approach, equipment and back-up plans are decided beforehand.
Protecting your kidneys
X-ray dye (contrast) is planned around your kidney function, kept within a set limit, and reduced by using intravascular ultrasound where possible.
Limiting radiation
Low-dose X-ray settings are used, and the dose is monitored throughout, with set limits to protect your skin.
Knowing when to stop
If limits are reached, or the risk of continuing outweighs the likely benefit, the procedure is stopped. A second planned attempt may be possible.
Imaging-guided stenting
Intravascular ultrasound or OCT is used to size each stent and check it is fully expanded, which helps the result last.
Your wellbeing first
If medication or bypass surgery would serve you better than a procedure, that is what will be recommended.
Risks
The risks, explained plainly.
Opening a CTO carries more risk than a routine stent. Serious problems are uncommon, and your own risks will be discussed with you before any decision.
- A tear or leak in the artery (perforation). About 4 to 5 in every 100 procedures at experienced centres. Most are sealed during the procedure; a small number need fluid drained from around the heart.
- Heart attack during the procedure. Usually small, but more likely than with a routine stent.
- Kidney strain from contrast. More likely if your kidney function is already reduced.
- Skin irritation from radiation. Uncommon, and more likely after very long procedures.
- Bleeding or bruising at the wrist or groin.
- Serious complications (death, stroke, emergency surgery or a major heart attack): about 1 to 3 in every 100 procedures at experienced centres. In a large European registry, they occurred in about 1 in 100 forward (antegrade) procedures and about 3 in 100 retrograde procedures (ERCTO 2024; PROGRESS-CTO registry).
The procedure
What happens on the day.
Most people stay one night and go home the next day. You will be advised when you can drive, exercise and return to work.
Preparation
Blood tests, including kidney function, and advice on which medicines to stop or continue.
Comfort
Medicine to help you relax, and local anaesthetic at the wrist or groin.
Crossing
Fine wires are guided to the blockage under X-ray and carefully passed through it.
Opening
Balloons and stents open the artery, sized and checked with imaging. This takes one to several hours.
Recovery
Blood-thinning tablets protect the stents. Do not stop them without speaking to your cardiologist.
After the procedure: call 000 for severe chest pain, fainting or sudden breathlessness. Seek same-day medical review for new chest pain, increasing breathlessness or dizziness.
For referring GPs
When to refer a CTO.
- Angina or exertional breathlessness despite at least two anti-anginal agents, with a known or suspected CTO on CTCA or angiography
- A large ischaemic territory, or unexplained LV dysfunction in the CTO territory, for heart-team assessment (PCI has not been shown to improve LVEF or survival; REVIVED-BCIS2)
- Patients whose CTO was not attempted or not opened, declined for bypass surgery, or wanting a second opinion
- Optimise anti-anginals, statin and antiplatelet therapy before or alongside referral. CTO PCI is for symptom relief, not prognosis. ACC/AHA/SCAI 2021 rates the benefit as uncertain (Class 2b); ESC 2024 is more supportive for refractory angina
- Please flag eGFR below 45 and metformin use. After stenting, DAPT usually continues for 6 months; please do not stop it early without discussion
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Please send angiogram images (a disc or PACS link), not just the report, with any CTCA, ischaemia testing, echo, eGFR and current medicines.
Referral informationQuestions
Common questions
Can a 100% blocked artery be opened?
Often, yes. In a European registry of over 8,600 procedures, about 89 in every 100 CTOs were opened successfully. Success depends on the blockage and on the operator's experience with these procedures.
Will opening a CTO help me live longer?
The clearest evidence is for fewer symptoms and a better quality of life. A survival benefit has not been shown in randomised trials, so the decision is usually guided by symptoms.
What happens if the artery can't be opened on the day?
The procedure is stopped and the reasons are explained to you afterwards. Options then include a second planned attempt, bypass surgery or adjusting your medication.
I've been told nothing more can be done. Can I get a second opinion?
Yes. Dr Ng sees patients who have been declined bypass surgery or who would like a second opinion. Ask your GP for a referral. About second opinions
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