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Health condition · Clinically reviewed

Coronary chronic total occlusion, a fully blocked artery, treated as a long-term condition.

A CTO is a coronary artery that has been 100 per cent blocked for three months or more. Medical therapy comes first, with specialist PCI or bypass surgery for the right patients.

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Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a registered UK clinician before publication.

  • 02

    Sourced from guidance

    Checked against ESC, BCIS, NICE and peer-reviewed sources you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK practice including hybrid CTO PCI algorithms and viability-guided revascularisation.

Key facts

Coronary CTO at a glance.

The essentials, in plain English. What a CTO is, why it forms and how it is treated in the UK today.

  • What it is

    A 100 per cent blockage of a coronary artery present for three months or more, usually with collateral supply from other arteries.

  • How common

    Found in roughly 15 to 25 per cent of patients undergoing coronary angiography for chest pain or ischaemia.

  • Why it forms

    Long-standing atherosclerosis is the main driver, sometimes with prior thrombosis, dissection or a healed SCAD event.

  • Collateral supply

    The distal vessel is often fed by collaterals from other arteries and graded on the Rentrop scale from 0 to 3.

  • How it is treated

    Optimal medical therapy first, with PCI or bypass surgery reserved for symptoms, viable myocardium or LV dysfunction.

  • Where PCI happens

    Complex CTO PCI is delivered by specialist high-volume operators at centres like the Royal Brompton, Papworth and the Golden Jubilee.

Why this guide matters

A whole-patient plan, not just a picture on the screen.

A CTO on angiography is one piece of a larger puzzle. Symptoms, viability, LV function and preference all shape the plan.

  • Medical therapy is always the base

    Antiplatelet, statin, ACE inhibitor and beta-blocker are the foundation, with anti-anginals layered on for symptoms.

  • Revascularisation is targeted

    PCI or bypass is offered for troublesome symptoms, large ischaemic burden or reduced LV function, not simply because a CTO exists.

  • Specialist centres change outcomes

    CTO PCI is a specialist skill. High-volume UK operators achieve 85 to 95 per cent success with modern hybrid techniques.

How the diagnosis is made

From first symptoms to a considered plan.

The steps a UK cardiologist will normally follow, in order, so you know what to expect and why.

  1. 01

    Assessing

    Symptoms and functional class

    A structured review of angina using the Canadian Cardiovascular Society scale and breathlessness with the NYHA class, plus current medications.

  2. 02

    Assessing

    ECG, stress testing and echo

    Resting ECG, exercise or pharmacological stress testing and an echocardiogram to assess LV function and regional wall motion.

  3. 03

    Assessing

    Coronary CT angiography

    Increasingly used to characterise the occluded segment, calcification, length and vessel course before invasive angiography.

  4. 04

    Confirming

    Invasive coronary angiography

    The gold standard for anatomic characterisation, feeding scoring systems such as the J-CTO and BCIS-CTO to predict procedure difficulty.

  5. 05

    Confirming

    Viability imaging

    Cardiac MRI with late gadolinium enhancement, PET or stress echocardiography identifies hibernating myocardium likely to recover with revascularisation.

  6. 06

    Planning

    MDT and specialist CTO review

    Interventional cardiology, cardiothoracic surgery and heart failure teams weigh anatomy, symptoms and preference before recommending a strategy.

  7. 07

    Planning

    Shared decision and consent

    Trial evidence, individual risk and patient goals are discussed openly before consenting to CTO PCI, CABG or continued medical therapy.

Typical timeline: weeks from first assessment to a settled, individualised plan.

Symptoms

What a CTO actually feels like.

Symptoms range widely, from typical exertional angina and breathlessness to entirely silent disease found by chance.

  • Stable angina on exertion

    Predictable chest tightness or heaviness brought on by activity, walking uphill or emotional stress, relieved by rest or GTN.

  • Unstable or crescendo angina

    Angina at rest, at lower thresholds or lasting longer than before, needing prompt cardiology assessment.

  • Breathlessness and heart failure

    Exertional dyspnoea, orthopnoea or ankle swelling can reflect ischaemic cardiomyopathy from a longstanding occlusion.

  • Reduced exercise tolerance

    A slow, gradual drop in the distance or intensity someone can manage, often blamed on age or fitness at first.

  • Asymptomatic and incidental

    Some CTOs are silent and only found on angiography performed for another reason, thanks to well-developed collateral flow.

  • Discovered during acute MI

    A CTO in a non-culprit artery is often uncovered during angiography for an acute heart attack elsewhere in the coronary tree.

  • Following a previous heart attack

    Occluded arteries after prior MI are common, particularly where the infarct was not fully reperfused or presented late.

  • Red flag - rest pain or arrhythmia

    Ongoing rest pain, syncope or ventricular arrhythmia in a patient with known CTO warrants urgent cardiology input.

Treatment

How coronary CTO is treated in the UK.

Optimal medical therapy for everyone, with revascularisation by specialist CTO PCI or coronary bypass for the right patients.

  • Optimal medical therapy

    Antiplatelet, statin, ACE inhibitor, beta-blocker and anti-anginals such as nitrates, ranolazine or ivabradine, alongside risk-factor control.

  • Risk factor modification

    Smoking cessation, blood pressure control, glycaemic management, weight and structured exercise underpin every treatment plan.

  • Antegrade CTO PCI

    Wire escalation, parallel wire or subintimal tracking and re-entry techniques such as CrossBoss and Stingray from the proximal side.

  • Retrograde CTO PCI

    Access via septal or epicardial collaterals with reverse CART, used when antegrade approaches fail or anatomy favours it.

  • Hybrid CTO algorithm

    A structured switch between antegrade and retrograde strategies, achieving 85 to 95 per cent success in experienced UK centres.

  • Coronary artery bypass

    Surgical revascularisation for suitable multivessel disease, sometimes combined with valve surgery, discussed at the Heart Team.

  • Cardiac rehabilitation

    A structured programme of exercise, education and secondary prevention after revascularisation or a cardiac event.

  • Implantable defibrillator

    Selectively offered to patients with severely reduced LV function after optimal therapy to reduce sudden cardiac death risk.

What this guide is based on

The sources behind every claim on this page.

UK and European guidance, specialist society standards and the major CTO trials, current at the time of last review.

Key references

Guidelines and trials we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your cardiologist knows your heart, arteries and history. They can tell you which parts of this guide apply to you.

  • European Society of Cardiology. Guidelines on myocardial revascularisation.

  • British Cardiovascular Intervention Society (BCIS). CTO PCI standards and audit data.

  • NICE. Stable angina management (CG126) and acute coronary syndromes (NG185).

  • DECISION-CTO, EURO-CTO, REVASC and PERFECT trials of CTO revascularisation.

Red flags

When a CTO needs urgent attention.

Most CTOs are managed electively. These are the situations where cardiology input cannot wait for the next clinic.

  • Unstable angina or NSTEMI

    Rest pain, prolonged episodes or troponin rise mean acute coronary syndrome pathways take precedence over elective CTO planning.

  • STEMI in another territory

    A new ST-elevation MI needs immediate primary PCI to the culprit vessel, with any known CTO addressed later.

  • Decompensated heart failure

    New or worsening breathlessness with fluid overload requires urgent assessment before considering elective revascularisation.

  • Ventricular arrhythmia

    Sustained VT, VF or unexplained syncope in ischaemic heart disease warrants urgent cardiology and electrophysiology input.

  • Severe LV dysfunction

    An ejection fraction below 35 per cent changes the risk profile and prompts detailed viability and device therapy discussions.

  • Uncontrolled diabetes or hypertension

    Poorly controlled risk factors erode the benefits of any revascularisation and should be addressed alongside CTO planning.

  • Chronic kidney disease

    Reduced renal function raises the risk of contrast injury during PCI and shapes both timing and technique.

  • Frailty and multimorbidity

    Frailty, dementia and competing life-limiting illness may tilt the balance towards medical therapy alone.

  • Suspected SCAD

    Spontaneous coronary artery dissection needs a bespoke conservative-first approach rather than routine CTO PCI.

Living with it

A long-term condition, with a clear plan.

Four things that make the biggest difference day to day. Medicines, movement, symptom awareness and staying in the system.

A quiet reminder

Consistency beats intensity, every time.

Small, steady habits kept up for months do more than a heroic week that does not last.

  1. 01 Medicines

    Take the tablets, every day

    Antiplatelet, statin, ACE inhibitor and beta-blocker are the backbone. Consistency is what changes long-term outcomes.

  2. 02 Movement

    Rehabilitate, then keep moving

    Cardiac rehabilitation is safe, effective and often underused. Aerobic and resistance work protect the heart and mind.

  3. 03 Symptoms

    Know your angina pattern

    Track what triggers pain, how long it lasts and how quickly GTN works. Change of pattern is the signal to call.

  4. 04 Team

    Stay in the system

    Regular reviews, blood tests and imaging catch drift early. A CTO is a long-term condition, not a one-off event.

Frequently asked

Everything we get asked about coronary CTO.

Quick answers on diagnosis, medical therapy, CTO PCI success rates and how UK Heart Teams decide.

  • What is a coronary chronic total occlusion?

    A CTO is a complete, 100 per cent blockage of a coronary artery that has been present for at least three months. It is usually caused by atherosclerosis and often has collateral vessels supplying blood to the artery beyond the blockage.

  • How common are chronic total occlusions?

    CTOs are found in around 15 to 25 per cent of patients who have a coronary angiogram. Many are silent because collateral circulation partly protects the downstream heart muscle from ischaemia.

  • How is a CTO diagnosed?

    A CTO is confirmed on invasive coronary angiography, often after suggestive findings on ECG, exercise testing, echocardiogram or coronary CT angiography. Cardiac MRI, PET or stress echo may be added to assess whether the muscle beyond the blockage is still viable.

  • Do all CTOs need to be opened?

    No. Treatment is guided by symptoms, ischaemic burden, LV function and viability. Optimal medical therapy is offered to everyone. Revascularisation by PCI or bypass is reserved for troublesome angina, breathlessness, large amounts of viable muscle or reduced ejection fraction.

  • How successful is CTO PCI in the UK?

    At experienced high-volume UK centres, dedicated CTO operators achieve success rates of 85 to 95 per cent using antegrade, retrograde and hybrid techniques. Success is lower at less specialised centres, which is why complex cases are often referred.

  • What does the evidence say about opening CTOs?

    Trials such as DECISION-CTO were neutral for hard endpoints like death and heart attack, but REVASC, EURO-CTO and PERFECT show meaningful gains in angina, quality of life and exercise tolerance. Decisions are made case by case with the Heart Team.

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