Percutaneous Coronary Intervention for Chronic Total Occlusions: Indications and Outcomes

Definition and pathophysiology

A chronic total occlusion (CTO) is a complete or nearly complete coronary arterial obstruction that has persisted for at least 30 days. CTOs are common among patients undergoing coronary angiography, with reported prevalence ranging from 18% to 52%. They frequently occur in patients with severe coronary artery disease, defined in the source material as stenosis greater than 70%, and are an important reason that patients are referred for coronary artery bypass grafting rather than percutaneous coronary intervention (PCI).

A CTO may be discovered incidentally during diagnostic angiography. Collateral vessels may maintain distal perfusion and permit visualization of the vessel beyond the occlusion when the patent donor artery is injected. The collateral circulation therefore has both physiological importance and procedural relevance.

The principal anatomical determinants of CTO PCI complexity are:

• The morphology of the proximal cap.

• The length, trajectory and composition of the occluded segment, including calcium.

• The quality of the distal target vessel.

• The configuration and adequacy of collateral channels.

Additional features associated with greater difficulty include a previously failed attempt, a blunt proximal stump, vessel bending, calcification and an occlusion length of at least 20 mm. These characteristics are incorporated into the J-CTO score, which estimates the likelihood of successful antegrade guidewire crossing within 30 minutes.

The clinical rationale for CTO PCI is principally the reduction of myocardial ischaemia and improvement of symptoms and quality of life. Restoration of patency may be particularly relevant when the occluded artery supplies viable myocardium with demonstrable ischaemia. However, randomized evidence has not shown a reduction in mortality or myocardial infarction with routine CTO PCI compared with medical therapy.

Clinical presentation and symptoms

A CTO may be asymptomatic and identified during angiography performed for another indication. When clinically significant, it may present with chronic angina, an anginal equivalent or exertional dyspnoea. Patients may continue to have lifestyle-limiting symptoms despite guideline-directed medical therapy (GDMT), prompting consideration of revascularization.

The likelihood that symptoms are attributable to the CTO is increased when non-invasive testing demonstrates significant inducible ischaemia and preserved viability in the myocardial territory supplied by the occluded artery. Conversely, an angiographically identified CTO without demonstrable ischaemia or viable myocardium provides a less compelling basis for intervention.

The source material does not provide a distinct symptom profile, physical-examination pattern or biomarker signature specific to CTOs.

Evaluation and physical examination

Evaluation should establish:

• The severity and functional impact of angina or anginal-equivalent symptoms.

• The response to GDMT.

• The extent of myocardial ischaemia.

• The presence of viable myocardium supplied by the occluded vessel.

• Left ventricular function.

• The anatomical complexity of the CTO and the suitability of the distal vessel.

• The patient’s procedural risk, comorbidities and preferences.

A multidisciplinary, shared decision-making process is appropriate when revascularization is being considered. The choice between PCI, coronary artery bypass grafting (CABG) and medical therapy should incorporate the clinical profile, coronary anatomy, left ventricular ejection fraction, procedural factors and anticipated outcomes.

The supplied material does not describe specific physical signs of CTO or a dedicated physical-examination algorithm.

Diagnostics

Non-invasive assessment of ischaemia and viability

Objective evidence of ischaemia is important before elective CTO PCI. Demonstration of both significant myocardial ischaemia and viability in the territory supplied by the occluded artery is generally accepted as a useful way to balance procedural risk against potential benefit.

Radionuclide perfusion imaging is particularly suitable because it can quantify the extent and severity of ischaemia. Stress echocardiography is another relevant modality. Positron-emission tomography (PET) provides additional quantitative information on myocardial blood flow and myocardial flow reserve, and may help assess the physiological importance of other coronary lesions and determine the extent of revascularization required.

Stress imaging may also characterize post-ischaemic dysfunction and assess whether abnormalities are reversible. In the source material, a patient with a left anterior descending artery CTO had severe reversible anterior and anteroseptal perfusion defects, preserved viability and a severely reduced myocardial flow reserve in the CTO territory.

Coronary angiography

Invasive coronary angiography defines the occlusion and its surrounding anatomy. The angiographic assessment should characterize:

• The proximal cap.

• The length and course of the occlusion.

• Vessel tortuosity and bending.

• Calcification.

• The distal vessel.

• The collateral circulation.

• The extent of disease in other coronary territories.

When collateral channels are present, injection of the patent donor artery can outline the vessel distal to the CTO and support retrograde procedural planning.

Computed tomography coronary angiography (CTCA) may also be used before CTO PCI. With appropriate coregistration, the segment not visualized angiographically can be integrated with CT images to guide guidewire advancement and clarify the course of the occluded artery.

Electrophysiology

The source material does not describe a specific electrophysiological role in the diagnosis or treatment of CTO PCI.

Procedural planning and technical strategy

CTOs are among the most complex coronary lesions and contribute substantially to the SYNTAX score. Antegrade guidewire crossing remains a central strategy, but retrograde techniques may be used when the distal vessel can be reached through suitable collateral channels.

The J-CTO score assists in estimating the probability of successful antegrade crossing within 30 minutes. A higher score reflects features such as prior failure, a blunt stump, bending, calcification and an occlusion length of at least 20 mm.

Success depends on lesion anatomy, the availability of dedicated equipment, operator experience and the use of complex antegrade or retrograde techniques. Contemporary equipment and procedural methods have increased CTO recanalization success rates to approximately 70–80% in the supplied material; another source describes success rates greater than 80% in experienced settings. CTO PCI success remains lower than the overall success rate of PCI, which is reported at approximately 95–99% for angiographic success in general cases.

Biomarkers and laboratory findings

No biomarker or laboratory abnormality is specific to a chronic total occlusion. The source material does not describe a diagnostic biomarker strategy for CTOs.

Laboratory testing is relevant to procedural risk assessment, particularly renal function. Chronic kidney disease is associated with greater risks during revascularization, including acute kidney injury, and with worse long-term outcomes than preserved kidney function. The supplied material does not specify a CTO-specific laboratory panel or biomarker threshold.

After PCI, small periprocedural myocardial infarctions may be detected only by elevations in creatine phosphokinase or troponin. Enzyme elevations greater than 10 times the upper limit of normal are associated with a less favourable long-term outcome, although this observation applies to PCI generally rather than specifically to CTO procedures.

Indications for CTO PCI

Symptomatic patients despite medical therapy

The principal indication is persistent, lifestyle-limiting angina or an anginal equivalent despite GDMT, provided the CTO is technically amenable to PCI. Revascularization is recommended in chronic coronary syndrome when symptoms persist despite guideline-directed treatment and there is functionally significant obstructive coronary disease.

For CTOs specifically, PCI may substantially reduce myocardial ischaemia and improve quality of life in experienced centres. Demonstrable ischaemia and viability in the CTO territory strengthen the rationale for intervention.

Selection of the revascularization modality

CTO PCI should not be considered in isolation from the overall coronary anatomy. Complete revascularization is generally preferred, particularly when all lesions causing ischaemia can be treated safely and effectively. Nevertheless, anatomical complexity, comorbidities, advanced age, frailty and procedural risk may make complete revascularization impractical.

CABG may be favoured when PCI is unlikely to achieve complete revascularization, when disease is diffuse or severely calcified, when there is diffuse in-stent restenosis, or when other surgical indications are present. Diabetes, left ventricular ejection fraction below 35% and contraindications to dual antiplatelet therapy are also factors favouring CABG in the broader revascularization decision.

In multivessel disease, the SYNTAX score is recommended to assess anatomical complexity. In patients with complex coronary disease, procedural risk and expected post-procedural outcomes should be assessed to support shared decision-making. A heart-team approach involving interventional cardiology and cardiothoracic surgery is recommended for relevant PCI-versus-CABG decisions.

CTO PCI is not routinely indicated solely for prognostic benefit

Available randomized trials have not demonstrated reductions in mortality or myocardial infarction with CTO PCI compared with medical therapy. The established benefits are primarily symptom relief, reduction of angina and improvement in quality of life.

Consequently, an asymptomatic or minimally symptomatic patient without demonstrable ischaemia or viable myocardium in the CTO territory has a less favourable rationale for elective CTO PCI. The source material does not provide a formal recommendation for intervention in such patients.

Late presentation after STEMI

Patients with an occluded infarct-related artery more than 48 hours after symptom onset, without persistent symptoms, should not undergo routine PCI of the occluded artery. They should instead be managed according to chronic coronary syndrome and CTO principles.

By contrast, in selected STEMI patients presenting 12–48 hours after symptom onset without persistent symptoms, a routine primary PCI strategy has been associated in the supplied material with improved myocardial salvage and long-term survival. This evidence concerns late STEMI presentation and should not be conflated with routine recanalization of a stable, persistently occluded infarct-related artery days after infarction.

Treatment and management

Guideline-directed medical therapy

Medical therapy remains the foundation of management for patients with CTOs, whether or not revascularization is performed. CTO PCI should generally be considered when symptoms remain limiting despite GDMT and when ischaemia, viability and anatomy support a favourable risk–benefit balance.

The supplied material does not list specific antianginal drug doses or a complete CTO-specific medical regimen. It does state that antiplatelet treatment is required in the context of coronary stent implantation.

PCI technique and stenting

When CTO PCI is undertaken and the occlusion is crossed, drug-eluting stents (DESs) are used to reduce late clinical recurrence. DESs are recommended in preference to bare-metal stents in all cases.

Intracoronary imaging should be used liberally to optimize stent deployment, particularly in complex CTO lesions. Intravascular ultrasound (IVUS) and optical coherence tomography (OCT) can assess stent expansion and apposition and may identify issues not evident on angiography. Imaging-guided PCI has been associated with improved outcomes in complex lesions, although the magnitude and consistency of benefit differ between individual studies and imaging modalities.

The broader guideline recommendations are:

Antiplatelet therapy after stenting

Stent thrombosis can occur acutely within 24 hours or subacutely between 1 and 30 days. Dual antiplatelet therapy (DAPT), consisting of aspirin plus a P2Y12 receptor blocker, reduces this risk. The P2Y12 options listed in the source material are clopidogrel, prasugrel and ticagrelor.

For second-generation DESs, a DAPT duration of 6 months is recommended in the supplied material, although longer treatment may be useful when atherothrombotic risk is high and bleeding risk is acceptable. After PCI for an acute coronary syndrome, treatment for up to 1 year should be considered.

Premature discontinuation is particularly hazardous during the first month after implantation and increases the risk of stent thrombosis approximately three- to nine-fold. Elective surgery requiring interruption of antiplatelet treatment should, where possible, be delayed until at least 3 months after DES implantation and preferably until after 6 months.

Stent thrombosis is associated with myocardial infarction in 30–70% of cases and death in 10–20% of cases in the supplied material.

Access and procedural safety

Radial access is the standard approach because it is associated with lower vascular and bleeding risk, greater comfort and shorter hospitalization than alternative access strategies. Selected low-risk patients may be eligible for same-day discharge after PCI.

Risk is increased in patients older than 65 years, those undergoing urgent or emergency procedures, patients with chronic kidney disease, STEMI, or shock. CTO PCI should therefore be performed in settings with appropriate equipment and experienced operators.

CTO PCI in chronic kidney disease

Chronic kidney disease complicates both pharmacological and revascularization decisions because of acute kidney injury, hyperkalaemia, hypotension and increased bleeding risk. Outcomes after revascularization are worse than in patients with preserved renal function.

In stable chronic coronary disease with advanced kidney disease and demonstrable ischaemia, an invasive strategy has not improved death or non-fatal myocardial infarction compared with intensive medical therapy in the supplied material. PCI increased the risk of stroke and initiation of dialysis in that population. These findings do not apply directly to patients with recent acute coronary syndrome, severe symptoms or heart failure with left ventricular ejection fraction below 35%, who were excluded from the cited trial.

In the absence of stronger evidence, revascularization is most clearly indicated in unstable disease or in patients with severe symptoms. Medical management alone is a reasonable option for patients with advanced chronic kidney disease and stable, minimally symptomatic disease.

Complications

Procedural complications

Serious complications of PCI are uncommon overall, but the risk is higher for CTO procedures and in patients with adverse clinical characteristics. Reported complications include:

• Death.

• Large myocardial infarction.

• Stroke.

• Coronary dissection.

• Acute thrombotic occlusion.

• Distal embolization of thrombotic or atherosclerotic material.

• Microvascular obstruction.

• Side-branch closure.

• Acute kidney injury.

• Stent thrombosis.

• Restenosis.

For elective PCI generally, mortality is reported as 0.1–0.3%, large myocardial infarction occurs in less than 3% and stroke in 0.1–0.4%. These figures are not CTO-specific.

Periprocedural myocardial infarctions are often small and detected only through post-procedural enzyme elevation. A rise in creatine phosphokinase or troponin greater than 10 times the upper limit of normal is associated with less favourable long-term outcome.

Stent thrombosis

All stents remain susceptible to thrombosis. Better initial deployment and DAPT reduce the risk. Second-generation DESs have lower rates of late and very late stent thrombosis than first-generation DESs.

Restenosis

Restenosis is the renarrowing of the treated coronary segment. Reported first-year restenosis rates are:

Modern-generation DESs have reduced restenosis to less than 10% in the broader PCI population described in the source material.

Clinical restenosis usually manifests as recurrent angina or related symptoms within 12 months, although presentation with NSTEMI or STEMI can occur. Risk factors include diabetes, myocardial infarction, long lesions, small vessels and a suboptimal initial result. Treatment generally consists of repeat PCI with balloon dilatation and another DES. Other options for symptomatic recurrent restenosis include drug-coated balloons, brachytherapy and CABG.

Guideline recommendations

The major recommendations relevant to CTO PCI can be summarized as follows:

• Revascularization is recommended to improve symptoms in patients with chronic coronary disease who have persistent angina or an anginal equivalent despite GDMT and functionally significant obstructive disease.

• Objective evidence of myocardial ischaemia should guide selection of lesions for revascularization.

• In CTO patients, assessment of ischaemia and viability in the subtended territory is useful for weighing benefit against procedural risk.

• PCI of a CTO is a reasonable option in appropriately selected patients with suitable anatomy and persistent symptoms, particularly when performed by experienced operators.

• CTO PCI improves angina and quality of life but has not demonstrated a reduction in mortality or myocardial infarction compared with medical therapy.

• Complete revascularization is generally preferred when safe and feasible, although functional completeness may be more clinically meaningful than purely anatomical completeness.

• The SYNTAX score should be calculated in multivessel obstructive disease to assess anatomical complexity.

• A heart-team approach and shared decision-making are appropriate when PCI and CABG are both potential strategies.

• IVUS or OCT guidance is recommended for anatomically complex PCI and should be considered more broadly to optimize stent implantation.

• Radial access is recommended as the standard PCI approach.

• DESs are recommended in preference to bare-metal stents.

• Routine PCI of an occluded infarct-related artery more than 48 hours after STEMI onset is not indicated in stable patients without persistent symptoms.

• In patients with advanced chronic kidney disease and stable, minimally symptomatic disease, medical therapy alone is a reasonable alternative to invasive revascularization.

Prognosis and follow-up

Clinical benefit

The principal expected benefit of successful CTO PCI is symptomatic: fewer anginal episodes, reduced ischaemia and improved quality of life. Benefits are most likely when symptoms persist despite GDMT and when testing demonstrates viable, ischaemic myocardium supplied by the occluded vessel.

Although randomized studies have shown improvements in angina and quality of life, they have not shown reductions in mortality or myocardial infarction. CTO PCI should therefore not be presented as routinely prognostic therapy in stable patients.

Long-term risks

Long-term outcome after PCI is strongly influenced by stent thrombosis, restenosis, progression of coronary disease and the completeness and functional adequacy of revascularization. If restenosis does not develop, long-term outcome is described as excellent in the supplied material.

Very late stent thrombosis and restenosis occurring after the first year are more likely to reflect neoatherosclerosis, whereas restenosis during the first year is more closely related to neointimal hyperplasia.

Follow-up strategy

Follow-up should reassess:

• Angina and exercise tolerance.

• Adherence to GDMT.

• Adherence to DAPT and bleeding complications.

• Recurrent symptoms suggestive of restenosis or stent thrombosis.

• Renal function in patients at risk of acute kidney injury or chronic kidney disease.

• Left ventricular function when clinically relevant.

• The need for repeat non-invasive ischaemia assessment or angiography if symptoms recur.

Routine repeat intervention in an asymptomatic patient is not supported by the information provided. Recurrent symptoms after CTO PCI require confirmation of significant restenosis or another flow-limiting lesion before repeat revascularization is undertaken.