What Is Chronic Total Occlusion of the Coronary Arteries?
Chronic total occlusion (CTO) of the coronary arteries refers to the complete and longstanding blockage of one or more coronary arteries, where the vessel’s narrowing reaches 100%. This results in a total loss of normal blood flow through the affected artery.
To be classified as chronic, the occlusion must have persisted for three months or longer. The process involves the gradual buildup of atherosclerotic plaque within the vessel wall, which progressively enlarges and eventually leads to complete blockage of the arterial lumen.
Unlike acute myocardial infarction, in which the artery becomes suddenly occluded and causes immediate symptoms of chest pain at rest, chronic total occlusions often do not produce symptoms at rest. This is due to the formation of collateral vessels, which supply blood to the heart muscle downstream of the occluded artery.
The atherosclerotic plaque is composed of fatty substances, cholesterol, calcium salts, inflammatory cells, and fibrous tissue, which accumulate over time along the arterial walls and restrict blood flow. Eventually, this accumulation can completely block the artery.
What Are the Symptoms of Chronic Total Occlusions?
Chronically occluded coronary arteries can cause a variety of symptoms related to insufficient blood supply to the heart muscle. These symptoms typically occur during physical exertion and are absent at rest, thanks to the collateral circulation supporting the affected heart area.
However, collateral vessels are usually small and delicate, and cannot meet the increased oxygen demand of the heart during exertion, resulting in anginal symptoms.
These include:
Chest pain, often described as pressure, heaviness, or burning in the center of the chest, which may radiate to the left arm, neck, or jaw. It is usually triggered by physical effort (e.g., walking, climbing stairs, lifting heavy objects) or emotional stress.
Shortness of breath, due to the heart’s inability to pump enough blood to meet the body’s needs, especially noticeable during activity or, in advanced cases, even at rest.
Fatigue and general weakness, due to reduced oxygen delivery to the heart tissues, even after mild exertion.
Other symptoms may include nausea, sweating, dizziness, or fainting, resulting from poor perfusion and oxygen supply.
Sleep disturbances may also occur, as these symptoms disrupt rest and are linked to cardiovascular dysfunction.
These symptoms arise as the heart tries to adapt to the reduced supply of blood and oxygen, making close monitoring and timely diagnosis critical to preventing serious cardiovascular complications.
What Causes Chronic Coronary Artery Occlusion?
The causes of coronary artery occlusion, leading to decreased blood flow to the heart, primarily include:
Progressive atherosclerotic disease, which causes the gradual narrowing and eventual total occlusion of the coronary arteries.
Collateral vessel development, which maintains partial blood flow to the affected myocardial area.
Thrombus (clot) formation due to rupture of atherosclerotic plaques, which may not cause symptoms (silent myocardial infarction) and lead to chronic occlusion and permanent necrosis of the heart tissue.
Atherosclerosis is the underlying process, involving the buildup of fatty substances, cholesterol, calcium salts, inflammatory cells, and fibrous tissue in the arterial walls. Over time, these plaques can completely obstruct the vessel.
This condition is worsened by risk factors such as high cholesterol, hypertension, diabetes mellitus, smoking, and obesity.
Another major contributor to total arterial occlusion is a history of coronary artery bypass grafting (CABG), which accelerates native vessel atherosclerosis.
Thrombosis is the second major cause of chronic total occlusions. When a plaque ruptures, it triggers the release of substances that promote clot formation. The resulting thrombus can fully occlude the artery, stopping blood flow and causing ischemia or even myocardial infarction.
In many cases, due to the absence of symptoms, patients do not seek immediate medical attention for coronary angiography or primary PCI (percutaneous coronary intervention). This leads to undiagnosed chronic occlusion, often discovered incidentally at a later stage.
All classic risk factors contribute to the development of atherosclerosis and thrombosis, including:
Elevated cholesterol
Arterial hypertension
Diabetes mellitus
Chronic kidney disease
Age
Sex
Smoking
Physical inactivity
Poor diet
Excess body weight
These factors worsen the atherosclerotic process and predispose to clot formation and vessel occlusion.
How Is Chronic Total Occlusion Diagnosed?
The diagnosis of chronically occluded coronary arteries involves a series of tests and procedures designed to assess the condition of the vessels and overall cardiovascular function.
Diagnosis is confirmed through invasive coronary angiography, which allows a full assessment of the problem, identifying:
The exact site of the occlusion
The length of the occluded segment
The collateral vessels supplying blood to the distal part of the chronically occluded artery and the corresponding heart muscle region
Additionally, CT coronary angiography provides not only confirmation of chronic total occlusion but also valuable information regarding the composition of the atherosclerotic plaque (e.g., soft plaque or calcified plaque), the precise location of the occlusion, and whether the blockage is near an arterial bifurcation.
Main Steps and Diagnostic Tests for CTO Assessment
1. Clinical Evaluation
The physician begins with a detailed history and symptom assessment—chest pain, dyspnea, and fatigue during exertion are key symptoms guiding the decision to attempt revascularization. Risk factors such as age, family history, hypertension, high cholesterol, diabetes, kidney disease, obesity, and a history of coronary artery bypass surgery (CABG) are evaluated.
2. Electrocardiogram (ECG)
This basic test records the heart’s electrical activity and may reveal rhythm disturbances or other abnormalities that indicate ischemia or a prior silent myocardial infarction.
3. Blood Tests
Laboratory tests assess cardiovascular risk factors (e.g., dyslipidemia, diabetes, kidney function) and the patient’s overall health status.
4. Echocardiogram (Transthoracic)
Evaluates overall heart function and regional wall motion abnormalities. In CTO, specific heart segments may appear hypo- or akinetic due to reduced blood flow.
Imaging and Functional Tests
5. Invasive Coronary Angiography
The gold-standard method for assessing coronary arteries. A catheter is introduced via the radial (wrist) or femoral (groin) artery and advanced to the coronary arteries. Contrast dye is injected to visualize the arteries under fluoroscopy and identify chronic occlusions.
6. Coronary CT Angiography (CCTA)
A non-invasive test involving IV contrast injection to visualize the coronary lumen and wall. If technically optimal, CCTA offers high sensitivity and specificity for identifying coronary artery disease.
It also allows:
Precise localization of the occlusion
Evaluation of plaque composition
Measurement of occlusion length
This data is crucial for planning PCI strategies (e.g., antegrade or retrograde approach, use of re-entry devices).
7. Cardiac MRI
Provides detailed images of the heart and assesses:
Global and regional heart function
Myocardial viability
Extent of permanent damage in the territory of the occluded artery
This is critical for deciding whether to revascularize: if the myocardium is completely scarred, benefit is minimal.
Stress MRI can assess reversible ischemia: the greater the ischemia, the stronger the indication for PCI.
8. Stress Echocardiography (Stress Echo)
A non-invasive test combining rest and stress echocardiography using dobutamine or exercise. Increasing stress levels help assess:
Chest discomfort, dyspnea, fatigue
ECG changes or arrhythmias
Wall motion abnormalities
Contrast agents may be used to enhance image quality in patients with poor acoustic windows. Stress echo also helps determine myocardial viability and ischemic burden—the more ischemia, the greater the need for revascularization.
9. Myocardial Perfusion Imaging (SPECT)
A non-invasive test using radioactive tracers (thallium or technetium) to assess myocardial blood flow before and after stress, either pharmacologically (e.g., regadenoson, dipyridamole) or via exercise.
Decreased tracer uptake during stress compared to rest indicates reversible ischemia. This test also provides insight into myocardial viability in the affected territory.
Choosing the Right Diagnostic Test
The choice of test or combination of tests depends on the patient’s clinical profile and the physician’s level of suspicion for coronary artery disease.
Accurate diagnosis is critical for effective management and for determining the appropriateness of revascularization in patients with chronic total occlusion.
How Is Chronic Total Occlusion of the Coronary Arteries Treated?
Chronic total occlusions (CTOs) of the coronary arteries are common. The prevalence of CTOs among patients undergoing diagnostic coronary angiography is estimated at 20–30%, and in patients with a history of coronary artery bypass grafting (CABG), the prevalence exceeds 50%.
The treatment of CTO involves a combination of medical therapy and interventional procedures, depending on the patient’s condition and the extent of the occlusion.
Medical Management
The initial approach typically includes conservative pharmacological treatment to control symptoms and improve cardiovascular health.
Patients are often prescribed:
Antiplatelet agents (e.g., aspirin, clopidogrel) to reduce the risk of cardiovascular events
Cholesterol-lowering drugs (e.g., statins) to slow or reverse atherosclerosis
Beta-blockers, nitrates, calcium channel blockers, and angiotensin-converting enzyme (ACE) inhibitors to reduce cardiac workload, improve function, and relieve angina symptoms
If symptoms persist despite optimal medical therapy—such as chest tightness, shortness of breath, and fatigue—revascularization is considered the most effective strategy to alleviate symptoms.
In addition, CTO revascularization may:
Reduce the risk of arrhythmias
Lower the danger of an acute myocardial infarction in another artery, a situation known as the “double jeopardy” theory
Percutaneous Coronary Intervention (PCI)
For patients with single or double-vessel disease, PCI with stent placement is one of the primary invasive treatments to restore blood flow in occluded arteries.
Revascularization of CTOs is technically more complex than PCI for non-occlusive lesions and requires:
Specialized tools such as dedicated guidewires, microcatheters, and re-entry devices
Techniques using antegrade (forward) or retrograde (reverse) approaches
In either approach, the guidewire may pass through the subintimal space (within the vessel wall), requiring dissection and re-entry techniques like:
Antegrade dissection and re-entry (ADR)
Reverse controlled antegrade and retrograde subintimal tracking (reverse CART)
In the hands of experienced interventional cardiologists, CTO PCI success rates reach 85–90%.
Risks of CTO PCI
The overall complication rate is 1–2%, particularly with retrograde access. Risks include:
Cardiac arrest / death: 0.4%
Stroke: 0.1%
Cardiac tamponade requiring pericardiocentesis: 0.5%
Coronary artery perforation: 3.2%
Periprocedural myocardial infarction: < 3%
Contrast-induced acute kidney injury: < 1%
Indications for CTO PCI
Angina symptoms or angina equivalents (e.g., exertional dyspnea)
Symptoms refractory to medical therapy
Multiple prospective clinical trials and retrospective studies have shown that successful CTO PCI significantly improves symptom burden and quality of life.
The decision for revascularization should follow a shared discussion between the cardiologist and the patient, weighing benefits versus procedural risks.
Surgical Revascularization (CABG)
If PCI is not feasible or unsuccessful, bypass surgery may be required. This involves creating a new pathway for blood flow around the blockage using a graft—either a healthy vein from another part of the body or a synthetic conduit.
Comprehensive Management
Managing CTO requires a multidisciplinary approach including:
Medical therapy
Interventional or surgical revascularization
Lifestyle modifications such as a heart-healthy diet, regular exercise, and smoking cessation
With appropriate treatment and follow-up, patients can experience significant improvement in quality of life and a reduced risk of major cardiovascular events.
