Continuing Education Activity

Chronic coronary occlusion or chronic total occlusion (CTO) has a wide spectrum ranging from subtotal to total coronary involvement. The diagnosis is made by clinical/laboratory findings and angiography. Treatment depends on the extent and severity of the disease, which includes lifestyle modifications, medical therapy, percutaneous intervention, and coronary artery bypass grafting. This activity reviews the evaluation and treatment of chronic coronary occlusion and highlights the role of the interprofessional team in the care of patients with this condition.

Objectives:

• Identify the etiology of chronic coronary occlusion.
• Review the appropriate steps for the evaluation of chronic coronary occlusion.
• Outline the management options available for chronic coronary occlusion.
• Summarize interprofessional team strategies for improving care coordination and communication to advance the care of chronic coronary occlusion and improve outcomes.

Introduction

Chronic coronary occlusion or chronic total occlusion (CTO) refers to complete luminal diameter stenosis with resultant thrombolysis in myocardial infarction (TIMI) grade flow 0 or 1.[1] In such, there is no anterograde flow due to collaterals.[2] The occlusion should be of at least three months' duration to be labeled as chronic.[3] The main vessels that are affected due to CTO are the right coronary artery (43% to 55%), the left anterior descending artery (approximately 24%), and the left circumflex artery (17%-20%).[4][5] Functional CTOs represent severe occlusion, but not a complete occlusion of the coronary arteries. Such functional CTOs have collateral circulations presenting as anterograde flow.[6] However, even such collateral flow is unable to sustain future ischemic events in functional CTOs, indicating a need for revascularization.[7]

Etiology

Chronic total occlusions arise from a coronary thrombus that later becomes organized and fibrotic.[8] 40% of patients with chronic coronary occlusion have had a history of myocardial infarction.[2] The risk factors of developing a chronic total occlusion are similar to those of coronary artery disease.

Epidemiology

The prevalence of total coronary occlusion seems to range from 18% to 35% of patients with coronary artery stenosis.[2][4][9] Chronic coronary occlusion is more predominant in males (85% to 98%) and the older population (median age around 64). However, a significant association of age and sex with procedural success has been inconsistent.[4][5] Increasing age seems to be associated with a higher risk of chronic coronary occlusion of the right coronary and left anterior descending arteries but not of the circumflex artery.[10]

Pathophysiology

CTO is due to complete or near-complete occlusion of a coronary artery, which is characterized by atherosclerotic plaque burden. Though such patients have collaterals, the collaterals are insufficient to sustain myocardial perfusion. This insufficiency leads to angina and ischemic symptoms.[11] Acute total occlusion (ATO) can present as an ST-elevated myocardial infarction.[12] It is important to recognize the difference between CTO and ATO. Management strategies of ATO versus CTO are totally different.[11] Furthermore, patients with CTO can present with acute coronary syndrome.[13]

Histopathology

Autopsy findings indicate that the total occlusion of coronary arteries happens due to the thrombus. The thrombus later gets reorganized with collagen dense fibrous tissues at the proximal and the distal end. As the lesion ages, the plaque becomes calcified and loses its previous microchannels.[14] Furthermore, histological studies have identified that the proximal part of the plaque is firmer than their distal part.[15] These histological changes are important when considering revascularization either through an anterograde or a retrograde approach.[16]

History and Physical

In general, history findings depend on the stage of coronary artery occlusion. The symptoms are related to myocardial ischemia or myocardial contractibility.[17] Patients can present with chest pain, shortness of breath, or tiredness. Patients with subtotal occlusion complain of chest pain, shortness of breath aggravated by exertion, and easy fatiguability. The symptoms usually resolve at rest. However, patients with total occlusion of coronary arteries have symptoms at rest and are refractory to medical therapy. Clinicians should take a detailed history to rule in or rule out important risk factors, i.e., family history, smoking, obesity, high blood pressure, decreased physical activity, excessive alcohol, diabetes, and a sedentary lifestyle.

Physical examination includes a complete general physical examination to look for xanthomas and general assessment of blood circulation followed by a detailed cardiovascular examination.

Evaluation

Electrocardiogram (EKG) can show ischemic changes in patients with chronic coronary occlusion. However, these findings are non-specific for diagnosis.[18] A chronic coronary occlusion is most often discovered on coronary angiography due to anginal chest pain, possible revascularization due to angina refractory to medical therapy, or diagnostic testing suggestive of myocardial ischemia or after a positive stress test. In coronary angiography, a catheter is inserted into a blood vessel of the leg or wrist. The catheter is advanced towards the heart, and the dye is injected into the blood vessels of the heart, which allows the clinician to see the flow of blood through coronary arteries and identify chronic coronary occlusion. Furthermore, patients with chronic coronary occlusion tend to be older, have comorbidities, and greater impairment of left ventricular function.[19]

Treatment / Management

Treatment mainly depends on the extent and severity of the disease and includes lifestyle modifications, medical therapy, and procedures like percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG).

Subtotal coronary occlusion is usually managed medically along the line of stable angina. Beta-blockers are preferred for initial treatment for the prevention of anginal symptoms.[20][21] Calcium channel blockers and long-acting nitrates are alternatives if beta-blockers are contraindicated or cause side effects; they can also be added as combination therapy if monotherapy is not successful.[22] Short-acting nitrates are used for immediate angina relief. Therapies known to prevent disease progression and reduce the incidence of adverse cardiovascular should also be started. These include aspirin, lipid-lowering therapy, smoking cessation, control of blood pressure, weight loss, and optimal management of diabetes mellitus.[23][24] Regular exercise and stress reduction are also recommended. The optimal management of these patients also requires periodic evaluation (every 6 to 12 months) of the patient's clinical status, using the history, physical examination, EKG, and echocardiogram.

Total coronary occlusion or subtotal occlusion refractory to medical therapy is managed by either percutaneous coronary intervention or coronary artery bypass grafting.[25][26]The choice of procedure depends on the involvement of coronary arteries.

In single-vessel disease, PCI is preferred over CABG. PCI is a minimally invasive procedure that involves an incision in the groin or wrist area. A wire is passed through the main blood vessel to the blocked artery in the heart. An opening is created in the blocked region with the help of guidewire. After this, a catheter is passed over the wire, then a balloon is inflated at the site of blockage to displace the plaque, and a stent is placed to normalize the blood flow and keep the artery open. In multivessel disease, CABG is the preferred.[27]

Differential Diagnosis

Many diseases presenting with chest pain and shortness of breath may resemble chronic coronary occlusion.

Most common of these are:

• Atherosclerosis
• Angina pectoris
• Unstable angina
• Coronary artery vasospasm
• Myocardial infarction
• Hypertensive heart disease
• Isolated coronary artery anomalies

Prognosis

Prognosis mainly depends on the severity of the disease. Those with subtotal chronic coronary occlusion have a better prognosis than with total chronic coronary occlusion. Total coronary occlusion is associated with a worse overall prognosis, with higher rates of death and non-fatal adverse cardiovascular events in several populations.[2][19] 

Patients with un-revascularized CTOs have been found to have higher mortality and a higher risk of major adverse cardiovascular events, including death from myocardial infarction compared to patients with multivessel coronary artery disease who are completely revascularized.[28][29]

Complications

The complications of the disease itself include a higher risk of cardiovascular events such as arrhythmias, myocardial infarction, and death. Complications can also occur during PCI, which includes major adverse cardiovascular events, myocardial infarction, significant Ellis grade ≥3 perforation, bleeding requiring treatment, acute kidney injury, and death and graft rejection in CABG.[30][31]

Deterrence and Patient Education

Successful revascularization improves long term survival, reduced need for coronary artery bypass graft, and an improvement in left ventricular systolic function in patients with CTO.[32][33] Smoking, high blood pressure, and diabetes are strongly associated with CTO.[34] Educating patients and establishing a supportive relationship are the most important steps in treating patients with chronic coronary occlusion. The clinician should educate the patients regarding the disease process, its nature and act to establish therapeutic goals like accomplishing lifestyle modifications, medication compliance, and adherence and explaining the risks/benefits of procedures. Moreover, patient education brochures and other materials related to disease should also be offered.

Enhancing Healthcare Team Outcomes

Chronic coronary occlusion has a wide spectrum, ranging from subtotal to total coronary involvement. Management of CTO should involve an interprofessional team that includes interventional cardiology, cardiac surgery, radiology, primary care, nursing staff, and pharmacists. The diagnosis is made by clinical/laboratory findings and angiography. Treatment depends on the extent and severity of the disease, which includes lifestyle modifications, medical therapy, percutaneous intervention, and coronary artery bypass grafting.

Review Questions

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• Comment on this article.

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Disclosure: Moghniuddin Mohammed declares no relevant financial relationships with ineligible companies.

Disclosure: Moien AB Khan declares no relevant financial relationships with ineligible companies.