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Chronic Total Occlusion (CTO)


Coronary artery disease (CAD) is the leading cause of death—and the most common type of heart disease—in the United States, where it affects around 18 million adults. It occurs when plaque builds up in the coronary arteries, reducing the amount of blood that reaches the heart.

But it’s important to know that there are differences in how blocked the coronary artery can become. When a coronary artery becomes completely blocked—not simply narrowed—it is called a total occlusion. And if a complete blockage lasts for 3 months or longer, doctors refer to it as “chronic total occlusion,” or CTO for short. People with CTO may experience chest pain, shortness of breath, and fatigue, and they are also at increased risk for heart attack and other serious heart problems.

CTO is a common condition. It may be seen in one in five individuals who undergo coronary angiography, an imaging test used to assess blood flow through the arteries. Fortunately, treatments are available that can help reduce chest pain and discomfort, along with other symptoms.

“The treatment of a CTO is more complex than a standard coronary angioplasty,” says Yale Medicine interventional cardiologist Glen Henry, MD. “Because the artery is completely closed often the path of the artery is not entirely clear. Usually two catheters are placed—one to clarify the path forward of the artery, and the other to show the collateral flow from other vessels to the affected region. Using special techniques these two regions are connected back together again, usually with the placement of stents. Sometimes more than one procedure is required to produce an optimal durable result.”

What is chronic total occlusion?

The heart is a muscle that needs to be constantly supplied with oxygen-rich blood to stay healthy. This oxygen-rich blood is delivered by the coronary arteries.

In people with CAD, plaque slowly accumulates within the walls of the coronary arteries, restricting blood flow to the heart (known as atherosclerosis). If enough plaque builds up, it can completely block the artery. Plaques can also suddenly block the artery when they cause blood clot formation, leading to acute coronary syndrome or heart attack.

CTO occurs when the complete blockage of a coronary artery lasts for three months or longer.

What are the risk factors for chronic total occlusion?

The risk factors for CTO are the same as those for CAD. They include:

What are the symptoms of chronic total occlusion?

Symptoms of CTO may include:

  • Chest pain or discomfort
  • Shortness of breath with activity and while at rest
  • Feeling tired

How is chronic total occlusion diagnosed?

To diagnose CTO, a doctor will review your medical history, conduct a physical exam, and order one or more diagnostic tests.

Ultimately, for diagnosis, a CTO must be documented by coronary angiography. In this test, a doctor inserts a catheter—a thin, flexible tube—into an artery in the wrist or groin, then guides it through the blood vessel to the heart. A contrast liquid is injected through the catheter and into the blood vessels near the heart, then X-ray images are taken. The contrast liquid allows doctors to see how blood flows through the coronary arteries and identify blockages. A CTO is diagnosed when a coronary artery is completely blocked. Often, there are small blood vessels (known as collaterals) that grow towards the blocked artery to maintain some blood flow to the affected region of the heart. In some cases, CTO is diagnosed in patients who are undergoing a coronary angiogram for another cardiovascular condition.

Your doctor may order additional tests to evaluate how well your heart and coronary arteries are working. These may include an echocardiogram (an ultrasound of the heart), a stress test, or a magnetic resonance imaging (MRI) scan to evaluate the function of the heart and assess the likelihood of a successful procedure. A stress test involves an electrocardiogram (EKG) of the patient’s heart while it is put under stress, usually by exercise such as walking on a treadmill or riding a stationary bicycle.

What are the treatments for chronic total occlusion?

The choice of treatment for CTO depends on the severity of the disease and symptoms. Treatments include:

  • Medications. A number of drugs may be used to ease the work of the heart, slow or stop arterial plaque buildup, and reduce symptoms. Medications may include anti-platelet medications, beta-blockers, ACE inhibitors, angiotensin receptor blockers (ARBs), calcium channel blockers, statins, and nitrates, among others. All of these medications are designed to reduce symptoms and improve quality of life. If limitations and symptoms remain, additional interventions may be necessary.
  • Percutaneous coronary intervention (PCI). In this minimally invasive procedure, an interventional cardiologist inserts a small tube called a sheath (similar to an IV) into a blood vessel in the wrist or groin. Next, a catheter (a smaller tube) is placed within the sheath and directed through it to the heart and ultimately to the affected coronary artery. The interventional cardiologist then inserts a thin guidewire through the catheter and across the narrowed or blocked section of the artery. This is followed by insertion of a second smaller catheter, equipped with a balloon that is inflated when it’s within the narrowed or blocked section of the artery. The balloon opens the artery and restores blood flow through it to the heart. The doctor may place a stent—a mesh tube—into the newly opened section of the blood vessel. The stent holds the artery open, allowing blood to flow through the artery.

  • Coronary artery bypass grafting (CABG). Also known as coronary artery bypass surgery or just bypass surgery, in CABG a surgeon grafts one end of a healthy vein or artery taken from elsewhere in the body to the aorta and the other end to the affected coronary artery at a point past the blockage. The blockage remains in place in the coronary artery, but the newly attached blood vessel reroutes blood around it, bypassing it. CABG is typically done by opening the chest through the sternum (breastbone).

What is the outlook for people with chronic total occlusion?

The goal of CTO treatment has several components. The first is to improve and hopefully resolve lifestyle-limiting symptoms of angina. The second is to maintain a lasting result; the third is to ensure that certain risk factors for CAD are well-controlled, with the aim of minimizing the risk of future CAD-related problems.

In addition to seeing a specialist for treatment, it is important that people with CTO—even after treatment—make heart-healthy lifestyle changes such as quitting smoking, exercising, getting blood pressure and cholesterol levels under control, and maintaining a healthy weight.

What stands out about Yale Medicine's approach to chronic total occlusion?

At Yale, our Complex Coronary Intervention Program focuses on the treatment of patients with severe coronary artery disease and, in particular, patients with CTO,” says Yale Medicine interventional cardiologist Yousif Ahmad, BMBS, PhD. “Our multidisciplinary team looks at each case in detail and works together to make the determination of the best treatment option for each patient. We have specialists who have undertaken specific, dedicated training in the performance of CTO PCI, so that we can offer our patients the best possible outcomes. We also perform these procedures with two dedicated and experienced operators, to make the procedure as safe and efficient as possible.”