Quick answer
What Is Optical Coherence Tomography?
Cardiac optical coherence tomography (OCT) is an imaging test from inside the coronary arteries using a thin catheter that emits infrared light. Its images are very detailed, helping to see plaque, choose the stent size, and make sure the stent is placed properly. OCT is done during catheterization and adds about 10 to 15 minutes to the procedure.
Sources01 / Understanding the procedure
About Optical Coherence Tomography
What Is Optical Coherence Tomography (OCT)
Optical coherence tomography, abbreviated OCT, is imaging from inside the coronary arteries using infrared light. The coronary arteries are the vessels that carry blood to the heart muscle. A very thin catheter is inserted during cardiac catheterization and records cross-sectional images of the vessel wall. In Indonesian, this test is called "tomografi koherensi optik", and it is also covered on the Optical Coherence Tomography page.
The term OCT is also used for an eye test that captures images of the layers of the retina. The light principle is similar, but cardiac OCT is performed inside the heart's blood vessels by an interventional cardiologist.
Why Doctors Recommend OCT
Coronary angiography only shows the outline of the vessel's inner channel, like a silhouette. OCT complements it by showing the vessel wall and plaque in detail. The doctor may recommend it to plan the stent size, check a stent after it is placed, find the cause of an old stent that has narrowed or become blocked, or find the cause of a heart attack that is not visible on angiography, for example a tear in the artery wall.
How OCT Captures Images
Light cannot pass through blood. For this reason, during the few seconds of image capture, blood in the artery is cleared with a flush of contrast dye while the catheter is pulled back automatically. The result is hundreds of cross-sectional images with detail about ten times finer than IVUS, a similar imaging method that uses sound waves. On the other hand, IVUS penetrates deeper and does not require a contrast flush.
Terms You May Read in the Report
Stent expansion assesses whether the stent has opened wide enough. Apposition assesses whether the stent sits firmly against the artery wall. Edge dissection is a small tear at the end of the stent. For plaque, the doctor may mention calcified plaque, lipid-rich plaque, or a thin fibrous cap, meaning plaque that ruptures more easily. The doctor will explain what these findings mean for you.
What Guidelines and Research Say
The 2024 ESC guidelines recommend imaging from inside the vessel, with IVUS or OCT, to guide stent placement in complex narrowings such as the left main coronary artery, branch points, and long narrowings. A pooled analysis of many studies shows that this approach reduces heart attacks, cardiac death, and repeat procedures compared with angiography guidance alone. In simple narrowings, angiography is often sufficient.
OCT, IVUS, and FFR
All three are performed during catheterization, but their purposes differ. OCT and IVUS show images of the vessel wall, while FFR measures flow pressure to assess whether a narrowing truly limits blood flow. The doctor may use more than one method in a single procedure.
02 / Understanding the procedure
When Is This Procedure Considered?
A doctor may consider this procedure in the situations below. The decision is always made after a thorough assessment.
- Planning a Stent in Complex NarrowingsFor example, narrowings at a branch point, long narrowings, or heavily calcified plaque.
- Checking a Stent After PlacementAssesses whether the stent is fully expanded and sits firmly against the wall, so it can be corrected in the same procedure.
- Finding the Cause of Problems with an Old StentWhen a stent has narrowed again or has a clot inside, to choose suitable treatment.
- Heart Attack with an Unclear CauseFor example, a suspected spontaneous tear in the coronary artery wall or a heart attack without a severe narrowing.
- Uncertain Narrowing on AngiographyWhen the shape of the narrowing or the type of plaque cannot be clearly seen from the angiography image.
Situations to Consider First
- Severely Reduced Kidney FunctionOCT requires additional contrast dye, so IVUS may be a more suitable option.
- Narrowing Right at the Origin of a Coronary ArteryBlood is hard to clear at a site that joins the aorta, so IVUS is often preferred.
- Unstable Emergency SituationsWith very low blood pressure or shock, the main treatment comes first.
- Very Narrow or Tortuous VesselsThe OCT catheter may not be able to pass, so the narrowing needs to be widened first with a small balloon.
03 / Before the procedure
How Should You Prepare?
OCT is performed as part of cardiac catheterization or PCI, so the preparation follows that procedure. The team will give you written instructions.
Tests before the procedure. Blood tests, including kidney function and blood clotting, and an ECG.
Medications. Bring a list of all your medications. Antiplatelet medications are usually continued, while other blood thinners and metformin may need to be adjusted. Do not change any medication without your doctor's instructions.
Kidneys and allergies. Tell the team if you have kidney disease or have ever had an allergy to contrast dye, because OCT requires additional contrast.
Fasting and a companion. Follow the fasting instructions from the team and arrange for a companion, because you are advised not to drive after the procedure.
Unsure about the preparation instructions? Ask our team before the procedure.
04 / During the procedure
How Is the Procedure Done?
OCT is performed in the cardiac catheterization room (cath lab) under local anesthesia, and you stay awake. The whole catheterization usually takes about one hour, longer if a stent is placed; the OCT step itself adds about 10 to 15 minutes.
Access and Angiography
A small tube is inserted through an artery in the wrist or groin. Contrast dye is injected to map the coronary arteries and identify the section to be examined.
Inserting the OCT Catheter
A thin guidewire is passed across the narrowing, and the OCT catheter is then advanced over the wire. Blood-thinning and vessel-widening medications are given to prevent clots and vessel spasm.
Recording the Images
Contrast is flushed for a few seconds while the catheter is pulled back automatically. You may feel warmth or brief discomfort in your chest.
Reading the Results
The doctor reviews the images on the screen right away to decide the stent size or to correct a stent that is not fully expanded, and OCT can then be repeated.
05 / Benefits and risks
Benefits and Risks Should Be Discussed Together.
Every medical procedure has benefits and risks. Your doctor will explain both for your situation before the procedure.
Benefits You Can Expect
- Detailed Images of the Vessel WallShows the type of plaque and the layers of the vessel wall that are not visible on angiography.
- A More Suitable Stent SizeThe stent diameter and length are chosen from vessel measurements taken directly.
- Corrections in the Same ProcedureA stent that is not fully expanded or not firmly attached can be expanded again right away.
- Fewer Repeat EventsIn complex narrowings, imaging guidance reduces heart attacks and repeat procedures compared with angiography alone.
- Finding Hidden CausesHelps identify the cause of a heart attack or a stent problem that is not visible on angiography.
The benefits of a procedure are not a promise of a cure. Ask how the results will affect your care plan.
Risks You Should Know
- General Catheterization RisksBleeding or bruising at the puncture site, which is usually mild and can be treated.
- Additional Contrast DyeCan affect kidney function, especially if kidney function was already reduced beforehand.
- Brief Chest DiscomfortWhile blood is cleared, flow to the heart muscle decreases for a few seconds and then returns.
- Vessel Spasm or Rhythm DisturbancesThese are rare and usually resolve quickly with medication.
- Injury to the Coronary Artery WallVery rare, for example a tear or clot that requires prompt treatment such as stent placement.
Risks can differ from person to person. A full explanation and consent are given after an individual assessment.
06 / After the procedure
What Is Recovery Like?
Recovery follows the catheterization or PCI performed at the same time.
After the procedure. A compression band is placed on your wrist for several hours, or you lie with your leg straight if the puncture was in the groin.
Length of stay. After stent placement, patients usually stay one night. If only the test is done, some patients can go home the same day.
Results. The doctor explains the OCT findings and the next plan, usually before you go home. Keep the procedure report for your next follow-up visit.
Drink water. If you have no fluid restrictions, drinking enough water helps your kidneys clear the contrast dye.
Warning signs to watch for. Go to the emergency room right away if you experience:
- Chest pain, shortness of breath, or cold sweats
- Bleeding or growing swelling at the puncture site
- The hand or leg used for the puncture becomes cold, pale, or numb
- A rash, itching, or shortness of breath after receiving contrast dye
Know the Signs That Need Prompt Care.
Follow the team's guidance on warning signs. If severe or sudden symptoms appear after the procedure, go to the nearest emergency department right away or call Heart Attack Center 1500 258.
07 / Team and support
Doctors and Procedure Support
The doctors below are listed for this procedure. Listed by name, not by ranking.
dr. Adrianus Kosasih, Sp.JP(K)
Interventional Cardiology
Coronary Intervention Procedures
Clinical focusPrimary Coronary Intervention · PCI for Acute Coronary Syndrome
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Dr. dr. Dafsah A. Juzar, Sp.JP(K)
Interventional Cardiology
Coronary Intervention Procedures +1 center
Clinical focusComplex Coronary Intervention · Cardiac Catheterization
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Dr. med. dr. Denio A. Ridjab, Sp.JP(K)
Interventional Cardiology
Coronary Intervention Procedures +2 centers
Clinical focusInterventional Cardiology · Coronary Artery Disease
View ProfileRotational Atherectomy System
A system for treating calcified plaque in the coronary arteries. A small diamond-coated burr spins at high speed over a guidewire…
Intravascular Lithotripsy (IVL) System
A special balloon catheter that emits pulses of sonic pressure waves to crack calcium in the coronary artery wall. It is used…
Intracoronary Imaging System (IVUS / OCT)
Imaging from inside the coronary artery using ultrasound (IVUS) or near-infrared light (OCT). It is used during catheterization…
The availability of technology and test support is confirmed with the team. Technology is chosen according to clinical need.
08 / Common questions
Before You Plan the Procedure.
Questions people often ask about cardiac OCT, from how it differs from eye OCT to the meaning of terms in the report.
Is cardiac OCT the same as eye OCT?
No. Both use the same light principle, but their purposes differ. Eye OCT captures images of the retinal layers from outside the eye without any procedure. Cardiac OCT, called "tomografi koherensi optik" in Indonesian, is performed from inside the coronary arteries with a catheter during catheterization to look at plaque and stents. Another explanation is covered on the Optical Coherence Tomography page.
Does OCT hurt?
You cannot feel the catheter moving inside the blood vessel, and the puncture site has already been numbed with local anesthesia. When contrast is flushed for a few seconds to capture images, some patients feel warmth or brief discomfort in the chest. This feeling usually goes away within seconds. Tell the team if the discomfort does not go away quickly.
Does every stent placement require OCT?
Not always. Imaging from inside the vessel is mainly recommended for complex narrowings, for example long narrowings, branch points, or heavily calcified plaque. For simple narrowings, the doctor may decide that angiography is sufficient. The doctor may also choose IVUS instead of OCT. Ask during your consultation whether this imaging is planned for you.
What does it mean if the OCT report says the stent is not fully attached?
It means there is a small gap between the stent and the artery wall, or the stent has not expanded as wide as expected. This finding is usually corrected right away in the same procedure by inflating a balloon again inside the stent, and then OCT is repeated. If you have questions about the terms in your report, ask your doctor at your follow-up visit.
Is OCT safe for the kidneys?
OCT requires additional contrast dye to clear the blood while images are taken. With normal kidney function, this additional amount is generally safe. If kidney function is already reduced, the doctor limits the amount of contrast, gives IV fluids, or chooses IVUS, which does not require additional contrast. Kidney function can be checked again after the procedure.
What is the difference between OCT, IVUS, and FFR?
OCT and IVUS both show images of the vessel wall from the inside. OCT uses light and is more detailed, while IVUS uses sound waves, penetrates deeper, and does not need a contrast flush. FFR does not produce images, but measures flow pressure to assess whether a narrowing needs to be opened. The doctor chooses based on the condition of your arteries.
Sources and Medical Review
Translated from the Indonesian edition medically reviewed by dr. Adrianus Kosasih, Sp.JP(K).
Sources as cited in the Indonesian edition.
- Räber L, Mintz GS, Koskinas KC, et al. Clinical use of intracoronary imaging. Part 1: guidance and optimization of coronary interventions. An expert consensus document of the European Association of Percutaneous Cardiovascular Interventions. Eur Heart J. 2018;39(35):3281-3300.
- Vrints C, Andreotti F, Koskinas KC, et al. 2024 ESC Guidelines for the management of chronic coronary syndromes. Eur Heart J. 2024;45(36):3415-3537.
- Ali ZA, Landmesser U, Maehara A, et al. Optical Coherence Tomography-Guided versus Angiography-Guided PCI. N Engl J Med. 2023;389(16):1466-1476.
- Holm NR, Andreasen LN, Neghabat O, et al. OCT or Angiography Guidance for PCI in Complex Bifurcation Lesions. N Engl J Med. 2023;389(16):1477-1487.
- Lee JM, Choi KH, Song YB, et al. Intravascular Imaging-Guided or Angiography-Guided Complex PCI. N Engl J Med. 2023;388(18):1668-1679.
- Stone GW, Christiansen EH, Ali ZA, et al. Intravascular imaging-guided coronary drug-eluting stent implantation: an updated network meta-analysis. Lancet. 2024;403(10429):824-837.