Understanding the technology
About This Technology.
The Intracoronary Imaging System produces pictures of a coronary artery from the inside. A thin catheter with a sensor is passed into the artery during catheterization. IVUS uses sound waves, while OCT uses light. Doctors use it to assess plaque and vessel size, choose the stent size, and check that a stent is fully expanded and well attached.
Seeing the Coronary Artery from the Inside
Coronary angiography shows the inner channel of a blood vessel filled with contrast dye as a shadow, like a silhouette. It shows where a narrowing is, but not the artery wall or the plaque within it. Intracoronary imaging adds that missing view. A thin catheter with a sensor at its tip is passed over a guide wire into the coronary artery, then slowly pulled back while it records cross-sectional images of the vessel from the inside.
IVUS and OCT: Two Ways of Seeing
- IVUS (intravascular ultrasound) uses ultrasound waves. They reach deep into the artery wall, which makes IVUS well suited to measuring vessel size and the amount of plaque, including in the left main coronary artery.
- OCT (optical coherence tomography) uses near-infrared light. It shows finer detail of the inner surface of the artery wall, but blood must be briefly cleared with a flush of contrast dye during recording.
Your doctor chooses between them based on the condition of the artery and the purpose of the examination.
When Doctors Use It
Before a stent is placed, images from inside the artery help your doctor identify the type of plaque, such as soft or calcified plaque, and measure the diameter and length of the narrowing to choose the stent size. After the stent is placed, imaging is repeated to confirm that the stent is fully expanded, sits firmly against the artery wall, and has no tears at its edges. It is also used to find the cause of renarrowing inside an older stent and to clarify angiography findings that are unclear.
What You Will Experience
IVUS or OCT is done in the cath lab as part of coronary angiography or PCI, so the preparation is the same as for that procedure. You will not feel the imaging catheter inside the artery. Beforehand, your doctor usually gives a medication through the catheter to widen the artery. The imaging adds a few minutes to the procedure, and OCT needs a small amount of extra contrast dye. The risk is low, such as spasm, a brief narrowing caused by the artery wall muscle tightening, and the team monitors you throughout.
Not Every Patient Needs It
Many procedures can be guided by angiography alone. Your doctor decides whether intracoronary imaging is needed based on the location and complexity of the narrowing, for example at a branch point, in the left main coronary artery, in a long narrowing, or with heavy calcification. IVUS and OCT show the shape and content of a narrowing; to judge whether it limits blood flow, your doctor uses a different measurement, FFR or iFR.
Clinical use
Uses and Benefits.
Whether this technology suits your condition is decided by a doctor after an evaluation.
- Assessing plaque type and the degree of calcium in the coronary artery wall
- Measuring vessel diameter and narrowing length before choosing a stent
- Confirming that a stent is fully expanded and firmly against the artery wall
- Checking for small tears at the stent edges after placement
- Finding the cause of renarrowing inside an older stent
- Clarifying unclear angiography findings
- Guiding PCI at artery branch points or in the left main coronary artery
Benefits for the Doctor's Assessment
Seeing the Artery Wall, Not Just Its Shadow
Angiography shows a silhouette of the artery channel. IVUS and OCT show cross-sections of the artery wall, so plaque and the true vessel size can be measured.
Stent Size Based on Direct Measurement
The diameter and length of the narrowing are measured from images inside the artery, so stent sizing does not rely only on estimates from angiography.
A Second Look After Stent Placement
Images taken after placement show whether the stent is fully expanded and firmly attached. If not, your doctor can expand it further with a balloon during the same procedure.
Recommended by Guidelines for Complex Narrowings
The 2024 ESC guidelines for chronic coronary syndromes recommend IVUS or OCT guidance during PCI of complex anatomy, such as the left main coronary artery, true bifurcations, and long narrowings.
Brief Technical Information
- Examination type
- Imaging from inside the coronary artery (intravascular)
- Imaging source
- Ultrasound (IVUS) and near-infrared light (OCT)
- Radiation
- None from the imaging catheter; the procedure is guided by cath lab X-ray
- Typical anesthesia
- Local anesthesia at the puncture site, as for catheterization
- Service location
- Cath lab, Coronary Intervention Procedures
