IVUS, or intravascular ultrasound, is an imaging technique that lets cardiologists see inside coronary arteries in real time during a catheter-based procedure. A tiny ultrasound probe on the tip of a catheter is threaded into the artery, where it sends out high-frequency sound waves (typically 20 to 40 MHz) and captures the echoes to build a detailed, 360-degree cross-sectional image of the vessel wall. Unlike a standard angiogram, which only shows the silhouette of blood flowing through the artery, IVUS reveals the artery wall itself: its layers, the size and composition of plaque buildup, and how well a stent sits after placement.
How IVUS Works
The IVUS catheter is a thin, flexible tube with a miniature ultrasound transducer near its tip. Before insertion, the catheter is flushed with saline and connected to a console that processes the ultrasound signals into images. You receive blood-thinning medication and a drug to prevent artery spasm before the catheter goes in. The cardiologist advances it through the coronary artery over a guidewire, typically past the area of interest, and then slowly pulls it back while the transducer spins and captures images.
This pullback can be done by hand or with a motorized device that moves at a steady speed. Automated pullback is especially useful because it lets the system measure lesion length precisely, helping the cardiologist pick the right stent size. The result is a continuous series of cross-sectional images, almost like slicing through the artery and examining each ring individually. Imaging depth reaches 5 to 10 mm, enough to see through the full thickness of the vessel wall including the outer boundary.
What IVUS Shows That Angiography Cannot
A coronary angiogram is the standard imaging tool during heart catheterization. It works by injecting contrast dye and taking X-ray images, producing a two-dimensional shadow of the artery’s inner channel. That shadow can reveal narrowings, but it has real blind spots. It cannot show what the artery wall looks like, how much plaque is hiding beneath the surface, or whether a narrowing is caused by hard calcium, soft fatty deposits, or scar tissue. Diffuse disease that narrows an artery evenly along its length can look deceptively normal on angiography because there is no healthy segment nearby for comparison.
IVUS fills those gaps. In one study of over 1,100 patients with stable coronary disease, IVUS detected calcium deposits in 73% of cases while angiography picked up calcium in only 38%. After a stent is placed, IVUS can identify problems that angiography misses entirely: underexpansion of the stent, gaps between the stent and the vessel wall (called malapposition), tissue bulging through the stent struts, small tears at the stent edges, and residual disease just beyond where the stent ends. Each of these issues raises the risk of the stent clotting or the artery narrowing again over time.
Identifying Plaque Composition
One of the most valuable features of IVUS is its ability to characterize what plaque is made of, not just how large it is. A specialized analysis called virtual histology processes the ultrasound signals and assigns color codes to different tissue types. Fibrous tissue appears dark green, fatty or fibro-lipidic tissue is light green, dead lipid-rich tissue (necrotic core) shows up red, and dense calcium is white. The vessel’s middle layer displays as grey, with the open channel appearing black.
This matters because not all plaques behave the same way. A plaque with a large necrotic core and a thin cap is considered vulnerable, meaning it is more likely to rupture and trigger a heart attack. A heavily calcified plaque, on the other hand, may need special preparation before a stent can expand properly. Knowing what a plaque is made of helps the cardiologist choose the right treatment strategy before committing to a particular approach.
When Cardiologists Use IVUS
IVUS is not used in every heart catheterization. It adds the most value in complex situations where the stakes of an imprecise result are highest. The most common scenarios include:
- Left main coronary artery disease. The left main supplies blood to most of the heart’s muscle, so accurate sizing and stent placement here are critical.
- Bifurcation lesions. Where an artery branches, plaque geometry is complex. IVUS helps the cardiologist decide between a single-stent approach and a two-stent technique.
- Long, diffuse disease. IVUS precisely measures lesion length and reference vessel diameter, reducing the chance of choosing a stent that is too short or too narrow.
- Stent optimization. After a stent is deployed, IVUS confirms that it has expanded adequately and is sitting flush against the artery wall. A minimum stent area below about 5.0 mm² in non-left-main arteries is a strong predictor of future problems.
- Ambiguous angiographic findings. When the angiogram is hard to interpret, perhaps because of overlapping vessels or borderline narrowing, IVUS provides a definitive measurement of how severe the blockage really is.
What the Guidelines Recommend
Major cardiology societies have increasingly endorsed IVUS use for complex procedures. The 2025 ACC/AHA/SCAI guidelines for acute coronary syndromes upgraded IVUS (and its companion technology, OCT) to a Class I recommendation for procedural guidance, the strongest endorsement, specifically to reduce complications in left main and complex lesions. The 2024 European Society of Cardiology guidelines made a similar Class I recommendation for IVUS or OCT guidance during stenting of complex anatomy in patients with chronic coronary syndromes, particularly left main, true bifurcation, and long lesions.
How IVUS Compares to OCT
Optical coherence tomography (OCT) is the other major intravascular imaging technology, and the two are complementary rather than interchangeable. OCT uses near-infrared light instead of sound waves and achieves roughly ten times the resolution of IVUS: 10 to 20 micrometers versus 100 to 150 micrometers. That makes OCT exceptional at visualizing fine surface details like thin fibrous caps over plaques or subtle stent strut coverage.
The trade-off is penetration depth. IVUS can image 5 to 6 mm into tissue, enough to see through large plaques and reach the outer wall of the artery. OCT penetrates only 1 to 2 mm, which means it sometimes cannot see through thick plaque or fully visualize the wall in large vessels. IVUS also does not require the artery to be flushed clear of blood during imaging, while OCT does. In practice, cardiologists often choose IVUS for large vessels and heavily diseased arteries, and OCT when fine surface detail matters most.
Safety and Risks
IVUS is generally safe, with an overall complication rate reported between 0.5% and 4%. The most common issues are temporary coronary artery spasm triggered by the catheter and small dissections (tears in the artery lining). One large observational study found that coronary dissection occurred in about 2.75% of cases where IVUS was used during emergency heart attack treatment, compared to 0.83% with angiography alone. However, many of these dissections are detected precisely because IVUS is better at finding them, and they can be treated immediately with additional stenting.
Serious complications like coronary rupture are rare. The procedure adds a few minutes to the overall catheterization time, and the catheter itself is small enough to navigate most coronary arteries without difficulty. For high-risk or complex procedures, the additional diagnostic information IVUS provides generally outweighs the modest increase in procedural risk.
What Happens After an IVUS-Guided Procedure
From your perspective as a patient, an IVUS-guided stent procedure feels much the same as one guided by angiography alone. The catheter insertion site, recovery time, and aftercare are identical. The difference happens during the procedure itself: your cardiologist gets a more complete picture of the artery and can make more precise decisions about stent size, placement, and expansion. The goal is to achieve at least 80% stent expansion relative to the reference vessel, with adequate contact between the stent and the artery wall along its full length. When those targets are met, the long-term risk of the stent clotting or the artery narrowing again drops meaningfully.