Intravascular Ultrasonography Procedures

Updated: Aug 07, 2023
Author: Kartika Shetty, MD, FACP; Chief Editor: Karlheinz Peter, MD, PhD 



Intravascular ultrasonography (IVUS) is an invasive imaging procedure that provides intravascular images of the coronary arteries and other blood vessels. Intravascular ultrasonography has played a critical role in enhancing the understanding of coronary atherosclerosis pathophysiology and has facilitated the refinement of diagnostic and therapeutic strategies for various vascular pathologies. Intravascular ultrasonography has become increasingly important in both clinical and research applications, and it has played an integral role in the evolution of interventional cardiology. Intravascular ultrasonography in interventional cardiology is an adjunctive procedure to coronary angiography; as such, any contraindication to coronary angiography applies to IVUS as well.[1]

Intravascular ultrasonography, a diagnostic tool that relies on sound waves to produce precise images of the vessel being evaluated, was originally introduced for peripheral artery imaging, but it was quickly adapted for coronary interventions. IVUS can be used for vessel measurement, preprocedural and postprocedural planning, treatment optimization, and detection of thrombus, dissection, or calcium severity. Angiography remains the standard imaging modality, but studies have shown that IVUS can provide more accurate imaging detail.[2, 3]

IVUS can characterize lesion morphology, quantify plaque burden, guide stent sizing, assess stent expansion, identify procedural complications, and evaluate stent failure with stent thrombosis or in-stent restenosis. IVUS can distinguish between calcified plaque, lipid, and neointimal proliferation and can identify calcified plaque that may not be possible with angiography alone. IVUS overcomes many of the limitations associated with angiography, since angiography produces a 2-dimensional image of a 3-dimensional structure using x-rays. IVUS assesses the vessel internally rather than externally.[4, 5, 1, 6, 7, 8, 9]

In general, risks and discomforts involved in IVUS include those associated with all catheterization procedures. Major complications, including dissection or vessel closure, are rare (< 0.5%). The most frequently reported complication is transient coronary spasm (occurring in 1-3% of examinations), which responds to intracoronary glyceryl trinitrate.

An expert consensus committee commissioned by the American College of Cardiology, in collaboration with the European Society of Cardiology, has provided a framework for standardization of nomenclature, methods of measurement, and reporting of IVUS results.[10]

(See the image below.)

A still intravascular ultrasonography image demons A still intravascular ultrasonography image demonstrating a normal coronary artery.


The following recommendations were made by the American College of Cardiology (ACC) regarding the use of IVUS for percutaneous coronary  intervention (PCI)[11] :

  • IVUS is a reasonable option to assess angiographically indeterminant left main coronary artery disease (CAD).
  • IVUS and coronary angiography are within reason 4-6 wk and 1 yr after cardiac transplantation to rule out donor CAD, detect rapidly progressive cardiac allograft vasculopathy, and provide prognostic information.
  • IVUS is a reasonable option to determine the mechanism of stent restenosis.
  • IVUS may be reasonable in assessing non–left main coronary arteries possessing angiographically intermediate coronary stenoses (ie, 50-70% diameter stenosis).
  • IVUS may be considered for the guidance of coronary stent implantation, especially in cases of left main coronary artery (LMCA) stenting.
  • IVUS may be reasonable for the determination of the mechanism of stent thrombosis.
  • IVUS for routine lesion assessment is not a recommendation if revascularization with PCI or coronary artery bypass graft (CABG) is not being contemplated.

The European Society of Cardiology (ESC) recommended the following for IVUS[12] : 

  • To assess the severity and optimize the treatment of unprotected left main coronary lesions.
  • To detect stent-related mechanical problems leading to restenosis. 
  • To optimize stent implantation.


Preinterventional IVUS allows assessment of plaque distribution, ostial involvement, lumen and vessel area and diameters, extent of calcification, and the presence of thrombi or dissections.[13, 14, 15] It can alter strategy and the decision to use a particular device.

Intravascular ultrasonography can be highly useful for percutaneous coronary intervention (PCI). PCI results can be optimized with the use of interactive IVUS during the procedure.[16]  However, the use of IVUS during PCI remains low, and additional prospective randomized, controlled trials are needed.[17]

Two major trials—the Strategy for Intracoronary Ultrasound-Guided PTCA and Stenting (SIPS) trial and the Balloon Equivalent to Stent (BEST) study—evaluated potential benefits and limitations of ultrasound-guided balloon angioplasty and routine stenting.[18, 19] In the SIPS trial, approximately 50% of patients in each group received a stent at the time of the index procedure. Acute gain was greater in the IVUS-guided group than in the angiography-guided group, but angiographic 6-month follow-up revealed no difference in the primary endpoint of minimum lumen diameter. Although no difference was noted in the secondary endpoint of short-term target lumen revascularization, long-term clinical follow-up showed a significant decrease in clinically driven target lumen revascularization in the ultrasound group as compared with the angiography group. In the BEST trial, at 6 months, 20 of 119 patients in the aggressive balloon angioplasty group and 21 of 116 patients in the routine stent implantation group had restenosis, along with no statistical difference in minimal luminal diameter or lumen cross-sectional area, thus fulfilling the prespecified criteria for noninferiority.

Although IVUS-guided balloon angioplasty is a noninferior alternative to routine stenting, this approach is certainly more time consuming and requires meticulous attention to detail, along with expertise in IVUS image acquisition and interpretation. Researchers have made apparent that the crossover rate is high, with more than 50% of patients requiring adjunctive stent implantation. In routine clinical practice, stent implantation has gained preference over IVUS-guided balloon angioplasty.[20]

The Multicenter Ultrasound Stenting in Coronaries (MUSIC) study established the safety and feasibility of IVUS-guided stent implantation.[21] Fitzgerald and associates evaluated whether routine ultrasound guidance of stent implantation improved clinical outcomes as compared with angiographic guidance alone in the Can Routine Ultrasound Influence Stent Expansion (CRUISE) trial.[22] Although no clinical outcome benefits were demonstrated with routine use of IVUS, more effective stent expansion was noted when compared with angiographic guidance alone.

Casella et al conducted a meta-analysis of studies on this topic and found that IVUS-guided stent implantation has a neutral effect on long-term death and nonfatal myocardial infarction compared with angiographic optimization.[23] However, study authors noted that IVUS-guided stenting significantly lowers 6-month angiographic restenosis and target vessel revascularization.

In their appraisal of IVUS and its application in routine angioplasty, Oxford and coworkers noted that IVUS is better than contrast angiography in key procedural variables, such as measuring postdeployment stent dimensions, confirming complete stent apposition, and excluding edge dissections that may predispose to both early and late complications, including in-stent restenosis.[24]  The clinical usefulness of ultrasound guidance in stent deployment maintains its value. Particularly for small vessels, bifurcation stenting, ostial lesions, long segments, and left main stenting, ultrasound can provide beneficial guidance.[25, 26]

Intravascular ultrasound plays a vital role in characterizing plaque structures and in planning debulking (atherectomy) procedures by differentiating between superficial (intimal) and deep calcium deposits.[27] Intravascular ultrasonography has emerged as superior to routine angiography for guiding selective plaque removal.[28] Rotational atherectomy is preferred over directional atherectomy in cases of superficial calcification.[29]

Interventional radiology applications of IVUS continue to expand, complementing intraprocedural angiography and helping to guide endovascular interventions. Vascular conditions can be visualized from the planar appearance of an opacified vascular lumen; perivascular targets are visualized on the basis of fluoroscopic landmarks. Common applications of IVUS include deep venous thrombosis, May-Thurner syndrome, nutcracker syndrome, transjugular intrahepatic portosystemic shunts, aortic interventions, peripheral arterial disease, and endovascular or perivascular biopsy.[30]

Technical Considerations

Intravascular ultrasonography consists of a miniature ultrasound-mounted catheter that is connected to an electronics console to reconstruct images transmitted by sound waves. The ultrasound signal is produced by passing an electrical current through the piezoelectric (pressure-electric) crystalline material of the transducer that expands and contracts when electrically excited.

After reflection from tissue, a portion of ultrasound energy returns to the transducer. The signal received is converted to electrical energy and is sent to an external signal processing system for amplification, filtering, scan conversion, user-controlled modification, and graphic presentation. The ultrasound beam upon reflection remains fairly parallel for a distance (near field) and then begins to diverge (far field). The quality of ultrasound images is greater in the near field because the beam is narrower and more parallel, resolution is greater, and the characteristic backscatter (reflection of ultrasound energy) from a given tissue is more accurate. Thus, larger transducers with lower frequencies are used for examination of large vessels because they create a deeper near field.

(See the video below.)

An intravascular ultrasonography run from a segment of normal coronary artery.

Periprocedural Care


A catheter consists of a miniaturized transducer and a console that reconstructs the image. High ultrasound frequencies, typically centered at 20 to 50 MHz, are used, providing excellent resolution.

Monorail rapid exchange intracoronary ultrasound catheters have an outer diameter ranging between 2.6 and 3.5 Fr (0.87-1.17 mm diameter) and can be advanced through a 6-Fr guide catheter.

Two different types of transducers are available for IVUS: the mechanically rotating transducer, and the electronically switched multielement array system.

A single rotating transducer is driven by a flexible drive cable at 1,800 rpm (30 revolutions per second) to sweep a beam almost perpendicular to the catheter. At approximately 1-degree increments, the transducer sends and receives ultrasound signals. Flushing with saline is required to provide a fluid pathway for the ultrasound beam because even small air bubbles can degrade image quality. In most mechanical systems, the transducer spins within a protective sheath while the imaging transducer is moved proximally and distally. This facilitates smooth and uniform mechanical pullback.

Electronic systems use an annular array of small crystals rather than a single rotating transducer. The transducers are activated sequentially to generate the image. The coordinated beam generated by groups of elements is known as a synthetic aperture array. Currently available electronic systems provide simultaneous colorization of blood flow.

The imaging console includes components and software necessary to convert the ultrasonography signal to a graphic image on the monitor. Three display modes are currently available:

  1. Cross-sectional tomographic views are single-cut cross-sectional images that are limited by spatial orientation and cannot provide information regarding length and distribution of plaque.
  2. In longitudinal imaging (L mode), computerized image reconstruction techniques present a series of evenly spaced ultrasound images along a single-cut plane to approximate the longitudinal appearance of the artery. Motorized transducer pullback and digital storage of cross-sectional images are necessary for L mode. [31]  
  3. Three-dimensional (3D) reconstructions of data are also available. [32]

Regarding patient preparation, local anesthesia and minimal general sedation are used, and the patient should lie supine on the angiography table.



Approach Considerations

The patient must be anticoagulated, usually with heparin, before the guidewire is inserted into the coronary artery. Unless this is contraindicated, image acquisition should be performed after intracoronary nitroglycerin is administered to avoid catheter-induced spasm.

Standard coronary interventional techniques and equipment (guiding catheter and 0.014-inch angioplasty guidewire) are used for catheter delivery during intracoronary ultrasound examination. The catheter is placed distal to the segment of interest. Subsequently, the operator retracts the transducer, either manually or with a motorized pullback device. During pullback, images are obtained and are recorded digitally for analysis.

Motorized pullback devices allow withdrawal at a constant speed (0.25 mm/sec or, most frequently, 0.5 mm/sec), which is essential in serial studies. Motorized pullbacks permit length and volume measurements and provide uniform and reproducible image acquisition for multicenter and serial studies. However, examination of important regions of interest may be inadequate because the transducer does not remain very long at any specific site in the vessel.

Normal Arterial Appearance

A standard intravascular ultrasound image consists of 3 main components: catheter, lumen, and arterial wall. An ultrasound reflection is generated at a tissue interface if an abrupt change in acoustic impedance occurs. In the normal artery, 2 such interfaces are usually observed: the first at the border between blood and the leading edge of the intima, and the second at the external elastic membrane, which is located at the media-adventitia border. For patients younger than 40 years, the reported normal value for intimal thickness is typically between 0.15 and 0.25 mm.[33] Most investigators use 0.25 to 0.50 mm as the upper limit of normal.

(See the videos below.)

An intravascular ultrasonography run from a segment of normal coronary artery.
An intravascular ultrasonography video highlighting the appearance of a branch from the main stem coronary artery. Note the coronary artery branch appearing at the 1'o clock position of the screen.

Quantitative Measurements

Border identification

Recognizing that all ultrasound techniques, including IVUS, require that measurements be performed at the leading edge of boundaries—never at the trailing edge—is important. Frequently in muscular arteries such as coronary arteries, 3 layers exist.[34] The innermost layer consists of a complex of intima and internal elastic membrane. This innermost layer is relatively echogenic as compared with the lumen and the media. The trailing edge of the intima (which would correspond to the internal elastic membrane) cannot always be distinguished clearly. Moving outward from the lumen, the second layer is the media. The third and outer layer consists of adventitia and periadventitial tissues, respectively. The boundary separating the true adventitia from surrounding perivascular tissues is not well defined on IVUS images.

Lumen measurements

Lumen measurements are performed using the interface between the lumen and the leading edge of the intima. Generally, the leading edge of the innermost echogenic layer should be used as the lumen boundary. The following basic measurements can be recorded according to operator preference:

  • Lumen cross-sectional area (CSA): area bounded by the luminal border

  • Minimum lumen diameter: shortest diameter through the center point of the lumen

  • Maximum lumen diameter: longest diameter through the center point of the lumen

  • Lumen eccentricity: 1 [(Maximum lumen diameter – minimum lumen diameter)/maximum lumen diameter]

  • Lumen area stenosis: (Reference lumen CSA – minimum lumen CSA)/reference lumen CSA

The reference segment used should be specified as proximal, distal, largest, or average.

Other special measurements facilitated by IVUS include the following:

  • External elastic membrane measurements

  • Atheroma measurements

  • Calcium measurements

  • Stent measurements (a postdeployment minimal stent area of 5 mm2 predicts increased likelihood of angiographic restenosis)

  • Remodeling

  • Length measurements

Qualitative Assessment

Atheroma morphology

Although IVUS cannot be used to detect and quantify specific histologic contents, certain image patterns can be very useful in estimating morphology and content of the atheroma.

Soft (echolucent) plaque refers to the acoustic signal that arises from low echogenicity rather than to structural characteristics of plaque. Although a zone of reduced echogenicity generally results from high lipid content in a mostly cellular lesion, it could also result from a necrotic zone within the plaque, an intramural hemorrhage, or a thrombus.[34, 35]

Fibrous plaques have an intermediate echogenicity between soft (echolucent) atheromas and highly echogenic calcific plaques.[33] Generally, the greater the fibrous tissue content, the greater the echogenicity of the tissue.

Ultrasound imaging is more sensitive than fluoroscopy for detecting coronary calcification.[36] Large calcifications may be associated with lesion stability. In contrast, microcalcifications are frequently found in lipid-rich necrotic core areas of unstable plaques and may not be well reflected in IVUS images.[37]

Plaques frequently contain more than one acoustical subtype.

A thrombus usually is recognized as an intraluminal mass, often with a layered, lobulated, or pedunculated appearance.[38] However, in vitro studies have revealed limitations of IVUS in the diagnosis of thrombi (sensitivity of 57% and specificity of 91%)—considerably inferior to conventional angiography.[39] Intravascular ultrasonography is unreliable in differentiating acute thrombi from echolucent plaques because of similar echogenicity and texture of lipid-laden tissue, loose connective tissue, and stagnant blood.

The intimal hyperplasia characteristic of early in-stent restenosis often appears as tissue with very low echogenicity, at times less echogenic than the blood speckle in the lumen. Use of appropriate system settings is critical to avoid suppressing this relative nonechogenic material. The intimal hyperplasia of late in-stent restenosis often appears more echogenic.

Evaluating dissections and other complications after intervention

Intravascular ultrasound is commonly used to detect and direct the treatment of dissections and other complications after intervention. Intravascular ultrasonography allows for detailed classification of dissection and assessment of dissection severity. Additionally, important characteristics of a dissection such as presence of a false lumen, identification of mobile flap(s), presence of calcium at the dissection border, and close proximity to stent edges are identified distinctly by IVUS.

Unstable lesions and ruptured plaques

Although no definitive features define a plaque as vulnerable on IVUS, a hypoechoic plaque without a well-formed fibrous cap is presumed to represent a potentially vulnerable atherosclerotic lesion.[40]

For patients studied after an acute coronary syndrome, ultrasound imaging may reveal ulceration, often with remnants of the ruptured fibrous cap evident at the ulcer edges. Various other appearances are common, including fissuring or erosion of the plaque surface.

Unusual lesion morphology

Intravascular ultrasonography can be used to characterize unusual lesion morphology such as aneurysms, pseudoaneurysms, and true versus false lumens.

Ambiguous lesions

Intravascular ultrasonography lends itself to the identification of technically difficult lesions, such as intermediate lesions of uncertain stenotic severity or ostial stenosis and disease at branching sites. Use of IVUS in these circumstances depends on the interventionist. Intravascular ultrasonography can also be helpful for delineating lesions involving tortuous vessels and left mainstem lesions. Intravascular ultrasonography has a particularly important role in defining areas with intraluminal filling defects, angiographically hazy lesions, sites with plaque rupture, and lesions with local flow disturbances. Intravascular ultrasonography can be used to determine vein graft morphology in situ as well.

In-Stent Restenosis and Drug-Eluting Stent Implantation

Of particular note is the role of IVUS in establishing the mechanisms of in-stent restenosis. Restenosis after balloon angioplasty is largely driven by concentric geometric remodeling, with neointimal hyperplasia playing a lesser role. However, in-stent restenosis is almost exclusively the consequence of exuberant neointimal proliferation.[40, 41]

Intravascular ultrasonography measurement of minimum stent area is recognized as the most powerful predictor of long-term patency and clinical outcomes.[40] Observations noted on IVUS were instrumental in the development of strategies to treat in-stent restenosis, including intracoronary brachytherapy. Most important, they led to the development of drug-eluting stents, which have dramatically reduced neointimal proliferation and the incidence of in-stent restenosis.[42]

In the ADAPT-DES study (Assessment of Dual Antiplatelet Therapy With Drug-Eluting Stents), implantation of drug-eluting stents guided by IVUS was associated with lower rates of stent thrombosis, myocardial infarction, and major adverse cardiac events (cardiac death, MI, or stent thrombosis) than that associated with angiography.[43]

The multicenter, randomized ULTIMATE  trial showed a lower incidence of 1-year target vessel failure (TVF) after IVUS-guided drug-eluting stent implantation than with angiographic guidance. In addition, at 3 years, TVF occurred in 47 patients (6.6%) in the IVUS-guided group and in 76 patients (10.7%) in the angiography-guided group.[44]

In a meta-analysis of randomized, controlled trials that compared IVUS- and angiography-guided DES implantation, IVUS was associated with significantly reduced incidence of cardiovascular mortality (OR: 0.45, CI: 0.25-0.80), target lesion revascularization (TLR) (OR: 0.56, CI: 0.41-0.77), and stent thrombosis (ST) (OR: 0.47, CI: 0.24-0.94).[45]

Special Disease Considerations

Assessment of transplant vasculopathy

Posttransplantation coronary artery disease is the leading cause of death beyond the first year after cardiac transplantation, with a reported incidence of nearly 20% a year.[46] Intravascular ultrasonography allows early assessment of plaque accumulation before luminal stenosis in comparison with other diagnostic methods, and studies have reported an association between disease severity as detected on IVUS and clinical outcomes.[47] Patients with more severe disease evident on IVUS studies had an increased incidence of death, myocardial infarction, or retransplantation.[48, 49]

Aortic, carotid, and peripheral vascular disease

The role of IVUS in noncoronary vascular disease is expanding. The various unique limitations of traditional angiography in defining the anatomy of peripheral vessels can be circumvented by IVUS.[50] With routine angiography, often angulated or orthogonal views are not possible and foreshortening is not apparent. Heavy calcification in arteries deep within the thorax, abdomen, pelvis, and thigh can obscure vessel borders even after digital subtraction. Intravascular ultrasonography can provide additional details on lesions in such cases.

Nevertheless, several IVUS artifacts or limitations remain to be resolved, including catheter obliquity, limited spatial resolution in very large vessels, and severe acoustic shadowing by calcific plaque.

Studies have shown that IVUS-guided peripheral intervention in arterial and venous diagnosis and treatment is superior to other imaging techniques alone.[51, 52, 53]

Left mainstem

The left mainstem has structural and anatomic characteristics different from those of other segments of the coronary tree, making management through percutaneous coronary intervention (PCI) a challenge. IVUS is important to assess the results of left mainsem stenting.[54]