Intravascular Ultrasound Flashcards
What is the lumen area defined as?
The area bound by the leading edge of the intima or the interface between the echo-dense intima and the echolucent blood elements in the lumen
Line B on Fig. Q27-1B illustrates this definition.
What does the vessel area represent?
The area bound by the EEM, identified as the interface between the leading edge of the echo-dense adventitia and the echo-lucent medial layer
Line C on Fig. Q27-1B illustrates this definition.
What does the difference between the lumen and EEM areas represent?
The atheroma area
This includes both the atheroma and the thickness of the media.
What is the minimum thickness of the atheroma measured from?
Line D on Fig. Q27-1B
True or False: The catheter artifact is used for clinical measurement.
False
The catheter tracing is not used for any clinical measurement.
What are the two important features of the true lumen?
- Trilaminar appearance of the wall
- Presence of side branches
What is IVUS-derived VH based on?
Advanced analysis of the radiofrequency backscatter of the ultrasound signal using a larger number of parameters
This includes a complex mathematical autoregressive model.
What is the predictive value of an FFR ≥ 0.75?
Predicts a low risk of death or cardiac events in the ensuing 2 to 3 years on medical therapy alone.
What does an IVUS left main lumen area ≥5.9 m² correlate with?
An FFR ≥ 0.75, both measures strongly predict event-free survival over a 3-year period.
What was the primary endpoint of the REVERSAL trial?
Percentage change in TAV
TAV was calculated as the sum of differences between EEM and lumen areas.
What is the remodeling response in lesions treated with balloon angioplasty or atherectomy?
- Adaptive remodeling: Increase in vessel area between 24 hours and 1 month
- Constrictive remodeling: Decrease in vessel area between 1 and 6 months
Define positive remodeling.
Expansion of the EEM of the arterial wall at sites of atherosclerosis to accommodate atheroma volume and preserve lumen size.
What indicates a remodeling index of >1.05?
Positive remodeling
What is the significance of a positively remodeled atheroma?
Usually larger in size and more likely to present with unstable coronary syndromes.
What is the definition of negative remodeling?
Local shrinkage of the vessel size at the site of disease.
What was the main finding in the ASTEROID trial regarding very intensive lipid-lowering therapy?
Significant reduction in PAV after 24 months of therapy, indicating regression of disease.
What does significant plaque burden with minimal calcification indicate in IVUS imaging?
Potential hemodynamically severe stenosis.
What should be done if there is a left main trunk dissection?
Urgent management is required.
Fill in the blank: The IVUS catheter artifact is seen in the _______.
true lumen of the vessel.
What is the role of IVUS in imaging false channels during cases of dissection or plaque rupture?
IVUS provides better visualization of false channels when saline or contrast is injected, enhancing echo density differences.
This allows real-time observation of fluid movement from the true to the false lumen.
What is the recommended management for left main coronary dissection if the patient is hemodynamically stable?
Urgent coronary bypass surgery is probably the treatment of choice.
If stabilization with IABP is possible, this may be pursued.
What is the acceptable alternative management for a patient with left main coronary dissection considered too unstable?
Emergent stenting of the left main is an acceptable alternative.
Immediate notification of the cardiac surgeon is essential in both scenarios.
What does IVUS imaging provide in comparison to contrast angiography?
IVUS imaging offers a detailed tomographic perspective of both the lumen and the wall of the artery.
It clarifies and complements the understanding of luminal silhouettes from angiography.
List some clinical situations where IVUS imaging is beneficial according to ACC/AHA guidelines.
- Assessment of stent deployment adequacy
- Evaluation of suboptimal angiographic results
- Determination of restenosis mechanisms
- Evaluation of difficult-to-image coronary anatomy
- Preinterventional assessment of coronary calcium extent
IVUS is the gold standard for identifying cardiac allograft vasculopathy.
What characterizes intimal hyperplasia as seen on IVUS imaging?
Intimal hyperplasia appears as echolucent tissue distinct from the speckle of blood elements in the lumen.
It indicates prior stent implantation.
What are the typical characteristics of vein graft lesions seen on IVUS?
Vein graft lesions are typically echolucent, heterogeneous in density, and represent mixtures of lipid pools, collagen, and thrombotic material.
Heavy calcification is rare in these lesions.
What is the significance of a minimum lumen diameter of <2 mm as seen on IVUS?
It indicates a hemodynamically significant stenosis likely to cause ischemia on a stress test.
This measurement correlates well with an FFR of <0.75.
What is the relationship between neointimal hyperplasia and late lumen loss in stented segments?
Late lumen loss is directly proportional to the degree of neointimal hyperplasia within stented segments.
Slot-tube stents reduce the negative remodeling response that contributes to restenosis.
What were the findings of the PROSPECT trial regarding adverse events related to nonculprit lesions?
Adverse events were related to an originally nonculprit lesion in 11.6% of patients.
Plaque burden ≥70%, MLA ≤ 4 m², and thin-cap fibroatheroma (TCFA) were predictors of future events.
What is the definition of underexpansion in stenting?
Underexpansion occurs when the minimal stent area is <5 m², indicating insufficient expansion during the procedure.
This can lead to significant intimal hyperplasia and diameter reduction over time.
What is a key predictor of target vessel revascularization (TVR) following stenting?
A small postprocedure minimum in-stent lumen area is the most important predictor of TVR.
Larger in-stent lumen areas are associated with lower rates of stent thrombosis and restenosis.
What did IVUS findings reveal about very late stent thrombosis in DES patients?
Patients with very late stent thrombosis had longer stents, more overlapping stents, and a higher prevalence of incomplete strut apposition.
The in-stent vessel area was significantly larger in the thrombosis group.
What are the FFR cutoff values correlated with clinical outcomes?
FFR cutoff values of 0.75 to 0.80 are associated with favorable clinical outcomes and a reduced need for revascularization.
Lesions with an FFR > 0.80 generally do not require revascularization.
What functional assessments can be used when encountering an intermediate lesion?
Pressure or flow measurements, morphologic delineation using IVUS imaging
IVUS stands for Intravascular Ultrasound, a technique for imaging blood vessels.
What are the FFR cutoff values associated with favorable clinical outcomes?
0.75 to 0.80
FFR stands for Fractional Flow Reserve, a measurement used to assess the significance of coronary artery lesions.
What IVUS measurements maximize sensitivity and specificity for identifying hemodynamically significant lesions?
Minimum lumen area <3.0 m², area stenosis >60%
Sensitivity refers to the ability to correctly identify significant lesions, while specificity refers to correctly identifying non-significant lesions.
What combination of IVUS criteria had 100% sensitivity and specificity in identifying significant lesions?
Lumen area <3.0 m² and area stenosis >60%
This finding was reported in a study by Takagi A, et al. in Circulation.
In another study, what minimal luminal area and area stenosis were the best indicators of hemodynamic significance?
Minimal luminal area ≤4 m², area stenosis >70%
This data was reported by Briguori C, et al. in the American Journal of Cardiology.
What were the independent predictors of events after deferring PCI in a retrospective analysis?
IVUS minimum lumen area, area stenosis
PCI stands for Percutaneous Coronary Intervention, a non-surgical method used to treat narrowing of the coronary arteries.
What minimum lumen area allows for reasonably safe deferral of PCI?
≥4.0 m²
A study indicated that with this minimum area, the event rate was acceptably low.
What does IVUS imaging help determine in complex CTO PCI?
Whether the wire is in the true or false lumen, extent of dissection
CTO stands for Chronic Total Occlusion, a condition where a coronary artery is completely blocked.
What advantage does IVUS imaging provide in assessing reference segments?
Typically results in selection of a larger stent diameter than angiography alone
This is important for ensuring proper fit and function of stents in coronary arteries.
What association has been suggested between IVUS use and clinical outcomes in stenting of the left main trunk?
Improved clinical outcomes, including reduction in overall mortality, need for revascularization, and stent thrombosis
Most evidence is derived from retrospective analyses.
What is a significant advantage of OCT over IVUS imaging?
Improved spatial resolution (20 to 40 μm)
This allows better definition of thin-cap fibroatheromas (TCFA) and dissection flaps.
What limitation does OCT have compared to IVUS imaging?
Does not allow penetration and imaging of the full thickness of the arterial wall
OCT provides exquisite resolution but only of the luminal 1 to 2 mm of the wall.
What deeper structures can IVUS measure that OCT cannot?
EEM, plaque thickness, and volume
EEM stands for External Elastic Membrane, crucial for assessing plaque burden.
What are the implications of measuring plaque thickness and volume?
Define future risk of clinical events, study remodeling, disease progression, and response to interventions
This was highlighted in the PROSPECT trial.
