Focus on the research utility of intravascular ultrasound - comparison with other invasive modalities

Intravascular Ultrasound for Assessment of Residual Coarctation of the Aorta after Balloon Angioplasty in Infants

Intravascular ultrasound (IVUS) has been introduced as an accurate and minimally invasive diagnostic technique for the assessment of vascular anatomy and its abnormalities. We believe that IVUS can be used for clarifying the reasons for failure of balloon angiography in infantile coarctation of the aorta (CoA), because post-balloon angioplasty tearing, intimal flap, thrombosis and pseudoaneurysm of the aorta can be evaluated by IVUS with greater sensitivity and specificity. We aimed to assess the outcome of balloon angioplasty of CoA using angiography as the gold standard and IVUS as a new method in infants, comparing the two techniques for the evaluation of the diameter and area of CoA segment pre- and post-procedure. This cross-sectional study was performed on 18 infants hospitalized with a final diagnosis of CoA. All the infants underwent angiography and were also assessed by IVUS to measure the preoperative and postoperative diameter of the narrow segment in the two anterior-posterior and lateral views. In assessment by IVUS, the mean diameter of the coarctation site increased from 2.10 ± 0.30 mm to 4.50 ± 0.94 mm (P < 0.001). Similarly, the average minimum area of the coarctation level increased from 5.26 ± 1.50 mm² to 13.77 ± 3.48 mm² after angioplasty (P < 0.001). Comparing these findings, angiography and IVUS showed a high level of agreement. In the assessment of a dissection flap, there was a high level of agreement between angioplasty and IVUS before the procedure, but IVUS had higher accuracy after the procedure. Our study showed that IVUS was more reliable than angiography in the assessment of residual coarctation. IVUS yielded high sensitivity (58.3%) and specificity (100%) for discriminating the presence and absence of residual coarctation as well as the need for repeating the procedure. The assessment of coarctation before and after angioplasty procedures in children is possible using the IVUS method, with high accuracy. IVUS can offer greater accuracy than angiography in the evaluation of the coarctation area, detecting tears, dissection and flaps, and assessment of residual coarctation.

Relationship between changes in coronary atherosclerotic plaque burden measured by intravascular ultrasound and cardiovascular disease outcomes: a systematic literature review

Objective Evidence from coronary imaging studies suggests an association between increased atherosclerotic plaque burden and cardiovascular disease (CVD) outcomes. A systematic review was performed to evaluate the relationship between coronary atherosclerotic plaque burden changes measured by intravascular ultrasound (IVUS) and CVD outcomes. Research design and methods Rigorous systematic review methodology was used to identify prospective studies of any design assessing the relationship between atherosclerotic plaque volume (percentage or total atheroma volume [PAV or TAV]) changes and CVD outcomes, using multivariable analyses. Main outcome measures CVD outcomes including major adverse cardiac events (MACEs) and major adverse cardiac and cerebrovascular events (MACCEs). Results Literature searches from inception to February 2015 retrieved 6958 records after de-duplication. From these four studies (14 papers) were included. One study reported a significantly lower rate of CVD outcomes associated with a greater reduction in PAV (hazard ratio [HR] 0.26, 95% confidence interval [CI] 0.07-0.83). One study reported that large plaque volume was significantly associated with a greater risk of major adverse cardiac events (MACEs) (HR 1.73, 95% CI: 1.02-2.96). Similarly, a third study reported a significant increase in MACE with an increase in baseline PAV (HR 1.51, 95% CI: 1.06-2.51). Only one potentially inadequately powered Japanese study did not find a statistically significant relationship between PAV changes and MACE. Conclusions The current evidence suggests an independent and statistically significant association between increases in coronary atherosclerotic plaque burden measured by IVUS and greater long-term risk of future CVD outcomes. However, this evidence comes from a limited number of studies which mainly focus on Japanese populations and populations after PCI. Further large prospective studies are required to confirm these findings.

Three-dimensional reconstruction of coronary arteries and plaque morphology using CT angiography--comparison and registration with IVUS

Background

The aim of this study is to present a new methodology for three-dimensional (3D) reconstruction of coronary arteries and plaque morphology using Computed Tomography Angiography (CTA).

Methods

The methodology is summarized in six stages: 1) pre-processing of the initial raw images, 2) rough estimation of the lumen and outer vessel wall borders and approximation of the vessel’s centerline, 3) manual adaptation of plaque parameters, 4) accurate extraction of the luminal centerline, 5) detection of the lumen - outer vessel wall borders and calcium plaque region, and 6) finally 3D surface construction.

Results

The methodology was compared to the estimations of a recently presented Intravascular Ultrasound (IVUS) plaque characterization method. The correlation coefficients for calcium volume, surface area, length and angle vessel were 0.79, 0.86, 0.95 and 0.88, respectively. Additionally, when comparing the inner and outer vessel wall volumes of the reconstructed arteries produced by IVUS and CTA the observed correlation was 0.87 and 0.83, respectively.

Conclusions

The results indicated that the proposed methodology is fast and accurate and thus it is likely in the future to have applications in research and clinical arena.

Nature or the natural evolution of plaque: what matters?

Progression to major acute cardiovascular events often is triggered by an atherosclerotic plaque complicated by rupture or erosion, namely the vulnerable plaque. Early and secure identification of these plaques would allow the development of individualized therapeutic and pharmacological strategies, applied in a timely manner. Imaging methods have a huge potential in detecting and monitoring the evolution of vulnerable plaque. Even though there are multiple invasive and noninvasive techniques, clinical application is for now a matter of choosing the relevant imaging feature for the prognosis, the methodo-logy of study and the target population.

Utility of optical coherence tomography to assess a hazy intracoronary image after percutaneous coronary intervention

Although its use in daily practice is not common, optical coherence tomography (OCT) is a powerful research tool in invasive cardiology. This report describes a hazy angiography image after percutaneous coronary intervention that has been assessed using OCT. Based on the results of the OCT, the patient underwent an elective coronary angioplasty with standard anticoagulation. After implantation of the stent, an intracoronary hazy image was seen on angiography. The use of OCT permitted a correct diagnosis and a successful treatment. This paper provides a discussion of the advantages and disadvantages of OCT, and a comparison with intravascular ultrasound.