Appropriate Use of Intravascular Ultrasound During Arterial and Venous Lower Extremity Interventions.

BACKGROUND: There has been growing use of intravascular ultrasound (IVUS) during lower extremity arterial and venous revascularization. Observational data suggest that the use of IVUS can improve periprocedural and long-term outcomes, but largescale prospective data remain limited. Consensus opinion regarding the appropriate use of IVUS during peripheral intervention is needed. OBJECTIVES: The purpose of this consensus document is to provide guidance on the appropriate use of IVUS in various phases of peripheral arterial and venous interventions. METHODS: A 12-member writing committee was convened to derive consensus regarding the appropriate clinical scenarios for use of peripheral IVUS. The group iteratively created a 72-question survey representing 12 lower extremity arterial interventional scenarios. Separately, a 40-question survey representing 8 iliofemoral venous interventional scenarios was constructed. Clinical scenarios were categorized by interventional phases: preintervention, intraprocedure, and postintervention optimization. Thirty international vascular experts (15 for each survey) anonymously completed the survey instrument. Results were categorized by appropriateness using the median value and disseminated to the voting panel to reevaluate for any disagreement. RESULTS: Consensus opinion concluded that IVUS use may be appropriate during the preintervention phase for evaluating the etiology of vessel occlusion and plaque morphology in the iliac and femoropopliteal arteries. IVUS was otherwise rated as appropriate during iliac and femoropopliteal revascularization in most other preintervention scenarios, as well as intraprocedural and postprocedural optimization phases. IVUS was rated appropriate in all interventional phases for the tibial arteries. For iliofemoral venous interventions, IVUS was rated as appropriate in all interventional phases. CONCLUSIONS: Expert consensus can help define clinical procedural scenarios in which peripheral IVUS may have value during lower extremity arterial and venous intervention while additional prospective data are collected.

Intravascular ultrasound in peripheral venous and arterial interventions: A contemporary systematic review and grading of the quality of evidence.

Although angiography has been the primary imaging modality used in peripheral vascular intervention, this technique has major limitations due to the evaluation of three-dimensional vessels in two dimensions. Intravascular ultrasound (IVUS) is an important adjunctive tool that can address some of these limitations. This systematic review assesses the appropriateness of IVUS as an imaging modality for guiding peripheral intervention through evidence collection and clinical appraisal of studies. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a cohort of 48 studies (29 arterial; 19 venous) detailing IVUS use in peripheral vascular intervention were extracted. Qualitative assessment of the studies evaluated pre- and postprocedure efficacy of IVUS and revealed that IVUS-guided peripheral intervention in arterial and venous diagnosis and treatment was superior to other imaging techniques alone. Each study in the cohort was further assessed for reliability and validity using the Oxford Centre for Evidence Based Medicine (CEBM) level of evidence scale. The majority of both arterial (79.3%) and venous (73.7%) studies received a 2b rating, the second highest level of evidence rating. The evidence to date indicates that IVUS results in better clinical outcomes overall and should be more widely adopted as an adjunctive imaging modality during peripheral intervention. (PROSPERO Registration No.: CRD42021232353).

Intravascular ultrasound guidance for lower extremity arterial and venous interventions.

This review details the utility of intravascular ultrasound (IVUS) for the management of peripheral artery and venous disease. The purpose of this document is to provide an update in the use of IVUS in peripheral arterial and venous pathology and demonstrate the use of IVUS as a practical diagnostic imaging procedure to evaluate and treat peripheral vascular disorders. IVUS, a diagnostic tool that relies on sound waves to produce precise images of the vessel being evaluated, was originally introduced to the medical community for the purposes of peripheral artery imaging, though it was quickly adapted for coronary interventions with positive outcomes. The utility of IVUS includes vessel measurement, pre- and post-procedural planning, treatment optimisation, and detection of thrombus, dissection or calcium severity. While angiography remains the standard imaging approach during peripheral intervention, multiple observational studies and small prospective trials have shown that in comparison, IVUS provides more accurate imaging detail, which may improve procedural outcomes. IVUS can also address limitations of angiography, including the need to administer contrast medium and eliminate the ambiguity associated with other forms of imaging. This review provides contemporary examples of where IVUS is being used during peripheral intervention as well as representative imaging to serve as a resource for the practising clinician.

End-diastolic fractional flow reserve: comparison with conventional full-cardiac cycle fractional flow reserve.

BACKGROUND: Diastolic fractional flow reserve (dFFR) has been shown to be highly sensitive for detection of inducible myocardial ischemia. However, its reliance on measurement of left-ventricular pressure for zero-flow pressure correction, as well as manual extraction of the diastolic interval, has been its major limitation. Given previous reports of minimal zero-flow pressure at end-diastole, we compared instantaneous ECG-gated end-diastolic FFR with conventional full-cardiac cycle FFR and other diastolic indices in the porcine model. METHODS AND RESULTS: Measurements of FFR in the left anterior descending and left circumflex arteries were performed in an open-chest swine model with an external occluder device on the coronary artery used to produce varying degrees of epicardial stenosis. An ultrasound flow-probe that was placed proximal to the occluder measured absolute blood flow in ml/min, and it was used as a gold standard for FFR measurement. A total of 17 measurements at maximal hyperemia were acquired in 5 animals. Correlation coefficient between conventional mean hyperemic FFR with pressure-wire and directly measured FFR with flow-probe was 0.876 (standard error estimate=0.069; P<0.0001). The hyperemic end-diastolic FFR with pressure-wire correlated better with FFR measured directly with flow-probe (r=0.941, standard error estimate=0.050; P<0.0001). CONCLUSIONS: Instantaneous hyperemic ECG-gated FFR acquired at end-diastole, as compared with conventional full-cardiac cycle FFR, has an improved correlation with FFR measured directly with ultrasound flow-probe.

Quantification of fractional flow reserve based on angiographic image data.

Coronary angiography provides excellent visualization of coronary arteries, but has limitations in assessing the clinical significance of a coronary stenosis. Fractional flow reserve (FFR) has been shown to be reliable in discerning stenoses responsible for inducible ischemia. The purpose of this study is to validate a technique for FFR quantification using angiographic image data. The study was carried out on 10 anesthetized, closed-chest swine using angioplasty balloon catheters to produce partial occlusion. Angiography based FFR was calculated from an angiographically measured ratio of coronary blood flow to arterial lumen volume. Pressure-based FFR was measured from a ratio of distal coronary pressure to aortic pressure. Pressure-wire measurements of FFR (FFR( P )) correlated linearly with angiographic volume-derived measurements of FFR (FFR( V )) according to the equation: FFR( P ) = 0.41 FFR( V ) + 0.52 (P-value < 0.001). The correlation coefficient and standard error of estimate were 0.85 and 0.07, respectively. This is the first study to provide an angiographic method to quantify FFR in swine. Angiographic FFR can potentially provide an assessment of the physiological severity of a coronary stenosis during routine diagnostic cardiac catheterization without a need to cross a stenosis with a pressure-wire.

Estimation of coronary artery hyperemic blood flow based on arterial lumen volume using angiographic images.

The purpose of this study is to develop a method to estimate the hyperemic blood flow in a coronary artery using the sum of the distal lumen volumes in a swine animal model. The limitations of visually assessing coronary artery disease are well known. These limitations are particularly important in intermediate coronary lesions where it is difficult to determine whether a particular lesion is the cause of ischemia. Therefore, a functional measure of stenosis severity is needed using angiographic image data. Coronary arteriography was performed in 10 swine (Yorkshire, 25-35 kg) after power injection of contrast material into the left main coronary artery. A densitometry technique was used to quantify regional flow and lumen volume in vivo after inducing hyperemia. Additionally, 3 swine hearts were casted and imaged post-mortem using cone-beam CT to obtain the lumen volume and the arterial length of corresponding coronary arteries. Using densitometry, the results showed that the stem hyperemic flow (Q) and the associated crown lumen volume (V) were related by Q = 159.08 V(3/4) (r = 0.98, SEE = 10.59 ml/min). The stem hyperemic flow and the associated crown length (L) using cone-beam CT were related by Q = 2.89 L (r = 0.99, SEE = 8.72 ml/min). These results indicate that measured arterial branch lengths or lumen volumes can potentially be used to predict the expected hyperemic flow in an arterial tree. This, in conjunction with measured hyperemic flow in the presence of a stenosis, could be used to predict fractional flow reserve based entirely on angiographic data.