Effect of Carotid Angioplasty and Stenting on Duplex Velocity Measurements in a Porcine Model

Letter to the editor on: "Effect of different targets of goal-directed fluid therapy on intraoperative hypotension and fluid infusion in robot-assisted laparoscopic gynecological surgery: a randomized non-inferiority trial"

This study examined how different goal-directed fluid therapy types affected low blood pressure and fluid infusion during robot-assisted laparoscopic gynecological surgery. They used carotid corrected flow time (FTc) and tidal volume stimulation pulse pressure variation (VtPPV) to check the patient's volume status and responsiveness. The findings indicated that various fluid therapy targets significantly influence intraoperative hypotension and fluid requirements. However, the study exclusively employed unilateral carotid ultrasound assessments, potentially overlooking physiological or pathological variations in blood flow between the left and right carotid arteries. This methodological choice raises concerns as guidelines recommend bilateral measurements for a more comprehensive evaluation. The lack of bilateral assessments could affect the study's reliability and reproducibility. Justifying the unilateral measurement approach is essential for validating clinical findings. Future research should adopt bilateral carotid ultrasound assessments or provide a detailed rationale for unilateral measurements to enhance the robustness and accuracy of clinical evaluations.

Effects of helical centerline stent vs. straight stent placement on blood flow velocity

As an approach to maintain patency in femoropopliteal stenting, a helical stent configuration was proposed, which showed improved patency in clinical trials. However, the effects of helical stent placement on the flow have not been quantitatively analyzed. The purpose of this study was to estimate flow velocities to quantify the influence of helical stent placement. Helical and straight stents were implanted in three healthy pigs, and the flow velocities were estimated using the time-intensity curve (TIC) in the angiography images. The angiographic images indicated thinning of the leading edge of the contrast medium through the helically deformed artery, which was not observed in the straight stent. The slower rise of the TIC peak in the helical stent indicated faster travel of this thinner edge. Arterial expansion due to stenting was observed in all cases, and the expansion rate varied according to location. All cases of helical stent implantation showed that velocity was maintained (55.0%-71.3% velocity retention), unlike for straight stent implantation (43.0%-68.0% velocity retention); however, no significant difference was observed.

Assessment of Large Animal Vascular Dimensions for Intra-Aortic Device Research and Development: A Systematic Review

Animal studies are often required to evaluate new cardiovascular medical devices before they reach the market. Moreover, first-generation novel devices including aortic endovascular prostheses and circulatory support devices are often larger than later iterations or tested in a limited range of sizes. One of the challenges in evaluating these devices is finding a model that is both accessible and anatomically similar to humans, as there is a paucity of data on vascular dimensions in large animals. We set out to complete a comprehensive review of available reports on vascular dimensions in swine, ovine, and bovine models, with a particular focus on the descending aorta and ilio-femoral arteries. We searched Embase and MEDLINE databases for reports of descending aorta and peripheral vascular dimension in large animal models. Data from swine, ovine, and bovine models were separated by weight into 3 categories: 40 to 60 kg, 61 to 80 kg, and >80 kg. We also incorporate our computed tomography angiography data from 4 large sheep and 9 calves into this review. Swine, sheep, and calf >80 kg may serve as the best models to maximize aortic diameter resemblance to humans. If device implantation can be achieved in aortas of smaller dimensions, care should be taken to ensure access site suitability such as the common femoral artery in these smaller animals.

Duplex Ultrasound Surveillance after Transcarotid Artery Revascularization (TCAR) in Clinical Practice

BACKGROUND

To propose a protocol for the routine clinical use of duplex ultrasound (DUS) assessment after transcarotid artery revascularization (TCAR) procedures, with its specific point of vascular access, based on DUS data from routine clinical practice.

METHODS

DUS data were retrospectively collected at 2 centers from a total of 97 patients who underwent a TCAR procedure with at least 30-day and up to 12-month follow-up. Peak systolic velocity (PSV), end diastolic velocity (EDV), and the internal carotid artery (ICA)/common carotid artery (CCA) PSV ratio were collected at baseline (≤30 days after the procedure) and compared with subsequent measurements.

RESULTS

Baseline data were established within 30 days after the procedure. There were no access site stenoses, pseudoaneurysms, or dissections detected in follow-up. Average hemodynamics measurements at 12 months after the procedure (36% of patients reached this time point to date) were PSV 167 ± 153 cm/sec, EDV 51 ± 55 cm/sec, and ICA/CCA PSV 2.3 ± 1.9. Five patients (5.2%) exhibited velocities indicative of ≥80% in-stent restenosis (ISR) at 12 months after the procedure. Two patients (2.1%) underwent repeat intervention for ISR based on high velocities and before significant clinical consequence. The other 3 patients (3.1%) were asymptomatic and are being managed medically and monitored for neurological symptoms. One intraprocedural stroke (1.0% of total treated) was observed.

CONCLUSIONS

This protocol not only illustrates the utility of using the CCA for the arterial access sheath for carotid stenting, but also successfully identifies patients with clinically significant restenosis >80%-99%. A surveillance regimen of baseline at ≤30 days after the procedure, followed by assessment at 6 and 12 months, and yearly thereafter appears to be a safe and effective protocol, based on the data available to date. A PSV >340 cm/sec and ICA/CCA ratio >4.15 is consistent with an 80-99% restenosis after TCAR. Although a small number, this study serves as a starting point for those who perform TCAR to specifically look at the CCA access site to rule out these potential pitfalls which did occur in the early trials.

A Review on the Comparison of Different Treatments for Carotid In-Stent Restenosis

Different treatment options for carotid in-stent restenosis (ISR) have been reported with good outcome, including carotid endarterectomy (CEA), repeated carotid angioplasty stenting (CAS) and percutaneous transluminal angioplasty (PTA) with drug-coated balloons (DCBs). However, the optimal treatment option for ISR has not yet been determined. A systematic literature search was performed in the databases of Medline, Embase, Cochrane library, and unpublished data from clinicaltrials.gov from 1990 to March 1, 2019. Studies were enrolled if they reported treatment strategies for carotid ISR treatment and met the inclusion criteria. After study inclusions, data were extracted and summarized. Totally 25 cross-sectional studies were included, containing 5 comparative studies, 16 studies using repeated PTA, and 4 studies adopting CEA treatment. Our study summarized the current available data, showing that all the studies could effectively relieve the carotid ISR by significantly improving the angiographic stenosis and decreasing the peak systolic velocity values. Meanwhile, CEA treatment had the best long-term effects in relieving restenosis, while re-PTA with stenting/balloon angioplasty had a certain rate of restenosis, ranging from 33% to 83%. Furthermore, re-PTA/stenting and balloon angioplasty treatment had less complications compared with CEA. Also, we analyzed the risk factors that might affect the long-term prognosis of carotid ISR patients. The therapeutic measures for carotid ISR had their own features, with CEA had the highest efficacy while re-PTA/stenting and balloon angioplasty were with less complications. More large-scale comparative clinical studies are needed to further ascertain the best strategies.

Restenosis after carotid artery stenting

As a common etiology for ischemic stroke, atherosclerotic carotid stenosis has been targeted by vascular surgery since 1950s. Compared with carotid endarterectomy, carotid angioplasty and stenting (CAS) is almost similarly efficacious and less invasive. These advantages make CAS an alternative in treating carotid stenosis. However, accumulative evidences suggested that the long-term benefit-risk ratio of CAS may be decreased or even neutralized by the complications related to in-stent restenosis (ISR). Therefore, investigating the mechanisms and identifying the influential factors of ISR are of vital importance for improving the long-term outcomes of CAS. As responses to intrinsic and extrinsic injuries, intimal hyperplasia and vascular smooth muscle cell proliferation have been regarded as the principle mechanisms for ISR development. Due to the lack of consensus-based definition and consistent follow-up protocol, the reported incidences of ISR after CAS varied widely among studies. These variations made the inter-study comparisons of ISR largely illogical. To eliminate restenosis after CAS, both surgery and endovascular procedures have been attempted with promising results. For preventing ISR, drug-eluting stents and antiplatelets have been proposed as potential solutions.

Optimal cut-off criteria for duplex ultrasound compared with computed tomography angiography for the diagnosis of restenosis in stented carotid arteries in the international carotid stenting study

Introduction

Previous studies that reported duplex-ultrasound cut-off criteria, based on blood velocity parameters, for the degree of stenosis in a stented carotid artery were either retrospective, or the reference test was carried out only when a patient was suspected of having restenosis at duplex ultrasound, which is likely to have resulted in verification bias. We performed a prospective study of diagnostic accuracy to find new blood velocity cut-offs in duplex ultrasound for in-stent restenosis.

Patients and methods

Stented patients within the international carotid stenting study were eligible. Patients had a carotid computed tomography angiography in addition to routine duplex ultrasound performed at a yearly follow-up. Duplex-ultrasound bloodflow velocity parameters were compared to the degree of stenosis on computed tomography angiography. The results were analysed using receiver-operating-characteristic curves.

Results

We included 103 patients in this study. On computed tomography angiography, 30 (29.1%) patients had a 30%-49% in-stent restenosis, 21 (20.4%) patients had 50%-69% in-stent restenosis and 5 (4.9%) patients a ≥70% in-stent restenosis. The cut-off value ≥50% stenosis was a peak systolic velocity of 125 cm/s (sensitivity: 63% (95% CI: 41-79), specificity: 83% (95% CI: 72-90)).

Discussion

This study provides a level 2b evidence for new cut-off values for in-stent restenosis. Unfortunately, we could not say anything about severe stenosis because of the low number of severe stenosis after one year.

Conclusions

The 125 cm/s cut-off value on duplex ultrasound is lower than found in previous studies and equal to unstented arteries. Duplex-ultrasound measurements made in stented carotid arteries should not be corrected for the presence of a stent when determining the degree of stenosis.

Morphological and hemodynamic patterns of carotid stenosis treated by endarterectomy with patch closure versus stenting: a duplex ultrasound study

OBJECTIVES

A duplex ultrasound study was performed to investigate morphological and hemodynamic patterns of carotid stenoses treated by endarterectomy with patch closure versus stenting.

MATERIALS AND METHOD

Twenty-nine carotid stenoses were treated with stenting and 65 with patch closure. Duplex ultrasound parameters (luminal diameter, mm; peak systolic velocity and end-diastolic velocity, cm/s) were measured 24 hours after the procedures and also at 12 months post-procedure. Residual stenoses (immediately postprocedure) and restenoses (within 12 months of procedure) were defined as narrowings of ≥ 50% on duplex ultrasound examination.

RESULTS

In stented patients, the luminal diameter of the proximal internal carotid artery increased in the interval between the 24-hour and 12-month post-procedure studies, while in the patch closure patients, the diameter decreased. Carotid hemodynamics normalized immediately after both patching and stenting and remained relatively stable thereafter up to 12 months. No statistically elevated flow velocities (in the absence of residual stenosis or restenosis) were observed in the patched or stented carotid arteries. No significant differences in residual stenosis rates were observed between the stenting group (3 cases, 10.34%) and the patch closure group (1 case, 1.53%, P = 0.08). At 12 months, 2 stenting patients (6.88%) and 2 patch closure patients (3.07%) had $50% restenosis (P = 0.58). One case of late stroke due to restenosis was observed in the stenting group; the patient died 12 months postoperatively, before receiving new intervention.

CONCLUSION

Measurements over time in luminal diameter signalized differences in arterial remodeling mechanisms between patched and stented carotids. Both stenting and patch closure were associated with carotid patency and flow restoration. This study does not support a general approach to new velocity criteria indiscriminately applied to stented or patched carotids.