Unsuccessful percutaneous mechanical thrombectomy in fibrin-rich high-risk pulmonary thromboembolism

Rescue stenting after failure of endovascular thrombectomy for acute vertebrobasilar artery occlusion: data from the PERSIST registry

BACKGROUND

Among acute vertebrobasilar artery occlusion (VBAO) patients, successful reperfusion is a strong predictor of favorable outcomes. However, failed reperfusion (FR) with endovascular thrombectomy (EVT) in VBAO was observed to occur in 18-50% of cases. We aim to evaluate the safety and efficacy of rescue stenting (RS) for VBAO after failed EVT.

METHODS

Patients with VBAO who received EVT were enrolled retrospectively. Propensity score matching was performed as the primary analysis to compare the outcomes between patients with RS and FR. Furthermore, a comparison between using the self-expanding stent (SES) and balloon-mounted stent (BMS) in the RS group was also conducted. The primary and secondary outcomes were defined as a 90-day modified Rankin Scale (mRS) score 0-3, and a 90-day mRS score 0-2, respectively. Safety outcomes included all-cause mortality at 90 days and symptomatic intracranial hemorrhage (sICH).

RESULTS

The RS group showed a significantly higher rate of 90-day mRS score 0-3 (46.6% vs 20.7%; adjusted OR (aOR) 5.06, 95% CI 1.88 to 13.59, P=0.001) and a lower rate of 90-day mortality (34.5% vs 55.2%; aOR 0.42, 95% CI 0.23 to 0.90, P=0.026) than the FR group. The rates of 90-day mRS score 0-2 and sICH were not significantly different between the RS group and FR group. There were no differences in all outcomes between SES and BMS groups.

CONCLUSIONS

RS appeared to be a safe and effective rescue approach in patients with VBAO who failed EVT, and there was no difference between using SES and BMS.

Long-Term Safety Analysis of a Fibrinogen Concentrate (RiaSTAP®/Haemocomplettan® P)

Fibrinogen concentrate treatment is recommended for acute bleeding episodes in adult and pediatric patients with congenital and acquired fibrinogen deficiency. Previous studies have reported a low risk of thromboembolic events (TEEs) with fibrinogen concentrate use; however, the post-treatment TEE risk remains a concern. A retrospective evaluation of RiaSTAP®/Haemocomplettan® P (CSL Behring, Marburg, Germany) post-marketing data was performed (January 1986-June 2022), complemented by a literature review of published studies. Approximately 7.45 million grams of fibrinogen concentrate was administered during the review period. Adverse drug reactions (ADRs) were reported in 337 patients, and 81 (24.0%) of these patients experienced possible TEEs, including 14/81 (17.3%) who experienced fatal outcomes. Risk factors and the administration of other coagulation products existed in most cases, providing alternative explanations. The literature review identified 52 high-ranking studies with fibrinogen concentrate across various clinical areas, including 26 randomized controlled trials. Overall, a higher number of comparative studies showed lower rates of ADRs and/or TEEs in the fibrinogen group versus the comparison group(s) compared with those that reported higher rates or no differences between groups. Post-marketing data and clinical studies demonstrate a low rate of ADRs, including TEEs, with fibrinogen concentrate treatment. These findings suggest a favorable safety profile of fibrinogen concentrate, placing it among the first-line treatments effective for managing intraoperative hemostatic bleeding.

The association between human blood clot analogue computed tomography imaging, composition, contraction, and mechanical characteristics

BACKGROUND

Clot composition, contraction, and mechanical properties are likely determinants of endovascular thrombectomy success. A pre-interventional estimation of these properties is hypothesized to aid in selecting the most suitable treatment for different types of thrombi. Here we determined the association between the aforementioned properties and computed tomography (CT) characteristics using human blood clot analogues.

METHODS

Clot analogues were prepared from the blood of 4 healthy human donors with 5 red blood cell (RBC) volume suspensions: 0%, 20%, 40%, 60% and 80% RBCs. Contraction was measured as the weight of the contracted clots as a percentage of the original suspension. The clots were imaged using CT with and without contrast to quantify clot density and density increase. Unconfined compression was performed to determine the high strain compressive stiffness. The RBC content was analysed using H&E staining.

RESULTS

The 5 RBC suspensions formed only two groups of clots, fibrin-rich (0% RBCs) and RBC-rich (>90% RBCs), as determined by histology. The density of the fibrin-rich clots was significantly lower (31-38HU) compared to the RBC-rich clots (72-89HU), and the density increase of the fibrin-rich clots was significantly higher (82-127HU) compared to the RBC-rich clots (3-17HU). The compressive stiffness of the fibrin-rich clots was higher (178-1624 kPa) than the stiffness of the RBC-rich clots (6-526 kPa). Additionally, the degree of clot contraction was higher for the fibrin-rich clots (89-96%) compared to the RBC-rich clots (11-77%).

CONCLUSIONS

CT imaging clearly reflects clot RBC content and seems to be related to the clot contraction and stiffness. CT imaging might be a useful tool in predicting the thrombus characteristics. However, future studies should confirm these findings by analysing clots with intermediate RBC and platelet content.

Clot friction variation with fibrin content; implications for resistance to thrombectomy

BACKGROUND

Despite significant advancements in the procedural efficacy of mechanical thrombectomy in patients with ischemic stroke in recent years, there still remains a portion of the population that does not achieve good recanalization. The reasons for this may be varied. We hypothesized that static friction between the clot and the vessel, or catheter wall might contribute to the difficulty in removing the clot.

OBJECTIVE

To determine if there is a relationship between clot composition and the resistance to sliding (friction) which might contribute to resistance to clot removal.

METHODS

As clot composition can vary significantly, we investigated five different types of clot in order to measure their respective frictional properties. To do this, a custom-made testing apparatus was created, consisting of various replaceable low-friction surfaces on which the clots could be placed. The surface was then gradually tilted until the clots began to slide; the angle at which this occurred is related to the coefficient of friction of the clots. The experiment was repeated on a bovine aortic surface in order to confirm the results.

RESULTS

We found that fibrin-rich clots (<20% red blood cell content) have a significantly higher coefficient of friction than clots with a red blood cell content >20%. This result was confirmed by repeating the experiment on a bovine aortic surface as a representation of the interaction between clots and the arterial wall.

CONCLUSIONS

The friction properties of clots were found to be related to the content ratio of fibrin to red blood cells. Future imaging techniques that could show fibrin and red blood cell content might help us to predict the 'stickiness' of a clot.