The RED 43 Catheter for Aspiration Thrombectomy of Distal Medium Vessel Occlusions (DMVOs): A Multicenter Experience

Clinical Question (PICO)

In adults presenting within 24 hours with clinically significant anterior- or posterior-circulation distal medium vessel occlusion (DMVO), including primary DMVO and secondary DMVO after treatment of a large-vessel occlusion (P), what are the angiographic efficacy and procedural safety outcomes of primary aspiration thrombectomy using the RED 43 catheter, with optional stent-retriever assistance (I), compared with the available external literature rather than a concurrent medical-therapy control (C)? The outcomes were first-pass effect (mTICI 2c/3 on the first pass), final successful reperfusion (mTICI ≥2b), 3-month functional independence, intracranial hemorrhage, subarachnoid hemorrhage, and mortality. The primary-versus-secondary DMVO comparison was defined in the study methods; it was descriptive, not a randomized treatment subgroup analysis.

Bottom Line

In 102 consecutive cases from four high-volume stroke centers, the RED 43 achieved first-pass effect in 57% of primary DMVOs and 61% of secondary DMVOs, with final successful reperfusion in 83% and 87%, respectively. Functional independence at 3 months was 57% overall (58% primary, 52% secondary); symptomatic intracranial hemorrhage occurred in one patient (1.0%), asymptomatic intracerebral hemorrhage in five (4.9%), and asymptomatic subarachnoid hemorrhage in seven (6.9%). The results support technical feasibility and a reassuring observed safety profile, but this uncontrolled retrospective series cannot establish that thrombectomy improves outcomes over medical therapy for DMVO.

Design

Trial type: Retrospective, multicenter consecutive-patient observational cohort; four high-volume comprehensive stroke centers; open-label procedural treatment with blinded outcome assessors reported by the authors.
N: 102 DMVO cases.
- Primary DMVO: 79 cases.
- Secondary DMVO after an index LVO: 23 cases.
Randomization: None. Treatment selection and procedural details were at the discretion of experienced neuroendovascular surgeons.
Setting: Four high-volume comprehensive stroke centers in the United States.
Enrollment: Patients presenting within 24 hours of symptom onset; the article reports a 2026 publication and does not specify a calendar enrollment range in the main text.
Mean follow-up: 3 months for modified Rankin Scale outcomes; procedural and in-hospital outcomes were also collected.
Analysis: Descriptive reporting of means/SDs and medians/IQRs using SPSS version 25.0; no concurrent medical-therapy control and no adjusted comparative model.
Primary outcome: First-pass effect, defined as mTICI 2c or 3 on the first pass, and successful recanalization, defined as mTICI ≥2b at the end of the procedure.

Population

Inclusion Criteria

Consecutive patients with anterior- or posterior-circulation DMVO presenting within 24 hours of symptom onset.
Occlusion in a distal M2, M3, or M4 MCA branch; A1, A2, or A3 ACA branch; or P1, P2, or P3 PCA branch, as defined by the participating investigators.
Primary DMVO requiring intervention or secondary DMVO developing after treatment of an index LVO.
Patients treated with primary aspiration using the RED 43 catheter; stent-retriever assistance was permitted when needed.
Patients presenting 6–24 hours after onset underwent additional imaging selection according to local standard of care.

Exclusion Criteria

The article does not specify a separate formal exclusion list; the cohort was defined by consecutive eligible DMVO cases treated with the RED 43 at the participating centers.
Cases not meeting the investigators’ clinical, angiographic, or local imaging criteria for intervention were not included.

Baseline Characteristics (overall or representative arm)

Mean age was 70 years (SD 14); 55 patients (53.9%) were men.
Median baseline NIHSS was 9 (IQR 6–14), and median ASPECTS was 9 (IQR 8–10).
Hypertension was present in 76 (74.5%), diabetes in 37 (36.2%), hypercholesterolemia in 57 (55.9%), and congestive heart failure in 21 (20.5%).
Intravenous thrombolysis preceded thrombectomy in 26 (25.5%); general anesthesia was used in 82 (80.4%).
Good CTA collaterals were reported in 74 (72.5%). The most frequent occlusion locations were distal M2 MCA (41, 40.2%) and M3/M4 MCA (34, 33.3%).

Interventions

RED 43 aspiration thrombectomy: The catheter was navigated over a microwire to the face of the distal thrombus, followed by mechanical suction after catheter-thrombus engagement. Stent-retriever assistance was available when required.
Primary DMVO pathway: RED 43 used for an initially distal occlusion in 79 cases; it was the first-line aspiration catheter in 65 (82.2%).
Secondary DMVO pathway: RED 43 used for a distal occlusion that developed after treatment of an index LVO in 23 cases; it was first-line in 17 (73.9%).
Technical adjuncts: A microwire alone was used for navigation in 99 cases; a stent retriever served as an anchor in three. Rescue switching to another aspiration catheter occurred in 6 primary cases (7.6%) and 2 secondary cases (8.7%).

Outcomes

Primary Outcome (first-pass effect and final successful reperfusion):

Primary DMVO: First-pass effect, mTICI 2c/3, 45/79 (57%); final successful reperfusion, mTICI ≥2b, 66/79 (83%).
Secondary DMVO: First-pass effect, 14/23 (61%); final successful reperfusion, 20/23 (87%).
By location, final successful reperfusion was 87.8% for distal M2 MCA, 82.3% for M3/M4 MCA, 75% for A1 ACA, 83.3% for A2/A3 ACA, 87.5% for P1 PCA, and 66.6% for P2 PCA. These were descriptive location subgroups; the paper reports no adjusted effect estimates, confidence intervals, or interaction P values.
The median number of passes was 1 (IQR 2), and median puncture-to-recanalization time was reported as 24 minutes (IQR 30). RED 43 use required one pass in 59 cases (57.8%), two passes in 32 (31.4%), and three passes in 11 (10.8%).
The authors compared their reperfusion rates with a prior meta-analysis of retrospective DMVO studies (84% for primary and 82% for secondary DMVO), but those external comparisons are not randomized estimates of RED 43 benefit.

Secondary Outcomes:

Good functional outcome, defined as mRS 0–2 at 3 months, occurred in 58% (46/79) of primary DMVO cases and 52% (12/23) of secondary DMVO cases, or 57% overall.
Median puncture-to-recanalization time was 24 minutes (IQR 30), and the median number of passes was 1 (IQR 2).
The article reports no prespecified treatment-effect subgroup estimates with 95% CIs or P values; the primary-versus-secondary and occlusion-location breakdowns are descriptive.

Adverse Events / Safety:

Symptomatic intracranial hemorrhage occurred in 1 primary DMVO patient (1.2%) and no secondary DMVO patients; the overall rate was approximately 1.0%. sICH required PH-2 and clinical deterioration with an NIHSS increase of at least 4 within 36 hours.
Asymptomatic intracerebral hemorrhage occurred in 4 primary (5.0%) and 1 secondary (4.0%) case; asymptomatic subarachnoid hemorrhage occurred in 5 primary (6.3%) and 2 secondary (8.7%) cases.
Three-month mortality was 1.2% (1/79) in primary DMVO and 4.3% (1/23) in secondary DMVO. Two patients died during hospitalization; the authors state that the reported complications were not device-related.
The median rescue-treatment rates were 7.6% for primary and 8.7% for secondary DMVO, after RED 43 deployment.

Figures

Illustrative case of RED 43 aspiration for an M3 MCA occlusion — *Figure 1.* Illustrative case for the use of the RED 43 aspiration catheter for a M3 MCA occlusion. The patient initially presented with left-sided weakness, left facial droop and dysarthria, and an NIHSS of 9. He was last seen well 6 hours before. A. Non-contrasted CT of the brain with an ASPECTS score of 10 showing no evidence of completed infarction prior to the mechanical thrombectomy. B. CT angiography of the brain showing a vessel cut-off of the superior division M3 segment of the right middle cerebral artery. He did not undergo CT perfusion. C-E. Initial posteroanterior (C) and lateral (D), with a late arterial phase (E) angiography of the right internal carotid artery showing a sharp cut-off (red arrow) of the superior division M3 segment of the right middle cerebral artery, with non-opacification of a large distal territory of the superior division (E). F-H. Post-thrombectomy posteroanterior (F) and lateral (G) with a late arterial phase (H) angiography of the right internal carotid artery showing complete restoration of flow through the superior division M3 segment of the right middle cerebral artery, with complete opacification of the territory. I. Post-thrombectomy MRI of the brain showing patchy infarct in the superior division M3 segment of the right middle cerebral artery territory. The patient did well and improved to NIHSS one and was discharged home with mRS of 1. At 3 months, his mRS improved to 0. MCA, middle cerebral artery; NIHSS, National Institutes of Health Stroke Scale; CT, computed tomography; ASPECTS, Alberta Stroke Early CT Scale; mRS, modified Rankin Scale.

Illustrative case of RED 43 aspiration for an A3 ACA secondary occlusion — *Figure 2.* Illustrative case for the use of the RED 43 aspiration catheter for an A3 ACA secondary occlusion. The patient initially presented with right-sided weakness and aphasia with NIHSS of 16. (A) Non-contrast CT showing evolving infarcts involving the left MCA territory without gross hemorrhagic conversion with ASPECTS of 7. (B) CTA demonstrating an occlusion of the left M1 segment of the MCA. (C) DSA of the left ICA showing no filling of the left MCA, with persistent perfusion of the ACA. (D) DSA of the left ICA following mechanical thrombectomy using a RED 62 device, showing successful recanalization of the middle cerebral artery; however, with residual stenosis of the M1 segment of left MCA. A new left distal A3 ACA occlusion is seen. (E) DSA of the left ICA after aspiration thrombectomy using a RED 43 device, demonstrating restored flow in the left distal A3 ACA segment. There remains residual stenosis of M1 segment of left MCA. (F) Follow-up DWI sequence showing no evidence of acute infarcts in the ACA territory. The patient improved neurologically and was discharged to inpatient rehabilitation with NIHSS of 7 and mRS of 3. At 3 months, his mRS improved to 2. ACA, anterior cerebral artery; NIHSS, National Institutes of Health Stroke Scale; CT, computed tomography; MCA, middle cerebral artery; ASPECTS, Alberta Stroke Program Early CT Score; CTA, computed tomography angiography; ICA, internal carotid artery; DSA, digital subtraction angiography; DWI, diffusion-weighted imaging; mRS, modified Rankin Scale.

Distribution of 90-day modified Rankin Scale scores — *Figure 3.* Distribution of mRS scores at 90 days for primary and secondary DMVOs. mRS, modified Rankin Scale; DMVO, distal medium vessel occlusion.

Criticisms

The retrospective design, lack of a medical-therapy comparator, and treatment by experienced operators create substantial confounding by indication and prevent a causal claim that RED 43 thrombectomy improves functional outcome.
The cohort is small, selected from four high-volume centers, and may not represent lower-volume hospitals, operators with less distal-access experience, or patients whose deficits were judged insufficient to justify intervention.
Vessel diameter was not independently measured, so some occlusions may not meet the stated 0.75–2.0 mm DMVO definition. The paper also permits a broad range of distal M2, ACA, and PCA locations with different anatomy and clinical stakes.
mTICI scores came from postoperative reports without central adjudication. Procedural heterogeneity is material: 20 cases received another catheter before RED 43 deployment, and the RED 43 was not first-line in all cases.
The secondary DMVO group is not a clean comparison group: its outcome is influenced by the original LVO, its treatment, infarct burden, and the newly developed distal occlusion.
The paper reports descriptive subgroup percentages without numeric confidence intervals, adjusted estimates, or interaction testing. External meta-analysis comparisons are not randomized controls.
The observed low hemorrhage rate is reassuring but imprecise: one sICH event in 102 cases leaves considerable uncertainty around the true rate, and perforation, dissection, vasospasm, and other procedural complications may be incompletely captured in retrospective records.

Funding

The article lists Penumbra as the funder. Penumbra manufactures the RED 43 catheter; the paper does not state in the extracted funding statement what role the funder had in study design, data analysis, or reporting. No trial registration is reported.

The paper

Authors. Goyal N, Khattar NK, Peterson J, Dashti R, Sims JJ, Baumeister M, Williams A, Amadi I, Ebersole K, Madigan D, Symonds D, Gottschlich M, Inoa-Acosta V, Frei D, Fiorella D.
Title. The RED 43 catheter for aspiration thrombectomy of distal medium vessel occlusions (DMVOs): a multicenter experience.
Journal. Journal of Neurointerventional Surgery.
Year. 2026.
DOI. 10.1136/jnis-2025-023132
PMCID. PMC13217124

Deep Dive — click to expand

What this is

This is a technical feasibility series for a difficult clinical problem: whether a small, navigable RED 43 aspiration catheter can reach and clear distal medium vessel occlusions without an unacceptable hemorrhagic or vessel-injury penalty. The headline is technically respectable—final reperfusion was 83% in primary and 87% in secondary DMVOs, first-pass effect was 57% and 61%, and 57% of the cohort reached mRS 0–2—but the paper is not an efficacy trial. It shows what selected expert operators achieved in treated patients, not what would have happened with medical therapy or no distal intervention.

1. Shadow Audit

The framing moves quickly from high reperfusion rates to “safe and effective,” while the central missing number is the outcome of comparable DMVO patients who were not taken for thrombectomy. The study itself acknowledges that the absence of a medical-therapy group prevents establishing the role of mechanical thrombectomy. That is not a footnote; in a condition where recent randomized trials of DMVO thrombectomy versus best medical therapy have not shown benefit, it is the decisive boundary.

The device-specific attribution is also softer than the title implies. RED 43 was the first-line aspiration catheter in 82.2% of primary and 73.9% of secondary cases, but 20 patients had another catheter used before RED 43. Seven primary and two secondary cases required rescue switching after RED 43 deployment. The final 83–87% reperfusion rates therefore describe a procedural strategy containing RED 43, not a pure test of RED 43 alone.

Finally, 57% functional independence is an outcome of a selected cohort with median NIHSS 9 and median ASPECTS 9, not a treatment effect. Secondary DMVO outcomes are especially hard to interpret because the original LVO determines much of the final disability.

2. Inversion Engine

The conclusion would invert if the observed technical success failed to translate into a net clinical benefit after accounting for spontaneous recovery, medical therapy, baseline selection, and distal-vessel injury. For the device claim, the inversion threshold is straightforward: a future comparator-controlled study would need to show that the incremental gain in 90-day functional independence is zero or negative despite similar reperfusion, or that any functional gain is offset by excess symptomatic hemorrhage, perforation, dissection, or disabling procedural complications.

This series cannot quantify that threshold because it has no control arm. Its observed sICH count—one of 102, approximately 1.0%—is too sparse to exclude a clinically important true rate, and the paper does not provide confidence intervals. The least expensive decisive test is not another single-arm series; it is a prospective, adjudicated comparative trial with treatment selection based on a prespecified clinical-imaging phenotype, central angiographic review, and 90-day utility-weighted disability as the primary endpoint.

3. Second-Order Catalyst

If the technical result is real, the first change occurs in the neurointerventional suite: the operator’s default distal strategy may move toward direct aspiration when the occlusion is reachable, the deficit is clinically meaningful, and the infarct core is limited. The study offers an operational template—navigate to the thrombus face, aspirate without routinely crossing the clot, and reserve stent-retriever anchoring or rescue aspiration for selected failures.

That should not become a blanket “treat every DMVO” rule. A reasonable next-day protocol would require documented disabling deficit, favorable tissue imaging where indicated, a target vessel within the center’s validated size and access range, and a registry field for the counterfactual decision not to intervene. The subgroup most likely to move first is the patient with a proximal M2 or accessible M3 occlusion and a substantial eloquent-territory deficit, not an incidental small-vessel occlusion with minimal symptoms.

4. Asymmetric Leverage

The payoff is potentially large because DMVOs comprise an estimated 25–40% of acute ischemic strokes with an evident arterial blockage. Even a modest absolute improvement across a large denominator could matter more than a spectacular result in a rare anatomy. A one-pass strategy is also operationally valuable: 57.8% of cases used one RED 43 pass, median puncture-to-recanalization time was 24 minutes, and rescue switching was under 9% in both primary and secondary groups.

But the asymmetry has a trap. A large apparent gain in reperfusion is not the same as a large gain in independence. The distance from mTICI 2b/2c/3 to patient-centered function is particularly wide in distal stroke, where small infarcts may be tolerated and procedure-related injury can erase the benefit. The leverage lies in identifying which clinically significant DMVO phenotype converts reperfusion into independence, not in maximizing angiographic success alone.

5. Paradigm Destroyer

This paper kills the reflex that a distal occlusion is automatically too small or too dangerous for aspiration. It does not kill the opposite reflex—that every visible distal occlusion should be treated. The current randomized DMVO evidence remains the guardrail, and this series is best used to refine technique and patient selection while comparative trials answer whether intervention helps.

The two-sentence protocol update is: “For a disabling, imaging-selected DMVO, discuss direct aspiration with the neurointerventionalist as a technically feasible option, preferably within a trial or prospective registry. Do not infer treatment benefit from reperfusion alone; record the untreated alternative, complications, and 90-day disability.”

MVP — Minimum Viable Proof

The minimum bedside-changing statement would be: in a prospective comparative study of imaging- and deficit-selected DMVO patients, a RED 43-based aspiration strategy increases 90-day functional independence or improves an ordinal disability outcome versus best medical therapy, with the 95% confidence interval excluding no benefit and no clinically important excess in sICH, perforation, dissection, or mortality. This series supplies the feasibility prerequisite—83–87% final reperfusion and approximately 1% observed sICH—but not the clinical proof.

Best Combination

Combine this paper with the negative or neutral randomized DMVO thrombectomy trials rather than treating it as a rebuttal to them. The synthesis is coherent: device and technique may matter, direct aspiration may avoid some of the hazards of crossing fragile distal vessels, and selected patients may still benefit; however, an expert-center single-arm series cannot rescue an indication that lacks comparative evidence. The next generation should test a prespecified aspiration-first strategy against best medical therapy, with central adjudication and clinically meaningful endpoints.

Overvalue Warning

First, do not translate 83% or 87% reperfusion into an 83% or 87% chance of good recovery. Reperfusion is a surrogate, and the cohort’s 57% overall functional independence rate has no untreated counterfactual.

Second, do not treat the 1% sICH rate as a stable device property. It is one event in 102 selected cases, with retrospective ascertainment, expert operators, uncertain generalizability, and no precision estimate reported. The true procedural risk could be meaningfully higher or lower.

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