Millipede AspiRation for Revascularization in Stroke (MARRS) Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Millipede AspiRation for Revascularization in Stroke (MARRS) Study (NCT05714501), a na na study. The primary outcome is ITT Cohort: Rate of Core Lab-adjudicated Reperfusion Success Within Three Passes.

2. Clinical Question

This is a descriptive question about performance under the study’s specified endpoint definition, rather than a question about a difference between randomized groups. The endpoint combines a reperfusion threshold with a limit on the number of passes and a restriction on additional therapy. These conditions define what counts as success; they do not, by themselves, establish how the device compares with other approaches.

The record also lists secondary outcomes covering functional independence, mortality, intracranial hemorrhage, serious adverse device effects, procedure-related serious adverse events, embolization to a new territory, and successful reperfusion at the end of the thrombectomy procedure. The listed outcomes indicate a broad assessment of clinical events and procedural performance, but their results are not reported in the registry record.

3. Trial Design

MARRS is a completed, single-group study of the Millipede System in acute ischemic stroke due to large vessel occlusions. The registry record lists the study as completed, with enrollment of 235, a start date of 2023-10-09, and a primary completion date of 2025-03-08. The intervention is classified as a device. The listed phase is NA.

The design is described as single group, with masking listed as none and allocation as NA. No randomized comparator is described. Consequently, the registry record does not support a direct, within-trial comparison of the device with a control treatment. Outcomes can be described for the study cohort, but differences from an unobserved control group cannot be estimated from this design alone.

The primary endpoint is an intent-to-treat measure of the number of participants achieving core lab-adjudicated reperfusion success within three passes, without additional therapy. The endpoint is intraprocedural and uses the mTICI scale, with success defined as mTICI 2b or greater. The record also lists secondary outcomes for clinical status, mortality, hemorrhage, device and procedure-related events, embolization, and reperfusion at the end of thrombectomy.

The registry lists 34 outcome measures and one analysis. It does not report the protocol’s detailed statistical analysis plan, the rationale for the enrollment target, planned interim analyses, or how each analysis population was defined. Those details should not be inferred from the single-group designation or the outcome list. The record identifies the sponsor as Perfuze.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Intent-to-Treat

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

Population: Intent-to Treat Population

6. Primary Endpoint

The registry lists the primary outcome as ITT Cohort: Rate of Core Lab-adjudicated Reperfusion Success Within Three Passes, measured over Intraprocedural.

The primary endpoint counts participants in the intent-to-treat cohort who achieved core lab-adjudicated reperfusion success within no more than three passes using the Millipede System, without additional therapy. Success is defined as mTICI 2b or greater. The mTICI scale ranges from 0 to 3, with higher scores indicating better reperfusion; the record describes 2b as substantial reperfusion, 2c as near complete, and 3 as complete.

This endpoint is used to describe a procedural performance outcome: whether the specified reperfusion threshold was reached under the specified pass and additional-therapy conditions. Requiring independent Core Lab adjudication provides a stated basis for classifying the imaging outcome; the registry record does not provide further details about adjudication procedures.

Because the endpoint is a participant count, a complete interpretation would ordinarily need the number meeting the definition and the relevant analysis denominator. A proportion could then describe the share meeting the criterion, and an uncertainty interval could show the precision of that estimate. The registry record gives the endpoint definition but does not report its result, denominator, or confidence interval. It is therefore not possible to quantify the observed rate or its precision from the posted record.

The endpoint is not itself a measure of longer-term function or safety. Those topics appear among the secondary outcomes, but their results are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies a binary primary outcome reported as a count of participants. In general, a binary outcome classifies each participant into one of two categories, such as meeting or not meeting an endpoint definition. A count is the number in one category; a proportion additionally requires the relevant denominator. For MARRS, the registry describes the success category but does not report the count achieving it or the endpoint denominator.

What does a confidence interval convey?

In general, a confidence interval communicates the uncertainty associated with an estimate. A narrow interval indicates greater statistical precision than a wide interval, while an interval around a proportion also helps readers judge which underlying rates remain compatible with the observed data and the analysis assumptions. A confidence interval is not a guarantee that the true value lies within its limits. No confidence interval for the primary endpoint is reported in the registry record, so its precision cannot be assessed.

What is the role of the intent-to-treat population?

In general, an intent-to-treat population is defined according to a study’s analysis rules and is intended to preserve the assigned or enrolled cohort for analysis. In a single-group device study, the exact operational definition still matters: the registry should specify which participants are included and how participants without an evaluable outcome are handled. The record names the intent-to-treat cohort for the primary endpoint but does not give its size or detailed membership rules. The listed enrollment of 235 cannot be assumed to be the endpoint denominator without that information.

How should the single-group design shape interpretation?

In general, a single-group study can estimate outcomes observed in its cohort, but it does not create a concurrent control group. It therefore cannot isolate the effect of an intervention from other influences on outcomes using a within-study treatment comparison. This design feature is relevant to MARRS because the record lists one group and no allocation comparison. The endpoint can be framed as a cohort performance measure, not as a randomized estimate of comparative benefit or harm.

What does the registry say about the statistical plan?

The record lists one analysis and 34 outcome measures. These summary entries do not describe the full statistical plan. The specified test, estimator, covariate adjustment, confidence-interval method, handling of missing outcomes, and any interim analyses are not reported in the registry record. They should not be inferred from the endpoint type or from the number of listed analyses.

In general, a binary endpoint may be analyzed by estimating a proportion and its uncertainty. The particular method should match the design, analysis population, and assumptions. With no primary estimate or interval posted, there is no basis to reconstruct the sponsor’s primary analysis or assess its precision from the record.

Why can over-dispersion matter?

In general, over-dispersion occurs when observed variability is greater than expected under a model’s assumptions. It matters because a model that understates variability can produce uncertainty intervals that are too narrow and tests that are too optimistic. This concept is not a reported feature of the MARRS primary endpoint, which is described as a participant count. The registry record does not state that an over-dispersion adjustment was used.

The registry’s sample-size assumptions describe a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is described as a stated fraction of the observed effect. The record does not provide the resulting planning values in the registry record reported for this analysis. These assumptions are not the MARRS design: MARRS is listed as single group, not as an equal-allocation two-arm study. Such planning illustrations are hypothetical design calculations, not observed power and not evidence about the study’s endpoint result.

In general, prospective sample-size planning asks how much information a proposed study might need under chosen assumptions. It does not measure the probability that a completed study has demonstrated an effect. Without the underlying observed effect and calculation results, the planning illustration cannot be interpreted quantitatively for MARRS. The registry also does not report the study’s own sample-size justification.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Millipede System")
n      <- c(180)
events <- c(160)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Millipede System  180  160  88.9  83.4  93.1  83.5  92.7  83.5  92.7

11. Multiplicity, Missing Data and Analysis Populations

The record lists 34 outcome measures, including the primary reperfusion endpoint and secondary clinical, safety, and procedural outcomes. Testing or estimating many outcomes can raise multiplicity concerns. In general, when numerous statistical tests are conducted, the chance of at least one apparently notable result can increase unless the analysis plan addresses the family of comparisons. A prespecified hierarchy or adjustment can help define how results should be interpreted. The registry record does not report a multiplicity strategy, so it is not possible to determine whether or how the outcomes were adjusted or prioritized beyond identifying a primary endpoint.

The record lists one analysis, but this summary does not establish the number of statistical tests, subgroup analyses, or model specifications that may have been planned or conducted. The detailed analysis plan and any interim analyses are not reported in the registry record. No conclusion about those procedures should be inferred from the count of listed analyses.

Missing-data handling is also not reported in the registry record. The primary outcome is assigned to an intent-to-treat cohort, but the record does not state the number with evaluable endpoint data, how missing outcome assessments were classified, or whether any sensitivity analyses were conducted. Missingness can affect an outcome estimate if participants without observed outcomes differ from those with observed outcomes; the direction and size of any such effect cannot be assessed without details.

Enrollment of 235 is not enough to determine the primary analysis denominator or the number of missing endpoint observations. The safety figures use a listed at-risk group of 180, which is not identified as the primary endpoint population. The available record therefore does not support treating those population counts as interchangeable.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 3.0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: ischaemic stroke (3.9%), pneumonia (2.8%), stroke in evolution (2.8%), myocardial infarction (2.2%), sepsis (1.7%).

The registry lists the Millipede System group with 180 participants at risk for serious adverse events and 57 affected by serious events. It separately lists 180 at risk for other adverse events and 81 affected by other events, alongside 25 deaths. These are descriptive registry counts. The record does not provide enough detail to infer overlap among event categories or to treat the counts as mutually exclusive participant groups.

The listed serious adverse event terms include ischaemic stroke at 3.9%, pneumonia at 2.8%, stroke in evolution at 2.8%, myocardial infarction at 2.2%, sepsis at 1.7%, and brain oedema at 1.7%. These terms and percentages should be read as the registry’s reported event summary, not as proof that the device caused the events. The record does not provide the event-level details needed to assess timing, relatedness, recurrence, or severity beyond the serious-event classification.

Safety counts do not by themselves establish comparative risk. This is a single-group study without a concurrent control group, and the record does not report a comparative safety estimate. The at-risk count of 180 should not be substituted for the enrollment figure or assumed to be the denominator for every other outcome. Further population definitions and analysis details are not reported in the registry record.

13. What the Result Does, and Does Not, Mean

The registry record establishes that MARRS was a completed, single-group study of the Millipede System in acute ischemic stroke due to large vessel occlusions. It specifies a primary endpoint based on core lab-adjudicated reperfusion success within three passes and without additional therapy. It also lists a range of clinical, procedural, and safety outcomes. These details explain what the study set out to assess.

The posted record does not report the primary endpoint result. It therefore does not show how many participants met the endpoint, the rate of success, or the precision of an estimate. The listed enrollment of 235 cannot fill that gap because the endpoint result and analysis denominator are not reported. A completed study status indicates that the registry labels the study completed; it does not supply a missing outcome estimate.

The safety section does report counts and selected serious-event terms with percentages. Those summaries describe events recorded for the study group. They do not establish that the Millipede System caused an event, nor do they estimate how event frequency compares with another treatment. A single-group design lacks a concurrent randomized comparator for that purpose.

In general, a study’s observed outcome, its statistical uncertainty, and a causal treatment comparison are distinct pieces of evidence. The primary outcome estimate and uncertainty are not reported in the registry record, and the design does not include a control group. Consequently, the record cannot support a quantitative conclusion about comparative performance or safety. It does support a description of the endpoint definition, study structure, and listed safety summaries, while leaving the main outcome result unknown.

14. Why This Trial Matters Statistically

MARRS is statistically informative as an example of how a device study can define a procedural performance endpoint separately from broader clinical and safety outcomes. Its primary criterion combines a reperfusion threshold, a limit on passes, and the absence of additional therapy. Each component affects which participants count as successes, so interpretation depends on the complete endpoint definition rather than on the label of reperfusion success alone.

The record also illustrates why design matters when reading outcome summaries. A single-group study can describe outcomes in its cohort, but it does not supply a concurrent control comparison. That distinction limits the claims that can be made from any observed rate, even when an outcome is clearly defined. It is especially important to distinguish descriptive performance from a comparative treatment effect.

Another statistical issue is the gap between a completed study and a posted result. The registry gives enrollment and endpoint definitions but does not report the primary endpoint count or estimate. Without that result, readers cannot evaluate the magnitude or precision of the primary outcome. The listed safety counts add descriptive information, but do not replace the primary endpoint result or create a control comparison.

Finally, the registry lists 34 outcomes but does not report a multiplicity strategy, missing-data methods, or a detailed analysis plan. These omissions limit assessment of how secondary findings should be interpreted. The record thus highlights the importance of complete reporting: design, population definitions, estimates, uncertainty, and analysis methods all contribute to a statistically responsible interpretation.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The principal limitation of the posted record is that the primary endpoint result is not reported. No count of participants achieving core lab-adjudicated reperfusion success, endpoint denominator, proportion, or confidence interval is available. The primary outcome’s magnitude and precision therefore cannot be assessed.

The single-group design provides no concurrent randomized comparator. Even a reported cohort outcome would not, by itself, quantify a causal difference from another treatment. The record also lists masking as none and allocation as NA; it does not provide further details about outcome adjudication beyond identifying an independent Core Lab.

The enrollment figure of 235 and the safety at-risk count of 180 refer to reported quantities, but the record does not explain their relationship or identify the primary endpoint denominator. It does not report the number of participants with missing or unevaluable primary outcome data, or how such cases were handled. The analysis population rules are not detailed.

The record lists 34 outcome measures but does not report a multiplicity plan or the detailed statistical analysis plan. Sample-size justification, planned interim analyses, and the methods used for the primary analysis are not reported in the registry record. The safety summaries likewise lack detail about event timing, recurrence, participant-level overlap, and causal attribution. These omissions constrain interpretation of both performance and safety without implying that unreported procedures were or were not conducted.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Millipede AspiRation for Revascularization in Stroke (MARRS) Study — NCT05714501.
• Registry record last updated 2026-07-10; status last verified 2026-06.
• Results first posted 2026-07-10.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

MARRS is a completed, single-group device study of the Millipede System for revascularization in acute ischemic stroke due to large vessel occlusions. The registry lists enrollment of 235, a study start date of 2023-10-09, and a primary completion date of 2025-03-08. The sponsor is Perfuze.

The primary endpoint is the count of intent-to-treat participants achieving core lab-adjudicated mTICI 2b or greater within three passes and without additional therapy. The primary endpoint result is not reported in the registry record. The record lists 34 outcome measures and one analysis, but does not report detailed analysis methods, missing-data handling, or a multiplicity strategy.

Safety summaries include 180 participants at risk for serious adverse events, 57 affected by serious events, 180 at risk for other adverse events, 81 affected by other events, and 25 deaths. These are descriptive counts from a study without a concurrent control group.