Evaluation of the Valiant Mona LSA Thoracic Stent Graft System in Descending TAA and Chronic Dissections: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluation of the Valiant Mona LSA Thoracic Stent Graft System in Descending TAA and Chronic Dissections (NCT02365467), a na phase not stated study. The primary outcome is 30 Day Composite Safety Endpoint.

2. Clinical Question

Statistically, the central question is descriptive: how often was at least one component of the composite recorded in the specified window among participants meeting the endpoint’s evaluability definition? Without a comparator group, the observed frequency cannot by itself distinguish outcomes associated with the device or procedure from outcomes that might have occurred under another strategy. The registry names safety and effectiveness as study aims, but does not report a numerical primary endpoint estimate or a comparative effectiveness result. The clinical question is therefore more limited than a randomized treatment comparison: it concerns the observed short-term experience in this enrolled cohort.

3. Trial Design

NCT02365467 is a completed feasibility study sponsored by Medtronic Cardiovascular. The registry gives the study title as “Evaluation of the Valiant Mona LSA Thoracic Stent Graft System in Descending TAA and Chronic Dissections.” The official title refers to descending thoracic aortic aneurysms and chronic dissections. The listed condition is aortic aneurysm, thoracic, chronic Type B dissection.

The registry identifies a single-group model, with one arm described as treatment with the Valiant Mona LSA device. It reports no allocation scheme and no masking. No separate control group is reported. Accordingly, the design does not support a randomized, masked comparison between device and control groups. The enrollment is 32. The listed study start is 2015-04-16, the primary completion date is 2019-09-20, and the status is completed.

The brief description distinguishes the feasibility study from its expansion. The feasibility study aimed to characterize device safety, including acute and 30-day safety and effectiveness, and to evaluate the current instructions for use. It also says the study could direct changes to delivery and deployment steps. The expansion aimed to characterize the device, particularly its acute and 30-day safety and effectiveness, in subjects enrolled with chronic Type B dissections. These aims describe the study rationale; they do not establish that any instruction or device change occurred.

The registry lists 2 outcome measures and 0 analysis entries. A sample-size justification, formal statistical analysis plan, detailed enrollment flow, and account of the number included in each analysis are not reported in the registry record. The study’s completion status and enrollment do not, on their own, establish that the primary endpoint was met or that all enrolled participants contributed to its analysis.

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.

Before assignment: A total of 32 subjects were enrolled in the study. 30 enrolled subjects were implanted with the study device. The 30-day primary endpoint was evaluated when 29 subjects completed the 30-day follow-up.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The analysis was performed on all enrolled subjects who were considered evaluable. The subjects were considered enrolled after arterial access is achieved and the Valiant Mona LSA Thoracic Stent Graft System was introduced into the vasculature. Subjects were evaluable if they had the event, or did not have the event and completed a follow-up 15 days or more after the index procedure.

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.

6. Primary Endpoint

The registry lists the primary outcome as 30 Day Composite Safety Endpoint, measured over 1 month.

The primary endpoint is the 30 Day Composite Safety Endpoint, expressed as a percentage of participants, with a timeframe of 1 month. It covers events from Day 0 through Day 30 after the index procedure. A participant meets the composite if any of its listed components occurs: aorta related mortality, stroke, paraplegia, or left arm/hand ischemia.

A composite combines multiple clinical events into one outcome. In general, this approach can capture a broader range of safety experiences than a single-event endpoint and can make a summary measure easier to interpret when several event types matter to the study question. Its meaning depends on the components: a composite percentage does not reveal which component occurred, how often each component occurred, or whether participants experienced more than one component. Component-level results are not reported in the registry record.

The registry describes the analysis population as all enrolled subjects considered evaluable. It says a subject was considered enrolled after arterial access was achieved and the device was introduced into the vasculature. The evaluability description begins by saying subjects were evaluable if they had the event, or did not, but the registry text ends before completing that rule. The number considered evaluable and the endpoint percentage are not reported in the registry record.

In general, this endpoint is used to summarize specified short-term safety events after the procedure. Its 30-day window does not address outcomes beyond that window, and the composite result would not, on its own, describe longer-term safety or effectiveness.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the primary endpoint as a percentage of participants and specifies a 95% confidence interval. The endpoint is binary at the participant level: for the defined observation window, a participant either experienced at least one listed component or did not, according to the endpoint rule. The registry names the components and timeframe, but does not report the event count, analyzed denominator, percentage, or interval estimate.

What a percentage describes

In general, a percentage for a binary endpoint is a proportion of participants with the event among the participants included in that analysis. The denominator matters: a percentage based on all enrolled participants can differ from one based on an evaluable subset. The registry says the primary analysis used enrolled subjects considered evaluable, but the number evaluable is not reported in the registry record. Its evaluability definition is also cut off after beginning to distinguish subjects who had the event from those who did not. The exact analysis denominator and rule therefore cannot be confirmed from the record.

What the confidence interval adds

In general, a confidence interval conveys the statistical uncertainty around an estimate arising from the observed data and analysis method. It does not describe every source of uncertainty, such as limitations in study design or how representative the enrolled group may be. A 95% confidence interval is named for this endpoint, but its limits and the point estimate are not reported in the registry record. No assessment of the endpoint’s numerical precision is possible without them.

What the composite combines

The endpoint combines aorta related mortality, stroke, paraplegia, and left arm/hand ischemia over the interval from Day 0 through Day 30. In general, a composite analysis counts participants meeting any qualifying component, so interpretation depends on both the overall frequency and the component pattern. A single composite percentage cannot tell a reader which component drove the result. Component-specific counts and percentages are not reported in the registry record. Nor does the record specify in the available description how multiple components in one participant would be represented in component-level summaries.

Design and comparison

The registry gives a single-group model and one device-treatment arm. In general, a single-group outcome analysis estimates what was observed in that cohort; it does not estimate a treatment contrast against a concurrent control. The registry reports no allocation scheme and no masking. A comparative hypothesis test, adjusted model, or other inferential procedure is not reported in the registry record. The registry lists 0 analysis entries, so there is no posted analysis detail from which to identify a model, covariate adjustment, or testing procedure.

The registry identifies a 95% confidence interval as the endpoint’s dispersion measure, but does not identify the interval calculation method. The statistical method used to produce the primary estimate and interval is not reported in the registry record. It would therefore be inappropriate to assume a particular formula or to reproduce an inferential result from the available endpoint description alone.

Planning assumptions and observed results

A planning illustration is described using a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect set to a stated fraction of the observed effect. The description says time-to-event planning gives a total number of events and other planning displays give participants per arm. These are planning assumptions, not a report of the study’s design: the registered study is single group. The original sample-size justification and any protocol-specific planning assumptions are not reported in the registry record. No numerical planning estimates or observed effect value are reported in the registry record, so those quantities cannot be characterized.

In general, a sample-size planning calculation asks how many observations might be needed under specified assumptions about an effect, variability, significance level, and power. It is sensitive to those assumptions. A planning illustration based on an observed effect is not the same as the trial’s original design calculation, and it is not observed power. It cannot establish that the study was adequately sized for the primary endpoint. The registry record does not report a sample-size justification or a power target for this study.

Analyses not described

The registry does not report an interim analysis plan, a formal method for missing outcomes, a multiplicity procedure, or an approach to sensitivity analyses. It also does not report how deviations from the endpoint definition were handled. These details can influence how a result should be interpreted, but their absence does not show that a particular method was or was not used outside the registry record. The available record supports describing the registered design and endpoint, not reconstructing unreported statistical procedures.

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("Endovascular Repair")
n      <- c(30)
events <- c(3)
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  Endovascular Repair  30  3  10.0  2.1  26.5  3.5  25.6  3.6  25.8

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 2 outcome measures but 0 analysis entries. It identifies one primary endpoint in the available information: the 30 Day Composite Safety Endpoint. The other outcome measure’s title, definition, and result are not reported in the registry record. A plan for prioritizing or adjusting analyses across multiple outcomes is not reported in the registry record.

In general, multiplicity arises when several outcomes or statistical tests are considered; without an appropriate plan, the chance of a false-positive finding across tests can increase. That general concern does not establish that a particular adjustment was required or omitted in this study. The registry record does not describe a testing hierarchy, multiplicity adjustment, or confirmatory hypothesis-testing strategy.

The primary endpoint population is described as enrolled subjects considered evaluable. The registry says enrollment followed arterial access and introduction of the device into the vasculature. The evaluability criterion is incomplete in the record, and the evaluable denominator is not reported. This prevents confirmation of how many enrolled participants contributed to the primary endpoint analysis.

A missing-data method, handling of withdrawals, and sensitivity analyses are not reported in the registry record. The endpoint definition indicates a 30-day observation window, but the record does not say how incomplete follow-up or unavailable event information was addressed. No interim analysis plan is reported. These gaps limit assessment of analysis populations and robustness; they do not establish that missing observations or interim analyses occurred.

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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: atrial fibrillation (15.6%), pneumonia (12.5%), aortic aneurysm (12.5%), stent-graft endoleak (9.4%), acute kidney injury (9.4%).

The registry lists an Endovascular Repair group with 32 participants at risk for serious adverse events and 30 affected. For other adverse events, it lists 32 at risk and 27 affected. It also reports 9 deaths. The registry does not state in the available information whether deaths were related to the device or procedure, or provide their causes.

The listed serious adverse event terms and percentages are atrial fibrillation, 15.6%; pneumonia, 12.5%; aortic aneurysm, 12.5%; stent-graft endoleak, 9.4%; acute kidney injury, 9.4%; and chronic obstructive pulmonary disease, 9.4%. These are registry-listed event terms; the record does not clarify whether participants could contribute to more than one term or how the percentages were calculated.

In general, participant counts and event-term percentages answer different questions: an affected-participant count describes people with reported events, while a term-specific percentage describes the registry’s presentation for that event term. These listings should not be added together or treated as a device-attributable risk estimate. The registry does not report attribution, comparative safety data, or a relationship between these listings and the primary composite endpoint.

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

The record establishes that a completed feasibility study evaluated the Valiant Mona LSA Thoracic Stent Graft System in a single group of 32 enrolled participants. It specifies a 30-day composite safety endpoint comprising aorta related mortality, stroke, paraplegia, and left arm/hand ischemia. The endpoint result is not reported in the registry record, so the frequency of the composite and the precision of its estimate cannot be described.

The study’s stated aims included characterizing safety and assessing safety and effectiveness acutely and at the 30 day visit. Aims are not results. The registry does not report a numerical effectiveness result, a comparator estimate, or component-level primary endpoint findings. The serious adverse event listings provide event counts and term percentages, but do not establish that an event was caused by the device or procedure. The reported deaths likewise cannot be attributed on the basis of the available information.

In general, a single-group feasibility study can provide descriptive information about outcomes in the enrolled cohort and can help characterize what was observed during the study. It cannot, by itself, estimate a controlled difference between treatment strategies. The absence of a reported comparator means that observed events cannot be interpreted as an estimate of what would have occurred under an alternative strategy.

The registry record also does not establish how representative the enrolled participants were of a broader population, whether all enrolled participants completed follow-up, or how incomplete endpoint information was handled. Those details are important for judging the scope of any result, but they are not reported in the registry record. The completed status does not resolve these uncertainties.

Thus, the study record supports a description of design, enrollment, endpoint definition, and listed adverse event figures. It does not support a numerical conclusion about the primary endpoint, a comparison with another treatment, or a causal conclusion about safety or effectiveness. Any such conclusion would require results and analysis details that are not reported in the registry record.

14. Why This Trial Matters Statistically

This study illustrates why design and outcome reporting must be read together. The registry identifies a clinically focused short-term composite endpoint and gives its observation window and components. Those details define what the endpoint was intended to capture. But without the event count, evaluable denominator, estimate, and confidence interval, the central outcome cannot be quantitatively interpreted.

The single-group design is also important. In general, a cohort’s event frequency is a descriptive result, while a comparison between groups is needed to estimate a contrast between treatment strategies. Here, the registry identifies one device-treatment arm and no separate comparator. The study can therefore be understood as a feasibility evaluation rather than a randomized comparative trial, and its stated aims should not be confused with evidence of comparative benefit or harm.

The endpoint’s evaluability language highlights another statistical issue: analysis populations need clear definitions. The registry says participants were considered enrolled after arterial access and device introduction, then describes an evaluable population, but the eligibility sentence is incomplete and the evaluable count is absent. Without those details, readers cannot tell precisely which participants form the denominator for the endpoint.

Finally, safety summaries require careful interpretation. Counts for participants with serious and other adverse events, event-term percentages, and deaths are distinct descriptions. Without attribution and component-level context, none should be treated as a causal estimate. The record’s limitations are informative in their own right: they identify which questions the registered design and posted results can answer, and which remain unresolved by the available information.

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 most consequential limitation for interpreting the primary endpoint is that its numerical result is not reported in the registry record. The event count, evaluable denominator, percentage, and 95% confidence interval are all absent. The evaluability description is incomplete, so the analysis population cannot be fully reconstructed from the record.

The single-group model and one treatment arm mean there is no reported concurrent comparator. As a result, the record does not support a controlled estimate of differences in safety or effectiveness. Allocation is listed as NA and masking as none. No adjustment for baseline factors or other comparative analysis is described.

The registry gives a total enrollment of 32, but does not report the number completing follow-up, the number with missing endpoint information, withdrawals, or reasons for non-evaluability. A missing-data approach and sensitivity analysis are not reported in the registry record. The other outcome measure’s definition and results are also not reported, and the registry lists 0 analysis entries.

Safety information is limited to the listed affected counts, deaths, and serious event terms with percentages. The available record does not report event attribution, causes of death, component-level results for the primary composite, or whether event-term listings overlap at the participant level. Longer-term results are not reported in the registry record. These limitations restrict interpretation to the design and descriptive safety information actually recorded; they do not establish that unreported events or analyses did or did not occur.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Evaluation of the Valiant Mona LSA Thoracic Stent Graft System in Descending TAA and Chronic Dissections — NCT02365467.
• Registry record last updated 2025-08-17; status last verified 2025-08.
• Results first posted 2022-10-21.
• 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

NCT02365467 is a completed, single-group feasibility study sponsored by Medtronic Cardiovascular. It enrolled 32 participants and evaluated the Valiant Mona LSA Thoracic Stent Graft System in descending thoracic aortic aneurysms and chronic dissections. The registry lists a 30 Day Composite Safety Endpoint, assessed from Day 0 through Day 30, comprising aorta related mortality, stroke, paraplegia, or left arm/hand ischemia.

The registry reports 2 outcome measures and 0 analysis entries. It does not report the primary endpoint estimate, event count, evaluable denominator, or confidence interval. Safety listings include 30 of 32 participants affected by serious adverse events, 27 of 32 affected by other adverse events, and 9 deaths. The record does not provide event attribution or a control-group comparison.