Valor II: The Valiant Thoracic Stent Graft System Clinical Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Valor II: The Valiant Thoracic Stent Graft System Clinical Study (NCT00413231), a na na study. The primary outcome is Percentage of Participants That Did NOT Experience Aneurysm-Related Mortality (Post-market Primary Endpoint).

2. Clinical Question

This question concerns aneurysm-related mortality-free status after device treatment, rather than a direct comparison of the device with another treatment. The study also lists secondary outcomes addressing deployment and delivery, perioperative mortality, neurological events, secondary procedures due to endoleak, major adverse events, aneurysm-related mortality, and aneurysm rupture. Those outcomes broaden the clinical description of device performance and safety, but their numerical results are not reported in the registry record.

3. Trial Design

The Valor II study evaluated the clinical performance of the Valiant Thoracic Stent Graft System in the treatment of descending thoracic aneurysms of degenerative etiology among subjects who were candidates for endovascular repair. The registry lists the study as completed and identifies Medtronic Cardiovascular as the sponsor. The recorded study start is 2006-12 and the primary completion is 2010-08.

The design is listed as single group, with allocation recorded as NA and masking recorded as none. There was no other arm. The registry describes 160 subjects enrolled, including 157 treated with the study device and three classified as intent-to-treat who did not receive it. These descriptions distinguish enrollment from treatment exposure; they do not establish that every endpoint used the same analysis population.

The primary endpoint was a post-market measure of the percentage of participants who did not experience aneurysm-related mortality. Its stated timeframe was 0 through 1825 days post treatment. The registry describes evaluation by comparison with a predefined performance goal based on an analysis of ARM-free rates from TEVAR data and results from the VALOR clinical study. The numerical performance goal, the detailed analysis procedure, and the endpoint result are not reported in the registry record.

A single-group design can describe outcomes observed after treatment, but it does not estimate a randomized between-group treatment contrast. The performance-goal comparison is not equivalent to a concurrent control arm: its interpretation depends on the goal and its supporting evidence, neither of which is numerically detailed in the registry record. The registry also does not report the randomization or masking procedures because it lists no allocation and no masking.

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.

0 to 30-day Post Treatment

Reasons for not completing this period:

30-day to 365-day Post Treatment

Reasons for not completing this period:

365-day to 60-month Post Treatment

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Subjects treated or intended to treat with the test device

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 Percentage of Participants That Did NOT Experience Aneurysm-Related Mortality (Post-market Primary Endpoint), measured over 0 through 1825 days post treatment.

The primary endpoint is the percentage of participants who did not experience aneurysm-related mortality during the period from treatment through 1825 days post treatment. The endpoint description calls this the ARM-free rate and identifies the population as subjects treated or intended to be treated with the test device. It is a binary outcome summarized as a percentage: each participant is classified according to whether aneurysm-related mortality occurred within the endpoint period.

An ARM-free endpoint expresses survival without a specified cause of death, rather than survival from any cause. It is used in this study as a measure of clinical performance over follow-up, with the rate evaluated against a predefined performance goal. General statistical context: a performance goal can provide a benchmark when a study has no concurrent control group, but the comparison is only interpretable with knowledge of the benchmark, its derivation, and the analysis rules. The registry describes the benchmark’s broad basis but does not report its value or the endpoint result.

The registry specifies a 90% confidence interval for the endpoint. In general, a confidence interval conveys the precision of an estimate under the statistical method used; its width depends on the data and method. No interval limits or point estimate are reported in the registry record, so the endpoint’s observed rate and precision cannot be assessed from that record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a percentage endpoint represent?

The primary outcome is a binary participant-level measure summarized as a percentage: participants either experienced aneurysm-related mortality within the stated period or did not. The reported endpoint is the percentage who did not experience it. This kind of summary is intuitive, but it depends on a clear definition of the event, a specified follow-up period, and a defined analysis population. The registry record gives the endpoint label and timeframe, but does not report the observed percentage, the event count, or the denominator used in analysis.

General statistical context: a percentage estimate is based on the observed classifications in the analysis population. It does not by itself describe the timing of events, account for different lengths of follow-up, or show what happened to participants whose endpoint status is unknown. For a time-to-event analysis, censoring and follow-up duration may matter; the registry’s primary outcome description identifies a percentage and a 90% confidence interval, but does not report the detailed method used to handle follow-up or incomplete status.

What does a confidence interval add?

The primary outcome specifies a 90% confidence interval. General statistical context: an interval communicates uncertainty around an estimate under the assumptions of the method used. A narrower interval generally indicates greater precision, while a wider interval indicates less precision. The interval does not guarantee that the true value lies within its particular limits, and it does not replace an assessment of the study design or the endpoint definition.

Because neither the endpoint percentage nor its interval limits are reported in the registry record, the precision of the estimate cannot be assessed. The confidence level alone does not reveal whether the interval is narrow or wide. Nor does it show whether the observed rate satisfied the predefined performance goal; that assessment would require the estimate and the benchmark, as well as the specified comparison rule.

How should a performance-goal comparison be read?

The registry describes a comparison of the ARM-free rate with a predefined performance goal. It says the goal was based on an analysis of ARM-free rates from TEVAR data and results from the VALOR clinical study. General statistical context: a benchmark comparison asks whether an estimate is consistent with a prespecified reference under a particular decision rule. The benchmark is not a concurrent control group, and it cannot ensure that the benchmark and study population are comparable.

Important details include the numerical goal, how it was selected, whether uncertainty in the historical evidence was considered, the statistical test or interval rule, and the analysis population. The registry record does not report the numerical goal or the full statistical procedure. It also does not report the endpoint estimate, so the comparison’s result cannot be reconstructed from the record.

What can a single-group design estimate?

A single-group study can describe outcomes among participants enrolled or treated under the study conditions. Without a concurrent comparison arm, it cannot directly estimate a randomized difference between treatments. Changes in outcomes over time or differences from a historical benchmark may reflect differences in populations, clinical practice, follow-up, or outcome ascertainment as well as any treatment-related effect. These are general limitations of non-concurrent comparisons, not claims about what occurred in this study.

The record lists allocation as NA, masking as none, and the model as single group. It therefore does not describe allocation to competing treatment arms or blinded outcome assessment. The extent to which endpoint adjudication or other assessments were independently performed is not reported in the registry record.

What do sample-size illustrations mean?

General statistical context: a planning calculation explores how a future study might perform under stated assumptions. The registry’s planning description says that illustrations use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with an effect to detect expressed as a fraction of an observed effect. It distinguishes participant counts per arm from total event counts for time-to-event calculations.

Those assumptions describe planning illustrations, not the design of this single-group study. The record does not report that these assumptions were the trial’s own design choices. Such calculations are not observed power, do not summarize the actual endpoint result, and do not establish that the study was adequately sized for its primary question. The study’s own sample-size justification is not reported in the registry record.

The record does not report the primary endpoint effect needed to evaluate calculations anchored to an observed effect. Any planning values should therefore be understood only as hypothetical design illustrations under their stated assumptions, not as additional evidence about the study outcome.

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("Valiant Thoracic Stent Graft System")
n      <- c(160)
events <- c(152)
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  Valiant Thoracic Stent Graft System  160  152  95.0  90.4  97.8  90.4  97.4  90.4  97.4

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 27 outcome measures, including the primary endpoint and secondary measures covering technical success, mortality, neurological outcomes, endoleak-related procedures, major adverse events, and aneurysm rupture. Considering multiple outcomes can raise multiplicity concerns: when many hypotheses are tested, the chance of at least one apparently notable result may increase. This is general statistical context, not a claim that any particular adjustment was or was not applied in this study.

The registry record does not report a statistical analysis plan, a multiplicity adjustment, an ordering or hierarchy for secondary endpoints, or which analyses were designated as confirmatory. It lists no analyses. The record also does not report numerical results for the primary or secondary outcomes. The endpoint’s 90% confidence interval is specified, but its limits are absent, and the procedure used to make the performance-goal comparison is not fully described.

Missing-data handling is not reported in the registry record. In particular, it does not describe the number of participants with incomplete endpoint status, the handling of loss to follow-up, imputation, censoring, or sensitivity analyses. These details are important because an endpoint percentage may depend on how unknown outcomes are treated.

The primary endpoint population is stated as subjects treated or intended to treat. Enrollment information distinguishes 157 treated subjects from three classified as intent-to-treat who did not receive the device. The record does not explain how this population description was implemented in the endpoint analysis or provide an analysis denominator. It also does not report whether any other analysis populations were used. Consequently, the record does not permit assessment of how missing data, population selection, or multiple outcomes affected the reported findings.

12. Safety Results

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

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: aortic aneurysm (13.8%), respiratory failure (10.0%), cardiac failure congestive (8.8%), stent-graft endoleak (8.1%), gastrointestinal haemorrhage (7.5%).

The registry lists a serious-adverse-event group with 160 at risk and 135 affected. It separately lists 160 at risk and 160 affected for other adverse events. These are the group counts as recorded; the registry record does not provide further detail about event definitions, follow-up windows, or whether the same participants could contribute to more than one event category. The deaths field is not reported in the registry record.

Among the listed serious terms, the registry gives Aortic aneurysm at 13.8%, Respiratory failure at 10.0%, Cardiac failure congestive at 8.8%, Stent-graft endoleak at 8.1%, Gastrointestinal haemorrhage at 7.5%, and Myocardial infarction at 7.5%. The denominator and observation period for these term-specific percentages are not reported in the registry record. They should not be added together: participants may experience more than one type of event, and the record does not state that the categories are mutually exclusive.

These figures describe adverse-event reporting; they do not by themselves establish cause, comparative risk, or the balance of benefit and harm. A single-group study has no concurrent control arm for estimating a between-group safety difference. General statistical context: interpretation of adverse-event summaries depends on consistent definitions, ascertainment, exposure time, and analysis populations. The registry record does not report all those details for the listed figures.

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

The record establishes what the study set out to assess: the percentage of participants without aneurysm-related mortality through 1825 days post treatment, compared with a predefined performance goal. It also identifies the study as a single-group evaluation of the Valiant Thoracic Stent Graft System and describes enrolled and treated populations. These details explain the study question and design, but are not outcome evidence by themselves.

The registry does not report the numerical primary endpoint result, its 90% confidence interval, or the value of the performance goal. It therefore does not show whether the stated benchmark was met, how large the ARM-free rate was, or how precisely it was estimated. The secondary outcome names likewise do not establish the frequency of those outcomes because their numerical results are not reported in the registry record.

Even if an endpoint estimate were available, a single-group result would describe outcomes in the study population rather than a randomized comparison with another treatment. A benchmark based on external data can provide context, but interpretation depends on the benchmark’s derivation and comparability. The registry record does not report enough numerical or methodological detail to assess that comparison.

The listed adverse-event information offers some descriptive safety data, including counts and selected term percentages. It does not establish that the device caused or prevented an event, and it cannot quantify a comparative safety effect without a suitable comparison. General statistical context: a point estimate, even when reported, should be read alongside its uncertainty, population definition, follow-up, and analysis methods.

Accordingly, the registry record supports a description of the study question, design, endpoint, and selected safety listings. It does not support a conclusion about whether treatment works or does not work. No medical advice or treatment decision follows from the information recorded.

14. Why This Trial Matters Statistically

This study is statistically notable for pairing a single-group device evaluation with a primary endpoint framed around a predefined performance goal. That setup raises a different interpretive question from a randomized trial: the focus is not a direct comparison between concurrently assigned groups, but the relationship between an observed rate and a benchmark. Understanding that relationship requires both the study estimate and the benchmark, as well as a clear comparison rule.

The endpoint also illustrates why an outcome definition is not a result. The registry specifies a 90% confidence interval and a follow-up period from treatment through 1825 days, but reports neither the interval limits nor the endpoint percentage. Without those values, readers cannot judge precision or the benchmark comparison. The absence of numerical results is consequential even when the intended outcome and analysis rationale are described.

The enrollment and treatment descriptions provide another important statistical distinction. The registry reports 160 enrolled subjects, 157 treated with the device, and three classified as intent-to-treat who did not receive it. The primary endpoint population is described as treated or intended to treat, but the record does not explain the analysis denominator. That distinction matters because enrollment, exposure, and endpoint analysis populations need not be interchangeable.

Finally, the registry lists numerous clinical outcomes and selected adverse-event terms, while detailed analysis methods and missing-data procedures are not reported. This makes the record useful for understanding the study’s scope, but limits assessment of multiplicity, precision, and the robustness of any analysis. These are broadly important issues when interpreting clinical evidence, especially when the design lacks a concurrent control group.

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 trial-specific limitation in the registry record is the absence of the primary endpoint result. Although the endpoint, timeframe, confidence level, and performance-goal rationale are described, the record does not report the ARM-free percentage, its 90% confidence interval, or the numerical performance goal. The primary question therefore cannot be answered from the registry entry.

The single-group design has no concurrent control arm. The stated comparison with a predefined performance goal depends on external evidence, but the goal’s numerical value and detailed derivation are not reported. The record also does not provide enough information to assess comparability between the study population and the data underlying the benchmark.

The registry distinguishes enrolled subjects from those treated with the device, but does not report the endpoint analysis denominator or explain how the stated population of treated or intended-to-treat subjects was implemented. Missing-data methods, loss-to-follow-up information, endpoint ascertainment details, and sensitivity analyses are not reported in the registry record. These omissions limit evaluation of the estimate even if it were available.

Other limitations include the absence of a reported statistical analysis plan, detailed multiplicity procedures, and numerical results for the listed secondary outcomes. The serious-event term percentages lack a reported denominator and observation period in the registry entry. The record describes no masking. These limitations concern what can be evaluated from the registry information; they do not establish that a procedure was absent from study conduct unless the record specifically says so.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Valor II: The Valiant Thoracic Stent Graft System Clinical Study — NCT00413231.
• Registry record last updated 2021-11-03; status last verified 2021-10.
• Results first posted 2012-04-05.
• 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

The registry describes a completed, single-group study of the Valiant Thoracic Stent Graft System for descending thoracic aneurysms of degenerative etiology in subjects who were candidates for endovascular repair. Medtronic Cardiovascular is listed as sponsor. The recorded study start is 2006-12 and primary completion is 2010-08.

The record reports 160 enrolled subjects, including 157 treated with the device and three classified as intent-to-treat who did not receive it. The primary endpoint is the percentage without aneurysm-related mortality from treatment through 1825 days, with a 90% confidence interval and comparison to a predefined performance goal. The numerical endpoint result, interval limits, and goal value are not reported in the registry record. The record also lists 27 outcome measures and selected adverse-event information, but does not report numerical results for the secondary outcomes or detailed analysis methods.