Visceral Manifold Study for the Repair of Thoracoabdominal Aortic Aneurysms: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Visceral Manifold Study for the Repair of Thoracoabdominal Aortic Aneurysms (NCT03113383), a non-randomized na study. The primary outcome is Safety Endpoint: Freedom From Major Adverse Events.

2. Clinical Question

This is therefore a device investigation framed around safety and preliminary effectiveness in patients whose anatomy is suitable for the proposed repair. It is not a comparison of the device with another treatment: the record identifies a single-group model and non-randomized allocation, and the two listed arm descriptions are alike. The registry does not give an effectiveness estimate or a primary safety outcome result. Accordingly, the posted information does not answer how frequently the stated outcomes occurred among participants, nor does it establish how those outcomes compare with an alternative approach. The endpoint wording identifies the intended questions, while the posted outcome information limits what can be concluded from this record.

3. Trial Design

The registry describes the study as a single-group investigation with non-randomized allocation and no masking. It lists the intervention as thoracoabdominal aortic aneurysm repair using a device. The sponsor is Vanderbilt University Medical Center. Enrollment is listed as 4, and the study status is terminated. The record gives a start date of 2017-08-18 and a primary completion date of 2018-03-02.

Two arm labels appear: Primary Arm and Expanded Selection Arm. Their descriptions both refer to use of the thoracic bifurcation and visceral manifold to repair thoracoabdominal aortic aneurysms in patients with appropriate anatomy. The adverse-event information lists 4 participants at risk in the Primary Arm and 0 in the Expanded Selection Arm. Because allocation was non-randomized and there is no like-for-like control comparison, the arm labels should not be read as evidence of a randomized treatment contrast. In particular, the record does not report participants in the Expanded Selection Arm.

The stated primary objective was to assess safety, expressed as freedom from major adverse events at 30 days, and preliminary effectiveness, including treatment success and technical success. Treatment success was also framed as an outcome to be achieved and maintained at one year. The registry record does not report the rationale for the enrollment target, eligibility details beyond appropriate anatomy, or the reasons the study was terminated. It does not report a protocol-level account of the two arm labels, or whether the planned enrollment and conduct changed. Those details should not be inferred from the arm names or the posted enrollment.

The phase is listed as not applicable. No randomization or masking procedures are described beyond the registry’s design classifications. The design information supports describing the study as a small, non-randomized device investigation, but does not support treating the listed arms as a controlled comparison.

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: No data was collected.

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 Safety Endpoint: Freedom From Major Adverse Events, measured over 30 days.

The primary endpoint is titled “Safety Endpoint: Freedom From Major Adverse Events.” Its stated timeframe is 30 days, and its description is freedom from major adverse events (MAE) at 30 days. The registry’s primary outcome population field says that no data was collected. Consequently, the endpoint’s definition and intended assessment are available, but no primary endpoint result is posted.

In general, a safety endpoint based on major adverse events is intended to summarize whether serious complications occur during a specified follow-up period. A fixed follow-up window makes the time covered by the endpoint explicit. It can help readers distinguish an early safety assessment from longer-term outcomes, which may be reported separately. The registry record also lists secondary safety endpoints concerning freedom from major adverse events and secondary effectiveness assessments, but does not provide primary endpoint results or details of how the endpoint was operationalized.

The record does not report the specific events included in the primary endpoint definition, how events were adjudicated, whether all participants completed the 30-day assessment, or the analysis population for that endpoint. It also does not give a numerator, denominator, estimate, or uncertainty measure for the primary outcome. The serious adverse-event figures elsewhere in the record are not a substitute for a reported primary endpoint result: the endpoint is explicitly described as freedom from major adverse events at 30 days, while the posted primary population states that no data was collected. Without a posted endpoint result and its analysis details, the safety question remains unanswered by the primary outcome entry.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the study as single-group, non-randomized, and unmasked. It reports no analyses. The statistical methods used for the outcomes are not reported in the registry record. This means the record does not show how outcomes were summarized, what analysis population was intended, whether missing observations were handled in a particular way, or whether estimates were adjusted for any characteristics. The descriptions below explain general statistical ideas relevant to this design; they are not claims about methods used in this study.

What does a single-group study estimate?

In general, a single-group study can describe outcomes observed among participants who received the intervention. A proportion, for example, would relate the number of participants with an outcome to the number assessed under a stated definition and follow-up window. Such a description can help characterize the experience recorded in the study. Without a suitable comparison group, however, it does not by itself estimate what would have happened to similar participants under another treatment or no intervention. Differences in patient characteristics, disease course, care setting, and other factors cannot be separated from the intervention’s contribution through a randomized contrast.

Here, the registry lists two arm labels, but allocation is non-randomized, the descriptions are similar, and the Expanded Selection Arm has no participants at risk in the posted adverse-event information. Thus, the labels do not create a meaningful treatment comparison in the posted data. The registry does not report a comparative analysis.

What would uncertainty measures convey?

In general, a confidence interval expresses the range of values reasonably compatible with an estimate under the statistical model and its assumptions. A narrow interval indicates greater statistical precision than a wide interval, while neither one establishes that an estimate is unbiased or clinically important. In a small study, estimates of proportions can be highly uncertain, especially when outcomes are uncommon or the denominator is limited. The registry record does not report a confidence interval for the primary endpoint, or a primary endpoint estimate around which such an interval could be interpreted.

A p-value, in general, summarizes how inconsistent observed data are with a specified null hypothesis under a statistical model. It is not a measure of effect size, probability that a hypothesis is true, or measure of clinical importance. No p-value or inferential analysis for the primary outcome is reported. With no primary outcome data, neither a confidence interval nor a test result can be reconstructed from the registry entry.

How should safety counts be understood?

In general, safety summaries may count participants with at least one event, total events, or events by category. Those quantities are not interchangeable. A participant can experience more than one event, and an event category can be defined at the participant level or event level. Interpretation requires knowing the unit of counting, the risk period, the event definitions, and whether events were assessed as related to the intervention. The registry reports adverse-event counts and percentages but does not provide all of these details. The figures should therefore be described as entries in the posted safety summary, not converted into a primary endpoint rate or causal claim.

The term “freedom from major adverse events” also depends on the study’s event definition and how follow-up is established. In general, a participant’s status at a fixed time can only be interpreted if the record clarifies which events count, how events are collected, and whether participants with incomplete follow-up are included or excluded. These details are not reported in the registry record. The primary outcome population field instead states that no data was collected.

What do the sample-size illustrations show?

The sample-size section is described as a planning illustration computed from an observed effect, rather than the trial’s own design. Its stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. For time-to-event tables, the stated quantity is the total number of events, using the Schoenfeld method; other tables describe participants per arm. These are general planning conventions and do not establish that the trial used these assumptions.

In general, a sample-size calculation asks how much information a hypothetical study would need to detect a chosen effect under specified assumptions. The result depends on the effect size, variability or event frequency, significance level, power target, allocation, and statistical model. Changing the assumed effect changes the planning requirement. Such calculations are not observed power, do not show what the trial actually achieved, and do not repair missing outcome data. The two-arm equal-allocation assumptions are also not a description of the registry’s single-group, non-randomized conduct. The registry record does not report the trial’s own sample-size justification.

Why does the design affect interpretation?

In general, random allocation can help balance measured and unmeasured prognostic factors between groups, supporting an interpretable treatment contrast. Non-randomized allocation does not ensure that balance. A comparison between groups, when groups differ in eligibility or selection, can reflect those differences as well as treatment. In this record, no like-for-like control comparison is reported, and one listed arm has no participants at risk. The appropriate statistical reading is descriptive: identify what the record reports, distinguish intended endpoints from observed results, and avoid attributing outcomes to the device when the record does not establish that relationship.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 14 outcome measures, including the primary safety endpoint, repeated entries for secondary safety endpoints, and secondary effectiveness assessments. It reports no analyses. The statistical plan for controlling the chance of false-positive findings across multiple outcomes or time points is not reported in the registry record. Without that information, the record does not show whether outcomes were prioritized beyond the stated primary endpoint, whether any testing hierarchy was specified, or how multiple comparisons would have been handled.

In general, multiplicity arises when several statistical questions are examined. Testing many outcomes can increase the chance that at least one result appears noteworthy by chance. A prespecified hierarchy or adjustment method can address this issue, but the registry does not report whether either was used. Since no outcome analyses are reported, there are no posted hypothesis tests to assess for multiplicity.

Missing-data methods are also not reported. The primary outcome population field states that no data was collected. The record does not explain whether this refers to the absence of primary endpoint observations, whether follow-up was incomplete, or why the endpoint data are unavailable. It does not give participant-level follow-up status or explain how missing observations would have been treated. Those details should not be inferred from the study’s termination or enrollment status.

The registry does not report the analysis populations for the primary or secondary outcomes. In general, analysis populations can differ according to whether they include all enrolled participants, those who received an intervention, or those with complete outcome information. These choices can affect the interpretation of a result. With no primary outcome data and no analysis description, it is not possible to determine which population would have been used or how exclusions may have affected the findings. Readers should treat the primary result as unavailable in this record rather than assume a particular missing-data method or analysis set.

11. 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

Serious events with the highest arm-level rate: multi-organ failure - (50.0%), stroke (25.0%), cardiac arrest (25.0%).

The adverse-event summary lists the Primary Arm with 4 participants at risk in the serious-event fields, 4 affected, and 4 deaths. It lists the Expanded Selection Arm with 0 participants at risk, 0 affected, and 0 deaths. These are the posted registry entries. The primary outcome field separately says that no data was collected, so these safety entries should not be presented as a reported result for freedom from major adverse events at 30 days.

The serious-event terms shown are Multi-organ failure - at 50.0%, Stroke at 25.0%, and Cardiac Arrest at 25.0%. The registry does not clarify the denominator for these percentages, whether event categories overlap, or whether the terms describe participants or event counts. It does not state the timing of the deaths, their causes, or whether they were assessed as related to the device or procedure. The record also does not give enough detail to connect these events to the primary endpoint definition or its 30-day timeframe.

In general, adverse-event summaries describe events recorded in a study; they do not, by themselves, establish that an intervention caused an event. Interpreting safety requires event definitions, follow-up context, assessment procedures, and a suitable comparison where a comparative risk is intended. None of those details should be assumed from the listed counts. The zero entries for the Expanded Selection Arm reflect that no participants are listed at risk there, not evidence of an event-free comparison group.

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

The record establishes that a study of the Visceral Manifold Thoracoabdominal Aortic Aneurysms stent graft system was registered to assess repair in patients with appropriate anatomy. It states a primary safety objective of freedom from major adverse events at 30 days and describes preliminary effectiveness objectives that include treatment success and technical success, with treatment success framed through one year. It also reports a terminated status and enrollment of 4.

What the record does not establish is whether the primary safety endpoint was met. Its primary outcome population field says no data was collected, and no primary endpoint estimate or analysis is reported. The listed adverse-event figures provide safety information in the registry, but the record does not explain the event definitions, timing, relationship to treatment, or connection to the primary endpoint. They cannot be used to infer a device effect or a comparative safety result.

The design also limits the possible interpretation. The study is classified as single-group and non-randomized. The two arm descriptions are similar, and the Expanded Selection Arm has no participants at risk in the adverse-event summary. There is therefore no posted like-for-like control comparison. Even a complete descriptive outcome summary from a single group would not, on its own, determine what outcomes would have occurred under an alternative treatment.

The sample-size material on the page is a planning illustration based on stated assumptions, not evidence that the study achieved a particular power or that a prespecified design was followed. It cannot compensate for unavailable primary outcome data. Overall, this registry entry documents the intended questions, design classifications, enrollment, status, and some safety entries. It does not provide a complete estimate of safety or effectiveness, a treatment comparison, or a basis for causal conclusions. The absence of a reported primary result is a limitation of the available record, not a result indicating either success or failure.

13. Why This Trial Matters Statistically

This study is statistically instructive because it shows why an endpoint description and an endpoint result are different things. The registry clearly states a primary safety question and a 30-day timeframe, but its primary outcome population says no data was collected. A well-defined question is useful for understanding the study’s intent; it cannot substitute for an observed estimate, denominator, or uncertainty interval.

The record also illustrates the importance of reading design classifications alongside arm labels. Although two arms are named, the study is classified as single-group and non-randomized, their descriptions are alike, and no participants are listed at risk in the Expanded Selection Arm. This context prevents treating the labels as a randomized or balanced comparison. Statistical interpretation depends on what information the design can support, not merely on the presence of group names.

Finally, the registry displays serious adverse-event entries while leaving important context unreported. Counts and percentages need clearly defined units, follow-up periods, event definitions, and denominators to support interpretation. They do not automatically answer a separately defined primary endpoint or establish causation. The distinction between observed event listings, planned outcomes, and inferential results is especially important in a terminated study with enrollment of 4.

The planning illustrations offer another useful distinction: hypothetical sample-size requirements are design calculations, not results and not observed power. Their assumptions describe an imagined two-arm equal-allocation setting, whereas this record is single-group and non-randomized. Keeping those roles separate helps prevent planning figures from being mistaken for evidence about the study’s outcomes.

14. 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 in this record is that the primary outcome population is described as having no data collected. The registry therefore provides no primary safety estimate for freedom from major adverse events at 30 days. It also reports no analyses. The reason for the unavailable primary data is not reported in the registry record, so it is not possible to distinguish among explanations from this entry alone.

Enrollment is listed as 4, and the study status is terminated. The record does not report why the study was terminated, whether enrollment ended as planned, or whether follow-up was completed. It does not provide participant characteristics, detailed eligibility criteria, or a description of the anatomical requirements beyond appropriate anatomy. These omissions limit assessment of who the findings would describe even if outcome results were available.

The registry’s two arm descriptions do not establish a control comparison. Allocation is non-randomized, the study model is single-group, and the Expanded Selection Arm has no participants at risk in the posted adverse-event summary. Any interpretation as a comparative study would therefore exceed the information reported. The record also does not give the event definitions, adjudication procedures, timing of serious events, relationship assessments, or denominator details for the displayed percentages.

The registry does not report the statistical analysis plan, sample-size justification, analysis populations, missing-data methods, or multiplicity approach. These details matter for judging how planned questions were to be analyzed and how results should be interpreted. The sample-size illustrations on the page use hypothetical assumptions and should not be taken as the study’s own design. Taken together, these limitations mean the registry supports a description of the intended investigation and posted safety entries, but not a complete efficacy or safety assessment.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Visceral Manifold Study for the Repair of Thoracoabdominal Aortic Aneurysms — NCT03113383.
• Registry record last updated 2022-11-08; status last verified 2022-10.
• Results first posted 2022-02-10.
• 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.

18. Record Summary

The registry record describes a terminated, non-randomized, single-group device study sponsored by Vanderbilt University Medical Center. It lists an enrollment of 4 and the condition thoracoabdominal aortic aneurysm. The study start is recorded as 2017-08-18, with primary completion on 2018-03-02.

The intervention is repair using the Visceral Manifold Thoracoabdominal Aortic Aneurysms stent graft system. The stated primary endpoint is freedom from major adverse events at 30 days. The study also describes preliminary effectiveness objectives involving treatment success and technical success, including treatment success at one year.

The registry says no primary endpoint data was collected and reports no analyses. Its adverse-event section lists 4 participants at risk and 4 affected in the Primary Arm, with 4 deaths; the Expanded Selection Arm has 0 participants at risk. The record does not provide the context needed to interpret those entries as a comparative treatment effect or as the primary endpoint result.