The Pivotal Study of the Aptus Endovascular AAA Repair System: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Pivotal Study of the Aptus Endovascular AAA Repair System (NCT00507559), a na na study. The primary outcome is Effectiveness: Composite Success Rate.

2. Clinical Question

This question joins technical performance and clinical events in a single endpoint. That can offer a broad view of procedural success, but the components differ in type and clinical meaning. A composite result alone would not show which components occurred or drove the overall result. The registry lists secondary safety and effectiveness outcomes, including serious adverse events, surgical conversion, rupture, aneurysm change, device-related outcomes, endoleak, and thrombosis. Their results are not reported in the registry record.

3. Trial Design

The registry describes a prospective, non-randomized, multi-center clinical study of the Aptus Endovascular AAA Repair System for abdominal aortic aneurysm repair. The study is recorded as a single-group model, with enrollment of 155. Its status is completed. The recorded start is 2007-09 and primary completion is 2010-03. Medtronic Cardiovascular is listed as sponsor.

The design is not a randomized comparison. The brief summary says that safety and effectiveness were evaluated against an open surgical repair historical control group. A historical comparison uses information from a separate group or prior experience rather than assigning participants concurrently to the intervention and comparator. The registry record does not report details of the historical control, such as its size, eligibility criteria, outcome ascertainment, or how its results were incorporated into the analysis. The record also cautions that the arms are not a like-for-like control comparison.

Allocation is recorded as NA and masking as none. The listed phase is NA. The intervention is a device, and the arm description gives no further details. The record specifies a 12-month timeframe for the primary endpoint, but does not report the follow-up schedule or the duration used for each secondary outcome.

The primary outcome is a binary composite success measure. The description says the result was to be compared with an estimated success rate of 80%. That benchmark is not the same as a randomized control group: it is a stated reference value, while the study itself is listed as single-group. The precise statistical test, confidence-interval procedure, analysis population, handling of missing outcomes, and other analysis details are not reported in the registry record. The record lists one analysis, but that count does not establish which methods were used or how fully the results were reported.

These design features shape interpretation. Prospective follow-up can organize outcome collection over time, but it does not remove the limitations of a non-randomized design. Without a concurrently assigned control group and fuller information about the historical comparator, differences between groups may reflect differences in participants, care, follow-up, or outcome definitions rather than the device alone.

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

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 Effectiveness: Composite Success Rate, measured over 12 months.

The primary endpoint is a composite success rate at 12 months, expressed as a number of participants. Success combines delivery success with the absence of Type I or Type III endoleak requiring intervention after the index procedure, migration greater than 10mm, aneurysm rupture, or conversion. The registry description states that this composite was compared with an estimated success rate of 80%.

A composite endpoint is used to bring multiple outcomes into one summary measure. In this case, it includes a technical event—delivery success—and several subsequent complications or interventions. Combining them can capture more than one aspect of performance in a single endpoint. It also means the overall result depends on the definition of success and on every included component. A participant who meets any failure condition would not meet the composite success definition as described.

The components may differ in frequency and importance, so an overall success figure would not reveal which component most influenced it. Separate component results would be useful for understanding the pattern, but those primary component counts are not reported in the registry record. The observed composite count or rate, its uncertainty, and the result of comparison with the 80% benchmark are also not reported in the registry record. Thus, the endpoint definition is available, but its observed performance cannot be assessed from the registry information presented.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The available statistical information is limited. The study is described as prospective, non-randomized, multi-center, and single-group, with a primary composite endpoint at 12 months. The registry record lists one analysis, but does not report the analysis method, the estimated primary result, its uncertainty, or a p-value. The methods below explain how such information is generally interpreted without attributing unreported procedures to this study.

What does a composite endpoint summarize?

A composite endpoint combines multiple events or conditions into one outcome. Here, success requires delivery success and the absence of the listed failures: Type I or Type III endoleak requiring intervention after the index procedure, migration greater than 10mm, aneurysm rupture, or conversion. A participant-level composite can be summarized as the number meeting the complete success definition, or as a rate when the relevant denominator is specified. The record describes the outcome as a number of participants but does not report the observed primary count or rate.

Composite endpoints can summarize several aspects of a procedure, but their meaning depends on the component definitions. A result for the combined endpoint does not show how often each component occurred. If one component is more common than others, it may have more influence on the composite. The registry description does not provide the component-level primary results, so the relative contribution of each condition cannot be assessed.

How should the 80% reference be understood?

The primary description says the composite was compared with an estimated success rate of 80%. This is a stated benchmark, not a concurrently randomized control group. In general, a single-group comparison with a fixed reference asks whether the observed result is compatible with a specified value under a chosen statistical method. The conclusion depends on the observed estimate, its uncertainty, and the prespecified testing approach. The observed result and the statistical procedure for this benchmark comparison are not reported in the registry record. It is not possible to infer a test result from the benchmark alone.

The brief summary also refers to an open surgical repair historical control group. Historical comparisons may provide context, but participants in separate study settings are not necessarily comparable. Differences in eligibility, follow-up, outcome definitions, or clinical practice can affect a comparison. The registry record gives no details of how the historical control was selected or analyzed and cautions that the arms are not a like-for-like control comparison. Random allocation, which can help balance known and unknown factors between concurrent groups, was not used.

What do uncertainty measures contribute?

In general, a confidence interval expresses the uncertainty around an estimated quantity under a specified statistical model and procedure. It helps distinguish a relatively precise estimate from one compatible with a broader range of values. A p-value, when used, assesses how compatible the data are with a specified null hypothesis under the assumptions of a test. Neither measure describes clinical importance on its own, and neither substitutes for a clear endpoint definition or an appropriate comparison.

The registry record does not report a primary confidence interval, p-value, or test procedure. It also does not report whether the 80% benchmark was prespecified in a statistical analysis plan, what confidence level or test direction was used, or whether any adjustment was made. Those details should not be inferred from the endpoint wording.

Why do the adverse-event counts need context?

The posted adverse-event figures are counts of participants with serious adverse events and other adverse events, each alongside a group at risk of 155. Such counts describe what was recorded in the study group. They do not establish whether an event was caused by the device or whether event occurrence differed from a comparator. A participant may experience events that meet more than one classification, so the categories cannot be assumed to be mutually exclusive. The record does not report event-level counts for the listed serious-event terms or a detailed definition of the percentages attached to those terms.

In general, adverse-event comparisons also depend on observation time, event definitions, ascertainment, and whether reporting concerns participants with events or total event episodes. Those details are not reported in the registry record. Deaths are not reported in the registry record.

What can be inferred from the analysis listing?

The record lists one analysis. That is a count of analyses recorded, not a description of the model, estimand, covariate adjustment, or treatment of incomplete follow-up. The primary outcome is binary in form: a participant either satisfies the defined composite success criteria or does not. General methods for binary outcomes include estimating a proportion and its uncertainty, but the specific method used in this study is not reported in the registry record. No new calculation can be reconstructed from the listed enrollment and adverse-event counts because those are not primary endpoint results.

The record also includes a planning illustration based on an observed effect, with stated assumptions of a two-sided significance level of 0.05, equal allocation, and a normal approximation. These are planning assumptions for illustration, not evidence of observed power and not necessarily the original design assumptions. The registry record does not report the original sample-size justification. Any planning illustration should be read as conditional on its stated assumptions and effect input, not as a finding that the study had a particular probability of detecting an effect.

Overall, the record supports explanation of the endpoint, study structure, and posted safety counts. It does not provide enough statistical output to evaluate the primary estimate, its precision, or the analysis choices behind it.

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("AAA Repair System")
n      <- c(155)
events <- c(4)
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  AAA Repair System  155  4  2.6  0.7  6.5  1.0  6.4  1.0  6.4

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary composite endpoint and several secondary safety and effectiveness outcomes. These include serious adverse events, surgical conversion, aneurysm rupture, aneurysm change, device-related outcomes, endoleak, and thrombosis. When multiple outcomes are examined, the chance of at least one apparently notable result can increase if each is tested separately. General approaches can include prespecifying a primary outcome, controlling the family-wise error rate, or treating secondary findings as exploratory. The registry record does not report whether multiplicity adjustments were planned or used, or how the secondary outcomes were prioritized.

The primary endpoint is described at 12 months, but the registry record does not report how missing or incomplete outcome data were handled. It does not say whether participants without an assessable 12-month outcome were counted as failures, excluded, imputed, or handled using another approach. These choices can affect a composite success estimate, particularly if missingness is related to participant status or outcome occurrence.

The record does not report a detailed analysis population, such as whether the primary analysis included all enrolled participants or a defined subset. It also does not report protocol deviations, losses to follow-up, or the number with evaluable primary outcomes. The analysis listing records one analysis, but does not provide enough detail to determine how the outcome populations were defined.

For the historical comparison, the registry record does not describe whether any adjustment or matching was applied. The comparator's eligibility, outcome definitions, and missing-data procedures are also not reported in the registry record. Without those details, neither multiplicity control nor the comparability of outcome data can be evaluated.

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: thrombosis in device (15.5%), peripheral ischaemia (13.5%), stent-graft endoleak (7.7%), angina pectoris (5.8%), myocardial infarction (5.8%).

The adverse-event record lists serious adverse events for 129 participants among 155 at risk, and other adverse events for 148 participants among 155 at risk. These figures describe participant counts in the AAA Repair System group. They are not comparative treatment effects and do not show whether events were caused by the device. The two categories should not be added: a participant could have had events recorded in both categories, and the registry record does not state that the categories are mutually exclusive.

The serious-event listing names thrombosis in device at 15.5%, peripheral ischaemia at 13.5%, stent-graft endoleak at 7.7%, angina pectoris at 5.8%, myocardial infarction at 5.8%, and embolism at 5.8%. The record does not give event counts for these terms or explain the denominator and counting rules for their percentages. They should therefore be read as the registry's listed percentages, not converted into participant counts or treated as mutually exclusive categories.

Deaths are not reported in the registry record. The record also does not provide the timing, duration of observation, event-level detail, or a comparison of these safety outcomes with the historical open surgical repair group. These limitations prevent a fuller assessment of frequency, comparative risk, or attribution.

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

The record establishes that a prospective, multi-center, non-randomized study evaluated the Aptus Endovascular AAA Repair System in a single-group design. It records enrollment of 155 and defines a 12-month composite success endpoint. It also describes an intended comparison with an estimated success rate of 80% and lists adverse-event counts. These details explain what the study set out to assess and what safety information is posted.

The record does not report the observed primary composite result. It therefore does not show how many participants met the success definition, the estimated success rate, or the precision of that estimate. The endpoint description alone cannot establish whether the observed result was above, below, or consistent with the benchmark. Nor does the record report component results that could clarify which events shaped the composite.

The study's non-randomized, single-group structure also limits comparative conclusions. The brief summary mentions an open surgical repair historical control group, but the record cautions that the arms are not a like-for-like control comparison. Without details about the historical group and the analysis, a difference from historical experience could not automatically be attributed to the device. The design does not support the same causal interpretation as a well-conducted randomized comparison.

The safety counts show that serious and other adverse events were recorded among participants at risk. They do not establish causation, comparative safety, or the number of event episodes. The listed serious-event percentages lack sufficient detail in the registry record to interpret their denominators or derive counts. Deaths are not reported in the registry record.

Accordingly, the posted information is most useful for understanding the study's design, endpoint definition, and reported adverse-event summaries. It does not provide enough outcome or analysis information to judge the primary composite result, its uncertainty, or comparative effectiveness. Absence of a reported result in this record is not evidence that an outcome did or did not occur.

14. Why This Trial Matters Statistically

This study illustrates a recurring statistical challenge in device evaluation: an endpoint can be clearly defined while the publicly recorded information remains insufficient to assess its observed result. The composite includes technical delivery success and the absence of several clinical or device-related events. That structure makes the endpoint broad, but it also makes component-level reporting important for interpreting what a composite success estimate would mean.

The study is listed as prospective and multi-center, yet its single-group, non-randomized design places substantial weight on the comparator. The brief summary describes an open surgical repair historical control, while the record cautions that the arms are not a like-for-like control comparison. This distinction matters statistically: a historical reference can contextualize results, but it does not provide the balance created by random assignment to concurrent groups. Clear reporting of comparator selection, outcome definitions, and analysis would be needed to evaluate the comparison.

The stated estimated success rate of 80% is also a useful reminder to distinguish a benchmark from an observed control outcome. A benchmark comparison depends on the observed result and its uncertainty, as well as the method selected in advance. The registry record does not provide those results or methods, so the benchmark does not by itself support a conclusion.

Finally, safety summaries require attention to denominators, event definitions, overlap between categories, and follow-up. The participant counts are informative as posted, but without further detail they cannot be turned into a comparative or causal assessment. Together, these features show why endpoint definitions, analysis transparency, and complete outcome reporting are essential to statistical 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.

Several limitations specific to this study constrain interpretation of the registry record. The primary endpoint is defined, but its observed count or rate, uncertainty interval, and test result are not reported in the registry record. The component-level results are also not reported, so the relative contribution of delivery success, endoleak requiring intervention, migration, rupture, or conversion cannot be assessed.

The study is listed as single-group and non-randomized. Although the brief summary refers to an open surgical repair historical control, the registry record explicitly cautions that the arms are not a like-for-like control comparison. Information about the historical comparator's selection, size, eligibility, follow-up, and outcome measurement is not reported in the registry record. This limits the interpretation of any intended comparison.

The analysis details are sparse. The record lists one analysis but does not report the statistical procedure, analysis population, handling of missing outcomes, or whether any adjustment was made. It does not report the number of participants with evaluable primary outcomes, losses to follow-up, or the multiplicity approach for the secondary outcomes. The original sample-size justification is not reported in the registry record.

The safety information is also incomplete for comparative interpretation. Serious and other adverse-event participant counts are posted, along with selected serious-event terms and percentages, but event counts and percentage denominators are not described. Event timing, exposure or observation duration, and attribution are not reported in the registry record. Deaths are not reported in the registry record. These limitations mean the posted safety summaries cannot establish comparative risk or causation.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: The Pivotal Study of the Aptus Endovascular AAA Repair System — NCT00507559.
• Registry record last updated 2021-11-03; status last verified 2021-10.
• Results first posted 2016-05-27.
• 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 record describes a completed, prospective, non-randomized, multi-center, single-group study of the Aptus Endovascular AAA Repair System for abdominal aortic aneurysms. Enrollment was 155; Medtronic Cardiovascular is listed as sponsor. The recorded start is 2007-09, and primary completion is 2010-03.

The primary endpoint is a 12-month composite success measure, described as compared with an estimated success rate of 80%. The observed primary result and its statistical precision are not reported in the registry record. The brief summary refers to an open surgical repair historical control, while the record cautions that the arms are not a like-for-like control comparison.

The adverse-event record lists 129 participants with serious adverse events and 148 with other adverse events, each among 155 at risk. It also lists selected serious-event terms with percentages. Further details needed to interpret these summaries, including event counts for those terms and comparative analyses, are not reported in the registry record.