Safety and Efficacy of the SurVeil™ Drug-Coated Balloon (AVess FIH): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Safety and Efficacy of the SurVeil™ Drug-Coated Balloon (AVess FIH) (NCT03734679), a na na study. The primary outcome is Number of Participants With Target Lesion Primary Patency at 6 Months Post Procedure.

2. Clinical Question

The study asks whether the SurVeil Drug-Coated Balloon can be used safely and perform as intended when treating obstructive lesions of arteriovenous access for hemodialysis. The official title describes subjects with lesions of arteriovenous fistulae, including native or synthetic grafts. The brief summary likewise identifies obstructive lesions of arteriovenous fistulae for hemodialysis as the clinical setting.

The primary question is framed around target lesion primary patency at 6 months after the procedure. The registry defines this in terms of freedom from clinically-driven target lesion revascularization or access thrombosis. In practical statistical terms, the endpoint asks whether the treated target lesion remains free of those specified events through the stated follow-up point. It does not, by itself, describe every aspect of access function or the participant’s broader clinical course.

The intervention is the SurVeil Drug-Coated Balloon. The record describes a prospective, multi-center, single-arm study, with no control group recorded. As a result, the study can describe outcomes observed after treatment in the enrolled group, but its design does not directly compare those outcomes with outcomes under another device or treatment strategy.

The registry records an enrollment of 12. It does not report participant characteristics, lesion details, eligibility criteria, or the number with evaluable primary-endpoint data. The posted record also does not report the observed six-month primary-patency count. Thus, the clinical question is identifiable, but the registry record does not contain the primary result needed to judge how often participants met the endpoint.

3. Trial Design

The registry describes a prospective, multi-center, single-arm study of the SurVeil Drug-Coated Balloon. Its official title states that the study assesses safety and performance in subjects with obstructive lesions of arteriovenous fistulae for hemodialysis, including native or synthetic grafts. The recorded condition is hemodialysis access failure. The study status is completed, and the registry lists enrollment of 12.

There is one recorded intervention, the SurVeil Drug-Coated Balloon, classified as a device. The model is single group, allocation is listed as NA, and masking is listed as none. This is not a randomized comparison, and the registry record does not identify a comparator arm. Consequently, outcomes in the treated group cannot be interpreted as a direct estimate of how the device compares with an alternative.

The record lists a start date of 2018-12-05 and a primary completion date of 2020-02-19. The study phase is listed as NA. Although the title describes a prospective, multi-center study, the registry record does not report the number or locations of participating centers, details of recruitment, treatment procedures, or follow-up completeness.

The named primary outcome is the number of participants with target lesion primary patency at 6 months post procedure. Secondary outcomes include absence of all-cause death up to 30 days, device- and procedure-related adverse events, secondary functional patency, subsequent reinterventions, and target-lesion patency assessed by duplex ultrasound. The registry lists these outcome types, but it does not report their observed results in the record described. The absence of a control group and the lack of posted outcome counts limit the conclusions that can be drawn from the design and record 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.

Before assignment: A total of thirteen (13) subjects were consented with the EC-approved informed consent for the trial; twelve (12) were enrolled and treated within the study and one (1) subject was a screen failure.

Overall Study

Reasons for not completing this period:

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 Number of Participants With Target Lesion Primary Patency at 6 Months Post Procedure, measured over 6 months.

The primary endpoint is the number of participants with target lesion primary patency at 6 months post procedure. The registry defines primary patency as freedom from clinically-driven target lesion revascularization or access thrombosis. Thus, the endpoint combines two clinically relevant reasons that patency may no longer be maintained: a need for a clinically driven procedure to treat the target lesion, or thrombosis of the access.

In general, a binary endpoint classifies each participant according to whether the specified condition is met by the assessment point. Reporting the count can make the outcome easy to interpret, but a count alone needs a clearly defined population at risk and an assessment of whether outcomes were available for everyone. The registry record does not report the number of participants evaluated for this endpoint, the number meeting the definition, or how missing assessments were handled.

This endpoint is used because it captures whether the treated lesion remains free of specified failures over the follow-up period. It is narrower than an overall measure of health or access function: it does not encompass every possible complication, treatment, or change in a participant’s condition. The record also names secondary measures of functional patency, reintervention, and ultrasound-defined target-lesion patency, which address related but distinct aspects of follow-up.

The six-month primary-patency result itself is not reported in the registry record. Without that result and its analysis denominator, the endpoint’s observed frequency and precision cannot be assessed from this record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a prospective, multi-center, single-arm design. The following statistical concepts are general explanations of how such data are commonly interpreted; they are not a description of methods confirmed for this study unless stated in the record.

What does a single-arm design allow?

A single-arm study observes outcomes in a group receiving the intervention, without a concurrent control group recorded in the registry. It can describe what happened among participants in that group, subject to the completeness and quality of follow-up. It does not directly estimate a difference between the intervention and another treatment. Even if an outcome appears favorable or unfavorable, a single-arm result cannot by itself show how outcomes would have differed under another approach.

The registry lists allocation as NA and masking as none. It does not report a randomization procedure, and the design is explicitly single group. Randomization is a general method for assigning participants to groups in a way that can reduce systematic differences between groups. Since no comparison group is recorded here, a randomized between-group treatment effect is not available to estimate.

How should a count endpoint be understood?

The primary outcome is expressed as a count of participants with target lesion primary patency at 6 months. The endpoint definition requires freedom from clinically-driven target lesion revascularization or access thrombosis. In general, a participant-level binary outcome is summarized by the number who meet the definition and the denominator assessed under a stated analysis population. The count is more interpretable when the denominator, follow-up status, and rules for incomplete assessment are also clear.

The registry record does not report the primary endpoint count, its analysis denominator, or an estimate of the proportion meeting the definition. No proportion should be inferred from the enrollment figure, because enrollment does not establish how many participants completed follow-up or were included in the endpoint analysis. The record also does not report a confidence interval for primary patency.

What would a confidence interval add?

As a general statistical concept, a confidence interval communicates uncertainty around an estimate. It is not a guarantee that the true value lies within a particular interval, and its interpretation depends on the method and assumptions used. For a binary outcome, an interval can show how uncertain an estimated event frequency is, particularly when the amount of data is limited. This study’s registry record does not report a primary-endpoint estimate or interval, so its precision cannot be judged from the record.

What is not known about the analysis?

The registry record does not report the statistical analysis plan, the analysis population, covariate adjustment, missing-data procedures, or whether any interim analyses were planned or conducted. It also does not report a sample-size justification for the clinical trial. These omissions mean that specific choices about estimation, censoring, handling of unavailable visits, or the interpretation of incomplete follow-up should not be assumed.

For time-to-event outcomes, general methods can account for the timing of events and incomplete observation, but their validity depends on definitions and assumptions. The registry identifies the primary outcome as a participant count at a stated time point; it does not report a time-to-event analysis for that endpoint. No particular survival method should therefore be attributed to this study.

How should planning illustrations be read?

The statistical planning description states that its illustrations use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It describes the effect to detect as a stated fraction of an observed effect. For time-to-event illustrations, the description refers to a total number of events using Schoenfeld; other illustrations refer to participants per arm. These are planning assumptions, not a description of the actual single-arm trial design. They should not be read as the trial’s observed power, and they do not replace a trial-specific sample-size justification. The registry record does not report such a justification.

In general, power is a design-stage probability tied to an assumed effect, variability, significance threshold, and analysis. Observed power calculated after seeing results is not a substitute for reporting an effect estimate and its uncertainty. Here, the primary outcome estimate is not reported in the registry record, so the planning description cannot establish the precision or evidential strength of the study’s primary result.

Why does over-dispersion matter in general?

For outcomes that count events, a simple model may assume that variability follows a particular relationship with the average event count. Over-dispersion means the observed variability is greater than that model expects. If present and not accounted for, uncertainty estimates can be too small and tests can appear more conclusive than warranted. This is a general consideration for count-data analyses; the registry record does not report an over-dispersion assessment or a count-model analysis for this study.

Overall, the record supports a description of the design and the intended endpoint, but not a reconstruction of the full statistical analysis. The primary result, its uncertainty, and several analysis decisions are not reported in the registry record.

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("SurVeil Drug Coated Balloon")
n      <- c(12)
events <- c(11)
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  SurVeil Drug Coated Balloon  12  11  91.7  61.5  99.8  64.6  98.5  64.0  98.1

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary endpoint and several secondary outcome types, including death, device- and procedure-related adverse events, secondary functional patency, subsequent reinterventions, and duplex-ultrasound-defined patency. It does not report an approach to multiplicity, such as adjustment of significance thresholds or a prespecified hierarchy for interpreting multiple outcomes. Because the endpoint results are not reported, the record also does not show how any multiple-outcome findings were handled in practice.

Multiplicity is a general concern when many outcomes or comparisons are examined: the chance of at least one apparently unusual result can rise as the number of tests increases. A prespecified outcome hierarchy or adjustment procedure can help clarify which analyses are confirmatory and how results should be interpreted. The record does not report whether such procedures were planned. The registry lists 0 analyses, so there are no posted analysis entries in the record from which to assess their methods.

The registry record does not report missing-data rules or the number of participants with complete primary-endpoint follow-up. It also does not identify an analysis population, such as an intention-to-treat or per-protocol population. Enrollment alone does not establish the endpoint denominator. Without those details, the effects of incomplete follow-up or exclusions cannot be evaluated.

The record names secondary outcomes but does not report their results or the analysis populations used for them. It does not report imputation methods, sensitivity analyses, or whether participants with unavailable assessments were treated as having an event, as event-free, or excluded. Those choices can affect interpretation, particularly when outcomes depend on follow-up through a defined time point. The registry record therefore leaves multiplicity and missing-data handling unresolved.

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: restenosis (16.7%), renal transplant (8.3%), haematoma nos (8.3%), physical deconditioning (8.3%), insomnia (8.3%).

The registry’s safety figures are descriptive counts for the SurVeil Drug-Coated Balloon group. Serious adverse events affected 8 of 12 participants at risk, other adverse events affected 9 of 12 participants at risk, and deaths were recorded as 0. These counts describe participants recorded as affected; they should not be converted into a comparative safety claim because the study has no control group.

The registry lists serious adverse-event terms and associated percentages: Restenosis, 16.7%; Renal transplant, 8.3%; Haematoma NOS, 8.3%; Physical deconditioning, 8.3%; Insomnia, 8.3%; and Confusion, 8.3%. The record does not provide event counts alongside these terms in the information, nor does it explain whether one participant could contribute to more than one term. The percentages should therefore be read as listed, without treating them as mutually exclusive categories or adding them together.

An adverse event occurring during a study is not automatically evidence that the intervention caused it. The figures describe recorded events, not a causal comparison. The record names some outcomes as CEC-adjudicated, but does not report adjudication details for these safety counts. It also does not provide timing, duration, severity beyond the serious-event classification, or participant-level context for each event. These omissions limit detailed interpretation of the safety profile.

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

The registry record establishes the study’s purpose, intervention, design, primary endpoint definition, and selected safety counts. It describes a prospective, multi-center, single-arm study of the SurVeil Drug-Coated Balloon in obstructive hemodialysis arteriovenous access lesions. The primary endpoint is target lesion primary patency at 6 months, defined as freedom from clinically-driven target lesion revascularization or access thrombosis.

However, the registry record does not report the observed result for that primary endpoint. It gives no count of participants meeting the definition, no endpoint analysis denominator, and no confidence interval. As a result, readers cannot determine from the record how often primary patency was observed or how precise an estimate would be. The endpoint definition alone is not an outcome result.

The record does report safety counts: serious adverse events affected 8 of 12 participants at risk, other adverse events affected 9 of 12, and deaths were 0. These counts should be interpreted as descriptive observations in the enrolled group. With no comparator group, they do not quantify how safety compares with another device or treatment. They also do not establish that an event was caused by the balloon.

The study’s single-arm design can contribute descriptive information about the enrolled group, but it cannot answer a comparative treatment question on its own. Differences between treated participants and an imagined alternative group cannot be estimated from this design. Nor does a completed study status substitute for outcome data: completion indicates the recorded study status, not that every endpoint result is available in the registry.

The record does not report participant characteristics, follow-up completeness, analysis populations, statistical methods, or missing-data procedures. These gaps further constrain interpretation. Accordingly, the record supports an account of what was studied and some recorded safety counts, but it does not support a conclusion about the observed primary-patency frequency, its precision, or comparative efficacy and safety.

14. Why This Trial Matters Statistically

This study is statistically informative as an example of the distinction between a clearly stated clinical endpoint and a result that can actually be evaluated. The registry gives a specific primary endpoint—target lesion primary patency at 6 months—and defines it through freedom from clinically-driven target lesion revascularization or access thrombosis. That definition makes the clinical event of interest identifiable. But the primary outcome count and its denominator are not reported, so the statistical estimate cannot be assessed.

The design also illustrates the limits of single-arm evidence. A group’s outcomes can be described, but without a comparator there is no direct estimate of the difference between the device and another treatment. This is not a flaw that can be repaired by interpreting the group’s observed counts as if they came from a controlled comparison. The distinction is central to matching the strength of a conclusion to the design.

Safety summaries require similar care. Counts of participants affected and listed adverse-event terms provide descriptive information, but they do not alone establish causality or comparative risk. Reporting denominators, definitions, timing, and event handling is important for understanding what those counts represent. The registry record reports some counts but leaves other details unresolved.

The record also highlights why statistical transparency matters beyond the endpoint definition. Analysis populations, missing-data rules, uncertainty intervals, and multiplicity procedures help readers judge how robust and precise results are. Those details are not reported in the registry record. The study’s completed status and enrollment figure cannot fill in missing outcome results or analysis methods.

For clinical researchers, the key statistical lesson is to separate three questions: what outcome was planned, what result was observed, and how uncertain or comparative that result is. The record answers the first question, gives limited descriptive safety information for the second, and does not provide enough information to answer the third for the primary endpoint.

15. Limitations

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

The principal limitation for interpreting this study from its registry record is that the primary endpoint result is not reported. Although target lesion primary patency at 6 months is defined, the record gives neither the number meeting the definition nor the number assessed. A primary estimate and its precision therefore cannot be evaluated.

The study is single-arm, with allocation listed as NA and masking listed as none. There is no recorded control group for a direct comparison. The record consequently cannot establish how outcomes differ from those under another treatment or device. The registry also does not report participant characteristics, lesion characteristics, eligibility criteria, or center details, limiting assessment of the group to which the observations might apply.

Follow-up information is incomplete in the record. It does not report endpoint completion, loss to follow-up, missing-data handling, or the analysis population. The record also does not specify the statistical analysis plan, confidence intervals, covariate adjustments, interim analyses, or multiplicity procedures. These details should not be assumed from the study title or endpoint list.

The safety counts are descriptive and do not establish causation. The record does not give event timing or participant-level overlap among serious adverse-event terms, and the listed percentages cannot be interpreted as independent categories without further information. While some outcome descriptions refer to CEC adjudication, adjudication details for the safety figures are not reported in the registry record.

Finally, the registry lists secondary outcome types but not their results. Enrollment of 12 and a completed status do not establish that all outcomes were assessed or reported. Taken together, the record supports a limited description of design and safety counts, but not a full assessment of primary efficacy, comparative performance, or the precision of the study findings.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Safety and Efficacy of the SurVeil™ Drug-Coated Balloon (AVess FIH) — NCT03734679.
• Registry record last updated 2025-02-06; status last verified 2025-01.
• Results first posted 2022-09-29.
• 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 NCT03734679, a completed, prospective, multi-center, single-arm study of the SurVeil Drug-Coated Balloon for obstructive lesions of arteriovenous access for hemodialysis. Enrollment is listed as 12. Allocation is NA, masking is none, and the phase is NA. The record lists a start date of 2018-12-05 and a primary completion date of 2020-02-19.

The primary endpoint is the number of participants with target lesion primary patency at 6 months post procedure, defined as freedom from clinically-driven target lesion revascularization or access thrombosis. The observed primary-endpoint result and analysis denominator are not reported in the registry record. Safety figures include serious adverse events affecting 8 of 12 participants at risk, other adverse events affecting 9 of 12, and 0 deaths. These are descriptive figures from a single-arm study, not comparative estimates.

The record names secondary outcomes covering death, adverse events, functional patency, reintervention, and ultrasound-defined patency, but their results are not reported. Analysis populations, missing-data procedures, and the statistical analysis plan are also not reported in the registry record.