STOP Persistent AF: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for STOP Persistent AF (NCT03012841), a na na study. The primary outcome is Percent of Subjects Free From Treatment Failure at 12 Months After the Pulmonary Vein Isolation (PVI) Ablation Procedure..

2. Clinical Question

This question combines an assessment of whether the procedure achieved the intended pulmonary vein isolation at the index procedure with follow-up for later events and treatment changes. It is a composite endpoint: any one of its defined components can count as treatment failure. Consequently, an overall percentage for the endpoint would not, by itself, indicate which component occurred or how often each component contributed. Component-level results are not reported in the registry record.

The study is descriptive with respect to its treated group. Without a concurrent comparator, the primary outcome can describe the observed course of enrolled participants under the trial’s treatment approach, but it cannot establish how that course compares with an alternative. The registry record also does not report the endpoint estimate needed to describe the observed proportion or its precision.

3. Trial Design

STOP Persistent AF is registered as a completed, single-group study of a cardiac cryoablation catheter for atrial fibrillation. The registry lists an enrollment of 186 and identifies the intervention as the Arctic Front Advance Cardiac CryoAblation Catheter. The treatment arm description says that enrolled participants were treated with that catheter. The study summary states an aim of demonstrating safety and effectiveness for the Arctic Front Advance and Freezor MAX catheters in drug-refractory, recurrent, symptomatic persistent atrial fibrillation; however, the listed intervention is the Arctic Front Advance device.

The registry records allocation as NA and masking as NONE. It identifies the model as SINGLE GROUP. There is therefore no randomized allocation or blinded comparison described in the record. This design can report outcomes observed among treated participants, but differences from an external or historical group cannot be interpreted as a randomized treatment contrast on the basis of this study alone.

The study began on 2017-03-02, had a primary completion date of 2019-08-13, and is recorded as COMPLETED. The phase field is NA. Further details of eligibility, the treatment procedure, follow-up completeness, and the statistical analysis plan are not reported in the registry record.

The primary outcome is a percentage of participants free from treatment failure at 12 months after the pulmonary vein isolation procedure. Three listed secondary outcomes concern changes in quality of life from baseline to 12 months: AFEQT, and the physical and mental components of SF-12. The registry lists five outcome measures and five analyses overall, but further descriptions of the additional measures and analyses are not reported in the registry record.

Because the study has a single treatment group, its design primarily supports estimation of outcomes within that group. It does not directly estimate a treatment effect relative to a control group. The record does not report a sample-size justification or explain how the enrollment target was selected.

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:

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.

Population: The baseline analysis population includes those subjects who were enrolled and underwent ablation with an Arctic Front Advance CryoAblation catheter.

6. Primary Endpoint

The registry lists the primary outcome as Percent of Subjects Free From Treatment Failure at 12 Months After the Pulmonary Vein Isolation (PVI) Ablation Procedure., measured over 12 Months.

The primary endpoint is the percentage of participants free from treatment failure 12 months after the pulmonary vein isolation procedure. Its stated unit is percentage of participants, and the registry specifies a 95% confidence interval as the dispersion measure. The endpoint result and its confidence interval are not reported in the registry record.

Treatment failure is a composite of several outcomes. It includes acute procedural failure, defined in part by inability to isolate all accessible targeted pulmonary veins or performing left atrial non-PVI ablations. It also includes documented AF, atrial tachycardia, or atrial flutter after the 90-day blanking period; reablation for recurrent arrhythmia after that period; specified increases or initiation of Class I or III antiarrhythmic drugs after that period; and left atrial radiofrequency ablation. The blanking period is defined as the first 90 days after the index procedure.

A composite endpoint can capture several ways in which the intended clinical course might not be maintained, rather than relying on a single type of event. Its overall percentage is meaningful only alongside the precise component definitions and follow-up period. Different components may represent different clinical events or decisions, so an aggregate result would not show which components drove it. Component-specific results are not reported in the registry record.

The endpoint is used to summarize whether participants met the trial’s prespecified definition of freedom from failure over the stated follow-up interval. It is not, by itself, a comparison with another treatment or proof that the procedure caused any observed outcome.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry defines the primary outcome as a percentage of participants free from treatment failure at 12 months. A percentage is a way to express the share of a specified group meeting a binary outcome definition: each participant is classified as meeting or not meeting the definition. The record’s stated unit is percentage of participants. It does not report the observed percentage, the number meeting the definition, or the denominator used in the primary analysis, so the result cannot be reconstructed from this record.

What does a 95% confidence interval convey?

A confidence interval describes statistical uncertainty around an estimate. In general, it gives a range of values compatible with the data and the method used to calculate the interval. It does not mean that a particular participant’s outcome is uncertain, nor does it show the range of outcomes for individuals. Its interpretation depends on the analysis and assumptions used. The registry identifies a 95% confidence interval as the endpoint’s dispersion measure, but its limits and calculation method are not reported in the registry record.

For a single-group percentage, the interval would help readers assess the precision of the estimated proportion. The point estimate and interval are complementary: the estimate describes the observed result, while the interval communicates uncertainty around it. Because neither the estimate nor the interval is posted in the registry record, neither the magnitude nor precision of the primary result can be assessed. No alternative interval can be calculated without the relevant outcome count and analysis details.

Why does the composite definition matter?

A composite endpoint treats the occurrence of any listed component as meeting the overall failure definition. This can make an endpoint capture several types of events within one outcome, but it also means that the overall result does not identify which component occurred. Here, the listed components range from inability to achieve specified procedural goals to later documented arrhythmia, repeat ablation, certain antiarrhythmic drug changes, and left atrial radiofrequency ablation. These components are not interchangeable descriptions of one event. Component-specific results would help explain the overall endpoint, but they are not reported in the registry record.

The 90-day blanking period is part of the registered definition. The record states that the blanking period is the first 90 days after the index ablation procedure and that certain rhythm events, reablations, and medication changes count toward failure after that period. The registry’s definition therefore distinguishes events according to their timing relative to the procedure. The timing and adjudication details for individual outcomes are not reported in the registry record.

What can a single-group design estimate?

A single-group study can describe outcomes observed among participants receiving the intervention. It does not create a randomized treatment contrast. Randomization, when used, aims to make comparison groups comparable in expectation; this record does not describe randomized allocation or a control arm. Thus, an outcome proportion from this study would not establish how the same population would have fared under an alternative approach. The record does not report a comparative estimand or an adjustment plan.

The registry’s sample-size assumptions describe a planning illustration based on an observed effect, with stated assumptions for a hypothetical two-arm calculation. Such illustrations are not observed power and do not establish that the trial was designed around those assumptions. The registry does not report the trial’s own sample-size justification, target effect, or any protocol-based power calculation. The illustration cannot be treated as evidence about the study’s actual design or its ability to detect a difference.

What analysis details remain unknown?

The registry lists five analyses but does not describe the primary endpoint analysis method. It does not report whether the analysis used a particular confidence-interval formula, whether any covariates were included, or whether any sensitivity analyses were conducted. The primary outcome’s analysis population, treatment of missing follow-up, and rules for classifying participants with incomplete information are also not reported in the registry record.

These details matter because estimates depend not only on the endpoint definition but also on which participants contribute data and how uncertainty is calculated. For example, excluding participants without complete follow-up and treating them as not meeting the endpoint are different approaches in general; neither approach can be attributed to this trial because its missing-data method is not reported. Likewise, there is no basis in the record to infer interim analyses, data-monitoring procedures, or a prespecified statistical plan.

The listed secondary quality-of-life outcomes involve change from baseline to 12 months for AFEQT and the physical and mental components of SF-12. The registry does not provide the actual changes, their uncertainty, or the methods used to analyze them. Without those details, the listed outcomes indicate what was measured but do not support conclusions about the direction, size, or precision of changes.

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("Modified Intent to Treat Group (mITT)")
n      <- c(165)
events <- c(90)
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  Modified Intent to Treat Group (mITT)  165  90  54.5  46.6  62.3  46.9  62.0  46.9  62.0

11. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures and five analyses. It identifies three secondary quality-of-life outcomes: change from baseline to 12 months in AFEQT, and change in the physical and mental components of SF-12. The primary outcome is freedom from treatment failure at 12 months. The registry does not report a multiplicity strategy, such as whether any adjustment was planned for evaluating multiple outcomes or analyses.

Multiplicity is a general statistical concern that arises when several outcomes or hypotheses are assessed. With more opportunities to identify a result, the chance of at least one apparently notable finding can increase, depending on the analysis and decision rules. Whether and how that concern was addressed in this study is not reported in the registry record. The number of listed outcomes alone does not reveal the intended hierarchy or the inferential role of each analysis.

Missing-data procedures are also not reported in the registry record. The number of participants with available 12-month primary endpoint data, the handling of participants who were lost to follow-up or otherwise lacked an endpoint classification, and any sensitivity analyses addressing missing information are not stated. The enrollment count cannot be assumed to equal the primary analysis denominator.

The record does not describe the analysis populations used for the primary or secondary outcomes. It does not state whether the analyses included all enrolled participants, only participants who received the intervention, or another defined group. No interim-analysis plan, stopping rule, or detailed statistical analysis plan is reported in the registry record. These omissions limit assessment of how the listed outcomes were analyzed and how robust the results would be to alternative reasonable methods.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: atrial fibrillation (5.4%), anaemia (1.1%), vascular pseudoaneurysm (1.1%), acute kidney injury (0.5%), acute myocardial infarction (0.5%).

The registry lists 186 enrolled subjects in the adverse-event group. It records 34 affected subjects in the serious adverse-event category and 52 in the other adverse-event category, with 186 at risk in each category. The death count is 0. These are safety counts, not estimates of the primary endpoint, and the registry record does not describe whether adverse events were judged related to the intervention.

The listed serious adverse-event terms include atrial fibrillation at 5.4%, anaemia at 1.1%, vascular pseudoaneurysm at 1.1%, acute kidney injury at 0.5%, acute myocardial infarction at 0.5%, and angina pectoris at 0.5%. These percentages are reported as registry values and should not be read as comparative risks because the trial has no randomized control group. The record does not provide additional detail on event timing, severity grading, duration, recurrence, or attribution.

Adverse-event counts and term percentages answer different descriptive questions from the primary outcome. The counts refer to affected subjects in the registry’s categories, while the listed terms identify selected serious adverse events. The record does not state whether a subject could contribute to more than one term, so the term percentages should not be added together or treated as mutually exclusive categories. These figures describe safety reporting within the enrolled group; they do not establish a causal relationship or a comparison with another treatment.

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

The record establishes that STOP Persistent AF was completed as a single-group study enrolling 186 participants and evaluating a cryoablation catheter in persistent atrial fibrillation. It defines a 12-month primary endpoint based on freedom from a composite of procedural and post-procedure treatment-failure events. The endpoint includes a 90-day blanking-period rule for several later events. These design and definition details clarify what the study set out to assess.

However, the primary endpoint’s observed percentage and 95% confidence interval are not reported in the registry record. The available registry information therefore cannot show how many participants met the endpoint or how precise the estimate was. Without that result, no conclusion about the observed primary outcome can be drawn from this record.

Even if the endpoint estimate were available, the single-group design would support a description of outcomes in the treated group, not a randomized comparison with an alternative. It would not, by itself, establish that the intervention caused the observed outcomes or that outcomes would differ under another approach. A comparison would require an appropriate comparator and a suitable design or explicit assumptions, neither of which is described.

The composite definition also limits what an overall result could say on its own. A combined percentage would not reveal whether procedural failure, later arrhythmia, repeat ablation, medication changes, or another component accounted for the outcome. Component-level results are not reported in the registry record.

The adverse-event information provides descriptive counts, selected serious adverse-event terms, and a death count of 0. It does not establish comparative safety or causation. Missing details about follow-up completeness, analysis populations, missing-data handling, and the statistical analysis plan further limit the assessment of the posted results. The registry record is therefore informative about the trial’s registered framework and selected safety reporting, but not about the primary endpoint’s numerical result or comparative effectiveness.

14. Why This Trial Matters Statistically

This trial is statistically notable because its primary outcome is a time-specific proportion in a single treatment group, while the registry record does not report the numerical result or its confidence interval. That combination makes it possible to discuss the endpoint’s structure and the intended measure of precision, but not the observed estimate itself. It illustrates why a registered outcome definition and a posted result are distinct pieces of information.

The endpoint is a composite with several clinically different components. Statistical interpretation of a composite requires attention to its full definition, because the overall estimate can conceal variation in the frequency or contribution of individual components. In this record, the definitions are detailed, including the 90-day blanking period, but component-specific outcome counts are not reported. Readers therefore cannot assess the composition of any endpoint result from the registry record.

The single-group design also illustrates the difference between describing an outcome and estimating a comparative treatment effect. A percentage among treated participants would describe that group’s observed outcome, whereas a randomized comparison is designed to estimate differences between assigned groups. The registry does not describe such a comparison. This distinction is important whenever the word “effectiveness” appears in a study objective: the objective alone does not establish that the design can quantify comparative effects.

Finally, the record lists multiple outcomes and analyses but does not report the analysis plan, multiplicity handling, or missing-data methods. These are not minor reporting details: they shape how estimates should be interpreted and how much confidence readers can place in the inferential results. The trial thus highlights the value of transparent reporting of both outcome values and analysis decisions, especially when the design is uncontrolled and outcomes are composite.

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 main limitation for statistical interpretation is that the registry record does not report the primary endpoint estimate or its 95% confidence interval. The primary outcome’s numerator and analysis denominator are also not reported, preventing independent assessment of the result or its precision.

The study is registered as SINGLE GROUP, with allocation recorded as NA and masking as NONE. It does not provide a randomized control group, so the study cannot supply a direct randomized comparison with another treatment. Outcomes observed among enrolled and treated participants should not be interpreted as comparative effects.

The primary endpoint combines multiple components, but component-specific results are not reported in the registry record. The detailed definition clarifies which events count, yet the aggregate result, if available, would still need component-level information to show what drove it. Follow-up completeness and the number of participants with 12-month outcome data are not reported.

The record does not report the primary analysis method, confidence-interval calculation, analysis populations, missing-data handling, or sensitivity analyses. It also does not report the trial’s sample-size justification, a multiplicity strategy, interim analyses, or a detailed statistical plan. The planning illustration described in the record is not evidence of the trial’s own design rationale or observed power.

The safety information is descriptive and lacks reported detail on attribution, timing, and the handling of subjects who may have experienced multiple event terms. No randomized comparator is available for interpreting the listed adverse-event frequencies as comparative risks. These limitations constrain what can be concluded from the registry record, without implying that unreported methods or outcomes were absent from the conduct of the trial.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: STOP Persistent AF — NCT03012841.
• Registry record last updated 2025-02-13; status last verified 2025-02.
• Results first posted 2020-08-21.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

STOP Persistent AF is recorded as a completed, single-group study sponsored by Medtronic Cardiac Ablation Solutions. It enrolled 186 participants with atrial fibrillation and listed the Arctic Front Advance Cardiac CryoAblation Catheter as the intervention. The registry records allocation as NA and masking as NONE.

The primary endpoint is the percentage of participants free from treatment failure at 12 months after pulmonary vein isolation, with a 95% confidence interval specified. Treatment failure includes procedural failure and selected later rhythm events, repeat procedures, medication changes, or left atrial radiofrequency ablation. The primary endpoint result and its confidence interval are not reported in the registry record.

Three listed secondary outcomes concern baseline-to-12-month changes in AFEQT and the physical and mental components of SF-12. The record lists 34 affected subjects in the serious adverse-event category, 52 in the other adverse-event category, and 0 deaths. It does not provide a randomized treatment comparison or the statistical details needed to assess missing data, analysis populations, or multiplicity.