Ablation of the Pulmonary Veins for Paroxysmal Afib: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Ablation of the Pulmonary Veins for Paroxysmal Afib (NCT00744874), a na phase 4 study. The primary outcome is Number of Participants With Successful Pulmonary Vein Isolation.

2. Clinical Question

This is a question about a procedural measure in a group of treated participants, not a randomized comparison of treatment strategies. The record also lists secondary outcomes concerning atrial fibrillation symptom severity, SF-36 quality of life, cumulative radiofrequency time for pulmonary vein isolation, total procedure time, and total fluoroscopy time. Their stated focus is on symptoms, quality of life, and procedural measures, but their observed results are not reported in the registry record. Without those results, the registered questions can be described, but their answers cannot be assessed from the record.

3. Trial Design

The registry record describes a completed phase 4, single-group trial of an RF ablation procedure for paroxysmal atrial fibrillation. Enrollment was 55. The listed start was 2007-10, and the listed primary completion was 2009-09. The sponsor was Medtronic Cardiac Rhythm and Heart Failure. These record details identify the study context; they do not establish how participants were selected or how representative they were of other patients.

The design has no concurrent control arm: allocation is listed as NA, the model is single group, and masking is none. As a result, the trial describes outcomes among participants who underwent the procedure but does not estimate a treatment contrast against an untreated group or another procedure. Changes over time, if measured, would likewise not by themselves separate an intervention effect from other explanations for change.

The registry record describes the enrolled group as participants with symptomatic, self-terminating paroxysmal atrial fibrillation who met investigator-identified inclusion and exclusion criteria. It does not report the detailed eligibility criteria, recruitment approach, or the characteristics of participants who were not enrolled. The intervention is called RF Ablation procedure, and the trial summary identifies the Ablation Frontiers Cardiac Ablation System.

The primary endpoint is framed as the number of participants with successful pulmonary vein isolation, with a 6-month timeframe. The registry record also lists nine outcome measures and several secondary-outcome topics, but it does not report outcome estimates or the analysis populations for those measures. The record lists zero analyses. Further information about the statistical plan, including any planned interim analyses, is not reported in the registry record. The design therefore supports a descriptive reading of the registered endpoint and safety counts, while offering no reported comparative analysis.

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: Subjects that had successful pulmonary vein isolation.

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 Successful Pulmonary Vein Isolation, measured over 6 months.

The primary endpoint is the number of participants with successful pulmonary vein isolation, with the registry timeframe stated as 6 months. Its description defines acute effectiveness as successful isolation of all pulmonary veins. Success was documented by absence of pulmonary vein potentials when assessed by electrogram tracings in sinus rhythm using the PVAC catheter.

This is a procedural endpoint: it records whether the specified electrophysiologic finding was achieved, rather than directly measuring symptoms, quality of life, or a comparison between treatment groups. Such a measure can describe technical or physiologic success according to the trial's stated definition. It does not, on its own, establish how participants felt, whether symptoms changed, or whether outcomes differed from what would have occurred under another approach.

The registry record's wording pairs a 6-month timeframe with a description that calls the measure acute effectiveness. It does not explain how the timing of the assessment relates to that description. The listed population is subjects that had successful pulmonary vein isolation, which does not clarify the denominator for evaluating how many participants succeeded. The observed number, denominator, and any uncertainty interval for the primary endpoint are not reported in the registry record. Consequently, the endpoint can be defined, but its observed frequency and precision cannot be evaluated from the posted record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods determine how observations are organized, summarized, and used to address a study question. For this trial, the registry record identifies a single-group design and a count-based primary endpoint, but detailed methods for analyzing that endpoint are not reported in the registry record. The concepts below are general explanations of how such information is usually interpreted, not claims about procedures used in this trial.

What does a single-group design estimate?

In a single-group study, an outcome can be described among participants who received the intervention. If the outcome is binary, each participant can be classified as meeting or not meeting the endpoint definition, subject to the study's assessment and missing-data rules. The proportion meeting the definition is often a useful descriptive summary, but the registry record does not report that proportion for this endpoint.

A single-group estimate is not a treatment contrast. Without a control group, differences attributable to the procedure cannot be separated from background changes, participant selection, concurrent care, measurement conditions, or other influences. A comparison with a historical expectation would require a defined reference and suitable assumptions; neither is reported in the registry record. The absence of a comparator also means that a conventional between-group effect estimate is not available from the registered design.

How should a binary endpoint be read?

A binary endpoint classifies an outcome into two categories, such as success or no success under the prespecified definition. A count alone does not convey the rate unless its denominator is known. For a meaningful rate, the analysis population and the number assessed must be clear. The registry record supplies an enrollment of 55, but does not report the number evaluated for the primary outcome or the outcome count. It would be inappropriate to treat enrollment automatically as the endpoint denominator.

Uncertainty is also important. A confidence interval describes a range of values compatible with the observed data under the chosen statistical method and assumptions. It communicates precision, not certainty that the true value lies within a particular range. No interval for the primary endpoint is reported in the registry record. Because the observed endpoint count is also absent, its precision cannot be reconstructed from the record.

What does a p-value contribute?

A p-value, when used, assesses how compatible observed data are with a specified statistical model or null hypothesis. It does not measure the size or clinical importance of an effect, and it cannot replace an estimate with an uncertainty interval. No primary endpoint p-value, hypothesis test, or analysis result is reported in the registry record. There is also no reported comparative hypothesis for the single-group endpoint.

Why do analysis populations matter?

Analysis populations define which participants contribute to an estimate. A study might distinguish all enrolled participants from those who received the procedure or those with an assessable endpoint, but the specific populations and rules must be stated rather than assumed. The registry record does not report a primary-outcome analysis population or describe how participants with unavailable assessments were handled. This omission matters because different denominator rules can lead to different descriptive results.

What do the planning assumptions mean?

The record describes a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The stated effect to detect is a fraction of the observed effect. These are assumptions for a hypothetical planning exercise, not a description of the actual single-group design. The record says such sample-size illustrations are not the trial's own design. They are planning illustrations, not observed power, and should not be read as evidence that the completed trial had a particular probability of detecting an effect.

The planning description distinguishes participants per arm for 80% power from total events for time-to-event calculations. No planning sample-size values or observed effect estimate are reported in the registry record. In particular, a two-arm equal-allocation assumption does not match the registered single-group design. It cannot be used to infer what sample size the investigators planned or why they chose the enrollment target.

Why can over-dispersion matter?

As a general statistical concept, over-dispersion occurs when observed variability is greater than a statistical model expects. It can make uncertainty estimates too narrow if a model assumes less variability than the data contain. This issue can arise in some count or clustered-data settings, but the registry record does not describe an over-dispersion analysis or provide data that would establish whether it was relevant to this endpoint. It should not be inferred from the count-based endpoint alone.

For this record, the most defensible statistical reading is therefore descriptive and bounded: the endpoint definition and design are registered, while the endpoint estimate, analysis details, uncertainty, and comparative results are not reported. General statistical concepts can explain what those missing elements would contribute, but cannot supply the trial's unreported findings.

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("Ablated Participants")
n      <- c(55)
events <- c(53)
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  Ablated Participants  55  53  96.4  87.5  99.6  87.7  99.0  87.7  98.9

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists nine outcome measures, including the primary endpoint and secondary outcomes concerning symptoms, quality of life, radiofrequency time, procedure time, and fluoroscopy time. When a study evaluates multiple outcomes or performs multiple tests, the chance of at least one apparently notable result can increase. Statistical approaches to multiplicity can adjust interpretation or testing, but the appropriate approach depends on the prespecified analysis plan and the role assigned to each outcome.

The record does not report a multiplicity strategy, a hierarchy of secondary outcomes, or statistical tests for these outcomes. It lists zero analyses. This does not establish that no analyses were performed outside the registry record; it means that analyses are not reported in the registry record. Without reported outcome estimates and a plan for interpreting multiple results, no multiplicity-adjusted conclusion can be assessed.

Missing-data handling is also not reported in the registry record. For the primary endpoint, the count assessed and the number with unavailable outcome status are not stated. No imputation method, sensitivity analysis, or rule for classifying missing assessments is described. These details matter because a complete-case result and a result that accounts for missing observations can answer different questions and rely on different assumptions.

The analysis populations are not specified. The record does not state whether the primary analysis included all enrolled participants, only participants who received the procedure, or only those with an evaluable assessment. Nor does it describe exclusions after enrollment. These omissions prevent a full assessment of how the endpoint would be calculated and how robust it would be to missing outcomes. The appropriate conclusion is that multiplicity, missing-data procedures, and analysis-population definitions are not reported in the registry record.

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 1% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: arrythmia, pro arrhythmia (5.5%), bleeding (1.8%), chest discomfort (1.8%), collapse after af recurrence (1.8%), dizziness (1.8%).

The registry record lists 55 participants at risk for serious adverse events and 9 affected. For other adverse events, it lists 55 at risk and 19 affected. These are participant counts in the registry safety summary, not a complete description of every event or its course. The record does not report the event-level details, timing, duration, or attribution needed to interpret individual cases.

The listed serious adverse-event terms are Arrythmia, pro arrhythmia at 5.5%, Bleeding at 1.8%, Chest Discomfort at 1.8%, Collapse After AF recurrence at 1.8%, Dizziness at 1.8%, and Sudden Deafness followed by tinnitus at 1.8%. These percentages are reported as registry entries; they should not be added together or treated as mutually exclusive categories, because the record does not specify whether participants could appear under more than one term. The wording and categorization are those recorded, and the entries do not establish that an event was caused by the procedure.

The deaths field is not reported in the registry record. The safety summary does not provide a comparison group, so it cannot quantify whether the listed counts are higher or lower than they would be under another approach. These figures describe the posted registry safety information only.

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

The registry record establishes that this completed phase 4 study enrolled 55 participants in a single group and evaluated an RF ablation procedure for paroxysmal atrial fibrillation. It specifies a primary endpoint based on successful isolation of all pulmonary veins, assessed by absence of pulmonary vein potentials on electrogram tracings in sinus rhythm using the PVAC catheter. It also gives a 6-month timeframe for that endpoint and lists several secondary outcome topics.

Those details define what the study set out to measure, but they do not provide the primary endpoint result. The observed number of participants with successful pulmonary vein isolation, the endpoint denominator, and any measure of uncertainty are not reported in the registry record. Therefore, the record does not establish the frequency or precision of procedural success. Results for the secondary outcomes are not reported either.

The trial design does not support a direct comparison with another treatment or with no procedure. With a single group and no comparator, a favorable-looking outcome, if reported, would remain a description of the enrolled participants rather than a controlled estimate of what the procedure changed. The registry information also does not resolve how representative the enrolled group was or how missing assessments were handled.

The safety summary reports 9 participants affected by serious adverse events and 19 affected by other adverse events, each among 55 at risk. The listed serious-event terms and percentages provide limited category-level information; they do not establish causation or a comparative safety profile. The deaths field is not reported in the registry record.

In short, the record documents the trial's design, endpoint definition, and aggregate safety counts, while leaving the principal outcome estimate and statistical analysis unreported. It can be used to understand the registered question and the limits of the available results, but not to infer an effect size, a probability of success, or a treatment comparison.

14. Why This Trial Matters Statistically

This trial illustrates an important distinction between a registered endpoint and a reported result. The endpoint is defined in procedural terms, yet the observed count and denominator are not reported in the registry record. Without both, readers cannot estimate the observed success frequency. Without an uncertainty interval or other analysis, they also cannot judge its statistical precision.

The single-group structure makes the design limitation visible. Counts in a treated group can describe what happened among participants who received a procedure, but a comparator is needed for a direct estimate of how outcomes differ between treatment strategies. The record lists allocation as NA and identifies a single group, so no like-for-like control comparison is available. This is a design feature, not a statistical defect that can be repaired by calculation from the reported information.

The record also demonstrates why an endpoint's denominator and analysis population are essential. An enrollment count does not necessarily equal the number assessed for an outcome. When the outcome count and assessment rules are absent, even a straightforward binary endpoint cannot be reconstructed responsibly. Missing-data rules and assessment timing add further context, especially because the record pairs a 6-month timeframe with wording that calls the endpoint acute effectiveness without explaining that relationship.

Finally, registry safety counts require careful interpretation. The numbers of participants affected and the listed event-term percentages describe the posted safety information, but do not show causation or comparative risk. The absence of reported outcome analyses, multiplicity procedures, and missing-data methods sets clear boundaries on what can be concluded statistically. The most useful lesson is to distinguish what the record defines, what it counts, and what it leaves unreported.

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 primary limitation for interpretation is that the registry record does not report the observed primary endpoint result. It also does not report the number assessed for that endpoint or an uncertainty interval. Enrollment of 55 does not resolve those omissions, because the record does not state that all enrolled participants contributed an evaluable primary outcome.

The design is single group, with allocation listed as NA and masking as none. There is no concurrent control group and therefore no direct treatment comparison. The record does not report whether outcome assessment was blinded or describe additional safeguards against assessment bias. Those details should not be assumed from the endpoint definition.

The endpoint description calls successful isolation of all pulmonary veins acute effectiveness, while its stated timeframe is 6 months. The registry record does not explain the timing or relationship between these terms. Its population description refers to subjects that had successful isolation, which does not clarify the denominator used to determine the number successful. These wording and reporting gaps make the endpoint's operational analysis unclear.

Detailed eligibility criteria, participant characteristics, and reasons for non-enrollment are not reported in the information described. The record also does not report analysis populations, missing-data procedures, outcome estimates for the secondary outcomes, statistical tests, or a multiplicity strategy. Although it includes planning assumptions for sample-size illustrations, it does not report the trial's own sample-size justification. The registry record does not report interim analyses or a detailed statistical plan.

Safety interpretation is limited by aggregate counts and listed terms. Event timing, duration, individual-level overlap, attribution, and details of the deaths field are not reported in the registry record. The absence of a comparator also prevents a controlled safety contrast. These limitations do not negate the registered information; they define the scope of what it can establish.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Ablation of the Pulmonary Veins for Paroxysmal Afib — NCT00744874.
• Registry record last updated 2018-09-19; status last verified 2018-09.
• Results first posted 2013-01-18.
• 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 phase 4, single-group trial of an RF ablation procedure for paroxysmal atrial fibrillation. Enrollment was 55, with a listed start of 2007-10 and primary completion of 2009-09. The primary endpoint was the number of participants with successful pulmonary vein isolation, with a 6-month timeframe and a definition based on absence of pulmonary vein potentials on electrogram tracings in sinus rhythm using the PVAC catheter.

The record lists nine outcome measures and zero analyses. It does not report the observed primary endpoint result, its denominator, or inferential analyses. Safety information lists 9 participants affected by serious adverse events and 19 affected by other adverse events, among 55 at risk in each category. The deaths field is not reported in the registry record. The design has no comparator, so the posted information supports description of the registered study and its reported counts, not a controlled treatment-effect estimate.