Dual Epicardial Endocardial Persistent Atrial Fibrillation(AF) Study (Staged DEEP): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Dual Epicardial Endocardial Persistent Atrial Fibrillation(AF) Study (Staged DEEP) (NCT01661205), a na na study. The primary outcome is Number of Patients With Pre-specified Safety Endpoints Occurring in the First 30 Days Post-index Procedure or Hospital Discharge, Whichever is Longer..

2. Clinical Question

The trial’s stated purpose was to assess safety and technical feasibility in people with persistent or long-standing persistent atrial fibrillation. Its staged procedure combined an epicardial approach with catheter technology, rather than evaluating either component in isolation. The registry lists a planned enrollment of 30, but the primary endpoint population description records different numbers at successive procedural stages. These are important distinctions: enrollment, anesthesia, completion of an epicardial procedure, and receipt of an endocardial procedure do not describe the same analysis population.

The primary question is descriptive. In a single-group feasibility trial, counting pre-specified safety events can characterize what occurred among treated participants. Without a concurrent comparison group, the record cannot establish whether the observed counts differ from what would have occurred under another treatment strategy. Nor does the endpoint alone answer whether the procedure was technically feasible across all enrolled participants; the registry lists acute procedure success as a secondary outcome, but its results are not reported in the information.

3. Trial Design

This was a completed, single-group feasibility trial sponsored by AtriCure, Inc. The registry lists the study start as 2012-08 and primary completion as 2015-12. Its planned enrollment was 30 participants. The phase and allocation are listed as NA, and masking is listed as NONE. The registry describes the intervention as a device procedure combining the AtriCure Bipolar System with catheter ablation.

The staged approach used minimally invasive thoracoscopic epicardial ablation together with catheter technology for mapping and additional lesion creation or gap closure as needed. The two phases were intended to occur 1-10 days apart during the same hospitalization. The intervention description says the catheter ablation was performed approximately 1-10 days apart. The study therefore evaluated a treatment pathway involving both procedural phases, not an isolated device exposure.

The registry’s population description reports that 26 subjects were anesthetized. Of those, 25 underwent the epicardial procedure per protocol; a physician decided not to treat one anesthetized subject. Another case was aborted and converted to open chest cardioversion. The description also records that 24 patients underwent endocardial treatment, but the text is cut off after that point. The complete definitions of all analysis populations and the disposition of every enrolled participant are not reported in the registry record.

No control arm is listed, and the study was not a randomized comparison. The data therefore describe participants who received or were considered for the staged procedure; they do not provide a direct estimate of a treatment difference. The primary endpoint was a count of participants with specified safety endpoints during the period through 30 days post-index procedure or hospital discharge, whichever was longer. Several secondary outcomes are listed, including acute procedure success, atrial fibrillation status, reinterventions, cardioversion, and symptom checklist change. Their numerical results are not reported in the registry record.

The record does not report a detailed statistical analysis plan, the planned analysis population for each outcome, or a sample-size justification. The study’s feasibility purpose should not be taken as evidence that a formal feasibility threshold was prespecified.

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: Five consented subjects were withdrew prior to treatment. Three did not meet the eligibility criteria, 1 subject was withdrawn by the investigator, and 1 subject withdrew consent.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Number of treated subjects. Although 26 subjects were anesthetized only 25 subjects underwent epicardial procedure per protocol. Physician decided not to treat one of the anesthetized subjects. Another case was aborted and converted to open chest cardioversion. Twenty-four patients underwent endocardial catheter procedures.

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: Number of Treated Subjects

6. Primary Endpoint

The registry lists the primary outcome as Number of Patients With Pre-specified Safety Endpoints Occurring in the First 30 Days Post-index Procedure or Hospital Discharge, Whichever is Longer., measured over 30 days post-index procedure or hospital discharge.

The primary endpoint counts participants with one or more pre-specified safety endpoints during the period from the index procedure through 30 days or hospital discharge, whichever is longer. The listed events are death, myocardial infarction, stroke or TIA, excess bleeding, pulmonary vein stenosis, atrio-esophageal fistula, phrenic nerve paralysis, pericardial effusion, and embolisms. The endpoint is expressed in participants, rather than as a rate per unit of follow-up time.

Counting participants is a way to summarize whether any of the specified events occurred during a defined observation period. A composite endpoint can bring several safety concerns into one summary, which may be useful in a feasibility study where the focus is monitoring a range of possible complications. However, the component events may differ substantially in clinical nature and frequency. A combined count does not show which event drove the result, whether participants had more than one event, or how severe each event was. Component-level results and definitions are needed to interpret those details.

The endpoint description identifies treated subjects as the population, but the registry text also reports different numbers at procedural stages. The complete endpoint denominator, event count, and any uncertainty interval are not reported in the registry record. The serious adverse-event counts elsewhere in the record should not be substituted for the primary endpoint result: the listed serious adverse-event summary is not identified as the same set of pre-specified endpoint events.

The endpoint is used to describe safety experience in this study, not to establish comparative safety. With no control group, it cannot determine whether the observed event experience is attributable to the procedure or how it compares with another approach.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the primary outcome as a count of participants with specified safety events. This is a binary outcome at the participant level: each participant can be classified according to whether an event meeting the outcome definition occurred during the specified observation period. The reported summary would ordinarily include the number meeting the definition and the denominator analyzed. Here, the endpoint definition is present, but its numerical result and complete denominator are not reported in the registry record.

What does a participant count describe?

A participant count is different from a count of every event occurrence. If one person has more than one qualifying event, a participant-level endpoint may still count that person once, depending on its definition. Conversely, an adverse-event listing may count event terms or occurrences rather than unique people. The registry summary does not explain the counting rules for the primary endpoint or provide its component-level results. For that reason, the adverse-event figures should be kept separate from the primary endpoint.

The endpoint has a defined follow-up window: 30 days post-index procedure or hospital discharge, whichever is longer. A fixed observation rule helps specify which events contribute to the endpoint. In practice, interpretation also depends on complete follow-up and consistent ascertainment. The extent of follow-up completeness, handling of participants without complete observation, and adjudication procedures are not reported in the registry record.

Why does the analysis population matter?

Different denominators can lead to different descriptive summaries. Enrollment describes who entered the study; anesthesia and completion of each procedural phase describe later points in the treatment pathway. The record lists planned enrollment of 30, then reports 26 anesthetized subjects, 25 undergoing the epicardial procedure per protocol, and 24 undergoing endocardial treatment. It gives reasons for two departures from the described pathway, but does not provide a complete participant flow or state which denominator was used for every outcome. The registry’s wording that the primary endpoint concerns treated subjects does not by itself resolve all denominator details.

General statistical explanation: a confidence interval presents a range of values compatible with the observed data under a specified statistical method. Its width reflects precision; fewer observations or fewer events generally provide less precise estimates. The registry information does not report a confidence interval for the primary endpoint. No numerical precision estimate should be inferred from the adverse-event summary alone.

What does the single-group design allow?

The study has one treatment group and no randomized comparator. Descriptive counts can summarize the experience observed in that group. They cannot separate the effects of the procedure from other explanations, such as participants’ underlying condition, concurrent care, or the circumstances that led to treatment. General statistical explanation: random allocation and a suitable comparison group can help make treatment groups comparable, but neither is present as a basis for a treatment contrast. This is not a claim about the trial’s conduct beyond the design stated in the registry.

The registry lists no analyses in the outcome record. A detailed statistical analysis plan, including any adjustment, missing-data approach, or inferential method, is not reported in the registry record. It would therefore be inappropriate to attribute a particular model, hypothesis test, or confidence-interval method to the investigators.

How should the planning illustrations be read?

The planning illustrations are described as based on an observed effect, with two-sided significance level 0.05, equal allocation between two arms, and a normal approximation. They describe hypothetical planning requirements for detecting a stated fraction of an observed effect; they are not observed power. The illustrations use a two-arm assumption, whereas the trial itself is described as single-group, so they should not be read as a description of the study’s design or as evidence that the trial was adequately sized. The trial’s own sample-size justification is not reported in the registry record.

General statistical explanation: power is a planning concept tied to a specified effect, variability, test, and design. It does not tell us the probability that a result is true, and retrospective power calculations based on an observed effect do not replace uncertainty intervals around the result. The planning section is useful only as an illustration under its stated assumptions; it does not change what the study observed.

Why might over-dispersion matter?

General statistical explanation: over-dispersion occurs when count data vary more than a model assumes. It can make standard errors too small if the model does not account for that extra variability. This trial’s primary outcome is a participant count for a binary event definition, not a reported repeated-event count model. The registry record does not report a model for recurrent events or an over-dispersion assessment, so such methods should not be presumed to have been used.

Overall, the available record supports a careful distinction between endpoint definition, observed adverse-event summaries, and planning illustrations. It does not supply a primary endpoint estimate, a full analysis specification, or enough detail to reconstruct an analysis independently.

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("AtriCure Bipolar System Combined With a Catheter A")
n      <- c(25)
events <- c(3)
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  AtriCure Bipolar System Combined With a Catheter A  25  3  12.0  2.5  31.2  4.2  30.0  4.4  30.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists several secondary outcomes in addition to the primary safety endpoint. These include serious device- or procedure-related adverse events, acute procedure success, atrial fibrillation status, reinterventions, direct current cardioversion, and change in atrial fibrillation symptoms. The record states that there are 8 outcome measures, but numerical results for these secondary outcomes are not reported in the registry record.

When many outcomes are assessed, the chance of at least one apparently notable result can increase if each is tested separately. General statistical explanation: multiplicity can be addressed in different ways, including prespecifying a primary outcome, adjusting inference, or treating secondary outcomes as exploratory. The registry information does not report a multiplicity strategy, a hierarchy among secondary outcomes, or which outcomes were formally tested. No adjustment or confirmatory status should be assumed.

The number of analyses recorded is 0 in the information. This does not establish that no analysis was performed; it means that analysis results are not available in the registry record presented for this page. A detailed statistical analysis plan is not reported in the registry record.

The available information also does not describe missing-data rules, follow-up completeness, outcome adjudication, or how participants who did not complete both procedural stages were handled for each endpoint. These omissions limit interpretation of denominators and potential bias. The primary endpoint description refers to treated subjects, while the procedural narrative gives different counts at successive stages. The exact analysis population for the primary endpoint and each secondary outcome is not reported in the registry record.

These reporting gaps do not establish that missing data or multiplicity changed the results. They mean that readers cannot assess those issues from the posted information. In particular, the listed secondary outcomes should be treated as outcomes named in the registry, not as evidence of statistically confirmed effects.

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: pericarditis (7.7%), renal failure (7.7%), diaphragmatic paralysis (7.7%), atrial fibrillation (3.8%), atrial tachycardia (3.8%).

The registry’s serious adverse-event summary lists 12 participants with serious adverse events among 26 at risk. It also lists 16 participants with other adverse events among 26 at risk. The summary does not give a complete account of how these categories relate to one another, so they should not be added together or interpreted as mutually exclusive groups. It also does not identify these totals as the primary endpoint result.

The listed serious-event terms include pericarditis, renal failure, and diaphragmatic paralysis, each reported at 7.7%, and atrial fibrillation, atrial tachycardia, and complete atrioventricular block, each reported at 3.8%. These are terms in the adverse-event summary. The registry information does not specify whether each term represents a unique participant, whether participants had multiple terms, or how the terms map onto the pre-specified primary safety endpoints.

The primary endpoint covers a defined set of events during 30 days post-index procedure or hospital discharge, whichever is longer. The adverse-event summary is not explicitly limited to that same set or window in the information. Consequently, the serious adverse-event figures should be read as a separate descriptive summary, not as a substitute for the missing primary endpoint count.

Because this was a single-group study, the adverse-event counts describe events observed in the treated group; they do not provide a comparison with another procedure. The death count is listed as not available in the record, so no conclusion about deaths should be drawn from that field.

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

The posted record documents a feasibility study of a staged epicardial and endocardial ablation approach, along with a defined primary safety endpoint and adverse-event summaries. It also records procedural flow: 26 subjects were anesthetized, 25 underwent epicardial procedure per protocol, and 24 underwent endocardial treatment. The record notes that a physician decided not to treat one anesthetized subject and that another case was aborted and converted to open chest cardioversion. These registry entries describe what the registry reports about the treatment pathway; they do not, by themselves, establish safety or effectiveness.

The serious adverse-event summary reports 12 participants with serious adverse events among 26 at risk and 16 with other adverse events among 26 at risk. The listed event terms offer additional descriptive detail, but the registry information does not show how they relate to the primary endpoint or whether they overlap at the participant level. The primary endpoint count itself is not reported in the registry record. That missing result prevents a direct assessment of the endpoint as defined.

The record does not include a concurrent control group or a randomized comparison. It therefore cannot show whether the staged approach changed the risk of an event relative to another strategy. It also cannot establish that any event was caused by the procedure. A single-group study can describe observed experience, but causal or comparative conclusions require evidence that this record does not provide.

The registry lists secondary outcomes such as acute procedure success, atrial fibrillation status, reintervention, cardioversion, and symptom change. Their results are not reported in the registry information. Accordingly, the record does not support conclusions about those outcomes either.

General statistical interpretation: an estimate is more informative when its denominator, uncertainty, outcome definition, and analysis population are clear. Here, the endpoint definition is available, but its result and precision are not. The appropriate conclusion is limited to the information actually posted: the study design and selected event summaries can be described, while the primary endpoint and comparative treatment effects cannot be evaluated from this record.

14. Why This Trial Matters Statistically

This trial matters statistically because it illustrates the difference between a feasibility study’s descriptive purpose and a comparative treatment evaluation. The registry describes a single group receiving a staged procedure and names safety and technical feasibility as central aims. Its design can document procedural experience and observed events, but it does not create a randomized contrast with another approach.

It also shows why denominator clarity is essential. The record lists planned enrollment of 30, then gives counts for anesthesia and completion of the two procedural stages. Those counts represent different points in the treatment pathway. Without a clearly stated denominator for each result, readers can misunderstand what a participant count summarizes. The registry text identifies the primary endpoint population as treated subjects, but the complete population definition and endpoint denominator are not reported.

A further statistical issue is the distinction between a named endpoint and a reported result. The registry gives a detailed list of safety events and a follow-up rule, yet the primary endpoint count is not reported in the record. Adverse-event counts do not automatically fill that gap because event categories, counting rules, and time windows may differ. Clear reporting of endpoint-specific counts and uncertainty would be needed to evaluate the primary safety question.

Finally, the planning illustrations assume equal allocation between two arms, while this study is described as single-group. That mismatch is a useful reminder that sample-size illustrations depend on their assumptions and should not be mistaken for the design actually conducted. They are not observed power and do not supply missing results. Together, these features make the trial a case study in reading registry records carefully: distinguish design from planning, participant flow from outcomes, and descriptive safety summaries from evidence of comparative benefit or harm.

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 most important limitation of the available record is that the numerical result for the primary safety endpoint is not reported. The endpoint definition and observation period are described, but its event count, denominator, and precision are unavailable. This prevents a direct assessment of the study’s primary question.

The trial is a single-group study with no randomized comparison. Its adverse-event figures describe the recorded experience in one group and cannot establish a difference relative to another procedure or no procedure. They also cannot isolate the contribution of the staged intervention from other influences.

The procedural narrative reports 26 anesthetized subjects, 25 who underwent epicardial procedure per protocol, and 24 who underwent endocardial treatment. It gives reasons for a physician’s decision not to treat one anesthetized subject and for another case being aborted and converted to open chest cardioversion. However, the available text is truncated and does not provide a complete participant disposition or endpoint-specific analysis populations.

The serious adverse-event and other adverse-event counts are not explicitly linked to the primary endpoint definition. The record does not clarify whether those groups overlap, whether event terms represent distinct participants, or whether the listed terms occurred within the primary endpoint window. The death count is not available in the record. These reporting limits make it important not to equate the adverse-event summary with the primary safety result.

The registry lists secondary outcomes but does not report their numerical results. A detailed statistical analysis plan, missing-data handling, outcome adjudication procedures, multiplicity approach, and sample-size justification are also not reported in the registry record. These absences limit assessment of analytic choices and precision; they do not establish that particular methods were or were not used outside what the record states.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Dual Epicardial Endocardial Persistent Atrial Fibrillation(AF) Study (Staged DEEP) — NCT01661205.
• Registry record last updated 2017-05-17; status last verified 2017-04.
• Results first posted 2017-05-17.
• 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 completed Staged DEEP study was a single-group feasibility trial of a staged epicardial and endocardial approach using the AtriCure Bipolar System and catheter ablation. The registry lists planned enrollment of 30 and a primary safety endpoint covering specified events through 30 days after the index procedure or hospital discharge, whichever was longer.

The procedural description reports 26 anesthetized subjects, 25 undergoing epicardial procedure per protocol, and 24 undergoing endocardial treatment. The serious adverse-event summary reports 12 participants with serious adverse events among 26 at risk and 16 with other adverse events among 26 at risk. The primary endpoint result and numerical results for the listed secondary outcomes are not reported in the registry record.

Because there was no control group, the record supports descriptive interpretation only. The available information does not establish comparative safety or treatment effects.