Combined Amiodarone and Electrical Cardioversion for Postoperative Atrial Fibrillation After Cardiac Surgery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Combined Amiodarone and Electrical Cardioversion for Postoperative Atrial Fibrillation After Cardiac Surgery (NCT01558128), a na na study. The primary outcome is Subject Rhythm.

2. Clinical Question

The clinical question is whether the sequential management approach is associated with conversion to normal sinus rhythm among participants with postoperative atrial fibrillation. It is a question about an outcome observed within a single group, not a randomized comparison of alternative strategies. Because the intervention includes cardioversion only for participants who remain in atrial fibrillation after amiodarone, the approach is conditional: the next step depends on the rhythm after the drug.

The registry lists cardiac disease as the condition and describes the intended population as cardiac patients who develop postoperative atrial fibrillation. It does not report detailed eligibility criteria, baseline characteristics, or how rhythm conversion was assessed. Those omissions limit how precisely the target population and outcome can be understood.

The registry record does not report how many participants reached normal sinus rhythm. It therefore cannot answer the primary clinical question from the posted outcome information. Even if a conversion count were available, a single-group result would describe outcomes under this approach; without a like-for-like comparator, it would not establish how outcomes differed from another strategy.

3. Trial Design

The registry identifies this study as a single-group intervention study with no masking. Allocation is recorded as NA, and there is no registered control arm. The listed intervention is amiodarone with cardioversion: a participant who converts to normal sinus rhythm after amiodarone receives no further intervention, while a participant who remains in atrial fibrillation is cardioverted. The record does not describe a randomized treatment assignment.

The recorded enrollment is 1. The study status is terminated. Its recorded start is 2012-03, and its primary completion is 2013-03. The reason for termination is not reported in the registry record. The record lists one primary outcome measure and no analyses.

The primary outcome timeframe describes follow-up during the hospital stay after surgery, with an expected average of 7 to 10 days, and again at a surgical follow-up appointment up to 6 weeks. These are the time points stated for outcome follow-up; the record does not give individual follow-up durations or clarify whether all participants completed follow-up.

A single-group design can describe what happened to participants receiving the registered approach, but it does not provide a concurrent estimate of what would have happened under another approach. Because allocation is NA and no control group is listed, any interpretation should remain descriptive rather than treating the study as a treatment comparison. Details such as eligibility criteria, the clinical setting, recruitment procedures, and the reason for termination are not reported in the registry record. The listed enrollment is small in scale, so the record offers little basis for estimating how outcomes might vary across a broader population.

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

Analysis population for the primary outcome, as defined in the registry: Converted to normal sinus rhythm

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 Subject Rhythm, measured over Participants will be followed for the duration of their hospital stay post surgery with an expected average of 7 to 10 days and again at surgical follow up appointment up to 6 weeks..

The primary outcome is titled “Subject Rhythm,” uses participants as its unit, and is described as measuring change from baseline cardiac rhythm. The stated outcome is participants who converted to normal sinus rhythm. It is a binary outcome: each participant either meets the stated conversion outcome or does not, according to the outcome definition. The registry record does not provide further operational details about rhythm measurement, confirmation, or the precise assessment used to classify conversion.

Rhythm conversion is relevant to the registered clinical question because the intervention is intended to address postoperative atrial fibrillation. A count of participants who reach normal sinus rhythm can describe whether the specified outcome occurred in the treated group. To interpret such a count, readers would also need the number assessed and clarity about missing assessments; the record does not report primary outcome counts or those details.

The follow-up timeframe includes the postoperative hospital stay, with an expected average of 7 to 10 days, and a surgical follow-up appointment up to 6 weeks. The registry does not specify which assessment time determines the primary outcome if rhythm status changes across follow-up. It also does not report a numerical result, an effect estimate, or an uncertainty interval for the primary outcome. Consequently, the endpoint definition is available, but the result needed to describe the observed conversion experience is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the binary outcome represent?

In general, a binary outcome classifies each participant into one of two states, such as meeting or not meeting a specified outcome definition. The registered primary outcome is conversion to normal sinus rhythm. Reporting a count for that outcome requires both the number meeting the definition and the number assessed under the relevant outcome rules. The registry record gives neither a primary outcome count nor an analysis population for this endpoint, so an outcome proportion cannot be interpreted from the posted results.

For a binary outcome, an interval estimate can express uncertainty around an estimated proportion. An interval is not a guarantee that the true value falls within a particular range; it describes uncertainty under the assumptions of the method used. With very limited observations, estimates can be imprecise, and the choice of interval method matters. No interval estimate or method for the primary outcome is reported in the registry record.

What can a single-group study establish?

In general, a single-group study can describe outcomes observed among participants receiving an intervention. It cannot directly estimate a difference between that intervention and a concurrent comparator when no comparison group is registered. This study lists amiodarone with cardioversion when needed, but no control arm or treatment allocation is recorded. Therefore, a result from the intervention group alone would not answer how outcomes compare with another management approach.

The primary description refers to change from baseline cardiac rhythm. A before-and-after observation can document whether rhythm status changed, but a change alone does not identify why it occurred. General sources of change can include the natural course of a condition and other care received during follow-up. The registry does not describe methods to distinguish those influences from the intervention.

What do the sample-size assumptions mean?

The registry record describes sample-size calculations as planning illustrations, not as the trial’s own design justification. The stated assumptions include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The illustration is described as targeting a stated fraction of an observed effect. The record also distinguishes time-to-event calculations, which use total events under a Schoenfeld approach, from other calculations, which use participants per arm.

Those assumptions describe a generic planning calculation; they do not make this single-group study a two-arm comparison. The registry does not report a trial-specific sample-size justification or a planned comparison. Nor does the registry report the primary outcome effect used for the illustration, the resulting planning sample sizes, or an inferential analysis. Any sample-size illustration should be read as planning information, not as evidence about what the study observed. Sample-size calculations do not show that a study had a particular probability of detecting an effect after the results are known; they are not observed power.

In general, over-dispersion means that variability in data is greater than a model assumes. It can make standard errors too small and intervals too narrow if the model does not account for that extra variability. The registry record does not report an over-dispersion model or a statistical analysis for the primary endpoint. With a binary outcome, the relevant analysis would depend on the study question, outcome definition, and available observations; no such analysis is recorded.

Why are no inferential results available?

A p-value evaluates how compatible data are with a specified statistical model and null hypothesis, under the assumptions of the analysis. A confidence interval conveys uncertainty about an estimate. Neither can be reconstructed from the registered outcome description alone. Because no primary outcome analysis or result is reported, there is no registry-based p-value, confidence interval, or adjusted effect estimate to interpret.

The record reports no analyses and does not state a statistical analysis plan. The choice of analysis population, handling of participants with missing assessments, and any adjustment for other variables are not reported in the registry record. These are important because the population included in an analysis and the treatment of unavailable outcomes can affect an estimate. The available information supports explaining the intended endpoint and general statistical concepts, but not reproducing or evaluating a specific analysis.

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("Amiodarone With Cardioversion")
n      <- c(1)
events <- c(1)
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  Amiodarone With Cardioversion  1  1  100.0  2.5  100.0  20.7  100.0  15.8  98.7

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure and no analyses. It does not report a statistical analysis plan, a prespecified hierarchy of outcomes, or any procedure for controlling multiplicity. Multiplicity concerns arise when several outcomes, time points, or comparisons are tested; repeated testing can increase the chance of a false-positive finding if it is not accounted for. The record does not provide enough information to determine whether such testing was planned or performed. The listed count of one primary outcome measure should not be taken as evidence that no other analyses occurred outside the registry record.

Missing data are not described for the primary outcome. The record does not state whether rhythm assessments were incomplete, how missing assessments would be handled, or whether follow-up was completed. The specified follow-up extends through the hospital stay, with an expected average of 7 to 10 days, and a surgical follow-up appointment up to 6 weeks, but this does not establish that every assessment was available.

The analysis population is not reported. The record does not say whether analyses were intended to include all enrolled participants, only those with available outcome assessments, or another population. It also does not report an approach to protocol deviations or exclusions. These omissions matter because the numerator, denominator, and interpretation of a binary outcome depend on who was assessed and how unavailable outcomes were treated. No missing-data method or population definition should be inferred from the registered design alone.

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 non-serious adverse event terms

The registry lists one safety group, titled “Amiodarone With Cardioversion.” It records 1 participant at risk for serious adverse events and 0 affected by serious adverse events. It records 1 participant at risk for other adverse events and 1 affected by an other adverse event. Deaths are recorded as 0. No serious adverse event terms are listed.

These entries are counts, not comparative estimates. There is no registered control group, so the safety counts cannot be used to compare the intervention with another approach. The registry record does not describe the other adverse event, its severity, timing, or relationship to treatment. The count for other adverse events should therefore not be assigned a clinical meaning beyond what the record states.

The small recorded enrollment and the lack of event descriptions limit interpretation. A count of 0 serious adverse events in this record does not establish that serious events cannot occur, and a count of 1 other adverse event does not by itself establish causation. The safety information is a limited account of the events recorded for this study, not a general estimate of risk.

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

The registry record describes a sequential approach for postoperative atrial fibrillation: amiodarone is used first, with electrical cardioversion if atrial fibrillation persists. It identifies conversion to normal sinus rhythm as the primary outcome and describes follow-up during the hospital stay and at surgical follow-up. These details explain the intended intervention and outcome, but the record does not report the primary outcome result.

Without a conversion count, an analysis, or a reported estimate of uncertainty, the posted information cannot show how often the primary outcome occurred in the study. It also cannot establish whether the intervention changed rhythm or whether any observed change, if one occurred, was caused by the intervention. The registry lists no comparator, so it cannot provide a treatment difference against another strategy.

The safety entries report 0 serious adverse events, 1 other adverse event, and 0 deaths, with the risk counts listed for the single safety group. The description of the other adverse event is not reported in the registry record. These counts are limited to the registered study and do not establish safety for a broader population or provide a comparison with other care.

The study status is terminated, but the reason is not reported. The record does not provide enough information to determine why it ended or whether all planned follow-up occurred. The appropriate reading is therefore narrow: the registry documents a study design, an intended rhythm outcome, a follow-up timeframe, and safety counts, but it does not supply a primary outcome result or a comparative estimate. No conclusion about efficacy or lack of efficacy can be drawn from the registry information alone.

14. Why This Trial Matters Statistically

This study illustrates why a registered clinical question and an interpretable result are different things. The registry describes a clear management sequence and identifies a rhythm outcome, but it reports no primary outcome analysis. Without an outcome count and an analysis population, readers cannot assess even the observed conversion frequency in the study.

It also shows the limits of a single-group design for comparative questions. A count of participants reaching normal sinus rhythm could describe the experience of the treated group, but it would not establish how that outcome differs from what would occur under another approach. A comparator is necessary for a direct estimate of such a difference, and no comparator is registered.

Registration details can still clarify what was intended: the treatment sequence, the stated follow-up, the primary outcome, the recorded enrollment, and the safety counts. But interpretation depends on reported results and methods as well as design. Here, no analyses are listed, and key information about outcome assessment, missing data, and the reason for termination is not reported in the registry record.

The safety entries also demonstrate why event counts need context. The record gives counts and participants at risk, but does not describe the other adverse event. Without detail or a comparison group, those entries are not a complete basis for judging the nature or comparative frequency of harms. The statistical lesson is that registry status, outcome definitions, analysis methods, and results each answer different questions; one should not be substituted for another.

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 direct limitation is that the registry record does not report a primary outcome result or any analyses. It therefore does not provide the conversion count, an estimate of the outcome frequency, or uncertainty around an estimate. The record also does not clarify the number assessed for the primary endpoint or how missing assessments were handled.

The single-group design has no registered comparator, and allocation is listed as NA. It cannot support a direct comparison with another treatment strategy. The record does not report detailed eligibility criteria, baseline participant characteristics, or methods for rhythm assessment and outcome classification. These omissions limit assessment of who the results would apply to and how consistently the endpoint was measured.

Although follow-up is described during the hospital stay and at a surgical follow-up appointment up to 6 weeks, completion of follow-up is not reported. The registry lists an enrollment of 1 and a terminated status, but the reason for termination is not reported. It is not possible to determine from the registry record whether the planned follow-up or analyses were completed.

The safety information is also limited: the other adverse event is not described, and the record does not provide comparative safety data. Finally, the record does not report a statistical analysis plan, an analysis population, or a trial-specific sample-size justification. These gaps constrain both clinical interpretation and statistical evaluation.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Combined Amiodarone and Electrical Cardioversion for Postoperative Atrial Fibrillation After Cardiac Surgery — NCT01558128.
• Registry record last updated 2017-05-23; status last verified 2017-04.
• Results first posted 2017-05-23.
• 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 concerns a single-group study of amiodarone with electrical cardioversion when atrial fibrillation persists after amiodarone in cardiac patients with postoperative atrial fibrillation. Masking is listed as none, allocation as NA, and the study model as single-group. The recorded enrollment is 1; the study status is terminated. The recorded start is 2012-03, and primary completion is 2013-03.

The primary outcome is conversion to normal sinus rhythm, described as a change from baseline cardiac rhythm. Follow-up is specified during the hospital stay, with an expected average of 7 to 10 days, and at surgical follow-up up to 6 weeks. No analyses are listed, and the primary outcome result is not reported in the registry record.

Safety entries list 0 serious adverse events, 1 other adverse event, and 0 deaths. The other adverse event is not described. The reason for termination, detailed analysis methods, and missing-data handling are not reported in the registry record.