This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Catheter Ablation Versus Medical Treatment of AF in Heart Failure (NCT01411371), a randomized na study. The primary outcome is Difference in Ejection Fraction Between Groups.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01411371 |
| Phase | NA |
| Condition | Atrial Fibrillation, Heart Failure |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 50 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Barts & The London NHS Trust |
| Results posted | Yes |
2. Clinical Question
Population
People with heart failure and persistent atrial fibrillation were eligible for the comparison described in the registry record. The record does not report further details about participant characteristics, such as age, heart-failure severity, or how long atrial fibrillation had been present.
Intervention
Catheter ablation was intended to restore normal sinus rhythm. The registry describes this as catheter ablation of persistent atrial fibrillation.
Comparator
The comparator was medical treatment alone for atrial fibrillation. The registry summary describes medical treatment as the alternative to an ablation procedure.
Primary question
The primary outcome concerned the difference in left ventricular ejection fraction between groups on echocardiography at 6 months. The posted results give a mean and 95% confidence interval for each group, but do not give a between-group estimate or statistical test.
The clinical question is whether the two assigned strategies were associated with different ejection-fraction results at the stated assessment time. This is a comparison of treatment groups in a randomized trial, rather than a comparison of changes within one group alone. The registry's hypothesis was that restoring sinus rhythm by catheter ablation would be superior to medical treatment in people with heart failure and persistent atrial fibrillation. That statement describes the investigators' hypothesis, not a conclusion established by the posted outcome figures.
The results also list outcomes concerning peak VO2, NYHA class, BNP, quality of life, end systolic volume, and heart-failure symptoms. They are secondary outcomes; the registry record does not provide numerical results for them in the posted results. The clinical question can therefore be evaluated from the reported figures only to the extent those figures address the primary measure. They describe the group means, but do not quantify the adjusted or unadjusted contrast between groups or its uncertainty.
3. Trial Design
The registry record describes a randomized, parallel-group trial with no masking. Participants were assigned to catheter ablation or medical treatment alone. The enrollment was 50. The trial is marked completed, and its phase is listed as NA. The sponsor is Barts & The London NHS Trust.
The study concerns the coexistence of atrial fibrillation and heart failure. The registry summary says that patients with heart failure and persistent atrial fibrillation were randomized to medical treatment of atrial fibrillation or catheter ablation intended to restore sinus rhythm. It gives no further eligibility criteria or description of the population that contributed to the primary endpoint.
The registry lists a start date of 2005-03 and a primary completion date of 2013-02. The primary endpoint was the difference in ejection fraction between groups, measured by echocardiography at 6 months. The posted outcome data are group-level means with 95% confidence intervals: the catheter-ablation group has a mean of 39.9 with an interval from 35.2 to 44.7, based on 23 participants; the medical-treatment-alone group has a mean of 31.0 with an interval from 25.5 to 36.6, based on 25 participants. These are arm-specific summaries, not a reported estimate of the difference between arms.
The record also identifies six secondary outcomes, including measures of exercise capacity, functional class, biomarkers, quality of life, ventricular volume, and heart-failure symptoms. It does not report numerical findings for those outcomes in the posted results. Details of the randomization procedure, allocation concealment, treatment adherence, follow-up procedures, and analysis population are not reported in the registry record. The record's no-masking designation indicates that masking is not listed, but it does not establish which trial personnel or participants knew treatment assignments.
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: After recruitment patients underwent a 3 month period of pharmacological optimization during which AF was rate controlled and heart failure drugs initiated and up titrated. This was before baseline investigations and randomization.
Overall Study
| Stage | Catheter Ablation | Medical Treatment Alone |
|---|---|---|
| STARTED | 24 | 26 |
| Primary End-point | 23 | 25 |
| COMPLETED | 23 | 25 |
| NOT COMPLETED | 1 | 1 |
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: Patients with persistent AF and heart failure
| Characteristic | Unit | Catheter Ablation | Medical Treatment Alone | Total |
|---|---|---|---|---|
| Participants analysed | 24 | 26 | 50 | |
| Age, Continuous | years | 55 (SD 12) | 60 (SD 10) | 58 (SD 11) |
| Sex: Female, Male: Female | Participants | 1 | 1 | 2 |
| Sex: Female, Male: Male | Participants | 23 | 25 | 48 |
| Region of Enrollment: United Kingdom | participants | 24 | 26 | 50 |
| Time in continuous AF | months | 24 (17 to 33) | 24 (12 to 48) | 24 (24 to 42) |
| Left ventricular ejection fraction | percentage | 32 (SD 8) | 34 (SD 12) | 33 (SD 10) |
| Left atrial diameter | mm | 52 (SD 11) | 50 (SD 10) | 51 (SD 10) |
6. Primary Endpoint
The registry lists the primary outcome as Difference in Ejection Fraction Between Groups, measured over 6 months.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | 95% Confidence Interval |
| Unit | percentage of LVEF |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is left ventricular ejection fraction, assessed by echocardiography at 6 months. Ejection fraction is a continuous measure of the proportion of blood in the left ventricle that is ejected with each contraction. The registry gives the unit as percentage of LVEF and specifies a mean as the summary measure.
As a general statistical point, a continuous endpoint retains more information about measured values than a simple classification into categories. A group mean describes the central level of the measure, while a confidence interval communicates uncertainty around that estimated mean. The registry reports 95% confidence intervals for each treatment group. Those intervals refer to the group-specific means; they are not the confidence interval for the contrast between groups.
The endpoint is clinically relevant to the study question because the trial was designed around heart failure and a proposed rhythm-restoration strategy. The registry's primary outcome definition focuses on ejection fraction at a fixed follow-up time, rather than on a time-to-event outcome. This makes clear what measurement was intended to anchor the primary comparison, but it does not by itself establish how the groups were compared statistically or how missing measurements were handled.
The title and outcome description refer to a difference between groups. However, the posted figures give separate means for catheter ablation and medical treatment alone, not a numerical difference. The registry record does not report a test or confidence interval for the between-group contrast. Accordingly, the arm-specific summaries should not be treated as a complete inferential result for the stated primary question.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
At the 6-month assessment, the posted mean ejection fraction is 39.9 for catheter ablation, with a 95% confidence interval from 35.2 to 44.7. For medical treatment alone, the mean is 31.0, with a 95% confidence interval from 25.5 to 36.6. The corresponding reported sample sizes are 23 and 25 participants. These numbers describe the observed group-level summaries in the registry record.
The central statistical limitation is that no between-group estimate is posted. The stated primary outcome is a difference between groups, but the registry gives neither a numerical contrast nor its confidence interval, and no p-value is reported. Therefore the arm-specific means cannot establish the size or precision of the treatment-group contrast. A comparison of the two separate confidence intervals is not a substitute for a confidence interval or test calculated for the difference itself.
As a general statistical point, uncertainty around a group mean and uncertainty around a contrast answer different questions. The first describes how precisely the mean is estimated for one group; the second describes how precisely the estimated difference between groups is known. The posted intervals are useful descriptions of the arm-level estimates, but they do not provide the inferential information needed to assess the primary between-group question directly.
The outcome counts also differ from the enrollment figure: the primary outcome summaries include 23 participants in the ablation group and 25 in the medical-treatment group. The registry gives no explanation for those denominators or account of participants without an endpoint measurement. The adverse-event risk groups have different counts again. These differences should not be interpreted as evidence about why observations are absent; reasons and handling of missing measurements are not reported in the registry record.
The registry identifies six secondary outcomes, but numerical results for those measures are not included in the posted results. It lists zero analyses. This does not permit reconstruction of a statistical analysis plan or establish that no analysis was conducted outside the record. The registry record does not report the test used for the primary comparison, whether the estimate was adjusted, or whether any prespecified analysis population was used.
Overall, the posted results show higher numerical mean ejection fraction in the catheter-ablation arm than in the medical-treatment arm at the specified follow-up, while leaving the between-group estimate and its uncertainty unreported. The descriptive direction and the inferential conclusion are not interchangeable. The results should be read as incomplete for the primary comparative question, not as a statistical test of the investigators' hypothesis.
9. Statistical Methods Explained
The primary endpoint is a continuous measure, and the registry summarizes it as a mean with a 95% confidence interval in each group. A mean gives the arithmetic center of the measured values. A confidence interval is an interval estimate intended to convey the uncertainty associated with an estimate under the assumptions of the method used. In general, a narrower interval indicates greater precision, while a wider interval indicates less precision. The registry record does not identify the method used to calculate these particular intervals.
What do the reported confidence intervals describe?
The interval from 35.2 to 44.7 belongs to the catheter-ablation group mean of 39.9. The interval from 25.5 to 36.6 belongs to the medical-treatment-alone group mean of 31.0. They describe uncertainty for separate arm-specific estimates. The primary outcome, however, is phrased as a difference between groups. A confidence interval for that difference would account for uncertainty in the contrast itself. It is not obtained by simply treating either group interval as the interval for the comparison.
As a general point, a 95% confidence interval is not a statement that there is a 95% probability that a fixed true value lies within this particular calculated interval. Its usual interpretation is tied to the long-run performance of the interval procedure under its assumptions. The registry does not report the assumptions or calculation method used for the endpoint intervals, so the posted values can be described, but their construction cannot be independently assessed from the registry record.
Why does the comparison estimate matter?
A randomized comparison is intended to estimate how outcomes differ between assigned groups. The estimate should be accompanied by an account of its uncertainty, commonly a confidence interval, and may also be accompanied by a test result. Those are the quantities needed to evaluate the primary contrast. Here, the registry posts means and intervals for each group but no numerical between-group estimate, confidence interval, or p-value. The record therefore does not support a conclusion about the statistical significance or precision of the stated contrast.
Random assignment is important because it aims to make groups comparable at the point of assignment, on average, under the randomization process. It does not remove the need to report the analysis method, participant flow, missing outcome handling, and the estimate for the treatment contrast. The allocation method and concealment procedures are not reported in the registry record. The trial is described as unmasked, so the record does not claim that treatment assignment was masked.
How should the sample-size illustrations be read?
The accompanying planning illustrations are based on the observed effect, rather than being the trial's own design calculation. The stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. These are planning assumptions, not observed results. Sample-size figures under those assumptions are illustrations of what a future design might require under the chosen inputs. They are not evidence that the completed trial had a particular probability of detecting an effect, and they are not observed power.
The registry record does not report the trial's own sample-size justification. It also does not report the effect size or analysis assumptions used when the study was planned. Thus the planning illustrations should not be treated as a reconstruction of the original design rationale. In general, planning calculations depend on the target effect, variability, significance level, allocation, and analysis method. If those inputs differ from the actual design or the effect used in an illustration, the resulting sample-size guidance will differ as well.
Why can over-dispersion matter?
As a general statistical concept, over-dispersion occurs when variability in observed data exceeds what a model assumes. It can make standard errors too small if the model does not account for the extra variability, and consequently can make confidence intervals too narrow or tests appear more decisive than warranted. This trial's primary measure is continuous and summarized with group means, but the registry record does not state that an over-dispersion issue was assessed or that a model susceptible to it was used. It is therefore a general consideration rather than a specific finding about this trial.
For continuous outcomes, the distribution of observations and the method used to estimate uncertainty can matter. The posted group means and confidence intervals do not provide enough information to assess the underlying distribution, influential observations, or the appropriateness of a particular model. No standard deviations are listed in the endpoint summaries, and the registry does not report a variance model or adjustment strategy.
What information is needed for a complete statistical reading?
A full interpretation would ordinarily benefit from the planned primary analysis, the between-group effect estimate and uncertainty interval, the treatment of missing measurements, the analysis population, and the handling of secondary outcomes. The registry record does not report these details. It lists no analyses, and the posted primary result is limited to arm-specific mean estimates. The interpretation should therefore remain descriptive and should not infer an unreported test, adjustment, or analysis plan.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists six secondary outcomes in addition to the primary ejection-fraction outcome. These include peak VO2, NYHA class, BNP, quality of life, end systolic volume, and heart-failure symptoms. Considering multiple outcomes can raise multiplicity concerns because, as a general statistical point, testing many hypotheses may increase the chance of at least one apparently noteworthy result by chance. A prespecified strategy can address that concern, but such a strategy is not reported in the registry record. Numerical results for the secondary outcomes are not reported in the posted results.
The registry record lists zero analyses. It does not provide an analysis plan describing how the primary and secondary outcomes were to be tested, whether any adjustment for multiplicity was planned, or how analyses were prioritized. It would be inappropriate to infer those choices from the outcome list alone.
The primary outcome sample sizes are 23 for catheter ablation and 25 for medical treatment alone, whereas enrollment is 50. The record does not explain the difference between enrollment and the endpoint denominators, identify reasons for unavailable measurements, or describe imputation or other missing-data methods. The adverse-event groups use their own at-risk counts. Without participant flow and endpoint availability information, the effect of missing data on the ejection-fraction comparison cannot be assessed.
The analysis population is not reported in the registry record. It is therefore unclear from the posted results whether participants were analyzed according to randomized assignment, according to treatment received, or under another definition. Details of protocol deviations and adherence are also not reported. These omissions limit assessment of how closely the reported summaries represent the randomized comparison.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Catheter Ablation | 3 | 24 | 12.5% |
| Medical Treatment Alone | 1 | 26 | 3.8% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Catheter Ablation | 0 of 24 |
| Medical Treatment Alone | 0 of 26 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Catheter Ablation | 0 of 24 |
| Medical Treatment Alone | 0 of 26 |
Most frequent serious adverse event terms
| Event term | Organ system | Catheter Ablation | Medical Treatment Alone |
|---|---|---|---|
| Procedural complication in AF ablation group | Cardiac disorders | 2 of 24 | 0 of 26 |
| Adverse events during follow up | Cardiac disorders | 1 of 24 | 1 of 26 |
Serious events with the highest arm-level rate: procedural complication in af ablation group (8.3%), adverse events during follow up (4.2%).
The adverse-event record gives an at-risk count of 24 for catheter ablation and 26 for medical treatment alone. It reports serious adverse events affecting 3 participants in the catheter-ablation group and 1 participant in the medical-treatment group. Other adverse events are recorded as 0 in each group, and deaths are recorded as 0 in each group. These figures are counts, and the at-risk denominators should be kept in view when reading them.
The registry also lists “Procedural complication in AF ablation group” at 8.3% and “Adverse events during follow up” at 4.2% among the top serious-event terms. The record does not provide enough detail to determine the full event-level breakdown or the relationship of each term to individual participants. These listed terms should not be treated as a complete account of all safety outcomes.
As a general statistical point, adverse-event counts describe what was recorded in the groups; they do not alone establish a causal treatment effect. Interpretation depends on definitions, observation periods, event severity, and completeness of reporting. The registry does not report detailed event definitions or additional safety-analysis methods. The at-risk counts also differ from the sample sizes used for the primary endpoint, and the record does not explain the difference.
12. What the Result Does, and Does Not, Mean
The posted primary outcome figures describe ejection fraction at 6 months in the two randomized groups. The catheter-ablation group mean is 39.9, with a 95% confidence interval from 35.2 to 44.7, based on 23 participants. The medical-treatment-alone group mean is 31.0, with a 95% confidence interval from 25.5 to 36.6, based on 25 participants. The numerical group means differ, but the registry does not report the between-group estimate or its uncertainty.
That distinction matters: group-specific estimates are not the same as a direct estimate of the difference between assigned strategies. Without the contrast and its confidence interval or test result, the precision of the primary comparison cannot be evaluated from the posted results. The figures therefore do not establish whether the observed numerical separation is compatible with a range of treatment effects that would be important, or whether a prespecified statistical criterion was met.
The trial was designed to compare catheter ablation with medical treatment for persistent atrial fibrillation in people with heart failure. Randomization is a design feature intended to support a fair comparison, but it does not fill in unreported outcome analyses. The registry's description of the investigators' hypothesis is not itself evidence that the hypothesis was confirmed. Nor should the lack of a posted test be interpreted as evidence that the groups were identical.
Six secondary outcomes are listed, but numerical results for them are not reported in the posted results. The serious adverse-event counts and other safety figures provide a limited account of recorded events, but they do not provide a complete safety profile or a formal comparison of risk.
In short, the posted data offer descriptive arm-level primary outcome summaries and selected adverse-event counts. They do not provide the inferential result for the primary between-group question, a documented multiplicity strategy, or enough information to assess missing-data handling and analysis populations. Those limits should accompany any interpretation of what the trial's registry results do and do not establish.
13. Why This Trial Matters Statistically
This trial illustrates an important distinction in clinical-trial reporting: a study may name a between-group difference as its primary outcome while the posted numerical results contain only separate summaries for each arm. Means and confidence intervals for each group are useful descriptions, but they do not replace the estimated contrast and its uncertainty. That distinction is central when interpreting a randomized comparison.
The record also demonstrates why denominators matter. Enrollment is 50, while the primary endpoint summaries are based on 23 and 25 participants, and adverse-event risk counts are 24 and 26. The available record does not explain these differences. Without participant flow and analysis-population details, readers cannot determine why the denominators vary or how missing outcome data may affect the reported summaries.
The distinction between descriptive and inferential evidence is also consequential. A numerical separation between arm means can attract attention, but a treatment-effect estimate and its uncertainty are needed to evaluate the primary comparison statistically. The registry does not report that contrast, a p-value, or the analysis method. The record therefore teaches a practical lesson: the outcome label and the arm-level numbers alone are not a complete statistical result.
Finally, the trial lists multiple secondary outcomes, yet the registry does not report their numerical findings or a multiplicity plan. This makes clear why a trial's outcome list should be read alongside its analysis plan and complete results. The registry record is useful for identifying the design and posted summaries, while also revealing where important inferential and reporting details are absent.
14. 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 posted primary results are limited to group-specific means and 95% confidence intervals. Although the outcome is described as a difference between groups, the registry does not report a numerical between-group contrast, a confidence interval for that contrast, or a p-value. The specific statistical test or model is also not reported, so the primary inferential result cannot be reconstructed from the registry record.
The primary endpoint denominators are 23 and 25, compared with total enrollment of 50. The registry does not report participant flow, reasons for missing measurements, or methods for handling missing data. It also does not identify the analysis population. These gaps prevent assessment of whether endpoint availability or analysis choices could have affected the reported group summaries.
Further trial details relevant to interpretation are not reported in the registry record, including participant baseline characteristics, allocation concealment, treatment adherence, protocol deviations, and detailed eligibility criteria. The record identifies the trial as randomized and unmasked, but does not provide enough information to assess how randomization was implemented or who knew the assigned treatment.
The six secondary outcomes are named, but their numerical results are not present in the posted results. The registry does not report a plan for handling multiple outcomes or a detailed statistical analysis plan. Safety reporting is also limited: counts and selected serious-event terms are listed, but full event definitions, event-level detail, and the method used for safety comparisons are not reported.
These limitations concern what can be concluded from the registry record; they do not establish that the missing analyses or documentation were absent from other trial materials. They do mean that the posted record alone does not support a complete evaluation of the primary contrast, secondary outcomes, or missing-data effects.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Catheter Ablation Versus Medical Treatment of AF in Heart Failure — NCT01411371.
- Registry record last updated 2026-09-21; status last verified 2026-09.
- Results first posted 2026-09-21.
- 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.
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18. Record Summary
The registry describes a completed, randomized, parallel-group, unmasked trial of catheter ablation versus medical treatment alone for persistent atrial fibrillation in people with heart failure. Enrollment was 50, and the primary endpoint was the difference in echocardiographic ejection fraction between groups at 6 months.
The posted endpoint summaries report a mean of 39.9 for catheter ablation, with a 95% confidence interval from 35.2 to 44.7 and 23 participants, and a mean of 31.0 for medical treatment alone, with a 95% confidence interval from 25.5 to 36.6 and 25 participants. No between-group estimate or test is reported. Six secondary outcomes are listed, without numerical results in the posted findings.
The safety record reports serious adverse events affecting 3 of 24 at risk in the catheter-ablation group and 1 of 26 at risk in the medical-treatment group; other adverse events and deaths are recorded as 0 in both groups. Details of the analysis plan, missing data, and analysis populations are not reported in the registry record.