A Study of the Effectiveness of Anti-Arrhythmic Medications After Atrial Fibrillation Ablation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of the Effectiveness of Anti-Arrhythmic Medications After Atrial Fibrillation Ablation (NCT00408200), a randomized na study. The primary outcome is Composite Endpoint: Atrial Arrhythmias Lasting >24 Hrs or Requiring Antiarrhythmic Drug Therapy; Need for Cardioversion/Repeat Ablation During the Study Period; Adverse Outcome/Intolerance of Antiarrhythmic Agent Requiring Cessation or Change of Drug.

2. Clinical Question

The clinical question is about the early period after the procedure, not about medication use in every setting or over longer follow-up. The primary endpoint combines several kinds of events: arrhythmias meeting the stated duration criterion or requiring anti-arrhythmic treatment, procedural escalation, and adverse outcomes or intolerance that led to changing or stopping an anti-arrhythmic agent. Because it is a composite, the overall comparison does not by itself show which component contributed most to the observed group counts.

The record also lists freedom from atrial arrhythmia as a secondary outcome. Its title refers to 6 months after the procedure, while the recorded timeframe is 6 weeks. That discrepancy is part of the record and cannot be resolved from the available information. The clinical question should therefore be read with the primary timeframe and the secondary timeframe distinction in mind.

3. Trial Design

The registry record describes a randomized, open-label, parallel-group trial of anti-arrhythmic medication after radiofrequency catheter ablation for paroxysmal atrial fibrillation. One group received membrane-active anti-arrhythmic medication after ablation; the other did not. The medication arm lists propafenone, flecainide, sotalol, and dofetilide. The record does not explain how a specific drug was selected, whether treatment could change during follow-up, or how adherence was assessed.

Enrollment is recorded as 110. The arm-level outcome counts list 57 participants in the no-medication group and 53 in the medication group. The primary outcome timeframe is 6 weeks. The trial status is completed. The registry record gives a start date of 2006-11 and a primary completion date of 2008-04.

Open-label means participants and study personnel were not masked to assigned treatment, according to the recorded masking information. The record does not report whether outcome assessors were masked, how randomization was generated, or how allocation was concealed. It also does not report the protocol’s handling of withdrawals, missed visits, crossovers, or deviations from assigned treatment.

The primary endpoint is a composite rather than a single event. Its components include atrial arrhythmias lasting >24 Hrs or requiring anti-arrhythmic drug therapy, need for cardioversion or repeat ablation during the study period, and an adverse outcome or intolerance requiring cessation or change of anti-arrhythmic agent. The primary endpoint is recorded as a participant count over 6 weeks.

The registry’s primary-outcome description states an assumed control incidence of 40%, a 50% reduction in the drug group, a planned sample of 160 patients, and 80% power, followed by an incomplete reference to a two-tailed error. Other details of that original design rationale, including the complete significance-level specification, are not reported in the registry record. The enrolled number differs from the stated planned sample; the record does not explain why.

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: Following consent/enrollment, subject and investigator were blinded to treatment arm until after the ablation procedure. Subjects were later withdrawn if the procedure was not completed, or if a disqualifying medication history or other protocol exclusion was identified.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Assuming an incidence of the composite primary end point of 40% in the control group and a 50% reduction in the composite primary end point in the drug treatment group, we calculated that 160 patients would have to be included in the study in order to obtain a power of 80% and with a 2-tailed error of 0.05.

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 Composite Endpoint: Atrial Arrhythmias Lasting >24 Hrs or Requiring Antiarrhythmic Drug Therapy; Need for Cardioversion/Repeat Ablation During the Study Period; Adverse Outcome/Intolerance of Antiarrhythmic Agent Requiring Cessation or Change of Drug, measured over 6 weeks.

The primary endpoint is a composite measure of participants experiencing one or more specified events during 6 weeks. It includes atrial arrhythmias lasting >24 Hrs or requiring anti-arrhythmic drug therapy; a need for cardioversion or repeat ablation during the study period; and an adverse outcome or intolerance of anti-arrhythmic medication that requires cessation or a drug change.

A composite can capture several clinically relevant ways a participant’s post-procedure course may lead to further treatment or a change in management. It can also give a broader summary than any one component alone. The trade-off is that the components may differ in seriousness, frequency, and clinical meaning. An overall composite count does not reveal whether the observed group contrast was driven mainly by arrhythmia, procedural escalation, or medication intolerance. Component-specific results are not reported in the registry record.

The posted primary counts are 24 participants in the no-medication group and 10 in the medication group. The denominators are 57 and 53, respectively. These are participant counts, not a measure of event severity or time until an event. The record does not describe whether participants with more than one component event were counted once in the composite or how competing events were handled.

Reading the result therefore requires keeping the endpoint definition in view: the comparison concerns the combined occurrence of the listed events over the stated short follow-up, rather than a single isolated arrhythmia outcome or a long-term measure.

7. Results Posted in the Registry

• AAD:YES: 18.9% (10/53) versus 42.1% (24/57) on control; risk difference -23.2 percentage points (95% CI -39.8 to -6.6), risk ratio 0.45 (0.24–0.85); unadjusted two-proportion z-test p = 0.008.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Freedom From Atrial Arrhythmia at 6 Months Post Procedure.

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • AAD:YES: 66.0% (35/53) versus 68.4% (39/57) on control; risk difference -2.4 percentage points (95% CI -19.9 to 15.2), risk ratio 0.97 (0.74–1.25); unadjusted two-proportion z-test p = 0.790.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between AAD:YES and the control. The interval gives the range of effects that remain compatible with the data.

The registry lists one secondary outcome, freedom from atrial arrhythmia. Its recorded counts and unadjusted comparison do not show the same clear directional separation as the primary composite comparison: the secondary estimate is close to zero and its confidence interval spans effects in both directions. The registry’s reported Fisher Exact result is p <0.05, while the unadjusted recalculated comparison has p = 0.79. The record does not explain this difference or provide enough detail to reconcile the analyses.

The secondary outcome should be interpreted alongside, but not substituted for, the primary result. The primary composite includes several types of event or intervention over 6 weeks, whereas the secondary endpoint is described as freedom from atrial arrhythmia. These outcomes are related to post-ablation rhythm events but are not interchangeable: one is a composite that includes additional criteria, and the other is a freedom-from-arrhythmia measure.

There is also a timing inconsistency. The secondary outcome title says 6 months post procedure, but its recorded timeframe is 6 weeks. Without clarification, it is uncertain which follow-up period the posted result represents. The registry record does not describe the relationship between the secondary endpoint’s time window and the primary endpoint’s follow-up period.

Secondary findings often carry less weight than a prespecified primary comparison because many outcomes may be examined, increasing the chance of at least one apparently unusual result. The record does not report a multiplicity adjustment, a hierarchy of secondary hypotheses, or a detailed analysis plan. Accordingly, the secondary finding should be viewed as limited supporting information rather than conclusive evidence. It does not erase the primary comparison, and the primary comparison does not resolve the secondary outcome’s analysis and timing uncertainties.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Freedom From Atrial Arrhythmia at 6 Months Post Procedure.

9. Statistical Interpretation

10. Statistical Methods Explained

What does the risk difference describe?

A risk difference compares the observed proportions with an event in two groups by subtracting one group’s proportion from the other’s. Here the comparison is medication minus no medication. A negative value indicates a lower observed proportion in the medication group; a positive value would indicate a higher observed proportion in that group. The primary risk difference is -0.232. It is a direct, absolute-scale summary of the group contrast, rather than a relative measure.

This is a general explanation of the statistic. The posted calculation is unadjusted and uses the arm-level event counts and participant counts. It does not account for other characteristics or for any modeling beyond that comparison. The registry record does not describe a separate adjusted primary analysis.

How should the confidence interval be understood?

A confidence interval expresses statistical uncertainty around an estimated effect under the calculation’s assumptions. A narrower interval means greater precision; a wider interval means less precision. Its limits describe effect values that are compatible with the data and method at the stated confidence level. It is not a range containing every participant’s outcome, and it is not a probability statement about where the fixed true effect lies.

For the primary comparison, the interval for the risk difference is -0.398 to -0.067. For the secondary comparison, it is -0.199 to 0.152. The different positions and widths indicate that the estimates have different levels of statistical uncertainty and that the secondary interval spans effects in both directions. These intervals are recalculated from posted summary counts; they are not described as adjusted model-based intervals in the registry record.

What does an unadjusted p-value convey?

A p-value describes how unusual data at least as incompatible with a specified null hypothesis would be if that null hypothesis and the statistical assumptions were true. It is not the probability that the null hypothesis is true, nor does it measure the size or clinical importance of an effect. The primary unadjusted p-value is 0.008. The secondary unadjusted p-value is 0.79.

The registry also records a Fisher Exact analysis for the secondary outcome, with p <0.05. That reported analysis and the unadjusted recalculated comparison are not identical entries in the record. The registry record does not give a confidence interval or a more detailed analysis specification for the reported Fisher Exact result. Differences in analysis method, coding, or endpoint interpretation cannot be resolved from the record alone.

Why does the composite endpoint need careful interpretation?

A composite combines multiple outcomes into a single endpoint. This can increase the number of participants contributing events and reflect several ways that a post-procedure course may lead to intervention or treatment change. But the combined estimate can conceal differences among components. For example, a composite result does not indicate whether one component was common while another was rare, or whether the components had comparable clinical importance. Component-specific counts and analyses are not reported in the registry record.

The endpoint includes both arrhythmia-related criteria and consequences such as cardioversion, repeat ablation, or medication intolerance requiring a change or cessation. The trial’s result therefore cannot be interpreted as an isolated estimate for any one of those outcomes. The registry does not provide component-level results or enough detail to assess how overlapping components were counted.

What can randomization and open-label conduct tell us?

In general, random assignment is intended to create groups that are comparable on average, including with respect to factors that were not measured. This helps support a causal comparison when allocation, follow-up, and analysis are handled appropriately. The registry record states that allocation was randomized, but does not report the sequence-generation method or allocation concealment. Those implementation details are not reported in the registry record.

Open-label conduct means treatment assignment was not masked. Knowledge of assignment can affect participant behavior, clinical decisions, or outcome assessment, depending on the outcome and trial procedures. The record does not state whether outcome assessors were masked or describe safeguards against assessment bias. These are uncertainties, not evidence that bias occurred.

What does the record say about the analysis plan?

The record’s primary-outcome description includes a design rationale based on a 40% control incidence, a 50% reduction in the drug group, 160 planned patients, and 80% power. The description ends with an incomplete reference to a two-tailed error. The complete significance-level specification, analysis plan, interim analyses, and sample-size justification beyond that text are not reported in the registry record. The posted planning illustrations use separate assumptions and should not be mistaken for the trial’s original design calculations.

For the primary endpoint, the record does not describe an inferential analysis method, adjustment strategy, or analysis population. The recalculated comparison is therefore best understood as a simple unadjusted analysis of the posted summary counts. It should not be attributed to a specific sponsor model. The record lists a Fisher Exact analysis for the secondary outcome, but does not report a corresponding detailed primary analysis.

11. Confidence Intervals and Precision

The primary risk-difference estimate is -0.232, with a 95% confidence interval from -0.398 to -0.067. The interval does not include zero, the value corresponding to no difference on the risk-difference scale. The estimate’s negative direction reflects a lower observed event proportion in the medication group in the unadjusted comparison. The interval still covers a range of possible effect magnitudes, so the point estimate should not be treated as exact.

The secondary risk-difference estimate is -0.024, with a 95% confidence interval from -0.199 to 0.152. This interval includes zero and values on either side. It is therefore compatible with a range of comparisons, including a lower or higher observed proportion in the medication group. The unadjusted p-value is 0.79. The registry’s separate Fisher Exact result is reported as p <0.05, without an accompanying confidence interval or further explanation of the analysis.

In general, a confidence interval reflects both the observed data and the method used to calculate it. A wider interval signals less precision about the effect’s magnitude. Precision is not the same as validity: an interval can be calculated precisely while important uncertainties remain about endpoint measurement, missing data, or analysis choices. The registry record does not report missing-data handling or an analysis population, which limits how fully the estimates can be assessed.

The secondary outcome’s title and recorded timeframe also disagree: the title refers to 6 months, while the timeframe is 6 weeks. That ambiguity affects interpretation of what period the estimate represents and cannot be settled from the registry record. In addition, the composite primary endpoint does not show the precision of each component separately; component-specific estimates are not reported.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size display gives planning illustrations in participants per arm, not total event counts. Its 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 set as the stated fraction of the observed effect. These are planning assumptions for the illustrations, not a full description of the original trial design.

The 80% power column gives the participants per arm estimated to provide an 80% chance of detecting the specified effect under those assumptions, if that effect is the true one. The 90% power column gives the corresponding estimate for a 90% chance. Power is a property of a proposed design under assumed conditions; it is not a measure of the probability that the study result is correct.

The rows scale the effect to 100%, 75%, and 50% of the observed effect. Smaller effects require more participants per arm to detect at the same target power, because a smaller group contrast is harder to distinguish from random variation. For the primary comparison, the illustrations give 61 and 81 participants per arm for 80% and 90% power when planning for 100% of the observed effect; for 75%, they give 114 and 152; and for 50%, they give 268 and 358. These are planning illustrations based on the recalculated observed effect, not the trial’s original design calculations.

The sample-size figures are not observed power. They do not show the probability that the completed trial detected an effect, and they do not establish whether the original study was adequately planned. The record’s own design description states an assumed control incidence of 40%, a 50% reduction, 160 planned patients, and 80% power; the complete two-tailed error specification is not reported in the registry record.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.421; treatment proportion p₁ = 0.189; average p̄ = 0.305.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6510 = 1.2760.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6300 = 0.5302.
4. n = (1.2760 + 0.5302)² / (-0.2324)² = 60.4, rounded up to 61 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
p0 <- 0.421052631578947                          # control proportion
p1 <- 0.188679245283019                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(408200)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 61 (80% power), 81 (90% power)
 75% of observed effect: n per arm = 114 (80% power), 152 (90% power)
 50% of observed effect: n per arm = 268 (80% power), 358 (90% power)
power.prop.test: 60.4 
Simulated power at n = 61 per arm: 0.806 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry record does not report whether the trial used a prespecified hierarchy for outcomes, adjusted for multiple comparisons, or treated secondary analyses as exploratory. When several outcomes or analyses are examined, the chance of finding a small p-value by chance can increase. Multiplicity procedures are general methods for controlling that risk, but the record does not establish whether any such procedure was used. The reported Fisher Exact result for the secondary outcome and the unadjusted recalculated comparison differ; the record does not explain whether that reflects a planned analysis, a different specification, or another issue.

Missing-data methods are not reported in the registry record. It does not say whether all randomized participants were included in the outcome analysis, how participants without outcome information were handled, or whether follow-up was complete. The arm-level counts have denominators of 57 and 53, but the record does not describe these as a particular analysis population or explain whether anyone was excluded after randomization.

The registry record also does not report an intention-to-treat, per-protocol, or other named analysis population for the primary outcome. It does not describe treatment crossover, adherence, withdrawals, or protocol deviations. These details help determine how closely an analysis preserves the randomized comparison and what population the result represents.

Interim analyses, stopping rules, and adjustments for interim looks are not reported in the registry record. Nor does the record provide a complete primary statistical analysis plan, a detailed method for handling the composite components, or an explanation of the difference between the listed secondary Fisher Exact result and the unadjusted recalculation. These absences limit assessment of whether analyses were prespecified and how robust the findings are to alternative analytic choices; they are not evidence that any particular procedure was or was not used.

15. 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.

The serious adverse event figures report zero serious events among 57 participants at risk in the no-medication group and zero among 53 participants at risk in the medication group. The other adverse-event figures also report zero events in both groups, with the same respective at-risk counts. No serious adverse event terms are listed.

These figures describe what the registry record reports; they do not establish that no adverse events occurred outside the recorded categories or that every possible safety outcome was assessed. The record does not report death counts: those values are missing, not stated as zero. The arm-level safety figures also do not provide event timing, severity details beyond the serious-event category, or information about how events were collected and coded.

Zero recorded events in these groups should therefore be read as an absence of reported events in the posted safety fields, not as proof of no risk. The registry record does not give enough detail to assess the completeness of safety follow-up or to compare specific types of harm.

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

The posted primary counts show fewer participants meeting the composite endpoint in the medication group than in the no-medication group, and the unadjusted recalculated risk difference is negative with a confidence interval that does not include zero. This is a statistical description of the recorded 6-week comparison. It does not by itself establish the effect of any particular drug, because the medication arm lists several possible agents and the record does not describe drug selection or separate drug-specific outcomes.

The result also does not isolate the effect on atrial arrhythmias alone. The composite combines arrhythmia criteria with cardioversion, repeat ablation, and medication intolerance or adverse outcomes that require a change or cessation. Without component-level results, the overall contrast cannot identify which events account for the group difference or how the components compare in importance.

The result should not be generalized automatically to longer follow-up, other ablation procedures, other patient groups, or other medication strategies. The primary outcome is recorded over 6 weeks, and the secondary outcome’s title and timeframe conflict. The record does not supply enough detail about eligibility, baseline characteristics, adherence, missing data, or analysis populations to assess how broadly the findings apply.

A confidence interval and p-value describe statistical uncertainty under a method; they do not determine clinical importance or establish causation on their own. Randomization is recorded, but details of its implementation and outcome assessment are not. The record also does not provide a complete primary analysis plan. These uncertainties should be considered alongside the observed contrast.

Thus, the appropriate reading is limited: the posted primary summary counts favor a lower observed composite event proportion in the medication group, while the magnitude and interpretation remain subject to uncertainty about the composite, analysis details, and follow-up. This statistical interpretation is not medical advice and does not establish what treatment an individual should receive.

17. Why This Trial Matters Statistically

This trial is statistically informative because it compares a randomized medication strategy with no membrane-active anti-arrhythmic medication after ablation, using a defined early post-procedure composite endpoint. The comparison illustrates how a randomized design can frame a treatment contrast, while the registry record’s limited reporting still constrains interpretation of the estimate.

The result also shows why an absolute measure such as a risk difference is useful. It describes the scale of the observed group contrast directly, while its confidence interval makes uncertainty visible. A p-value alone would not convey the range of effect magnitudes compatible with the posted counts. Neither statistic, however, resolves what drove a composite result or whether the difference is clinically important.

Several statistical issues are especially relevant: the composite combines distinct outcomes; the secondary endpoint has a discrepancy between its title and recorded timeframe; and the registry lists a Fisher Exact result that differs from the unadjusted recalculated comparison. The record does not report a complete analysis plan, missing-data approach, or multiplicity strategy. These features underscore the importance of clear outcome definitions, prespecified analyses, and transparent reporting.

The sample-size illustrations also demonstrate how planning depends on the effect one seeks to detect. Smaller target effects require larger participant counts per arm under the stated assumptions. Those illustrations are not observed power and do not substitute for the trial’s original design rationale. The record does include some original planning assumptions, but its description of the two-tailed error is incomplete and does not explain the difference between planned and enrolled numbers.

Overall, the study is a useful case for separating an observed association, statistical precision, endpoint composition, and limitations of registry reporting rather than treating a single p-value as a complete account.

18. 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 registry record leaves several trial-specific questions unresolved. It does not report baseline characteristics, eligibility details beyond the study’s focus on paroxysmal atrial fibrillation, or the distribution of participants across relevant clinical subgroups. This limits assessment of how similar the randomized groups were in the posted outcome sample and how applicable the results may be beyond the enrolled population.

The medication arm includes propafenone, flecainide, sotalol, and dofetilide, but the record does not state how the choice among these agents was made, how long medication was used, or whether treatment could be changed. There are no drug-specific outcomes, adherence summaries, or crossover details. The estimate therefore applies to the recorded medication strategy as a group, not to a separately assessed effect for each listed agent.

The primary endpoint combines several event types, but component counts are not reported. The record does not explain how multiple component events for one participant were handled. Open-label status is recorded, while masking of outcome assessors and methods to reduce ascertainment bias are not reported. Missing-data handling, withdrawals, and the analysis population are also not described.

The secondary outcome title refers to 6 months, whereas its recorded timeframe is 6 weeks. The registry also lists a Fisher Exact analysis with p <0.05 for that outcome, while the unadjusted recalculation gives p = 0.79. The record does not reconcile either the timing or the difference in results. Finally, the primary-outcome design description gives some planning assumptions but ends with an incomplete reference to a two-tailed error and does not explain why enrollment was 110 when the stated planned sample was 160.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: A Study of the Effectiveness of Anti-Arrhythmic Medications After Atrial Fibrillation Ablation — NCT00408200.
• Registry record last updated 2013-03-07; status last verified 2012-06.
• Results first posted 2013-03-07.
• 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.

22. Record Summary

The registry record describes a completed, randomized, open-label, parallel-group trial of anti-arrhythmic medication after radiofrequency catheter ablation for paroxysmal atrial fibrillation. Enrollment is 110. The primary endpoint is a composite of specified arrhythmia events, cardioversion or repeat ablation, and medication intolerance or adverse outcomes requiring a drug change or cessation, assessed over 6 weeks.

The primary counts are 24 of 57 participants in the no-medication group and 10 of 53 in the medication group. The unadjusted recalculated risk difference is -0.232, with a 95% confidence interval from -0.398 to -0.067 and p = 0.008. These figures describe the posted summary comparison, not a complete account of the trial’s analysis plan.

The registry lists one secondary outcome, but its title and timeframe are inconsistent, and its reported Fisher Exact result differs from the unadjusted recalculation. Missing-data methods, analysis populations, multiplicity procedures, and several trial conduct details are not reported in the registry record. The results should be interpreted with those reporting limitations in mind.