A Multi-centre Study Comparing the Effects of AZD2927 and Placebo on the Electrical Activity in the Heart in Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Multi-centre Study Comparing the Effects of AZD2927 and Placebo on the Electrical Activity in the Heart in Patients (NCT01396226), a randomized phase 2 study. The primary outcome is Left Atrial Effective Refractory Period.

2. Clinical Question

The primary outcome is a continuous electrophysiological measurement, recorded in milliseconds. The registry describes the outcome as the change in left atrial effective refractory period from before the infusion to the first and second assessments during infusion. It does not report numerical values for those changes or a between-group estimate.

The question is therefore about the measured electrophysiological response over the specified assessment period, not about a clinical event or a long-term outcome. The registry also lists secondary electrophysiological measures, including ventricular effective refractory period, paced QT interval, atrio-ventricular effective refractory period, and several conduction intervals. Their presence indicates that the study assessed more than one cardiac electrical measurement; it does not establish what any measurement showed.

The record does not report a single primary-outcome comparison that combines the two during-infusion assessments. It also does not provide the numerical results needed to judge the size or precision of a change. The clinical question can be described from the design and endpoint definition, but the answer cannot be determined from the registry results recorded.

3. Trial Design

This was a Phase II, randomized, double-blind, parallel-group, placebo-controlled study sponsored by AstraZeneca. It was conducted in patients with arrhythmia who were undergoing an invasive electrophysiological procedure. The registry records an enrollment of 20 participants.

Participants were assigned to receive a single dose of AZD2927 or a single dose of placebo, each administered as an intravenous infusion. A parallel-group design compares separate groups assigned to different interventions. Random allocation is intended to reduce systematic differences between groups at the point of assignment. Double masking means that the registry classifies the study as masked at two levels, but the record does not identify which specific people were masked or describe the masking procedures.

The primary outcome was left atrial effective refractory period, measured in milliseconds. The stated timeframe was baseline to the last assessment during infusion, and the outcome description refers to changes from before infusion to the first and second assessments during infusion. The record identifies the primary-outcome population as the FAS but does not explain the membership or analysis rules for that population.

The registry lists eight secondary outcomes, including measures of ventricular and atrio-ventricular refractoriness, paced QT interval, and conduction intervals. It reports 13 outcome measures overall. It does not report an analysis for the primary endpoint or other outcomes in the results record. The study is marked completed, but its status does not substitute for outcome estimates or a description of the statistical methods used.

The record does not report the planned allocation ratio, the randomization method, the intended sample-size justification, or whether any interim analyses were planned. Those design details should not be inferred from the overall enrollment or the participant counts listed for adverse events.

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: Full A analysis Set (FAS)

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 Left Atrial Effective Refractory Period, measured over Baseline to last assessment during IP infusion.

Left atrial effective refractory period is an electrophysiological measure of the time interval during which atrial tissue is not ready to respond to another electrical impulse. In this study it was measured in milliseconds. The registry identifies it as the primary outcome and describes change from before the infusion to the first and second assessments during the infusion.

As a continuous measure, the endpoint can describe the magnitude and direction of change rather than only whether a participant crossed a predefined threshold. A mean summarizes the average measured value or change in a group; a standard deviation describes how spread out individual measurements are around that mean. These are general statistical interpretations of the summary measures identified in the record, not reported trial findings.

Using an electrophysiological endpoint is relevant to a study focused on cardiac electrical activity during an invasive procedure. Such a measure captures a physiological response over the stated assessment period. It is not, by itself, a measure of symptoms, longer-term clinical events, or how participants feel or function.

The registry does not provide the endpoint values, changes, standard deviations, or a between-group estimate. It also does not provide one numerical comparison that resolves the first and second assessments into a single result. Consequently, the endpoint definition explains what was measured, but the posted record does not establish the observed size, direction, or precision of the response.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry classifies the primary outcome as a continuous measure summarized by a mean and standard deviation. These are descriptive statistics: the mean represents a group average, while the standard deviation describes the spread of participant measurements around that average. Neither statistic alone expresses the uncertainty in a comparison between groups. A confidence interval is commonly used for that purpose, but no confidence interval for the primary outcome is reported in the registry record.

What does a change score represent?

A change score compares a measurement after an intervention begins with a baseline measurement. In general, it can make the time contrast explicit: the quantity of interest is how the measured value differs from its earlier value. In this study, the registry defines change from before the infusion to the first and second assessments during infusion. It does not report the numerical change at either assessment, how baseline values were summarized, or how the two assessments were incorporated into an analysis.

When outcomes are measured at multiple times, an analysis can treat each time point separately or model the pattern across times. Those approaches answer different questions and can rely on different assumptions. The registry record does not state which approach was used. The fact that the primary outcome was not reduced to one comparison means that a single primary estimate cannot be described from the recorded results.

Why does randomization matter?

In general, random assignment aims to make groups comparable, on average, with respect to factors measured before treatment and factors that are not measured. It supports a fair comparison when the allocation process is implemented as planned and the analysis preserves the intended comparison. Randomization does not guarantee that groups will be identical, particularly in a small study. The registry identifies the study as randomized but does not report the sequence-generation method, allocation concealment procedures, or the final group sizes for the primary analysis.

What does double masking contribute?

Masking is intended to limit the influence of knowledge about assigned treatment on conduct, assessment, and reporting. The record describes the trial as double-blind, but does not specify who was masked, how masking was maintained, or whether it was assessed. It is therefore appropriate to describe the stated design, but not to assume details about its implementation.

How should statistical significance and precision be understood?

In general, a p-value evaluates how compatible observed data are with a specified null model, given the model assumptions. It is not the probability that a treatment effect is true, and it does not describe the size or clinical importance of an effect. A confidence interval is useful alongside an estimate because it conveys uncertainty and the range of effects compatible with the data and analysis assumptions. The registry does not report a p-value, confidence interval, or primary-outcome estimate, so these interpretations cannot be applied to a trial result.

What do the planning assumptions mean?

The sample-size planning illustration is described as a planning exercise based on the observed effect, not as the study's own design justification. Its stated assumptions are a two-sided significance level of 0.05, equal allocation between groups, a normal approximation, and an effect to detect set to a stated fraction of the observed effect. Such illustrations estimate participants per arm for 80% or 90% power under the selected assumptions. They are not observed power and do not show the probability that this completed study detected an effect. The registry record does not report the trial's sample-size justification or its own planned power calculation. No numerical planning results are stated in the record.

In general, planning estimates depend on assumptions about the effect to detect, variability, allocation, and the statistical test. Changing those assumptions can change the resulting sample-size estimate. A planning illustration should therefore be read as conditional on its assumptions, not as a description of the number of participants actually analyzed or as proof of a result.

Why can over-dispersion matter?

General statistical context: over-dispersion occurs when observed variability is greater than a model assumes. If a model understates variability, its standard errors may be too small and its confidence intervals too narrow. This can make evidence appear more precise than it is. The primary endpoint is continuous, and the registry does not report a model or a dispersion assessment; over-dispersion is therefore a general concept rather than a documented feature of this analysis.

The record does not identify the trial's statistical test, model, adjustment variables, missing-data procedure, or approach to multiple outcomes. The general concepts above explain how such choices can affect interpretation, but they should not be mistaken for methods reported as having been used in this study.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 13 outcome measures, including the primary left atrial effective refractory period and secondary electrophysiological outcomes. It does not report a multiplicity strategy, such as a testing hierarchy or adjustment for multiple comparisons. When several outcomes or time points are tested, the chance of at least one apparently unusual result can increase if each is assessed independently. This is a general statistical concern; the record does not establish which tests were performed or how any multiplicity was handled.

The primary outcome description includes two during-infusion assessments, and the record indicates that it was not reduced to one comparison. No numerical result for either assessment is reported. The record also does not specify whether the assessments were intended as separate primary tests, how they were ordered, or what rule would determine an overall conclusion.

Although the primary population is named as the FAS, the registry does not define that population or state how participants were included in each analysis. It does not report the number contributing primary-outcome data, missing observations at each time point, reasons for missingness, or the method used to handle missing data. In general, missing-data methods rely on assumptions about why measurements are absent; different assumptions can produce different estimates. No specific assumption or method can be attributed to this trial from the record.

The statistical analysis plan, interim analyses, and any prespecified procedures for handling multiple outcomes or missing data are not reported in the registry record. These omissions limit assessment of how the planned analyses relate to the listed outcomes and how robust any estimates might be. They do not establish that no such procedures existed; they mean that the record does not describe them.

11. 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 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry lists serious adverse events for two groups. In the AZD2927 group, 0 serious adverse events were recorded among 12 participants at risk. In the placebo group, 0 were recorded among 6 participants at risk. These are the recorded group counts; the registry does not provide serious-event terms, and it does not report deaths.

The record also lists other adverse events: 2 among 12 participants at risk in the AZD2927 group and 1 among 6 participants at risk in the placebo group. These other events are distinct from the serious adverse event counts. No event descriptions are included in the registry record recorded, so their nature, severity, timing, and relationship to treatment cannot be characterized.

Adverse-event counts are descriptive and should be read with their listed numbers at risk. They are not a substitute for a statistical comparison, and the registry record does not report an inferential analysis of safety outcomes. The enrollment of 20 should not be assumed to equal the number contributing to each safety or efficacy outcome; the adverse-event risk groups are reported separately.

Zero recorded serious events in these groups means that none are listed in the registry entries, not that the study establishes the absence of risk. With a small study and no further event details or follow-up description in the record, the safety figures have limited scope for characterizing uncommon events or comparative safety.

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

The record describes a randomized, double-blind, placebo-controlled comparison of a single intravenous infusion of AZD2927 with placebo during an invasive electrophysiological procedure. It identifies change in left atrial effective refractory period as the primary outcome and specifies baseline and two during-infusion assessments. It also lists secondary electrophysiological measures and adverse-event counts.

What the record does not provide is the primary endpoint's numerical result. There is no reported group mean change, standard deviation, between-group estimate, confidence interval, or p-value. Therefore, the size, direction, and precision of the primary comparison cannot be judged. The record also does not give numerical analyses for the listed secondary outcomes.

In general, a measured difference in an electrophysiological endpoint would describe a physiological contrast over the assessment period. It would not automatically establish a difference in symptoms, long-term clinical events, or other outcomes not measured by that endpoint. Likewise, a statistically precise estimate and a clinically meaningful effect are distinct considerations; this record does not provide the estimates needed to assess either.

The adverse-event entries describe counts in the recorded at-risk groups. They do not establish that one group is safer, nor do they rule out events not observed in this study. The record's reported enrollment and safety counts also do not explain how many participants contributed to each primary or secondary analysis.

Accordingly, the appropriate interpretation is limited to the study's question, design, outcome definitions, and recorded safety counts. A conclusion about the observed electrophysiological effect would require numerical outcome results and enough information about the analysis to interpret their uncertainty. Those results and details are not reported in the registry record.

13. Why This Trial Matters Statistically

This trial is statistically notable as a small randomized comparison centered on a continuous electrophysiological outcome measured at more than one time during infusion. Its design raises familiar questions about how repeated measurements are summarized, how the comparison between groups is defined, and how precision is communicated. The registry record does not report the numerical outcome analysis needed to answer those questions for this study.

The combination of an overall enrollment of 20 and multiple listed outcome measures makes transparent reporting especially useful for interpretation. Readers need to know which participants contributed to each endpoint, what comparison was prespecified, and how uncertainty was quantified. The record identifies the primary population as the FAS but does not describe its membership or provide endpoint-specific analysis counts.

General statistical principle: a study's design and its result are separate pieces of evidence. Randomization and masking describe methods intended to support a fair comparison, while estimates and their uncertainty show what the measured data indicate. Neither the design labels nor a planning calculation can replace the missing outcome estimate.

The sample-size illustration is described as conditional on assumptions and based on an observed effect. Planning calculations can help express the precision or sample size associated with chosen assumptions, but they do not constitute observed power and do not establish what the trial found. The record also does not report the original sample-size justification or the statistical analysis plan.

The study therefore illustrates why registry entries are most informative when outcome values, analysis populations, methods, and uncertainty measures are all reported. Here, the design and endpoint are identifiable, but the registry result does not permit a statistical conclusion about the primary treatment contrast.

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 main limitation for statistical interpretation is that the registry does not report numerical primary-outcome results. Means, standard deviations, changes at the individual assessments, a between-group estimate, confidence intervals, and p-values are absent. Without them, neither effect size nor precision can be evaluated.

The primary outcome includes the first and second assessments during infusion, but no single comparison is reported and the record does not explain how the repeated assessments were analyzed. This leaves the target comparison unclear beyond the endpoint description. The record also does not report the statistical model, adjustment variables, or analysis plan.

Although the primary population is identified as the FAS, its membership and the number of participants contributing to each measurement are not reported. Missing data, reasons for missingness, and methods for handling unavailable measurements are also not described. The registry lists 20 enrolled participants but does not provide endpoint-specific sample sizes.

The study lists 13 outcome measures, but the record does not describe a multiplicity strategy or provide numerical secondary-outcome analyses. This limits assessment of how the outcomes were prioritized and how uncertainty across multiple measures was handled. The record does not report an original sample-size justification, interim-analysis plans, or details of randomization and masking procedures.

Finally, the safety entries provide counts but not event terms or further clinical descriptions. The listed at-risk groups are small, and the record does not report deaths. These limitations concern what can be learned from the registry record; they do not establish that unreported procedures or data were absent from the study itself.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Multi-centre Study Comparing the Effects of AZD2927 and Placebo on the Electrical Activity in the Heart in Patients — NCT01396226.
• Registry record last updated 2012-11-27; status last verified 2012-11.
• Results first posted 2012-10-23.
• 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.

18. Record Summary

NCT01396226 is recorded as a completed, randomized, double-blind, parallel-group Phase II study sponsored by AstraZeneca. It compared a single intravenous infusion of AZD2927 with a single intravenous infusion of placebo in patients with arrhythmia undergoing an invasive electrophysiological procedure. Enrollment was 20.

The primary outcome was change in left atrial effective refractory period, measured in milliseconds, from before infusion to the first and second assessments during infusion. The record identifies the analysis population as the FAS and lists 13 outcome measures overall, including secondary electrophysiological measures.

The registry does not report numerical primary or secondary efficacy results, an analysis plan, or details of missing-data and multiplicity procedures. It lists 0 serious adverse events among 12 participants at risk in the AZD2927 group and 0 among 6 at risk in the placebo group; other adverse-event counts were 2 and 1, respectively. Deaths are not reported.