Cryoablation of AF: Improving the Use of the Achieve Catheter: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Cryoablation of AF: Improving the Use of the Achieve Catheter (NCT01843465), a registered phase not stated study. The primary outcome is Real-time Documentation of Pulmonary Vein Disconnection.

2. Clinical Question

The study asks whether maneuvers using the Achieve catheter can help document pulmonary vein disconnection in real time during cryoballoon ablation for atrial fibrillation. The registry describes the assessment as taking place during the ablation procedure and focuses on whether disconnection can be documented, and on the catheter maneuver needed to do so.

The registry summary motivates the study by noting that documentation with the Achieve catheter may be possible in only about to 50% of pulmonary veins, according to data from high-volume centers. That wording is incomplete, so it should not be treated as a precise benchmark. The registry does not report the study's observed percentage, the number of veins documented in real time, or the distribution across maneuver categories. The question is therefore clear at the level of the intended measurement, but the posted record does not establish what the study found.

3. Trial Design

The registry identifies this as a completed clinical study sponsored by Clinique Pasteur. It records a start date of 2013-04 and a primary completion date of 2013-07. Enrollment is listed as 34, and atrial fibrillation is the stated condition. The registered title concerns improving assessment of pulmonary vein disconnection with the Achieve catheter during atrial fibrillation cryoablation.

The study is described around one intervention, maneuvers for documenting disconnection, and one named group, cryoablation of atrial fibrillation. The record does not state allocation, and it does not describe a randomized comparison. It therefore should not be read as a trial comparing a maneuver strategy against a control group on a like-for-like basis. The registry does not report whether the maneuver strategies were assigned prospectively, applied sequentially, or selected during procedures.

The listed primary outcome is real-time documentation of pulmonary vein disconnection during the cryoablation procedure. The outcome description says documentation would be coded as yes or no and that affirmative documentation would be expressed as a percentage of total pulmonary veins, together with the maneuver used. The registry states that 128 pulmonary veins were assessed in the study sample. This is an outcome description and sample detail, not a report of the observed endpoint result.

The record lists one outcome measure and zero analyses. It does not report a statistical analysis plan, a sample-size justification for the study, an interim-analysis plan, or details about how the maneuver categories were assigned. These details are not reported in the registry record. The completed status indicates the recorded trial status, but does not by itself supply the missing outcome estimates or establish that all planned analyses were posted.

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: 2 patients were not considered eligible due to previous atrial fibrillation ablation.

Overall Study

Analysis population for the primary outcome, as defined in the registry: According to the different pulmonary vein anatomies in the study sample, 128 pulmonary veins were assessed.

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 Real-time Documentation of Pulmonary Vein Disconnection, measured over atrial fibrillation cryoablation procedure.

The primary endpoint concerns whether pulmonary vein disconnection can be documented in real time during atrial fibrillation cryoablation using the Achieve catheter. The registry's outcome description specifies a yes-or-no classification for the possibility of real-time documentation. It also describes expressing affirmative documentation as a percentage of the total pulmonary veins and recording the maneuver required.

The maneuver categories are standard position (type 1), withdrawal position (type 2), and need of pacing (type 3). A pulmonary vein for which real-time documentation is not possible is classified as type 4. These categories distinguish whether documentation was possible and, when it was, the stated approach used. They are descriptions of the endpoint coding, not results showing how often any category occurred.

In general, a procedural documentation endpoint can be useful when the study question concerns whether a measurement or observation is obtainable during the procedure itself. A yes-or-no classification makes the basic outcome interpretable, while the maneuver categories add information about how the observation was obtained. The endpoint does not, by itself, measure later clinical outcomes or establish the consequences of documenting disconnection.

The registry reports that 128 pulmonary veins were assessed, but it does not report how many were documented in real time, the percentage documented, or the counts in each maneuver category. Those results are not reported in the registry record. The endpoint definition should therefore be separated from the outcome estimate: the former is described, while the latter is unavailable in the posted record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a count-based procedural measure with a planned binary classification and accompanying maneuver categories. Understanding what the record does and does not contain requires separating the endpoint definition, the unit of observation, and the analysis results. The endpoint definition is present; the numerical outcome results and statistical analyses are not.

What does the yes-or-no classification mean?

The registry describes whether real-time documentation of pulmonary vein disconnection was possible as yes or no. It then specifies that affirmative findings would be expressed as a percentage of total pulmonary veins and accompanied by the maneuver used. The categories identify standard position (type 1), withdrawal position (type 2), need of pacing (type 3), and no real-time documentation (type 4). This structure distinguishes a basic occurrence classification from additional procedural detail.

In general, a proportion communicates the share of observations meeting a defined outcome. To interpret one, readers need both the number meeting the definition and the relevant denominator, as well as clarity about which observations are included. The registry says 128 pulmonary veins were assessed, but does not report the numerator or the observed percentage. The endpoint description alone cannot be used to reconstruct either value, and no such calculation is made.

Why does the unit of observation matter?

Enrollment is reported for participants, while the primary outcome is described in terms of pulmonary veins. These are different observational levels. In general, several veins assessed in one participant may share anatomy, physiology, procedural technique, or other characteristics. Such within-participant dependence is called clustering. If observations are correlated, statistical methods that assume every vein is independent may understate uncertainty.

That is a general methodological issue for outcomes where multiple observations may arise from one participant. The registry record does not report whether the analysis used a participant-level summary, a model that accounted for clustering, or another approach. It also does not explain how veins were selected or whether all assessed veins contributed to the proposed percentage. Those analysis details are not reported in the registry record.

What would uncertainty measures add?

In general, a confidence interval describes a range of values compatible with the observed data under a specified statistical method. Its width conveys precision: a narrower interval indicates greater precision under that method, while a wider interval indicates greater uncertainty. The interval is not a guarantee that the true value lies within it, and its interpretation depends on the analysis assumptions being suitable.

No primary outcome estimate or confidence interval is reported in the registry record. Therefore, precision cannot be assessed for the proportion of veins documented in real time or for any maneuver-specific result. A stated count of assessed veins does not substitute for an estimate and its uncertainty.

Why can over-dispersion matter?

In general, over-dispersion occurs when the variation in count data is greater than a statistical model expects. It can arise when observations are more heterogeneous or more dependent than the model assumes. If over-dispersion is ignored, standard errors may be too small and confidence intervals may be too narrow. It can also affect tests of statistical significance.

The primary outcome is described in terms of counts and a percentage, but the record does not report a fitted model, a variance estimate, or an assessment of over-dispersion. There is no basis to say whether this issue arose in the study or how it was handled. The explanation is general and does not imply that the endpoint necessarily required a particular model.

What can planning calculations tell readers?

In general, sample-size calculations explore how much information a future study might need to detect a specified effect under stated assumptions. They depend on choices about the effect to detect, statistical significance level, allocation, model, and other design features. A planning illustration is not evidence that an observed study had a particular power, and it does not demonstrate that a result is true or clinically important.

The stated planning assumptions refer to a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and detection of a stated fraction of an observed effect. The sample-size outputs are planning illustrations, not observed power. The registry record does not report a two-arm randomized comparison or a primary outcome effect estimate. The assumptions should therefore be read as a hypothetical planning framework, not as a description of the actual study design or a post hoc estimate of its power.

What is missing from the analysis record?

The registry lists one outcome measure and zero analyses. It does not report the primary outcome numerator, percentage, confidence interval, model, hypothesis test, or handling of within-participant dependence. It also does not report whether any adjustments were made for anatomy, maneuver selection, or other factors. These details are not reported in the registry record. Without them, neither the statistical approach nor its assumptions can be evaluated from the registry entry.

The distinction between no posted analysis and a result of no effect is essential. An absent estimate does not establish that documentation was frequent, infrequent, improved, unchanged, or impossible. The record describes the intended measurement and some safety counts, but the primary statistical findings remain unavailable.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure, the real-time documentation of pulmonary vein disconnection. It also describes several maneuver categories within that outcome. These categories are part of the endpoint definition; the record does not state whether each was treated as a separate statistical comparison or whether subgroup comparisons were planned.

Multiplicity arises in general when several hypotheses or outcomes are tested, because the chance of at least one apparently notable result can increase as the number of tests grows. Statistical plans may address this through prespecified primary outcomes, adjustment procedures, or a clear distinction between confirmatory and exploratory analyses. The registry record does not report a multiplicity strategy, adjustment, or analysis hierarchy. It would be inappropriate to infer that no multiplicity issue existed simply because one outcome measure is listed.

The record does not report how missing outcome observations were defined or handled, whether every assessed vein had complete documentation data, or whether any participant or vein was excluded from analysis. It also does not specify an analysis population, such as whether results were to include all enrolled participants or only those with evaluable procedures. These details are not reported in the registry record.

Likewise, no statistical analysis plan, interim-analysis plan, imputation method, or sensitivity analysis is described. The registry lists zero analyses, so there are no posted analytic results from which to determine how missingness, multiplicity, or analysis populations were handled. This absence limits interpretation of both the planned endpoint and any potential precision estimate.

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 2.9% reporting threshold.

Most frequent non-serious adverse event terms

The registry lists one group, Cryoablation of Atrial Fibrillation. For serious adverse events, 34 were recorded as at risk and 0 as affected. For other adverse events, 34 were recorded as at risk and 2 as affected. The record does not list serious adverse event terms.

These are counts for the categories recorded in the registry, not a comparison between study arms. They should not be combined into a single adverse-event total: the record does not explain whether the categories overlap, how events were classified, or what period of observation was used. The number of deaths is not reported in the registry record.

In general, safety counts need context to support interpretation, including definitions, ascertainment procedures, event timing, severity, and follow-up. The registry does not report those details for these counts. The counts therefore describe what was entered in the adverse-event fields but do not establish a comprehensive safety profile or a causal relationship with a particular maneuver. They also do not answer the primary question about real-time documentation.

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

The registry record is informative about what the study set out to measure. It describes an assessment of real-time pulmonary vein disconnection documentation with the Achieve catheter during atrial fibrillation cryoablation. It also specifies how documentation and maneuver categories were intended to be coded. The entry reports enrollment of 34 and 128 pulmonary veins assessed.

What the record does not supply is the primary endpoint result. There is no reported number or percentage of pulmonary veins documented in real time, no distribution across the maneuver categories, and no reported analysis. The completed status does not fill in those missing results. Without an outcome estimate, the record cannot show how often documentation was achieved or how precise any estimate might be.

The endpoint is procedural and descriptive. Even if its result were available, a proportion of veins with documented disconnection would answer a question about documentation during the procedure. It would not by itself establish later clinical effects, the value of one maneuver relative to another, or a causal advantage over a control strategy. The registry does not describe a randomized or like-for-like comparator comparison.

The safety counts also have a limited meaning. The registry records 0 affected in the serious adverse event category and 2 affected in the other adverse event category, with 34 at risk in each category. Those entries do not resolve the missing primary endpoint and do not provide the clinical context needed for a broad safety interpretation. The deaths field is not reported in the registry record.

In general, the strength of an inference depends on the design, the completeness of reported results, and the suitability of the analysis. Here, the study question and outcome definition can be described, but the primary findings and key analysis details are absent. The appropriate reading is therefore bounded: the record documents a completed study with a defined procedural outcome and listed adverse-event counts, but it does not permit a quantitative conclusion about the outcome or a comparative treatment effect.

13. Why This Trial Matters Statistically

This study raises a statistical issue that is easy to overlook: the outcome is defined for pulmonary veins, while enrollment is defined for participants. When several veins are assessed within one person, observations may not be independent. In general, accounting for this structure matters because the apparent amount of information can differ from the amount of independent information. The registry does not report how this issue was addressed.

The endpoint also separates whether real-time documentation was possible from how it was achieved. That distinction can make a procedural measure more informative than a single success count, because maneuver categories describe the approach associated with the documentation. At the same time, such categories require clear definitions and a transparent account of how decisions were made. The registry describes the categories, but does not provide their observed distribution or the rules used to select among maneuvers.

The record illustrates the difference between a trial's stated aim and its statistical evidence. The aim was to assess strategies intended to improve catheter-based documentation. Without reported outcome analyses or a comparator, readers cannot determine the magnitude of documentation, assess precision, or attribute any difference to a strategy. The completed status and endpoint definition do not substitute for these results.

Finally, planning calculations and observed evidence answer different questions. A sample-size illustration based on an assumed fraction of an observed effect describes a hypothetical design scenario, not the power achieved by this study. The stated assumptions include equal allocation between two arms, while the registry does not describe a like-for-like two-arm comparison. Keeping planning assumptions distinct from an actual analysis is central to sound interpretation.

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 of the registry record is the absence of the primary outcome results. Although 128 pulmonary veins are reported as assessed, the count documented in real time, the corresponding percentage, and the maneuver-specific results are not reported. The record lists zero analyses, so there is no posted estimate or uncertainty measure to evaluate.

The design information is also limited. Allocation is not stated, and the registry does not describe a like-for-like control comparison. It does not say how maneuvers were selected or whether the different approaches were compared within participants, across participants, or in another way. Any claim about one maneuver improving documentation relative to another would therefore be unsupported by the record.

The registry does not report how the analysis handled the relationship between pulmonary veins assessed within the same participant. It also does not describe missing data, exclusions, analysis populations, prespecified subgroup analyses, multiplicity procedures, or the statistical analysis plan. These omissions make it difficult to assess whether a proposed analysis would have matched the endpoint structure or how robust any estimate might be.

The summary's benchmark wording, only about to 50% of pulmonary veins, is incomplete and should not be treated as a precise external rate. The entry also does not report event definitions or the timing and duration of adverse-event collection. The serious adverse event and other adverse event counts therefore have limited context.

These limitations concern what is reported in the registry record. They do not establish that the study did not collect further data or conduct analyses; those details are simply not reported in the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Cryoablation of AF: Improving the Use of the Achieve Catheter — NCT01843465.
• Registry record last updated 2013-12-13; status last verified 2013-10.
• Results first posted 2013-12-13.
• 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

The registry describes a completed study sponsored by Clinique Pasteur, with a start date of 2013-04, primary completion date of 2013-07, and enrollment of 34. The condition is atrial fibrillation. The study assessed maneuvers for documenting pulmonary vein disconnection with the Achieve catheter during cryoablation.

The primary outcome concerns real-time documentation during the procedure, with yes-or-no coding and categories for standard position, withdrawal position, pacing, or no real-time documentation. The record reports 128 pulmonary veins assessed but does not give the outcome counts, percentage, or maneuver distribution. It lists one outcome measure and zero analyses.

For the listed group, the registry records 0 affected in the serious adverse event category and 2 affected in the other adverse event category, with 34 at risk in each. Deaths are not reported in the registry record. Allocation, a control comparison, and key statistical analysis details are also not reported. The study question and measurement are described, but the posted record does not provide the primary findings needed to quantify the result.