POLARx™ Cardiac Cryoablation System Post Market Clinical Study (POLAR SMART): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for POLARx™ Cardiac Cryoablation System Post Market Clinical Study (POLAR SMART) (NCT05282823), a registered phase not stated study. The primary outcome is Safety Event Free Rate.

2. Clinical Question

3. Trial Design

POLAR SMART is a completed post-market clinical study of the Boston Scientific Cardiac Cryoablation System. The registry describes its purpose as collecting real-world clinical data on safety, effectiveness and procedural success. The condition listed is paroxysmal atrial fibrillation, and the treatment description concerns participants clinically indicated for pulmonary vein isolation ablation.

The registry record lists an enrollment of 295. The study start date is 2022-08-26, and the primary completion date is 2024-10-29. Its status is COMPLETED. These record-level details describe the study’s registration and timing; they do not establish that every enrolled participant contributed data to every endpoint or analysis.

The registered primary outcome is the Safety Event Free Rate, measured in participants over 12 months. The outcome description defines it as freedom from procedure- and device-related adverse events after the index procedure. Failure Free Rate is listed as a secondary outcome. The registry record lists 3 outcome measures and 0 analysis entries. It does not provide the other outcome definitions or an analysis plan in the available information.

The record does not state allocation, and it does not support treating any groups as a randomized, like-for-like comparison. The adverse-event figures are presented for Treatment Subjects. Consequently, the design and posted figures are best read as descriptive registry information about the treated study group, not as a controlled estimate of comparative treatment effects. The registry record does not report a sample-size justification, a protocol-level statistical plan, or interim analyses.

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

Reasons for not completing this period:

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: Includes all treatment subjects

6. Primary Endpoint

The registry lists the primary outcome as Safety Event Free Rate, measured over 12 months.

The primary endpoint is the Safety Event Free Rate at 12 months. Its stated unit is participants, and its description defines the outcome as freedom from procedure- and device-related adverse events after the index procedure. This makes the endpoint a participant-level binary outcome: for the endpoint definition, a participant either meets the event-free criterion or does not.

In general, a participant-level safety endpoint can provide a direct summary of how often a specified safety condition is met during the stated follow-up period. Its interpretation depends on the event definition, the time window, and which participants are included in the analysis. The registry record specifies the event relationship and follow-up period, but the primary endpoint result and analysis population are not reported in the available information.

The name “Safety Event Free Rate” should not be mistaken for a reported rate. No event-free participant count or rate is given in the registry record. The adverse-event figures listed separately do not by themselves establish the primary endpoint result: the record does not state that their definitions, follow-up, or analysis population match the primary endpoint definition. Nor should the adverse-event counts be subtracted from an at-risk count to derive an event-free count. Such a calculation would require information about endpoint correspondence and participant-level overlap that is not reported.

The endpoint is used to organize safety reporting around a defined period after the index procedure. It does not, on its own, establish a causal effect or comparative safety advantage. Those interpretations require an appropriate analysis and design, neither of which is reported as a comparative result in the available record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a participant-level binary endpoint mean?

In general, a binary endpoint classifies each participant into one of two outcome states according to a defined rule. For the registered primary endpoint, the stated rule concerns freedom from procedure- and device-related adverse events after the index procedure during the 12-month timeframe. A count of participants meeting that rule and a count not meeting it can be used to describe the outcome. The registry record does not report those primary endpoint counts or the resulting rate, so no such estimate can be reconstructed from the posted information.

A rate is interpretable only alongside its denominator and outcome definition. The denominator identifies the participants included in the calculation, while the definition determines what qualifies as an event and how the follow-up window is applied. In general, differences in these choices can change the meaning of an estimate. The available record gives the primary endpoint’s unit, description and timeframe, but does not report the endpoint’s analysis population, its event-free count, or missing-outcome handling.

How should uncertainty be understood?

In general, a confidence interval expresses the uncertainty around an estimated quantity under a specified statistical method. It gives a range of values compatible with the data and method at the stated confidence level; it is not a guarantee that the true value lies within that range. A narrow interval indicates greater precision than a wide interval, all else being comparable. The registry information available for this study does not report a confidence interval for the primary endpoint or the listed adverse-event counts. Therefore, their statistical precision cannot be assessed from an interval estimate.

In general, a hypothesis test addresses a defined null hypothesis using a specified test and analysis population. A p-value is not a measure of the size or clinical importance of an effect, and it does not replace an estimate with an uncertainty interval. No outcome analyses are listed in the registry record, and no p-values or test methods are reported. It is not possible to infer a hypothesis-testing result from the event counts alone.

Why does the design affect interpretation?

In general, random allocation can help make treatment groups comparable with respect to both measured and unmeasured characteristics, supporting a causal comparison when the trial is otherwise appropriately conducted and analysed. A nonrandomized or unspecified allocation does not provide the same basis for attributing differences to treatment. Here, the registry record does not state allocation and identifies no like-for-like randomized control comparison. The posted information should therefore be interpreted descriptively rather than as a comparative causal estimate.

In general, an analysis population specifies which participants contribute to an outcome estimate. Different definitions can answer different questions, particularly when participants do not complete follow-up or do not have outcome data. The record lists enrollment of 295 and an adverse-event risk set of 293, but does not explain the relationship between these values or identify the primary endpoint analysis population. No conclusion about exclusions or missing outcomes should be inferred from that difference.

What do the planning assumptions mean?

The registry information describes a planning illustration based on an observed effect, not the study’s own design. Its stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. For time-to-event tables, the stated method uses the total number of events under the Schoenfeld approach; other planning entries are expressed as participants per arm. The actual calculated planning values are not included in the registry entries, so none can be quoted.

In general, a planning calculation estimates the amount of information that may be needed to detect a chosen effect under specified assumptions. It is not a count of observed participants or events, and it is not observed power. Results depend on the assumptions, including the effect size chosen for planning and the statistical model. Because this illustration is based on an observed effect and is not identified as the study’s original design calculation, it should not be presented as evidence that the trial was prospectively powered according to those assumptions. The registry record does not report its own sample-size justification.

In general, over-dispersion occurs when variation in count data is greater than expected under a model that assumes a particular mean-variance relationship. If present and ignored, standard errors may be too small and uncertainty may be understated. This concept is not a reported finding about POLAR SMART: the available record does not describe a count-data model or an over-dispersion assessment. It is relevant only as a general consideration when selecting methods for count outcomes.

Finally, a statistical method cannot compensate for missing endpoint definitions, incomplete reporting, or a design that does not support the intended comparison. The registry lists 3 outcome measures and 0 analysis entries, but does not describe adjustment methods, estimands, confidence intervals, or sensitivity analyses. Those methodological details are not reported in the registry record.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Treatment Subjects")
n      <- c(293)
events <- c(285)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Treatment Subjects  293  285  97.3  94.7  98.8  94.7  98.6  94.7  98.6

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists 3 outcome measures, identifies Safety Event Free Rate as primary, and names Failure Free Rate as a secondary outcome. It does not provide the complete definitions or results for all outcome measures in the available information. It also lists 0 analysis entries. The statistical plan, including any prespecified testing sequence or multiplicity adjustment, is not reported in the registry record.

In general, assessing several outcomes can create multiplicity: if each is tested separately, the chance of at least one apparently notable result can increase. Prespecifying which outcome is primary and how secondary outcomes will be interpreted can help distinguish confirmatory questions from exploratory ones. No particular multiplicity procedure should be attributed to this study without a reported plan. The available information does not establish whether formal hypothesis tests were conducted.

Missing-data handling is also not reported. In general, participants may lack an outcome assessment for reasons such as incomplete follow-up, but the available registry information does not say whether this occurred or how it was handled. It does not describe imputation, censoring, sensitivity analyses, or rules for assigning endpoint status. The listed enrollment and adverse-event risk-set figures do not reveal the reason for their difference, and they should not be used to infer missingness or exclusions.

The primary endpoint analysis population is not specified. It is therefore unclear from the registry record which participants would contribute to a primary endpoint estimate, and no population-specific result can be assessed. These gaps limit evaluation of both multiplicity and the potential impact of unavailable outcome data.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: atrial fibrillation (af) (1.7%), gastrointestinal (1.0%), neurological (1.0%), sinus bradycardia (0.7%), gastroparesis (0.7%).

For Treatment Subjects, the registry reports 293 participants at risk and 25 affected for serious adverse events. It separately reports 293 at risk and 30 affected for other adverse events. The deaths field is 0. These figures should be read as the adverse-event counts and risk sets recorded, not as a complete account of all safety outcomes or as the primary Safety Event Free Rate.

The registry also lists serious adverse-event terms with percentages: Atrial Fibrillation (AF), 1.7%; Gastrointestinal, 1.0%; Neurological, 1.0%; Sinus Bradycardia, 0.7%; Gastroparesis, 0.7%; and Cancer, 0.7%. The record does not explain whether a participant could appear under more than one term, whether the percentages refer to participants or events, or how the terms were assigned. The categories should not be added together or treated as mutually exclusive.

In general, “at risk” identifies the population used as a denominator for a particular safety summary, while “affected” identifies those recorded with the specified outcome. The registry does not explain the relationship between the two risk sets or the enrollment count, so the denominator should be retained as stated for each summary. The adverse-event figures are descriptive; the record does not report a comparative safety analysis, uncertainty intervals, or a causal estimate.

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

The study record describes a completed post-market investigation of a cryoablation system in participants with paroxysmal atrial fibrillation. Its primary safety question is framed as freedom from procedure- and device-related adverse events after the index procedure over 12 months. The record also gives adverse-event counts for Treatment Subjects and names Failure Free Rate as a secondary outcome.

What the posted figures do show is that the adverse-event record lists 25 affected for serious adverse events and 30 affected for other adverse events, each with 293 at risk, and records 0 deaths. It also lists several serious adverse-event terms and their percentages. These observations describe the registry entries. The primary endpoint result itself is not reported, and the secondary outcome result is not reported in the available information.

What these figures do not show is whether the system caused or prevented an event, how its outcomes compare with another treatment, or how precise an estimated outcome is. The record does not state allocation, does not establish a randomized like-for-like comparison, and does not provide confidence intervals or analysis results. A completed status does not resolve these omissions.

In general, safety counts are most informative when their event definitions, follow-up, analysis population, and denominator are clear. Those details are only partly. The adverse-event counts cannot be assumed to match the primary endpoint’s definition or follow-up, and there is no basis for deriving an event-free rate from them. The record also does not state whether adverse-event categories overlap.

Accordingly, the appropriate interpretation is bounded: the registry provides descriptive safety reporting for the treated group, but does not report enough information to quantify the primary endpoint or establish a comparative effect. This distinction is important because an observed count is not, by itself, an estimate of treatment benefit, harm relative to an alternative, or statistical certainty.

14. Why This Trial Matters Statistically

Post-market studies can add information about how a device is evaluated in clinical practice after it is on the market. POLAR SMART is explicitly described as collecting real-world clinical data on safety, effectiveness and procedural success for the Boston Scientific Cardiac Cryoablation System. That context makes clear why the registry includes a safety endpoint and adverse-event reporting rather than presenting only a treatment-effect comparison.

Statistically, the record illustrates the importance of separating an endpoint’s name from its result. “Safety Event Free Rate” identifies a defined question, but without the event-free count, denominator, and analysis, it does not provide a rate. The posted serious and other adverse-event counts are relevant descriptive information, yet they cannot be substituted for the primary endpoint because the record does not establish that the outcome definitions and populations align.

The study also highlights why design information matters. Allocation is not stated, and the registry does not describe a randomized, like-for-like control comparison. This limits what can be concluded from group data: descriptive safety reporting is not equivalent to an estimate of comparative effects. Reporting the design and analysis population is necessary for readers to understand what question an estimate answers.

Finally, registry completeness affects statistical interpretation. The primary result, uncertainty estimates, analysis methods, missing-data handling, and sample-size justification are not reported in the available record. These omissions do not negate the descriptive information, but they constrain the strength and precision of conclusions that can be drawn from it. The case is a useful reminder that outcome definitions, denominators, and analysis methods are essential companions to counts.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The primary endpoint result is not reported in the available registry information. Although the endpoint is defined as freedom from procedure- and device-related adverse events after the index procedure over 12 months, no event-free count, rate, or uncertainty estimate is available. The secondary Failure Free Rate is named, but its result is not reported.

The registry does not state the allocation method, and the study is not described as a randomized comparison. The treatment group therefore should not be interpreted against another group as a like-for-like control contrast. The record does not provide details sufficient to assess confounding or comparative effectiveness.

Although enrollment is listed as 295, the adverse-event risk sets are listed as 293. The registry record does not explain the difference or specify which analysis population applies to the primary endpoint. Missing-data rules, follow-up completeness, and endpoint-specific denominators are not reported. It is not possible to determine from the available information whether the adverse-event categories overlap or how their percentages were calculated.

The record lists 0 analysis entries and does not report the statistical analysis plan, confidence intervals, hypothesis tests, multiplicity handling, or sensitivity analyses. It also does not report the study’s own sample-size justification or any interim analyses. The planning assumptions described in the registry are an illustration based on an observed effect, not evidence of the actual design rationale. These limitations restrict assessment of the endpoint’s precision and the robustness of any effect interpretation.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: POLARx™ Cardiac Cryoablation System Post Market Clinical Study (POLAR SMART) — NCT05282823.
• Registry record last updated 2025-12-02; status last verified 2025-10.
• Results first posted 2025-12-02.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

POLAR SMART (NCT05282823) is a completed post-market clinical study sponsored by Boston Scientific Corporation. It concerns the Boston Scientific Cardiac Cryoablation System for participants with paroxysmal atrial fibrillation. The registry lists enrollment of 295, a study start date of 2022-08-26, and a primary completion date of 2024-10-29.

The primary outcome is Safety Event Free Rate at 12 months, defined as freedom from procedure- and device-related adverse events after the index procedure. Failure Free Rate is listed as a secondary outcome. The primary result and secondary result are not reported in the available registry information. The record lists 3 outcome measures and 0 analysis entries.

For Treatment Subjects, the adverse-event record lists 293 at risk and 25 affected for serious events, 293 at risk and 30 affected for other events, and 0 deaths. The record does not state allocation and does not establish a randomized, like-for-like control comparison. Its adverse-event figures are descriptive and do not establish a comparative effect or the primary endpoint rate.