WATCHMAN FLX™ CT Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for WATCHMAN FLX™ CT Study (NCT05324371), a na na study. The primary outcome is Number of Participants With Any Hypoattenuated Thickening (HAT) on the Surface of the Device.

2. Clinical Question

3. Trial Design

The registry describes WATCHMAN FLX CT as a prospective, single-arm, single-center, post-market investigation. Participants with non-valvular atrial fibrillation received WATCHMAN FLX device implantation, and imaging was used to assess tissue coverage on the device. The study is listed as completed, with an enrollment of 25. The phase is listed as NA.

The primary endpoint concerns any hypoattenuated thickening (HAT) on the device surface. CT assessments were planned at 14 days, 45 days and 3 months post implant, with the description identifying a core lab assessment. The stated endpoint timeframe is 14 days to 3 months post implant. The brief description also mentions serial advanced imaging, including CT and TEE; the official title names CT, magnetic resonance imaging and transesophageal echocardiography.

There is no control arm or randomized allocation. Masking is listed as none. The record identifies one device arm, rather than distinct groups assigned to different interventions. Therefore, the study design can describe observed findings among enrolled participants, but it does not establish a randomized treatment contrast. Further protocol details, including eligibility criteria and the timing or role of each imaging modality beyond the endpoint description, are not reported in the registry record.

The record lists a start date of 2022-11-09 and a primary completion date of 2024-05-30. Those dates describe the registry timeline; they do not establish when individual participants completed each imaging assessment. The registry record lists zero analyses and does not report an inferential statistical analysis for the primary endpoint.

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.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Any Hypoattenuated Thickening (HAT) on the Surface of the Device, measured over 14 days to 3 months post implant.

The primary endpoint is the number of participants with any hypoattenuated thickening (HAT) on the surface of the device, assessed using CT imaging by a core lab. Assessments were planned at 14 days, 45 days and 3 months after implant; the stated timeframe is 14 days to 3 months post implant. This is a participant-count endpoint: its intended quantity is how many participants meet the endpoint definition, not the number of separate HAT findings or the amount of thickening.

In general, imaging endpoints can characterize an anatomical or device-related observation during follow-up. A count of participants with any finding can be easier to interpret than a measurement of its size or severity, but it does not by itself describe the finding’s clinical importance. Interpretation also depends on how the endpoint is defined, how images are read, whether all scheduled assessments are available, and how findings across timepoints are combined.

The registry record does not provide a numeric HAT count, a proportion, an uncertainty interval, or further operational details about how a participant is classified when results differ across assessments. It also does not report the endpoint’s relationship to clinical events. Those omissions limit interpretation of the endpoint as a clinical outcome.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a participant count represent?

The primary endpoint is a count of participants with any HAT on the device surface. In general, a count endpoint records how many people meet a defined event or finding criterion. It differs from a continuous measure, such as the size of a finding, and from a time-to-event outcome, which incorporates when an event occurs. The endpoint description does not define a severity scale or report the amount of thickening. Its stated focus is whether any HAT is present.

A participant count should be interpreted with its analysis population and observation rule. For repeated imaging, an analysis must specify how findings across visits contribute to one participant’s endpoint status. For example, a record might classify a participant based on any qualifying finding across visits or report each timepoint separately. The registry describes serial measurement at 14 days, 45 days and 3 months, but the precise aggregation rule is not reported in the registry record. No observed count is reported.

What would uncertainty communicate?

In general, a confidence interval describes the range of values reasonably compatible with an estimate under the statistical model and its assumptions. For a binary outcome, an estimate might be a participant proportion, accompanied by an interval that conveys sampling uncertainty. An interval does not correct for biased enrollment, missing outcome data, measurement error, or an unsuitable model. Its interpretation also depends on the study design and the method used to calculate it.

The registry record does not report a confidence interval or a primary endpoint estimate. It is therefore not possible to judge from the posted results how precisely the endpoint was estimated. With a single-group study, any interval for the endpoint would describe uncertainty about the observed group’s endpoint rate under the chosen method. It would not create a comparison with a control group or establish a causal treatment effect.

Why does the single-group design matter?

In general, a comparator helps distinguish an outcome observed after an intervention from the outcome that might have occurred under another condition. Random allocation can support a fairer comparison by balancing prognostic factors on average, though it does not remove every source of uncertainty. This study has one device arm, allocation listed as NA, and no separate control group. Its design therefore supports a descriptive account of observations among participants, not a randomized estimate of the difference between interventions.

Masking is listed as none. In general, knowledge of an assigned intervention can influence some aspects of study conduct or outcome assessment, depending on the outcome and safeguards used. The primary endpoint involves CT imaging and a core lab assessment, but further details about image-reader masking, adjudication or quality assurance are not reported in the registry record. No assumption about those procedures can be made from the masking field alone.

What do the planning assumptions mean?

In general, a sample-size calculation asks how many participants a future study might need to detect a specified effect under chosen assumptions. The record’s stated planning illustration uses 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 an observed effect. It specifies participants per arm for non-time-to-event outcomes. These assumptions describe a planning exercise, not an observed study result, and do not establish that the trial was designed or powered according to them.

The record does not report a sample-size justification for this trial. The study itself is described as single-group, whereas the planning assumptions refer to two equally allocated arms. The illustration should therefore not be read as a description of the actual trial design or as evidence of observed power. The number of participants enrolled is 25, but that figure alone does not indicate the precision of an unreported endpoint estimate.

What can be concluded from the posted analysis record?

The registry lists zero analyses and reports no numerical primary endpoint finding. Consequently, no sponsor analysis, model, test statistic, p-value, adjusted estimate, or inferential conclusion is available for this endpoint in the registry record. The primary result cannot be independently recalculated from summary statistics because those summary statistics are not posted. General statistical methods can explain how a count might be analyzed, but they cannot supply the absent result or establish which method was used.

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("14 Days", "45 Days", "3 Months")
n      <- c(24, 23, 23)
events <- c(5, 3, 2)
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  14 Days  24  5  20.8  7.1  42.2  9.2  40.5  9.4  40.7
ARM  45 Days  23  3  13.0  2.8  33.6  4.5  32.1  4.7  32.4
ARM  3 Months  23  2  8.7  1.1  28.0  2.4  26.8  2.7  27.0

11. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when a study makes several statistical comparisons or tests outcomes repeatedly. In general, the more hypotheses examined, the greater the chance that at least one result appears notable by chance unless the analysis plan addresses that issue. Repeated measurement can also raise questions about whether each timepoint is a separate endpoint, whether a combined endpoint is used, and which result is considered primary.

The registry identifies one primary outcome measure: the number of participants with any HAT on the device surface, assessed over 14 days to 3 months post implant. Its description refers to measurements at 14 days, 45 days and 3 months. The record does not report a multiplicity adjustment, a hierarchy of timepoints, or a rule for combining findings across visits. It lists zero analyses, so no testing strategy or analysis results are available to clarify those issues.

Missing-data handling is also not reported in the registry record. It does not state how missing CT images, uninterpretable scans, missed visits, withdrawals or incomplete follow-up were handled. The enrollment of 25 cannot be assumed to equal the number with evaluable scans or the analysis population at each timepoint. The record does not provide a participant flow or endpoint-specific denominator.

The analysis population is not reported in the registry record. It is therefore unclear which participants, if any, were included in a primary endpoint analysis and what criteria determined inclusion. Without those details and a posted result, it is not possible to assess the impact of missing observations or whether the analysis followed a prespecified plan. These are uncertainties about reporting; they do not establish that data were missing or that a particular method was used.

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: pneumonia (12.0%), cerebral haemorrhage (8.0%), aortic valve incompetence (4.0%), atrial fibrillation (4.0%), gastric ulcer (4.0%).

The registry reports serious adverse event figures for the Device Arm: 25 participants at risk and 10 affected. It reports other adverse event figures for the same arm: 25 at risk and 4 affected, along with 1 death. These are registry counts; the record does not report further details about event timing, duration, severity criteria, attribution to the device, or whether events occurred in the same participants.

The listed serious adverse event terms include Pneumonia at 12.0%, Cerebral Haemorrhage at 8.0%, and Aortic Valve Incompetence, Atrial Fibrillation, Gastric Ulcer and Gastric Ulcer Haemorrhage at 4.0% each. These percentages are event-term entries, not necessarily mutually exclusive categories. A participant may have more than one event, so they should not be added to infer a total number of participants. The record does not provide the corresponding term-specific participant counts in the posted list.

These safety figures describe events recorded in a single-group study. They do not establish whether an event was caused by the device or how the frequency would compare with another treatment or a control group. The registry record does not report a comparator, exposure-adjusted rates, or an assessment of causal relationship for these terms. The reported death is a count, and further details are not reported in the registry record.

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

The study addresses an imaging question: how often any HAT was identified on the surface of WATCHMAN FLX devices during the stated follow-up period. It is described as a prospective, single-arm, single-center post-market investigation, with serial imaging and a core lab CT assessment for the primary endpoint. The record lists 25 enrolled participants and names assessments at 14 days, 45 days and 3 months post implant.

The registry record does not report the number of participants with HAT. It also does not provide an endpoint estimate, confidence interval, analysis population, or handling of missing imaging. Those absences mean the posted record does not allow a reader to assess the observed frequency or its precision. The study’s completed status does not substitute for a reported endpoint result.

The design also limits what the study could establish even if the endpoint count were reported. With no comparator group and no randomized allocation, observations in the device arm cannot determine what would have happened under another treatment or no intervention. The study is not a randomized test of clinical benefit, and the registry does not report a relationship between HAT and clinical outcomes such as stroke or bleeding.

The safety figures describe adverse events recorded in the device arm, but the posted information does not establish causation or provide a comparative safety estimate. As with the primary endpoint, counts in a single group are descriptive and should be interpreted in the context of event definitions, follow-up and data completeness; those further details are not reported in the registry record.

Accordingly, the record supports identifying the study question, its imaging schedule and its broad design. It does not support a numerical conclusion about HAT prevalence, comparative effects, clinical consequences, or the causes of reported adverse events.

14. Why This Trial Matters Statistically

Statistically, this study illustrates the distinction between a clearly stated endpoint and a reported endpoint result. The registry defines a participant-count outcome for HAT on the device surface and specifies an imaging period. Yet it lists zero analyses and gives no observed endpoint count. Without that result, neither the magnitude of the observed finding nor its precision can be evaluated from the registry record.

The design is also important to interpretation. A single-group study can describe what was observed among enrolled participants, but it has no internal control group for estimating a treatment contrast. Its prospective and post-market features describe the study context; they do not, by themselves, address confounding or establish causation. The lack of random allocation and a comparator should therefore shape any interpretation of both imaging and safety observations.

Serial imaging makes the definition of the participant-level endpoint consequential. An analysis needs a clear rule for combining assessments across 14 days, 45 days and 3 months, along with an account of missing or uninterpretable scans. These details are not reported in the registry record. Their absence matters because the endpoint is based on repeated observations but is framed as a count of participants.

Finally, safety counts and imaging findings answer different questions. Event counts can describe reported events in the study arm, while the imaging endpoint describes a device-surface finding. Neither alone demonstrates a causal relationship or a comparative effect. Careful statistical reading keeps the design, endpoint definition, completeness of follow-up and availability of results in view.

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.

Several trial-specific reporting limitations constrain interpretation. The registry record lists 25 participants enrolled but does not report how many completed the imaging schedule or had evaluable CT results. It provides no participant flow, endpoint denominator, or analysis population. As a result, enrollment cannot be treated as the number assessed for the primary outcome.

The endpoint description identifies serial CT assessment at 14 days, 45 days and 3 months, but does not specify the rule for combining those readings into a participant-level count. Further details about HAT classification, image quality, reader procedures, adjudication, and treatment of conflicting assessments are not reported in the registry record. Such details would help readers understand how consistently the endpoint was measured.

The study is single-center and single-arm, with allocation listed as NA and masking listed as none. There is no randomized comparator. These design features limit comparative interpretation and do not support estimating a causal difference from another treatment. The record also does not report detailed eligibility criteria or participant characteristics, limiting assessment of who the findings might describe.

The primary endpoint result and any inferential analysis are absent from the registry record, which lists zero analyses. No confidence interval, statistical model, or missing-data method is reported. Although adverse event counts and selected serious event terms are listed, details about event attribution, timing and overlap among participants are not reported. These gaps should be treated as limits of the available record, not as evidence that a particular outcome or procedure did or did not occur.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: WATCHMAN FLX™ CT Study — NCT05324371.
• Registry record last updated 2025-07-01; status last verified 2025-05.
• Results first posted 2025-07-01.
• 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

WATCHMAN FLX CT is described as a prospective, single-arm, single-center, post-market investigation of device tissue coverage in participants with non-valvular atrial fibrillation. The record lists 25 enrolled participants, one device arm, no masking, and a completed status. The primary outcome is the number of participants with any HAT on the device surface, assessed by core lab CT from 14 days to 3 months post implant, with measurements described at 14 days, 45 days and 3 months.

The record lists zero analyses and does not report the primary endpoint count or an estimate of its precision. It also reports adverse event counts for the device arm and selected serious event terms. The single-group design has no randomized comparator, so the registry information is descriptive and does not provide a comparative treatment effect.