Reveal In-Office Implants: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Reveal In-Office Implants (NCT01168427), a registered phase not stated study. The primary outcome is Procedure-related Complications Rate Requiring Resolution by Surgical Intervention.

2. Clinical Question

The study asked whether implantation of a Reveal Insertable Cardiac Monitor in an office or clinic setting could be assessed for safety and feasibility, rather than being performed in a traditional hospital operating room, cardiac catheterization laboratory, or electrophysiology laboratory. The registry lists the primary endpoint as the number of participants with a procedure-related complication requiring resolution by surgical intervention.

This is a procedural safety and feasibility question, not a comparison of device effectiveness across treatment groups. The registry also lists secondary outcomes concerning adverse events, staff, procedural techniques, physician satisfaction, and R-wave amplitude. Their detailed results are not reported in the registry record.

3. Trial Design

This completed registry study evaluated Reveal in-office implants. The listed intervention was a Reveal DX or Reveal XT Insertable Cardiac Monitor, and the study rationale was to gather evidence about the safety and feasibility of performing implantation in an office or clinic instead of a traditional hospital operating room, cardiac catheterization laboratory, or electrophysiology laboratory.

The record reports enrollment of 66 participants. Its primary outcome population is described as patients with a Reveal device indication who enrolled and were implanted per protocol. The adverse-event results identify an Implant Cohort, with 65 participants at risk in the serious and other adverse-event categories. The reason the cohort count differs from the enrollment count is not reported in the registry record.

The registry does not describe a randomized allocation or a control arm. It explicitly cautions that this is not a randomized comparison and that the arms are not a like-for-like control comparison. The posted information therefore supports interpretation as a cohort evaluating an implantation setting, rather than as a comparative trial that can estimate a treatment contrast between settings.

The study start is recorded as 2010-08, and primary completion is recorded as 2011-05. The status is COMPLETED. The registry lists six outcome measures and one analysis, but a detailed statistical analysis plan is not reported in the registry record. Further details about recruitment, follow-up completeness, site structure, and allocation are also not reported in the registry record.

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:

Analysis population for the primary outcome, as defined in the registry: Reveal device indicated patients, enrolled in the study and implanted per protocol

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 Procedure-related Complications Rate Requiring Resolution by Surgical Intervention, measured over From Implant to 90 days post-implant procedure.

The primary endpoint concerns participants who experienced a procedure-related complication that required resolution by surgical intervention. The stated timeframe runs from implantation to 90 days after the implant procedure. The registry says the objective is to estimate the proportion of patients with such a complication at 90 days using the Kaplan-Meier method.

This endpoint focuses on complications with a specified level of consequence: an event must be procedure-related and require surgical intervention to meet the stated definition. It is therefore narrower than a count of all adverse events. An adverse event that does not require surgical intervention would not, on the wording of this endpoint, qualify as a primary endpoint event, although it could be recorded under a separate safety outcome.

Using a time-to-event method can be useful when participants have different lengths of observed follow-up or when some follow-up ends before the time horizon of interest. In general, Kaplan-Meier estimation uses the timing of events and accounts for participants whose event status becomes unknown after their last observed follow-up, under assumptions about censoring. The registry does not report the primary endpoint estimate, its uncertainty, or the event timing, so the result cannot be quantified from the record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes the primary endpoint as a proportion estimated with the Kaplan-Meier method over the period from implantation to 90 days after the procedure. It also describes the endpoint as the number of participants with procedure-related complications requiring surgical intervention. Those descriptions point to an event-count concept and a time-to-event estimation approach. The primary numerical result itself is not reported in the registry record.

What does a time-to-event estimate represent?

In general, a time-to-event analysis uses both whether an event occurred and when it occurred. Participants who have an event contribute information up to the event time. Participants who have not had an event by their last known follow-up may contribute information until that point, after which their event status is censored. Kaplan-Meier estimation combines the observed event times to estimate the probability of remaining event-free over time, or equivalently the cumulative probability of an event by a specified time.

That approach can make use of incomplete follow-up without automatically treating every participant lost before the endpoint as either an event or a non-event. Its interpretation depends on appropriate handling of follow-up and on assumptions about censoring. In general, censoring should not be systematically related to the unobserved event risk in a way that biases the estimate. The registry entries do not report how many participants were censored, when follow-up ended for each participant, or how censoring was assessed.

Why is the event definition important?

The primary outcome requires a procedure-related complication that is resolved by surgical intervention. This wording distinguishes the endpoint from broader safety counts, which can include events that do not meet the primary definition. A count of participants with any adverse event cannot be substituted for a count meeting the primary endpoint unless the event definitions and participant-level classifications show that they are the same. Those details are not reported in the registry record.

The wording also matters for interpretation of the time horizon. The registry identifies a 90-day endpoint, but a time horizon alone does not provide the result. Estimation requires the event and follow-up information needed for the analysis. Neither an estimate nor its uncertainty is reported among the registry entries available for this account.

What would uncertainty communicate?

In general, a confidence interval describes a range of values compatible with the data under the analysis method and its assumptions. A narrow interval indicates greater precision than a wide interval, while neither interval width nor the point estimate alone determines whether an outcome is clinically important. No confidence interval for the primary endpoint is reported in the registry record, so its precision cannot be assessed.

Likewise, a statistical test or p-value would address a specified hypothesis, but a meaningful test requires a defined comparison or benchmark. The record does not report a control group or a primary hypothesis test. The study’s stated purpose is to gather evidence about safety and feasibility in an office or clinic setting; the record does not report a formal decision threshold for those objectives.

How should planning calculations be read?

Any sample-size calculations associated with the posted analysis are planning illustrations, not evidence about the number of participants actually observed to have an event. The stated illustration assumptions use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. The registry describes no randomized two-arm comparison, so those assumptions do not describe the documented study design. Such calculations must not be interpreted as observed power or as a justification for the study’s enrollment. The trial’s own sample-size justification is not reported in the registry record.

More broadly, over-dispersion is a general concern when variability exceeds what a simple model assumes; it can make standard errors too small if not accounted for. The primary endpoint is described as a binary participant outcome analyzed with Kaplan-Meier, and no over-dispersion adjustment is reported. This general concept does not establish that over-dispersion was present in this study.

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("Implant Cohort")
n      <- c(65)
events <- c(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  Implant Cohort  65  2  3.1  0.4  10.7  0.8  10.5  0.9  10.5

11. Multiplicity, Missing Data and Analysis Populations

The registry lists six outcome measures, including the primary procedure-related complication endpoint and secondary outcomes related to adverse events, staffing, procedural techniques, physician satisfaction, and R-wave amplitude. The registry record does not report how the outcomes were ordered or whether testing across multiple outcomes was adjusted to control the chance of false-positive findings. A multiplicity strategy, if any, is not reported in the registry record.

The record identifies one analysis, but the detailed statistical analysis plan is not reported in the registry record. It is therefore not possible to determine from the posted information whether the analysis was prespecified in full, whether alternative analyses were considered, or how any deviations were handled. The record also does not report interim analyses or stopping rules.

Missing-data handling and analysis populations are not described in the available details. The stated primary population includes participants enrolled and implanted per protocol, while the adverse-event counts identify 65 participants at risk and enrollment is 66. The reason for this difference, and whether it reflects missing follow-up, eligibility, or another circumstance, is not reported in the registry record. No assumption should be made about how the participant was treated in the primary analysis.

These omissions limit assessment of the strength and robustness of the estimates, especially because the primary endpoint result itself is not reported. They also mean that the adverse-event risk counts should be interpreted as the counts recorded for those categories, not as a full account of the analysis population or follow-up completeness.

12. 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 adverse-event record lists the Implant Cohort with 65 participants at risk in the serious category and 0 participants affected. For other adverse events, it lists 65 participants at risk and 6 participants affected. The outcome information describes participants with an event as counts. These figures are descriptive counts in the posted safety record.

The serious-event count does not equal the primary endpoint result. The primary endpoint is limited to procedure-related complications requiring resolution by surgical intervention through 90 days, whereas the safety category is labelled serious adverse events. The registry record does not report whether any safety event met the primary endpoint definition. The other adverse-event count likewise cannot be read as a count of primary complications.

Counts alone do not describe the timing, type, duration, severity details, relatedness assessments, or clinical course of each event. Those details are not reported in the registry record. The meaning of “at risk” for the safety categories is not further defined in the registry entries, and the reason the risk count is 65 when enrollment is 66 is not reported. The counts should therefore be read as posted, without converting them into a rate or assuming a specific explanation for the difference.

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

The study record describes an effort to gather evidence about the safety and feasibility of performing Reveal monitor implantation in an office or clinic setting. It identifies a primary endpoint focused on procedure-related complications requiring surgical intervention by 90 days after implantation. However, the primary endpoint estimate is not reported in the registry record, so the central outcome cannot be quantified or assessed for precision from the registry entries.

The recorded safety counts show 0 participants affected among 65 at risk for serious adverse events and 6 affected among 65 at risk for other adverse events. Those counts provide limited descriptive information. They do not establish how many participants experienced the specific primary endpoint, and no event-level details are available to connect the safety categories with the endpoint definition.

The record does not document a like-for-like control group, so it cannot answer whether an office or clinic setting produces better, worse, or equivalent outcomes to the traditional settings named in the study rationale. It also does not establish comparative effectiveness or support a causal estimate of the effect of choosing one setting over another.

More generally, a completed study record is not by itself a complete account of every design and analysis detail. The reason for the difference between enrollment of 66 and safety risk counts of 65, the primary estimate, its confidence interval, missing-data handling, and detailed outcome results are not reported in the registry record. The appropriate reading is therefore limited to the study objective, the endpoint definition, and the posted adverse-event counts, with the unreported information left unresolved.

14. Why This Trial Matters Statistically

Statistically, this study illustrates the distinction between describing an objective and reporting an estimate. The registry specifies a clinically interpretable event definition and a follow-up horizon: a procedure-related complication requiring surgical intervention by 90 days after implantation. It also names Kaplan-Meier estimation. Yet, without a reported estimate and uncertainty interval, the primary safety question cannot be answered quantitatively from the posted record.

It also illustrates why outcome definitions must be kept separate. A serious adverse event, an other adverse event, and a complication requiring surgical intervention are not interchangeable categories. The adverse-event counts are useful as descriptive safety information, but they cannot stand in for the primary endpoint unless their definitions and classifications align.

The design context shapes what statistical conclusions are possible. The study rationale contrasts office or clinic implantation with traditional hospital settings, but the registry does not describe a randomized control comparison. The study can therefore be read as an evaluation of a procedural approach in its recorded cohort, not as a head-to-head estimate of differences between settings.

Finally, the count of 65 participants at risk alongside enrollment of 66 shows why analysis populations and follow-up accounting matter. The record does not explain the difference, so readers should not infer its cause. Transparent reporting of the endpoint estimate, uncertainty, population definitions, follow-up, and analysis methods would be necessary for a fuller statistical assessment.

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 limitations specific to this record constrain interpretation. The primary endpoint is described, but its result is not reported in the registry record. There is consequently no posted primary estimate or confidence interval with which to assess magnitude or precision. The event times and participant follow-up information needed to evaluate the Kaplan-Meier analysis are also not reported.

The study rationale names traditional hospital settings, but the record does not describe a like-for-like comparison group. It therefore does not provide a direct statistical comparison between office or clinic implantation and those settings. Allocation details are not reported, and the record explicitly cautions that the study is not a randomized comparison.

Enrollment is reported as 66, while the safety risk counts are 65. The registry record does not explain this difference. The available details also do not describe missing-data procedures, analysis populations beyond the stated primary population, or the degree of follow-up completeness. These gaps prevent assessment of whether the reported safety counts represent all enrolled participants or a defined subset for a particular reason.

Although the registry lists secondary outcomes, their detailed results are not reported in the registry record for this account. A full statistical analysis plan, sample-size justification for the study itself, interim analyses, and multiplicity handling are not reported in the registry record. The planning assumptions described for sample-size illustrations do not establish the trial’s design or justify its enrollment.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Reveal In-Office Implants — NCT01168427.
• Registry record last updated 2018-02-28; status last verified 2018-01.
• Results first posted 2012-07-26.
• 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

The registry record describes the completed Reveal In-Office Implants study, sponsored by Medtronic Cardiac Rhythm and Heart Failure. It lists arrhythmias, cardiac, as the condition; Reveal DX or Reveal XT Insertable Cardiac Monitor as the intervention; enrollment of 66; a study start of 2010-08; and primary completion in 2011-05.

The stated purpose was to gather evidence about safety and feasibility of implanting the monitor in an office or clinic rather than a traditional hospital operating room, cardiac catheterization laboratory, or electrophysiology laboratory. The primary endpoint concerns procedure-related complications requiring surgical intervention through 90 days after implantation, estimated using Kaplan-Meier. Its numerical result is not reported in the registry record.

The Implant Cohort safety counts list 0 affected among 65 at risk for serious adverse events and 6 affected among 65 at risk for other adverse events. The record does not describe a like-for-like comparator, and it does not explain the difference between enrollment and the safety risk counts.