Long-term Evaluation of the Linox Family ICD Leads Registry (GALAXY): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Long-term Evaluation of the Linox Family ICD Leads Registry (GALAXY) (NCT00836589), a registered phase not stated study. The primary outcome is Percentage of Subjects Who Are Free of Complications Related to the Linox ICD Lead.

2. Clinical Question

3. Trial Design

GALAXY is a registry study of the Linox family ICD leads. Its stated objective was to confirm long-term safety and reliability when the Linox Lead System was used with BIOTRONIK ICDs. The registry aimed to characterize lead failures from implant through 5 years, including failures contributing to loss of pacing or defibrillation therapy. The listed intervention is ICD therapy in an ICD lead registry, and the listed group is a Data Collection Group.

The enrollment was 1997. The registry record lists a start date of 2008-12, primary completion in 2016-12, and status as completed. Allocation is not stated. The record does not describe randomized assignment or a control group, so these data do not constitute a randomized comparison. A between-group treatment effect is not defined by the information in the record.

The primary outcome concerns the percentage of subjects free of Linox ICD lead-related complications over 5 years. The endpoint description defines these complications as serious adverse events requiring additional invasive intervention to resolve or specific non-invasive actions. The evaluable population consists of unique subjects completing 5-year follow-up and/or experiencing a primary endpoint adverse event. The number of evaluable subjects is not reported in the registry record.

Secondary outcomes include serious adverse events excluded from the primary outcome, pacing threshold, sensing, and pacing impedance measurements at scheduled follow-ups through 5 years, and electrical parameters by Linox lead model. The registry record lists 10 outcome measures and one analysis. Details of follow-up completeness, measurement schedules, and the statistical plan beyond the endpoint description are 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: The evaluable subject population is the sum of the total unique subjects who completed the 5-year follow-up and/or who experienced a primary endpoint adverse event.

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 Percentage of Subjects Who Are Free of Complications Related to the Linox ICD Lead, measured over 5 years.

The primary endpoint is the percentage of subjects who are free of complications related to the Linox ICD lead through 5 years. The record describes the endpoint as a serious-adverse-event-free rate. A qualifying complication was a serious adverse event requiring additional invasive intervention to resolve or specific non-invasive actions. This definition focuses on complications considered consequential enough to require an intervention or action, rather than every reported event.

The endpoint is intended to summarize lead-related safety over extended follow-up. A complication-free proportion can give a direct account of how many evaluated subjects remained free of the defined event during the specified follow-up period. Its interpretation depends on the endpoint definition, the population included in the denominator, and the handling of follow-up that is incomplete or unavailable.

The registry defines its evaluable population as unique subjects who completed the 5-year follow-up and/or experienced a primary endpoint adverse event. The actual evaluable denominator, observed complication-free rate, and 95% confidence interval are not reported in the registry record. Consequently, the endpoint’s numerical estimate and precision cannot be assessed from the posted results. The endpoint also does not, by itself, provide a comparison with another lead or device strategy.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary measure is a percentage of subjects free of a defined complication through 5 years. In general, a percentage summarizes the share of a specified analysis population meeting an outcome definition. Its meaning depends on who enters the denominator and what qualifies as an event. In GALAXY, the primary event is a lead-related serious adverse event requiring additional invasive intervention to resolve or specific non-invasive actions. The analysis population is described as unique subjects who completed 5-year follow-up and/or experienced a primary endpoint adverse event.

The record names a 95% confidence interval for the primary outcome. General explanation: a confidence interval expresses uncertainty around an estimate under the model and assumptions used for the analysis. A narrower interval indicates greater precision than a wider interval, while neither interval width nor the estimate alone establishes a causal treatment effect. The primary rate and the confidence interval limits are not reported in the registry record, nor is the number of subjects in the defined evaluable population. The estimate and its precision therefore cannot be reviewed.

The endpoint is not described as a time-to-event estimate. It is reported in the record as a percentage of subjects, with the timeframe of 5 years. General explanation: a percentage at a follow-up horizon and a time-to-event analysis answer related but distinct questions. A time-to-event method uses the timing of events and can account for differing observation times under its assumptions. A simple proportion instead depends on the defined denominator and how subjects with incomplete follow-up are handled. The registry record does not report further details about the primary analysis method or handling of incomplete observation.

The secondary outcomes include pacing threshold, sensing, and pacing impedance measurements at scheduled follow-ups through 5 years, as well as individual electrical parameters by Linox lead model. These are measurement outcomes rather than the primary complication-free percentage. General explanation: repeated measurements describe device or lead characteristics over follow-up, and their interpretation depends on the timing of measurements, the number of observations at each visit, and how missing measurements are handled. Those details and the numerical measurement results are not reported in the registry record.

Adverse-event summaries require attention to the unit being counted. The record reports serious adverse events, other adverse events, and deaths for the Data Collection Group, with 1997 at risk for both adverse-event categories. It does not state whether the reported counts represent unique subjects, event episodes, or a particular analysis population. Nor does it give the relationship between those counts and the primary endpoint’s evaluable population. The listed serious-event terms are reported as percentages, but their denominators and rules for multiple terms per subject are not reported in the registry record. General explanation: event counts and subject counts can differ when a person experiences more than one event, so the counting unit is essential for interpreting a summary.

The registry record lists one analysis, but a detailed statistical analysis plan is not reported in the registry record. In particular, the record does not specify adjustment methods, subgroup analysis procedures, or approaches to missing data. No method should be presumed from the endpoint name or the fact that a confidence interval is specified. The registry also lists multiple secondary outcomes. General explanation: when many outcomes are examined, the chance of observing a seemingly notable result by chance can increase, depending on the testing strategy. Whether and how multiplicity was addressed is not reported in the registry record.

Planning illustrations based on an observed effect are not the trial’s observed power. The listed planning assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with effects to detect expressed as fractions of the observed effect. These are planning assumptions, not evidence that this registry had randomized arms or used that design. Allocation is not stated, and the record does not describe a like-for-like control comparison. Such illustrations should not be read as results from the enrolled cohort or as a substitute for the missing primary estimate.

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("Data Collection Group")
n      <- c(777)
events <- c(706)
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  Data Collection Group  777  706  90.9  88.6  92.8  88.6  92.7  88.6  92.7

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary endpoint and multiple secondary outcomes, including adverse events, pacing threshold, sensing, and pacing impedance measurements, with some measures described by lead model. The record does not state how the family of outcomes was handled statistically. Whether formal multiplicity adjustment was planned or performed is not reported in the registry record. General explanation: testing or interpreting many outcomes can increase the opportunity for chance findings, so readers should distinguish a prespecified primary question from secondary or exploratory measurements. No conclusion about a multiplicity procedure can be drawn from the listed outcomes alone.

The primary endpoint uses an evaluable population defined as unique subjects who completed 5-year follow-up and/or experienced a primary endpoint adverse event. The number of subjects in that population and the number who completed follow-up are not reported in the registry record. The record does not describe how missing endpoint status, incomplete follow-up, withdrawal, or unavailable measurements were handled. It also does not report the extent or pattern of missing data. These omissions prevent assessment of whether the reported population, if a numerical primary result were available, represents all enrolled subjects or a selected subset.

The registry gives an adverse-event summary with 1997 at risk for serious and other adverse events, but the relation of those risk sets to the primary endpoint population is not stated. A risk set for an adverse-event summary should not automatically be treated as the denominator for the primary complication-free rate. The primary result and its denominator are not reported in the registry record.

A detailed statistical analysis plan, including any rules for multiplicity or missing data, is not reported in the registry record. General explanation: prespecified rules help clarify which analyses were intended and how incomplete observations affect estimates. Without those rules and the associated numerical information, the robustness of the endpoint analysis cannot be evaluated.

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: infection not due to secondary infection (1.4%), icd lead impedance out of range, low impedance, potential insulation break (1.3%), icd lead dislodgement (occuring <= 180 days post-implant procedure) (1.2%), icd lead impedance out of range, high impedance, potential conductor fracture (0.9%), ra lead dislodgement (0.9%).

The registry reports 215 serious adverse events among 1997 at risk, 31 other adverse events among 1997 at risk, and 429 deaths for the Data Collection Group. These are posted safety counts and should be kept distinct from the primary endpoint: the primary outcome concerns lead-related complications, uses a defined evaluable population, and is expressed as a serious-adverse-event-free rate. The primary rate and its denominator are not reported in the registry record.

The record lists serious-event terms with percentages, including infection not due to secondary infection at 1.4%, low impedance or potential insulation break at 1.3%, early ICD lead dislodgement at 1.2%, and several other terms at 0.9%. Those term percentages are not interchangeable with the primary endpoint. Their denominators and whether a subject could contribute to more than one term are not reported in the registry record. General explanation: a term-level percentage describes the reported frequency for that term under its counting rules; without its denominator and counting unit, it should not be interpreted as a subject-level risk.

The registry record does not explain how deaths relate to lead complications, follow-up completion, or the primary evaluable population. These counts alone do not establish the cause of events or a comparative safety difference.

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

The GALAXY registry was designed to characterize long-term safety and reliability of the Linox Lead System used with BIOTRONIK ICDs, including lead failures that could contribute to loss of pacing or defibrillation therapy. The registry identifies a five-year primary endpoint based on the percentage of evaluable subjects free of specified lead-related complications. That objective and endpoint definition describe the question of interest, but the primary numerical result is not reported in the registry record.

Without the primary rate, its 95% confidence interval, and the evaluable denominator, the posted results do not permit a quantitative assessment of the observed complication-free proportion or its precision. The adverse-event counts and term percentages provide safety information, but they cannot be substituted for the endpoint because they may refer to different event definitions, populations, or counting units. The record does not provide enough detail to resolve those relationships.

The registry is not described as randomized, and allocation is not stated. The record does not establish a like-for-like control group. Accordingly, the cohort data do not estimate a randomized comparison between the Linox lead system and another device, nor do they establish what outcomes would have occurred under an alternative strategy. Descriptive event data and causal comparative evidence answer different statistical questions.

The record also lists electrical measurements and additional adverse-event outcomes. These could characterize device performance and safety if their numerical results and analysis details were available, but those values are not reported in the registry record. Details of missing follow-up, measurement availability, multiplicity, and the statistical plan are also absent. General explanation: conclusions about long-term percentages depend not only on observed events, but on who was followed, how outcomes were defined, and how incomplete observations were treated.

The appropriate reading is therefore bounded: the registry record establishes the intended five-year safety question and reports selected adverse-event summaries, but it does not report the primary endpoint estimate needed to answer that question quantitatively. The posted information does not establish comparative effectiveness or prove the presence or absence of a treatment effect.

14. Why This Trial Matters Statistically

Long-term device registries raise statistical questions that differ from those in a short, controlled comparison. The GALAXY registry targeted complications and lead failures from implant through 5 years, including failures that could contribute to loss of pacing or defibrillation therapy. Such follow-up makes the definition of the analysis population and the handling of incomplete observation central to interpretation. The record defines an evaluable population, but does not report its size or how missing follow-up was handled.

The primary endpoint combines a clinical event definition with a subject-level percentage. Readers need to know which adverse events qualify, which subjects enter the denominator, and how uncertainty is quantified. GALAXY specifies a serious-adverse-event-free rate and a 95% confidence interval, but does not report the rate or interval limits. This illustrates an important statistical distinction: a well-defined endpoint is not itself a result, and an uncertainty measure cannot be evaluated when the estimate is absent.

The registry also lists multiple forms of evidence, including adverse-event summaries and electrical measurements such as pacing threshold, sensing, and pacing impedance. General explanation: complementary outcomes can describe different aspects of safety and device performance, but they are not interchangeable. Their denominators, follow-up availability, and analysis methods matter. Where those details are not reported, conclusions must remain limited to what the record explicitly states.

Finally, the registry does not describe a randomized comparison or a control group. Its central statistical contribution, if the primary result were reported, would be descriptive evidence about the observed cohort rather than a randomized estimate of a difference between lead strategies. The absent primary result and analysis details limit even that descriptive interpretation. Recognizing these limits helps keep the registry’s stated aim separate from what its posted numerical results can establish.

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 most important limitation for interpreting the primary question is that the registry record does not report the primary serious-adverse-event-free rate, its 95% confidence interval, or the number of subjects in the evaluable population. The endpoint is defined, but its magnitude and precision cannot be assessed. The record also does not report how many enrolled subjects completed 5-year follow-up.

The evaluable population includes unique subjects who completed follow-up and/or experienced a primary endpoint adverse event. Details explaining how this rule was implemented, how subjects with incomplete follow-up were treated, and how other missing data were handled are not reported in the registry record. This limits assessment of the denominator and potential effects of incomplete observation.

The safety summaries list 215 serious adverse events, 31 other adverse events, and 429 deaths, with 1997 at risk for each adverse-event category. The record does not clarify the event-counting unit, the relation of these summaries to the primary endpoint population, or how deaths were handled in relation to lead outcomes. The denominators for the listed serious-event term percentages are also not reported in the registry record.

Allocation is not stated, and no like-for-like control group is established. Therefore, the record does not provide a randomized comparison. A detailed statistical analysis plan, including procedures for multiplicity, missing data, and analysis of the secondary electrical measurements, is not reported in the registry record. These omissions constrain both quantitative interpretation and assessment of how robust any analysis may be.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Long-term Evaluation of the Linox Family ICD Leads Registry (GALAXY) — NCT00836589.
• Registry record last updated 2019-02-15; status last verified 2018-09.
• Results first posted 2019-02-15.
• 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 completed GALAXY registry enrolled 1997 patients indicated for an ICD to evaluate the long-term safety and reliability of the Linox Lead System used with BIOTRONIK ICDs. The registry record lists a start date of 2008-12 and primary completion in 2016-12. Its primary endpoint was the percentage of subjects free of Linox ICD lead-related complications through 5 years, expressed as a serious-adverse-event-free rate.

The endpoint’s evaluable population was defined as unique subjects who completed 5-year follow-up and/or experienced a primary endpoint adverse event. The primary estimate, 95% confidence interval, and evaluable denominator are not reported in the registry record. The record lists adverse-event counts of 215 serious events, 31 other events, and 429 deaths, and includes secondary outcomes involving adverse events and electrical measurements. Allocation is not stated, and the record does not establish a control comparison. Further details on the statistical plan, missing data, and multiplicity are not reported in the registry record.