Extravascular ICD Pivotal Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Extravascular ICD Pivotal Study (NCT04060680), a non-randomized na study. The primary outcome is Safety Outcome - Freedom From Major Complications Related to the EV ICD System and/or Procedure at 6 Months Post-implant.

2. Clinical Question

3. Trial Design

The Extravascular ICD Pivotal Study (EV ICD) is listed as a completed, non-randomized, single-group device study. It enrolled 393 participants and lists tachycardia and ventricular arrhythmia as conditions. The intervention is defibrillation using the Extravascular ICD. The registry record gives the sponsor as Medtronic Cardiac Rhythm and Heart Failure.

The pivotal study description says participants would be implanted with an extravascular ICD and undergo requisite electrical testing. The record also describes a continued access group for the United States. Those descriptions identify two study contexts, but do not make the continued access group a randomized control. Because allocation was non-randomized and the study model is single-group, differences between the pivotal and continued access groups cannot be interpreted as treatment effects from a controlled comparison.

The listed primary safety endpoint concerns subjects who underwent an implant attempt. It captures the first qualifying major complication related to the device system and/or procedure through six months (182 days) post-implant, as determined by an independent Clinical Events Committee. The record lists two outcome measures and two analyses, but does not report the primary endpoint’s numerical result, statistical estimate, or confidence interval.

The study is marked completed. Its listed start date is 2019-09-16 and its primary completion date is 2022-04-28. Phase is listed as NA. The registry record does not report the randomization process, masking procedures, a protocol sample-size justification, interim analyses, or the detailed statistical plan. The enrollment figure alone does not show how many participants contributed data to each endpoint or analysis.

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: Among 356 enrolled subjects, 40 exited the study without having an implant attempt of the Extravascular ICD System due to: adverse event (2), physician decision (7), procedure not attempted (4), sponsor request (1), withdrawal by subject (10), and other reasons (16).

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Subjects who underwent an implant attempt of the Extravascular ICD System

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: Subjects who underwent an implant attempt of the Extravascular ICD System

6. Primary Endpoint

The registry lists the primary outcome as Safety Outcome - Freedom From Major Complications Related to the EV ICD System and/or Procedure at 6 Months Post-implant, measured over 6 Months (182 days) post implant.

The primary safety endpoint is freedom from major complications related to the EV ICD System and/or procedure at six months post-implant. The registry record defines a qualifying event as a subject’s first occurrence of a major complication, determined by an independent Clinical Events Committee, that occurs on or before six months (182 days) post-implant. The endpoint population is subjects who underwent an implant attempt.

Using the first qualifying complication gives the endpoint a clear event-based definition: a participant’s initial event is what counts for this measure, rather than a tally of every subsequent complication. The six-month time point sets a common follow-up window for assessing early safety after implantation. Independent committee determination can provide a consistent review of whether events meet the endpoint definition; the registry record does not describe the committee’s procedures or adjudication rules in further detail.

The endpoint is expressed as freedom from complications, but the record does not report how many participants were free from a major complication, how many experienced one, or an estimated rate. It also does not report a confidence interval or other measure of precision. As a result, the endpoint definition is available, but its observed numerical outcome is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What the endpoint counts. The primary endpoint is a binary participant-level outcome: whether a participant had a first qualifying major complication by the specified follow-up time, or remained free of such a complication. The registry record defines the qualifying event as major, related to the EV ICD System and/or procedure, and determined by an independent Clinical Events Committee. In general, a binary endpoint records whether an event happened, rather than how many times it happened or how severe it was on a continuous scale. The record does not report the observed count or the statistical estimate for this endpoint.

What a rate or proportion would mean. In general, an event proportion describes the number of participants with an event relative to the number assessed in the relevant analysis population. For this trial, the endpoint population is subjects who underwent an implant attempt. The total enrollment of 393 does not establish that this many participants entered that endpoint population or had complete follow-up. The number who underwent an implant attempt and the number included in the endpoint analysis are not reported in the registry record. A rate calculated using an inappropriate denominator could misrepresent the endpoint, so the population definition and follow-up status matter.

Precision and confidence intervals. In general, a confidence interval describes the uncertainty around an estimate under a specified statistical model and procedure. It helps distinguish a relatively precise estimate from one compatible with a wide range of values. An estimate without an interval gives less information about precision. The registry record does not report a primary endpoint estimate or confidence interval, so the precision of the primary safety result cannot be assessed from the listed endpoint description. A confidence interval, if reported, would not by itself correct limitations arising from a non-randomized design or incomplete information about the analysis population.

Study design and comparisons. The study is identified as non-randomized and single-group. In general, random allocation can help make treatment groups comparable on average, whereas a non-randomized comparison may reflect differences in who entered each group, when they entered, or how they were followed. The pivotal and continued access groups are both named in the record, but no randomized comparison is described. Their counts should therefore be treated as descriptive group information, not as an estimate of what would have happened under an alternative intervention. The registry record does not report an adjusted comparative analysis or a protocol-defined comparator.

Events and event adjudication. The endpoint definition uses the first occurrence of a qualifying complication and assigns its determination to an independent Clinical Events Committee. In general, adjudication is a process for applying endpoint criteria to event information. It can support consistent classification, but its value depends on the criteria and procedures used. The record does not report the committee charter, adjudication rules, or how disagreements were handled. Nor does it give the number of events adjudicated for this primary endpoint.

Serious adverse-event counts. The registry record lists serious and other adverse-event counts by enrolled group, alongside deaths and selected serious-event terms with percentages. These figures have a different role from a defined primary endpoint analysis. In general, adverse-event summaries describe events recorded during a study, while a primary endpoint follows a specific definition, population, and time window. An adverse event’s seriousness does not, by itself, establish that it was caused by the device or procedure. The record does not provide the event definitions, attribution rules, or detailed timing needed to resolve those questions for each listed count.

Planning illustrations. The registry record describes a sample-size planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. In general, a planning calculation estimates the sample size associated with chosen assumptions; it is not a summary of the data collected. These assumptions are not reported as the trial’s own design justification, and the illustration should not be read as observed power. The registry record does not report a protocol sample-size justification. The numerical planning results and the effect fractions are not reported in the registry information.

What cannot be reconstructed. The record lists two outcome measures and two analyses, but does not give the detailed statistical methods, model specifications, analysis populations, missing-data procedures, or handling of multiplicity. General statistical principles cannot fill those record-specific gaps. Without the primary outcome count and denominator, an unadjusted estimate cannot be recalculated from the endpoint description. Any such estimate would require information 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("Implant Attempt")
n      <- c(316)
events <- c(293)
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 Attempt  316  293  92.7  89.3  95.3  89.3  95.1  89.3  95.1

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists two outcome measures and two analyses. It does not report whether the analyses were confirmatory or exploratory, which outcomes were considered primary for inferential purposes beyond the listed primary safety endpoint, or whether any adjustment for multiple testing was planned or used. Multiplicity refers, in general, to the increased chance of a false-positive finding when several statistical hypotheses are tested. Whether and how that issue was addressed is not reported in the registry record.

The record also does not describe missing-data handling, participant withdrawal, loss to follow-up, or the extent of incomplete endpoint assessments. The primary endpoint has a defined six-month (182 days) follow-up window, but the description does not state how participants without a complete assessment were handled. In general, missingness can affect an estimate if participants with unobserved outcomes differ from those whose outcomes are known. The registry record does not provide enough information to evaluate that possibility.

The primary endpoint population is subjects who underwent an implant attempt. The total enrollment of 393 does not establish the size of this analysis population, and the number included in the primary analysis is not reported in the registry record. The record does not describe additional analysis populations or explain how deviations from the endpoint definition were handled. These gaps limit interpretation of both the denominator and the analysis process.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: device inappropriate shock delivery (6.5%), cardiac failure (4.2%), atrial fibrillation (3.9%), hypotension (3.1%), lead dislodgement (2.8%).

The registry record lists serious adverse events by enrolled group. For Enrolled Pivotal, it lists 356 at risk and 172 affected by serious events; it lists 356 at risk and 20 affected by other events, and 7 deaths. For Enrolled Continued Access, it lists 37 at risk and 6 affected by serious events; it lists 37 at risk and 2 affected by other events, and 1 death. These are descriptive counts, not a randomized comparison.

The serious-event terms with listed percentages are device inappropriate shock delivery at 6.5%, cardiac failure at 4.2%, atrial fibrillation at 3.9%, hypotension at 3.1%, lead dislodgement at 2.8%, and atrial flutter at 2.7%. The record does not report the denominator or further calculation details for these percentages in the information available. It also does not establish that the terms are mutually exclusive, so they should not be added together.

In general, “serious” describes an event category and does not itself establish that an event was caused by the intervention. These adverse-event figures should also be distinguished from the primary safety endpoint, which has a particular definition, population, and six-month follow-up window. The registry record does not state that the adverse-event counts are the primary endpoint counts.

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

The registry record establishes that the study examined a safety endpoint defined as freedom from a first major complication related to the EV ICD System and/or procedure through six months (182 days) post-implant. It identifies the endpoint population as subjects who underwent an implant attempt and says an independent Clinical Events Committee determined whether an event qualified. These details explain what the primary safety question concerns.

However, the record does not report the primary endpoint’s observed count, estimate, or confidence interval. It therefore does not show how often participants experienced a qualifying complication or how precisely an estimated freedom-from-complication result might be known. Enrollment of 393 cannot fill that gap because the endpoint population may differ from total enrollment, and its size is not reported in the registry record.

The listed adverse-event counts and serious-event percentages provide additional descriptive safety information, but they do not answer the primary endpoint question. They also do not establish causation. The design is non-randomized and single-group, so the record does not support a randomized comparison with an alternative intervention. The continued access group should not be treated as a control group simply because it is listed separately.

In general, statistical interpretation depends on the outcome definition, the population assessed, the estimate, and its precision. Here, the endpoint definition and selected safety counts are available, but the primary endpoint estimate and key analysis details are not reported in the registry record. The appropriate conclusion is therefore limited: the record describes the study’s intended safety measure and reports selected adverse-event figures, but it does not provide the numerical primary result or a controlled estimate of comparative effect. No conclusion about treatment benefit or lack of benefit follows from these omissions.

14. Why This Trial Matters Statistically

This study illustrates why an endpoint definition alone is not enough to interpret a clinical trial result. The registry record specifies a first major complication, a relationship to the device system and/or procedure, independent committee determination, a population that underwent an implant attempt, and follow-up through six months (182 days). Each element defines which observations would count toward the primary safety outcome.

For a statistical interpretation, those details need to be paired with the observed event count, the number of participants assessed, and an estimate with an indication of precision. The record does not report those primary endpoint results. That absence makes it impossible to tell from the registry information how the endpoint was distributed among participants or how uncertain an estimate would be.

The design is also statistically important. Non-randomized, single-group studies can describe outcomes among enrolled participants, but do not have the randomized counterfactual comparison that supports a causal contrast between assigned interventions. The pivotal and continued access groups are not a like-for-like control comparison based on the record. Treating their separate counts as evidence of comparative effect would go beyond the design information reported.

Finally, the record distinguishes a primary safety endpoint from broader adverse-event summaries. Selected serious-event counts and terms can help characterize what was recorded, but they are not interchangeable with the defined endpoint. This case underscores the importance of checking the endpoint population, follow-up window, event definitions, analysis methods, and missing-data information before interpreting either a point estimate or a list of adverse events.

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 main limitation for interpretation is that the registry record does not report the primary safety endpoint result. There is no primary event count, freedom-from-complication estimate, or confidence interval in the record described. The endpoint population is defined as subjects who underwent an implant attempt, but the number of such subjects and the number assessed at six months are not reported. Total enrollment of 393 cannot be assumed to be the primary analysis denominator.

The study is listed as non-randomized and single-group. It therefore does not provide a randomized comparator, and the continued access group should not be treated as one. The registry record does not report a controlled analysis that could address differences between these groups. The record also does not provide detailed participant characteristics that would allow assessment of group comparability.

Important analysis details are not reported in the registry record, including the statistical model, confidence interval method, missing-data handling, multiplicity procedures, and analysis populations. The record lists two outcome measures and two analyses, but does not explain their inferential roles. It does not report the protocol’s sample-size justification, interim analyses, or detailed statistical plan.

The adverse-event summaries have their own interpretive limits. Definitions and attribution rules are not described in detail, and the denominator or calculation method for listed serious-event percentages is not stated in the registry information. The record does not establish that event terms are mutually exclusive or that serious events were caused by the device or procedure. These limitations restrict interpretation to the reported descriptions and counts.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Extravascular ICD Pivotal Study — NCT04060680.
• Registry record last updated 2024-11-19; status last verified 2024-04.
• Results first posted 2023-07-03.
• 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 Extravascular ICD Pivotal Study (EV ICD) is listed as a completed, non-randomized, single-group device study with 393 enrolled participants. Its intervention is defibrillation using the Extravascular ICD. The primary safety endpoint is freedom from a first major complication related to the device system and/or procedure through six months (182 days) post-implant, determined by an independent Clinical Events Committee, among subjects who underwent an implant attempt.

The registry record lists adverse-event counts for Enrolled Pivotal and Enrolled Continued Access groups and selected serious-event terms with percentages. It does not report the numerical primary endpoint result, its estimate, or a confidence interval. Detailed statistical methods, missing-data procedures, and multiplicity handling are also not reported in the registry record. The non-randomized, single-group design does not support treating the continued access group as a randomized control.