CardioMEMS HF System OUS Post Market Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for CardioMEMS HF System OUS Post Market Study (NCT02954341), a registered phase not stated study. The primary outcome is Freedom From Device/System Related Complications.

2. Clinical Question

This is a post-market safety question, not a question about whether the device improves heart-failure symptoms or outcomes relative to another treatment. The primary endpoint is framed as freedom from complications, but the registry record does not report the corresponding participant count, proportion, estimate, or uncertainty interval. As a result, the question can be described from the endpoint definition, but its answer cannot be established from the posted primary-endpoint results.

The record identifies 321 participants as the enrollment and marks the study completed. Those details describe the study record, but they do not establish how many participants contributed data to the primary endpoint or whether all enrolled participants completed follow-up. Such details are not reported in the registry record.

3. Trial Design

The CardioMEMS HF System OUS Post Market Study is identified as a post-market study evaluating device use in patients with NYHA Class III heart failure in a commercial setting. It is marked completed, with enrollment of 321. The registry lists the start as 2016-07 and primary completion as 2023-12-08. It identifies Abbott Medical Devices as the sponsor.

The intervention is the CardioMEMS HF System, classified as a device. The record does not describe a comparator group or state an allocation method. It also does not describe the study as a randomized comparison; the registry specifically indicates that it is not a randomized comparison and that allocation is not stated. Consequently, there is no basis for interpreting any group contrast as a randomized treatment effect or as a comparison between like-for-like arms.

The primary endpoint applies to patients who signed the study informed consent and underwent CardioMEMS implant. Its stated timeframe is Two year. The registry also lists 3 outcome measures, but records 0 analyses. The primary-endpoint result itself is not reported in the registry record.

Safety information is reported for a Safety Population, with 304 participants at risk for each of the serious and other adverse-event summaries. These safety counts should not be treated as the primary endpoint result: the registry does not link them to the endpoint’s definition or provide a primary-endpoint analysis. Enrollment and safety-population counts describe different record entries, and the registry does not explain the relationship between them.

Other design details—including site structure, eligibility criteria beyond the described endpoint population, follow-up procedures, monitoring schedules, and the full statistical analysis plan—are not reported in the registry record. The commercial-setting and post-market descriptions establish the broad context, but do not fill in those methodological details.

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: Patients who signed the study Informed Consent and underwent CardioMEMS implant

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: Patients who underwent a successful implant constitute the Effectiveness Population

6. Primary Endpoint

The registry lists the primary outcome as Freedom From Device/System Related Complications, measured over Two year.

The primary endpoint is titled “Freedom From Device/System Related Complications.” It is measured as a count of participants over a Two year timeframe, in the population of patients who signed the study informed consent and underwent CardioMEMS implant. The registry defines a device/system-related complication as an adverse event that is, or is possibly, related to the wireless pressure sensor or external electronics and has at least one specified characteristic.

The listed characteristics are treatment with invasive means, except intramuscular medication or right heart catheterization used for diagnostic purposes; resulting in the participant’s death; or resulting in explant of the device. This definition focuses the endpoint on complications with specified clinical or procedural consequences, rather than on every adverse event regardless of seriousness or relationship to the device.

In general, a participant-level binary safety endpoint distinguishes participants who meet the event definition from those who do not within the specified follow-up period. A count can then describe how many participants meet one of those categories, but interpretation also requires the relevant denominator and a clear account of follow-up and missing outcomes. A proportion or uncertainty interval can help convey precision, but neither is reported for this primary endpoint in the registry record.

The endpoint is useful as a focused post-market safety measure because it applies an explicit device-related event definition. It does not, by itself, assess symptom change, comparative benefit, or all possible harms. The registry record does not report the observed count of participants free from complications or the count who experienced a qualifying complication.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the primary outcome as a participant count and describes it as freedom from device/system-related complications. This is a binary-outcome framework: a participant either meets the specified event definition during the relevant follow-up or does not. The definition includes an adverse event that is or may be related to the wireless pressure sensor or external electronics, together with at least one specified seriousness characteristic. Those characteristics include invasive treatment, with stated exceptions; death; or device explant.

What does a participant count tell the reader?

A count is a direct description of how many participants fall into an outcome category. To assess its scale, readers ordinarily need to know the denominator: the number of participants eligible for assessment and the number whose outcome status is known. A proportion expresses the count relative to that denominator, while a confidence interval describes the uncertainty around an estimate. In general, a confidence interval is a range of values compatible with the data and analysis assumptions; it conveys precision, not certainty that the true value lies within the reported range.

For this endpoint, the registry record gives the population definition and timeframe but does not report the primary result, denominator for the analysis, proportion, or confidence interval. It is therefore not possible to assess the estimated frequency of endpoint events or its precision from the posted primary-endpoint information. The safety population’s at-risk count is reported separately and should not be assumed to be the primary endpoint denominator.

How should the study design affect interpretation?

The record describes a post-market study in a commercial setting and does not identify a comparator or allocation method. It specifically indicates that the study is not a randomized comparison and that allocation is not stated. In general, random allocation can help balance measured and unmeasured factors between comparison groups. Without a randomized comparison, observed outcomes can describe the study population, but they do not by themselves isolate a treatment effect from other explanations, such as differences in participant characteristics, clinical care, or follow-up.

The registry’s sample-size assumptions describe a planning illustration, not the study’s own design. The illustration is based on the observed effect and specifies a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect to detect expressed as a stated fraction of the observed effect. These assumptions do not establish that the study had two actual arms or used that analysis. They also do not constitute observed power. Sample-size calculations are planning exercises: their results depend on assumptions about the effect and design, and they cannot retrospectively show how likely a study was to detect an effect that occurred.

The record does not state the trial’s sample-size justification or analysis plan. It also does not report an effect estimate for the primary endpoint from which readers could assess the planning illustration. Those details are not reported in the registry record.

What do the safety summaries represent?

The safety information reports affected participants and participants at risk for serious and other adverse events. In general, participant counts differ from event counts: one participant may experience more than one event, and a set of event terms may describe overlapping categories. The record does not provide enough detail to determine the counting convention for the listed serious-event terms or whether participants could appear under multiple terms. The terms and their percentages should therefore be read as registry descriptions, not as exclusive partitions of the safety population.

Over-dispersion is a general issue in some event-count analyses: variability can exceed what a simple model assumes, especially when events cluster within participants or populations are heterogeneous. It is relevant when a suitable count model is being fitted, but the registry record does not report such a model for this study. The primary outcome is described as a participant count, and no analysis methods are registered. It would be inappropriate to claim that an over-dispersion adjustment was used or was needed in the study’s analysis.

For time-to-event outcomes, analyses can account for how long participants are observed and when events occur. The primary endpoint is described as a participant count within a Two year timeframe, not as a reported time-to-event estimate. The record does not give event times, censoring details, or a time-to-event analysis. Follow-up completeness and the treatment of participants without known endpoint status are also not reported in the registry record.

Finally, a reported analysis would ordinarily identify its population, outcome definition, estimator, uncertainty measure, and handling of missing data. The registry gives an endpoint definition and a safety population, but records 0 analyses. The statistical methods used for the primary endpoint and safety summaries are not reported in the registry record. As a result, descriptive counts can be quoted as recorded, but inferential claims about precision, comparative effects, or adjusted associations cannot be reconstructed from the information available.

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("Safety Population")
n      <- c(304)
events <- c(304)
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  Safety Population  304  304  100.0  98.8  100.0  98.8  100.0  98.8  100.0

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 3 outcome measures and records 0 analyses. It does not identify which outcomes were treated as primary or secondary beyond the primary endpoint described in the record, and it does not report a multiplicity strategy. In general, when researchers test several outcomes or conduct multiple comparisons, the chance of a false-positive finding can increase. Methods for addressing multiplicity may include prespecifying a primary outcome, adjusting tests, or treating additional outcomes as exploratory. No such approach is reported in the registry record, so it is not possible to assess whether or how multiplicity was handled.

The primary endpoint population is defined as patients who signed informed consent and underwent CardioMEMS implant. Safety results are reported for a Safety Population. The record does not describe the criteria used to form that safety population, how it relates to the endpoint population, or whether other analysis populations were used. Those details are not reported in the registry record.

Missing-data handling is also not described. The record does not state whether all participants had endpoint status assessed, how incomplete follow-up was handled, or whether any imputation or sensitivity analysis was used. In general, missing outcomes can affect interpretation if participants with unknown status differ from those with complete follow-up. Without counts and methods describing missingness, the direction or size of any such effect cannot be determined.

The absence of registered analyses should not be taken to mean that no analyses were performed; it means the registry record does not contain analysis entries. The analysis plan, multiplicity procedures, and missing-data methods are not reported in the registry record.

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: decompensated heart failure (44.1%), other (43.1%), infection (14.1%), abnormal heart rate or rhythm (13.2%), renal failure (10.5%).

The Safety Population summary reports 225 participants affected among 304 at risk for serious adverse events and 17 affected among 304 at risk for other adverse events. The record also lists 90 deaths. These figures are registry safety summaries, not the result of the primary endpoint analysis.

The listed serious-event terms and percentages are Decompensated Heart Failure (44.1%), Other (43.1%), Infection (14.1%), Abnormal heart rate or rhythm (13.2%), Renal Failure (10.5%), and Chest pain - cardiac (4.6%). The registry does not state the denominator or counting convention for these term percentages, or whether a participant can contribute to more than one term. They should not be read as mutually exclusive categories or combined into a total.

The record does not say whether the deaths were related to the device, the study, or a particular adverse event. It also does not report timing, causes, or how deaths relate to the serious-event count. The primary endpoint includes death only when it is part of an adverse event judged or possibly judged related to the device/system and meeting the endpoint definition. The separate death count cannot be assumed to represent that endpoint criterion. These safety figures describe what the registry records; they do not establish causation or provide a comparison with another group.

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

The record provides useful context: this was a completed post-market study of the CardioMEMS HF System in a commercial setting, with enrollment of 321, and it defines a safety endpoint for implanted participants. It also reports adverse-event summaries for a Safety Population. These details describe the study and its recorded safety information.

They do not answer the primary safety question. Although the endpoint is defined as freedom from device/system-related complications over a Two year timeframe, the registry does not report the result for that endpoint. No primary endpoint count, denominator, estimate, or confidence interval is included. Therefore, the record does not establish how often participants were free from qualifying complications or how precisely that outcome was estimated.

The adverse-event figures should not be mistaken for a causal estimate. The registry does not describe a randomized comparison or a like-for-like control group. Observed safety counts in a study population can document events, but without an appropriate comparison they cannot show that the device caused or prevented an event, or determine what outcomes would have occurred under another treatment.

The endpoint is also narrower than overall clinical benefit or harm. It focuses on specified device/system-related complications and seriousness characteristics. It does not, on its own, establish changes in symptoms, heart-failure status, survival, or quality of life. The record does not report results for those questions in the information.

Accordingly, the posted record supports a description of the study design context, endpoint definition, and safety counts. It does not support a conclusion about the primary endpoint’s observed frequency, a treatment effect, or comparative safety. Missing analysis and follow-up details also limit assessment of precision and completeness. These are limits of what the registry record reports, not evidence that the study did or did not conduct analyses outside the registry.

14. Why This Trial Matters Statistically

Post-market studies address device use in clinical settings after market introduction. Statistically, their safety findings are most informative when the event definition, population, follow-up, denominator, and analysis are clear. The CardioMEMS HF System study record gives a specific device/system-related complication definition and identifies the intended endpoint population. That specificity helps readers understand what the primary safety outcome was designed to capture.

At the same time, an endpoint definition is not an endpoint result. The record identifies a Two year timeframe but does not report the number of participants who met the endpoint categories or an uncertainty estimate. This distinction is important: a carefully defined outcome cannot be interpreted quantitatively without its observed data and analysis.

The record also illustrates why design context matters. A post-market study in a commercial setting can describe outcomes in its enrolled population, but the registry does not identify a randomized comparison or comparator. Without a like-for-like comparison, event counts do not isolate effects attributable to the device. Descriptive safety information still has value, but it answers a different question from a comparative trial.

Finally, the distinction between event terms and participants matters. The safety summaries count affected participants, while the listed serious-event terms carry percentages whose denominator and overlap rules are not reported. Readers should avoid treating the categories as a complete partition or interpreting them as independent estimates. The record’s missing primary analysis, multiplicity information, and missing-data methods further limit statistical interpretation. Together, these features show why registry records need both transparent definitions and complete results for reliable 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.

The most consequential limitation is that the registry record does not report the primary endpoint result. The endpoint is defined, and its timeframe and population are stated, but the record gives no primary outcome count, denominator, estimate, or confidence interval. No quantitative conclusion about freedom from device/system-related complications can be drawn from that information.

The study is not described as a randomized comparison, and allocation is not stated. No comparator is reported, so the safety counts cannot be interpreted as a controlled estimate of device-related risk or benefit. The record also does not explain the relationship between the primary endpoint population and the Safety Population.

Although enrollment is listed as 321, the record does not report endpoint follow-up completeness or explain how that enrollment relates to the 304 participants at risk in each safety summary. The reason for any difference is not reported in the registry record. The listed count of deaths is not accompanied by causes, timing, or attribution, and cannot be treated as a count of device-related deaths.

The serious-event term percentages lack a stated denominator and counting convention. The record does not say whether terms overlap or whether participants can be represented more than once. The analysis plan, methods for missing outcomes, multiplicity procedures, and confidence-interval methods are also not reported. The registry lists 3 outcome measures and 0 analyses, leaving the inferential approach unclear.

Finally, the study’s sample-size justification and actual analysis plan are not reported. The planning illustration assumptions do not establish the study’s design or analysis. These gaps restrict assessment of precision, completeness, and causal interpretation, even though the registry provides a clear endpoint definition and descriptive safety information.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: CardioMEMS HF System OUS Post Market Study — NCT02954341.
• Registry record last updated 2025-02-24; status last verified 2024-11.
• Results first posted 2025-02-24.
• 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 CardioMEMS HF System OUS Post Market Study is a completed post-market study of device use in patients with NYHA Class III heart failure in a commercial setting. The registry lists Abbott Medical Devices as sponsor, enrollment of 321, a start of 2016-07, and primary completion on 2023-12-08.

The primary endpoint is freedom from device/system-related complications among patients who signed informed consent and underwent implant, over a Two year timeframe. The registry defines qualifying complications by their relationship to the device/system and specified seriousness characteristics, but does not report the endpoint result.

The Safety Population summary reports 225 participants affected among 304 at risk for serious adverse events, 17 affected among 304 at risk for other adverse events, and 90 deaths. The record lists 3 outcome measures and 0 analyses. It does not report a comparator, allocation method, primary-endpoint analysis, missing-data methods, or the relationship between safety and endpoint populations. The descriptive safety figures do not establish causation or a comparative treatment effect.