Efficacy and Safety of ICD Remote Monitored Exercise Testing to Improve Heart Failure Outcomes: REMOTE HF-ACTION: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Efficacy and Safety of ICD Remote Monitored Exercise Testing to Improve Heart Failure Outcomes: REMOTE HF-ACTION (NCT04629066), a randomized na study. The primary outcome is Abbott Implantable Cardioverter-defibrillator (ICD) or Cardiac Resynchronization Therapy Defibrillator (CRT-D) Device Measured Daily Physical Activity (PA).

2. Clinical Question

3. Trial Design

REMOTE HF-ACTION is recorded as a completed, randomized, parallel-group pilot trial with no masking. It was conducted at a single center, and the registry records enrollment of 13. The brief summary describes an intended study of 50 medically stable outpatients; the enrollment figure for the completed trial is 13. The recorded start date is 2021-04-27, and the primary completion date is 2022-03-15.

Participants were assigned to usual care or usual care plus a remote prescription for aerobic exercise. The brief summary describes planned allocation in a 1:1 fashion. The exercise prescription was to be created by an exercise physiologist using remotely collected patient information and device measures. The usual-care arm continued regularly scheduled heart-failure team visits and medical therapy prescribed by that team. Because masking is recorded as none, participants and study staff were not masked to assignment according to the registry.

The primary outcome was device-measured daily physical activity at 12 weeks after randomization. The posted arm summaries contain endpoint data for 5 participants in usual care and 6 in the remote-exercise group; the registry notes that data were not collected on two participants. Secondary outcomes included change in the KCCQ heart-failure symptom severity score, the number of specified clinical events in a combination outcome, and the KCCQ symptom severity score. The registry does not report the randomization procedure, allocation concealment, or further operational details of trial conduct.

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: Data not collected on two participants.

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 Abbott Implantable Cardioverter-defibrillator (ICD) or Cardiac Resynchronization Therapy Defibrillator (CRT-D) Device Measured Daily Physical Activity (PA), measured over 12 weeks after randomization.

The primary endpoint is mean daily physical activity, measured in minutes per day by an Abbott implantable cardioverter-defibrillator or cardiac resynchronization therapy defibrillator. The measurement was taken at 12 weeks after randomization. In this trial, device-recorded activity provides a continuous measure of movement over time rather than a count of clinical events or a participant-reported symptom score.

As a general statistical point, a continuous endpoint can retain information across the range of observed values: participants are not reduced to categories such as having or not having an event. The mean describes the group’s average, while the standard deviation describes how dispersed individual measurements are around that average. These summaries address different features of the data and should be read together.

The registry reports a mean of 129.3 minutes per day with a standard deviation of 77.96 for usual care, and a mean of 171.4 minutes per day with a standard deviation of 74.59 for remote exercise. The posted endpoint summaries do not include a confidence interval or a formal comparison between groups. Device-measured activity is the primary outcome specified in the registry; the record does not establish how closely it corresponds to other aspects of health or daily functioning.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a mean and standard deviation describe?

The primary outcome is continuous: it is recorded in minutes per day. A group mean gives the arithmetic average of the recorded measurements. The standard deviation describes the spread of participant measurements around that mean. For usual care, the reported mean is 129.3 minutes per day and the standard deviation is 77.96. For remote exercise, the mean is 171.4 minutes per day and the standard deviation is 74.59. The mean and standard deviation answer different questions: one describes the center of the observed measurements, and the other describes their variability.

As a general statistical point, the standard deviation is not a measure of the uncertainty in a mean estimate. Uncertainty in an estimated group mean or group contrast is commonly expressed with a confidence interval or a standard error. The registry does not report a confidence interval or standard error for this primary comparison. A reader should therefore not treat the reported standard deviations as if they posted the missing interval estimate.

What would an inferential comparison add?

A formal comparison would estimate the contrast between the randomized groups and quantify the uncertainty around that estimate under a stated analysis method. A confidence interval helps show which values remain compatible with the data and the model; it is not a guarantee that the true value lies within the interval. A hypothesis test could also be reported, but the registry record contains no posted test statistic or p-value for the primary continuous outcome. The record marks the two-arm continuous comparison as not estimable in the posted analysis.

As a general matter, statistical significance and clinical importance are not interchangeable. A test result alone would not establish whether a change mattered to participants, and a non-significant result would not prove that groups were identical. Here, because no inferential comparison is posted, neither statistical significance nor equivalence can be judged from the registry summaries.

What do the planning assumptions mean?

The registry describes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. It describes the effect to detect as a stated fraction of the observed effect. These are planning assumptions, not a report of the trial’s own design justification or an estimate of the trial’s observed power. Numerical participant counts for such planning illustrations are not reported in the registry record.

As a general statistical point, a sample-size calculation estimates the number of participants needed under specified assumptions to target a chosen probability of detecting an effect of a chosen size. Its result depends on those assumptions and does not establish that the trial actually had that probability of detecting an effect. A planning exercise based on an observed effect is especially distinct from an independent, prespecified design justification. The registry does not report a sample-size justification for the completed trial, and the stated planning illustration should not be read as observed power.

What does the normal approximation assume?

A normal approximation uses a mathematical model in which an estimator’s sampling distribution is treated as approximately normal for the purpose of a calculation. As a general statistical explanation, such approximations can be less dependable when data are sparse, highly irregular, or based on very small groups. The record states that a normal approximation was used for the planning illustration; it does not identify a model for an inferential analysis of the primary outcome.

For this endpoint, the registry posts group means and standard deviations but does not describe a distributional assessment, transformation, adjusted model, or robust analysis. It also does not report whether baseline physical activity was incorporated into an analysis. Those methods cannot be inferred from the summary statistics alone. The appropriate reading is therefore limited to the recorded group summaries and the stated planning assumptions, not an assumed analysis model.

How should observed and recalculated results be distinguished?

The registry’s primary-outcome values are posted group summaries, not recalculated treatment effects. No recalculated comparison is reported for this endpoint. In general, a recalculation from posted summary statistics would be an unadjusted analysis and could differ from a sponsor’s prespecified analysis if one were available. The registry does not post a sponsor analysis for this comparison, so no such result can be used to resolve the missing inferential information.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Usual Care", "Remote Prescription for Aerobic Exercise")
n   <- c(5, 6)
m   <- c(129.3, 171.4)
sp  <- c(77.96, 74.59)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Usual Care  5  129.300  77.960  32.500  226.100
CARM  Remote Prescription for Aerobic Exercise  6  171.400  74.590  93.123  249.677

11. Multiplicity, Missing Data and Analysis Populations

The registry identifies three secondary outcomes: change in the KCCQ heart-failure symptom severity score, a combination of heart-failure hospitalization and other specified events, and the KCCQ symptom severity score. Multiple outcomes can create a multiplicity issue because testing several outcomes increases the opportunity for at least one apparently noteworthy result by chance. As a general statistical point, an analysis plan may address this through a prespecified hierarchy or adjustment method. The registry record does not report a multiplicity strategy, and no secondary-outcome analysis results are posted.

The primary endpoint notes that data were not collected on two participants. The arm summaries include 5 participants for usual care and 6 for remote exercise. The record does not explain why the endpoint data were unavailable, whether missingness differed by assignment for any reason, or whether any imputation or sensitivity analysis was performed. It also does not report an analysis population such as intention-to-treat or per-protocol, or how participants were handled in analyses after randomization.

As a general principle, missing outcome data can affect both the precision and interpretation of a comparison. The consequences depend on why data are missing and on the assumptions used in analysis; those details are not reported in the registry record. The posted summaries should therefore be understood as summaries of the endpoint data that were collected, not as evidence that missing observations had no effect.

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: stent placement (14.3%).

The registry reports serious adverse events among participants at risk in each arm: 1 affected participant out of 7 at risk in usual care, and 0 out of 6 at risk in the remote-exercise group. For other adverse events, the record reports 0 affected participants out of 7 at risk in usual care and 1 out of 6 at risk in the remote-exercise group. No deaths are reported in either arm.

The top serious adverse-event term is listed as Stent Placement at 14.3%. The record does not specify in that term listing which arm the event belongs to, so the term should not be assigned to an arm based on the listing alone. The serious-event figures are descriptive counts from this trial; their small denominators provide limited precision for comparing safety between groups.

As a general statistical point, an event count is not a complete assessment of risk. Interpretation also depends on event definitions, observation time, clinical context, and how events were collected. The registry does not provide enough detail to make those broader assessments. The reported figures should not be treated as proof of either a safety difference or equivalent safety.

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

The main result reported for the primary endpoint is a higher observed group mean for device-measured daily physical activity in the remote-exercise arm than in usual care: 171.4 versus 129.3 minutes per day at 12 weeks after randomization. The corresponding standard deviations are 74.59 and 77.96. These are summaries of the measurements collected for the endpoint, not a reported adjusted treatment effect or a formal test of the group contrast.

The result does not establish that the remote exercise prescription caused the observed difference. The registry provides no confidence interval, p-value, or formal primary-outcome comparison, and notes missing endpoint data for two participants. The small endpoint groups and observed variability mean that the group means alone do not show how precisely the contrast is estimated. Nor do these summaries establish equivalence or rule out an effect in either direction.

The finding also concerns a specific device-measured activity outcome at a specified follow-up time. It does not by itself demonstrate a change in symptoms, hospitalizations, quality of life, or other outcomes. The registry lists secondary outcomes concerning KCCQ symptoms and a combination of clinical events, but does not post their analysis results. No conclusion about those outcomes can be drawn from the primary endpoint summaries.

As a general statistical interpretation, a pilot trial can describe feasibility and generate estimates for future research, but observed estimates from a small study can be imprecise. The registry does not report a statistical design justification or a formal analysis that would support broader efficacy claims. The posted data are best read as preliminary descriptive evidence about device-measured activity in the enrolled trial population, with important uncertainty and limitations.

14. Why This Trial Matters Statistically

This trial is statistically informative because it illustrates the distinction between a trial’s randomized design and the evidence contained in its posted analysis. Random assignment creates a framework for comparing groups, but the primary outcome record contains group summaries rather than a formal contrast with uncertainty. Readers need both the observed values and an estimate of precision to judge what the comparison can support.

The gap between the intended enrollment described in the brief summary and the enrollment recorded for the completed trial also matters for interpretation. The trial is identified as a pilot, and the primary endpoint summaries are based on small groups. In that setting, standard deviations convey substantial variability, while the absence of a confidence interval leaves uncertainty about the group contrast unquantified in the posted results.

The record also highlights the importance of transparent reporting about missing data, analysis populations, and multiplicity. It notes that primary endpoint data were not collected on two participants, but does not report the reasons or handling of those observations. It lists secondary outcomes without analysis results or a multiplicity strategy. These omissions limit the ability to reconstruct the inferential analysis and assess how robust conclusions might be.

As a general lesson for clinical research, a numerical difference in group means is not interchangeable with a demonstrated treatment effect. Clear reporting of the estimand, analysis method, uncertainty, and missing-data approach is needed to move from description to inference. The available record offers a focused example of why those elements are important, particularly for a pilot with limited outcome data.

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 primary limitation is the small recorded enrollment and the still smaller endpoint groups: the mean and standard deviation are posted for 5 usual-care participants and 6 remote-exercise participants. Data were not collected on two participants for the primary outcome. The registry does not state why those data were missing or how missingness was addressed beyond reporting the observed endpoint summaries.

No formal comparison, confidence interval, or p-value for the primary endpoint is reported. The registry also does not report the analysis population, adjustment for baseline activity, a statistical analysis plan, or a sample-size justification. It therefore is not possible to assess the planned estimand or determine whether the posted summaries correspond to a prespecified analysis. The planning illustration’s assumptions do not substitute for a trial-specific design justification or an inferential analysis.

The registry records no masking, so participants and study staff knew the assigned group. The primary endpoint is device-measured, but the record does not describe details of data quality, adherence to the exercise prescription, or how incomplete device measurement was handled. The study is described as single-center, which also limits how confidently findings can be extended to other settings or populations.

Finally, the record lists secondary outcomes but does not post their analyses, and it does not report a strategy for handling multiplicity. Safety counts are descriptive and based on small risk denominators; the listing of the top serious term does not specify its group assignment. These limitations prevent strong conclusions about efficacy, safety, or effects on outcomes beyond device-measured physical activity.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Efficacy and Safety of ICD Remote Monitored Exercise Testing to Improve Heart Failure Outcomes: REMOTE HF-ACTION — NCT04629066.
• Registry record last updated 2023-09-28; status last verified 2023-09.
• Results first posted 2023-08-01.
• 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

NCT04629066 is a completed, randomized, parallel-group, unmasked, single-center pilot trial sponsored by Duke University. The recorded start date is 2021-04-27, primary completion date is 2022-03-15, and enrollment is 13. The brief summary describes a planned study of 50 medically stable outpatients with heart failure, reduced ejection fraction, and an implanted ICD or CRT-D.

The primary endpoint was Abbott device-measured daily physical activity at 12 weeks after randomization. The registry reports means and standard deviations by arm, but no formal comparison for this continuous outcome; data were not collected on two participants. Three secondary outcomes are listed without posted analysis results. Serious and other adverse-event counts and deaths are reported by arm, but the safety summaries are descriptive. The record does not report the statistical analysis plan, analysis populations, missing-data methods, or multiplicity approach.