Micra Accelerometer Sensor Study 2: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Micra Accelerometer Sensor Study 2 (NCT02930980), a na na study. The primary outcome is Waveform and Components of Accelerometer Signal.

2. Clinical Question

3. Trial Design

MASS2 is recorded as a completed, single-group study of investigational software loaded onto a Micra device. The registry record lists an enrollment of 43 and the condition as bradyarrhythmia. The study start date is 2016-10-14, and the primary completion date is 2017-04-25. Its phase is listed as NA.

The stated purpose was to characterize accelerometer signals during different postures and activities and to understand the source of sensed motion. The stated aim was to test feasibility for future enhancements in device functionalities. The intervention is described as investigational software loaded on the Micra device. Allocation is listed as NA, and masking as none. There is no like-for-like control group described in the record, so comparisons between intervention and control arms do not apply.

The primary outcome concerns the waveform and components of the accelerometer signal, measured using the Micra accelerometer’s three axes. The stated measurement timeframe is approximately two hours after software download. The record describes exclusions from analysis for some enrolled subjects, but it does not report the final analysis population or its size. It also does not report numerical results for the primary outcome. One outcome measure is listed, while the number of analyses is listed as zero.

Information about the protocol’s sample-size justification, prespecified statistical plan, interim analyses, or any control condition is not reported in the registry record. The registry status is completed, but completion status alone does not supply outcome estimates or establish how the data were analyzed.

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

Analysis population for the primary outcome, as defined in the registry: Of the 43 subjects enrolled, 12 with Atrial tachycardia / Atrial fibrillation and 2nd degree or greater atrioventricular block were excluded from analysis since the A4 signal is absent or variable. An additional 4 subjects in sinus rhythm were excluded from analysis due to frequent pacing or telemetry noise, resulting in 27 subjects for analysis.

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 Waveform and Components of Accelerometer Signal, measured over For approximately two hours after software download.

The primary endpoint is titled “Waveform and Components of Accelerometer Signal.” It describes accelerometer signal measured by the three-axis Micra accelerometer, with axes labelled V1, V2, and V3. The listed outcome summary is the mean, with standard deviation as the measure of dispersion. The unit is g, representing acceleration. Measurements were taken for approximately two hours after software download.

The registry record identifies four signal components: A1, associated with ventricular systole; A2, associated with ventricular diastole; A3, associated with early passive filling; and A4, associated with active filling. It further describes A4 as associated with atrial contraction and active filling. The record says that the A4 signal can be absent or variable in the specified atrial tachycardia or atrial fibrillation and atrioventricular-block population, which is why those subjects were excluded from analysis.

In general, characterizing a waveform and its components can help describe the timing and structure of a measured signal. A mean conveys its average level, while a standard deviation describes the spread of observations around that mean. Those summaries do not, by themselves, establish why a signal occurs or whether it differs across conditions. Numerical estimates, comparisons, and a detailed analysis of the waveform are not reported in the registry record, so the endpoint’s observed values and precision cannot be assessed from the record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry lists the primary outcome as a continuous measure summarized by a mean and standard deviation. These summaries answer different descriptive questions. In general, the mean describes the central level of a set of measurements, while the standard deviation describes how dispersed the measurements are around that mean. Neither statistic alone describes every feature of a waveform, and neither establishes a cause for observed signal patterns. The record does not provide numerical means or standard deviations for the identified components.

What does the three-axis measurement represent?

The Micra accelerometer measurement is described as using three axes, labelled V1, V2, and V3. A three-axis sensor records motion along different directions. The registry also identifies waveform components A1, A2, A3, and A4, associating them respectively with ventricular systole, ventricular diastole, early passive filling, and active filling. A4 is described as associated with atrial contraction and active filling. These labels describe the intended interpretation of signal components; the record does not provide numerical estimates or a method for determining the components from the waveform.

The unit is g, which the record identifies as a unit of acceleration. The measurement timeframe is approximately two hours after software download. This timeframe identifies when measurement was intended to occur; it does not state how many measurements were taken, how they were summarized over time, or whether the measurement period was the same for every subject. Such details are not reported in the registry record.

How should a standard deviation be understood?

In general, a standard deviation describes the spread of observations around their mean on the same measurement scale. A smaller spread indicates that observations are more clustered around the mean, while a larger spread indicates greater dispersion. It is not a measure of uncertainty in the mean itself. A confidence interval, when calculated and reported, addresses uncertainty around an estimate under a specified statistical method. The registry record does not report confidence intervals or the methods used to calculate them.

For a waveform, a mean and standard deviation can provide a concise summary, but these summaries may not capture timing, shape, or changes across posture and activity. The study’s stated purpose involves different postures and activities, yet the registry record does not give a breakdown of outcome summaries by posture, activity, axis, or component. It also does not report whether repeated measurements were modeled or how within-subject dependence was handled. These are material details for interpreting repeated sensor observations, and they cannot be inferred from the listed endpoint description.

What does the single-group design permit?

The study is listed as single-group, with allocation NA and masking none. In general, a single-group descriptive study can characterize measured signals in the studied group, but without a control group it cannot estimate a between-group contrast. Lack of masking may also be relevant when human decisions affect measurement or classification, although the record does not describe whether such decisions were involved. The registry does not report a comparison group, randomization procedure, or blinding procedure.

The registry lists one outcome measure and zero analyses. It does not report a statistical analysis plan, prespecified contrasts, handling of multiple measurements, or a method for accounting for repeated observations. It would therefore be inappropriate to attribute an unreported analytic approach to the study. The planned sample-size illustrations use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They are planning illustrations, not observed power, and those assumptions do not describe the single-group design listed for MASS2.

In general, over-dispersion means that variation in data is greater than expected under a chosen statistical model. It can make model-based uncertainty estimates too small if the model does not account for the extra variation. The registry does not report a model, a dispersion assessment, or a finding of over-dispersion for this study; this concept is relevant only as general statistical context, not as a reported feature of MASS2.

What can be concluded from the posted analysis information?

The registry describes the measurement and signal-component labels, but reports no numerical primary-outcome results and lists zero analyses. Thus, readers cannot assess the observed means, standard deviations, uncertainty, or any formal comparison from the registry record. The protocol’s statistical plan, sample-size justification, and interim-analysis approach are not reported in the registry record. Those absences limit the ability to distinguish prespecified methods from exploratory work or to evaluate the precision and robustness of any result.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure and zero analyses. It does not report a multiplicity adjustment, a hierarchy of endpoints, or a prespecified set of statistical tests. The endpoint description includes three sensor axes and four labelled waveform components, but the record does not state whether these were analyzed as separate outcomes or how any multiple comparisons were handled. It would therefore be inappropriate to assume either that a multiplicity problem was present or that it was addressed.

Information about missing data is not reported in the registry record. The record does describe subjects excluded from analysis: 12 with specified atrial tachycardia or atrial fibrillation and second-degree or greater atrioventricular block because the A4 signal is absent or variable, plus an additional 4 subjects in sinus rhythm due to frequent pacing or a reason recorded only as beginning with “telemet.” The final analysis population, the handling of missing measurements, and the analysis denominator are not reported.

The analysis-population definition is also not reported in the registry record beyond those exclusion statements. The record does not explain whether exclusions were determined before or after measurements, whether all enrolled subjects received the software, or how incomplete or unusable signals were treated. These details matter because the reported endpoint depends on identifiable signal components, and the stated exclusion reason for the first group directly concerns A4. Without an analysis population and an explicit missing-data approach, the representativeness of the analyzed measurements and the potential effects of exclusions cannot be evaluated.

11. 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.

The serious adverse event figures are reported for the Investigational Software group, with 43 at risk and 0 affected. The other adverse-event figures also list 43 at risk and 0 affected, and deaths are listed as 0. No top serious adverse-event terms are listed. These are the recorded counts in the registry; they are not estimates of comparative risk because no control group is reported.

In general, an at-risk count gives context for the group in which events were monitored or recorded, while an affected count gives the number with the specified event category. A recorded count of zero does not establish that an event is impossible, nor does it establish the frequency that would occur in a different population or over a different observation period. The registry record does not report detailed safety-monitoring procedures, event definitions, the safety observation period, or further event-level information.

The at-risk figures should not be treated as the primary-outcome analysis population. The record reports exclusions from the signal analysis, but it does not say whether the safety population used the same inclusion rules. The serious adverse event counts describe the listed registry figures only and do not provide a masked or randomized safety comparison.

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

MASS2 addresses a measurement and feasibility question: how the Micra accelerometer signal and its labelled components can be characterized after investigational software is loaded onto the device. The registry record describes a three-axis sensor, signal components associated with phases of ventricular activity and filling, and a measurement period of approximately two hours after software download. It also states that the study aimed to understand the source of sensed motion during different postures and activities.

What the record does not establish is the observed size or variability of any signal component. Although the primary outcome is specified as a mean with standard deviation, numerical results are not reported. The record also does not report analyses comparing components across axes, postures, or activities. Therefore, no conclusion about the direction, magnitude, consistency, or statistical precision of any observed pattern can be drawn from the registry information.

The study is listed as single-group and unmasked, with no control comparison. It cannot, on the basis of the design information in the record, establish a difference between software and a control condition. Nor does the registry’s description of a feasibility aim amount to a reported finding that a future device enhancement is feasible or beneficial. The posted information concerns sensor characterization, not a clinical-effect estimate.

The exclusions are important to the scope of interpretation. The registry states that some subjects were excluded because A4 was absent or variable and describes an additional exclusion reason only partially. It does not report the final analysis population or the numerical results. Consequently, the applicability of any characterization to the full enrolled group or to people outside the study cannot be assessed from the registry record.

The safety counts are recorded as zero affected for serious and other adverse events, with zero deaths, in the listed group. Those counts should be read as registry event counts, not as proof that no risk exists. Overall, the record defines the measurement question and design, but lacks outcome estimates and analysis details needed to judge the measured signal patterns or their precision.

13. Why This Trial Matters Statistically

This study is statistically notable because its stated purpose is to characterize a device sensor signal rather than compare clinical outcomes between randomized groups. That distinction determines what kinds of conclusions the design could support. A single-group measurement study can describe waveform features, but it does not provide a direct contrast against a control condition. The registry lists no allocation and no masking, and no comparator group is described.

The endpoint also illustrates how a measurement can be scientifically specific while still requiring careful reporting. The record names three accelerometer axes and four signal components, associates those components with cardiac-cycle events, and specifies a mean and standard deviation. Yet numerical summaries, analysis denominators, and analyses are not reported. Without those results, the endpoint’s values and precision remain unknown to readers of the registry record.

Participant exclusions bear directly on the interpretation of a component-based endpoint. The record explains that A4 can be absent or variable in one excluded group and gives an incomplete description of a further exclusion. Reporting the analysis population and the treatment of excluded or unusable signals would help readers understand which observations underlie a characterization and how broadly it applies. Those details are not reported in the registry record.

The record also demonstrates why planning illustrations must be distinguished from evidence about a completed analysis. The stated planning assumptions refer to a two-arm allocation and a fraction of an observed effect, while the listed study design is single-group and the registry reports zero analyses. Any such illustration is not observed power and does not substitute for a reported estimate, uncertainty interval, or analysis plan. These distinctions are essential when interpreting a completed study whose registry entry records the research question and measurement framework but not the primary outcome results.

14. 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 trial-specific limitation in the registry record is the absence of numerical primary-outcome results. The endpoint is described, but no means, standard deviations, confidence intervals, or inferential results are reported. The record lists zero analyses, so it does not show how the measurements were summarized or whether any formal comparisons were conducted.

The analysis population is unclear. The record reports that 12 subjects with specified rhythm and conduction characteristics were excluded because A4 was absent or variable, and that an additional 4 subjects in sinus rhythm were excluded due to frequent pacing or a further reason beginning with “telemet.” The final number analyzed, the complete reason for the latter exclusion, and the relationship between the analysis population and the safety population are not reported in the registry record.

The design is single-group, with allocation listed as NA and masking listed as none. No comparator group is described, limiting the kinds of comparative conclusions the study design could support. The record also does not report whether measurements were compared across posture or activity, whether the three axes or four components were analyzed separately, or how repeated measurements were handled.

Other methodological details are not reported in the registry record, including the statistical analysis plan, sample-size justification, missing-data approach, prespecified comparisons, and interim analyses. The timeframe is stated as approximately two hours after software download, but measurement frequency and consistency of observation time are not specified. These gaps prevent a full assessment of the precision, completeness, and scope of the signal characterization.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Micra Accelerometer Sensor Study 2 — NCT02930980.
• Registry record last updated 2019-03-11; status last verified 2018-11.
• Results first posted 2019-03-11.
• 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.

18. Record Summary

NCT02930980, titled “Micra Accelerometer Sensor Study 2,” is recorded as completed. It is a single-group study of investigational software loaded onto a Micra device, with enrollment of 43 and bradyarrhythmia listed as the condition. The study start date is 2016-10-14 and the primary completion date is 2017-04-25. Phase is listed as NA, allocation as NA, and masking as none.

The primary outcome concerns the waveform and components of the Micra three-axis accelerometer signal, summarized as a mean with standard deviation in g for approximately two hours after software download. The record describes A1 through A4 and notes exclusions from analysis, but does not report the final analysis population or numerical primary-outcome results. One outcome measure and zero analyses are listed.

Serious adverse events are listed as 0 affected among 43 at risk; other adverse events are also listed as 0 affected among 43 at risk, and deaths are listed as 0. Numerical outcome analyses, the statistical plan, and further details of exclusions are not reported in the registry record.