This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Electrical Coupling Information From The Rhythmia HDx System And DirectSense Technology In Subjects With Paroxysmal Atrial Fibrillation (NCT03232645), a na na study. The primary outcome is Local Impedance and Local Impedance Change at Day Zero and PVI Gaps at the Month 3 Assessment.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03232645 |
| Phase | NA |
| Condition | Paroxysmal Atrial Fibrillation |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 62 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Boston Scientific Corporation |
| Results posted | Yes |
2. Clinical Question
Population
Participants had de-novo paroxysmal atrial fibrillation and were indicated for catheter-based ablation. The study enrolled 62 subjects. The primary endpoint analysis included 51 subjects; the registry says 7 were removed because their electro-anatomical maps were not technically usable for that endpoint analysis. The registry does not report further details about the characteristics of those excluded from the analysis.
Intervention
The study used the Rhythmia HDx mapping system with DirectSense technology and the IntellaMap Orion mapping catheter during pulmonary vein ablation. The stated objective was to characterize local impedance information collected during mapping and ablation, with the aim of informing use of the feature and further development of a future lesion-indexing feature.
Comparator
There was no randomized treatment comparator or separate control arm. For the primary endpoint, the comparison was between anatomical segments classified as blocked and segments classified as reconnected at the 3-month assessment. The registry describes each pulmonary vein pair as divided into 8 segments using tags on the left atrium geometry.
Primary question
At the index ablation procedure, were baseline DirectSense local impedance or local impedance change values associated with whether a pulmonary vein segment was blocked or reconnected at the 3-month assessment? The registry describes a comparison of these impedance measures across the segment classifications. It does not report the numerical endpoint results, so the direction and magnitude of any observed association cannot be stated from the registry record.
3. Trial Design
This was a prospective, single-group, non-randomized study of a device-based ablation procedure. The listed intervention was ablation using the Rhythmia HDx mapping system with DirectSense technology. The registry lists no masking. Enrollment was 62, and the study status is completed. The registry record gives the study start as 2018-01-08 and primary completion as 2020-06-23.
The study was designed to collect information about the use of DirectSense local impedance during catheter-based endocardial mapping and ablation in people with de-novo paroxysmal atrial fibrillation. The stated purpose was to characterize local impedance data in cases requiring pulmonary vein isolation, generate usage guidance, and support further development of a future lesion-indexing feature. The registry lists phase as NA and allocation as NA.
Although the overall study had a single group, the primary endpoint involved a within-study comparison: impedance measures recorded at the index procedure were compared for pulmonary vein segments classified as blocked or reconnected at the 3-month assessment. This is not a comparison of randomized treatment assignments. Segment-level classifications also should not be mistaken for independent treatment groups; the registry does not report how any dependence among segments from the same subject was handled analytically.
The primary endpoint analysis included 51 subjects. The registry states that 7 subjects were removed because their electro-anatomical maps were not technically usable for the specific endpoint analysis. It does not explain the difference between the enrollment total and the stated analysis count, nor does it provide a complete participant flow. The protocol’s sample-size justification and any planned interim analyses 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
| Stage | Rhythmia HDx and DirectSense Technology |
|---|---|
| STARTED | 62 |
| COMPLETED | 58 |
| NOT COMPLETED | 4 |
Analysis population for the primary outcome, as defined in the registry: 51 subjects were included in the analysis as 7 subjects were removed because the electro-anatomical maps were not technically usable per the specific endpoint 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.
| Characteristic | Unit | Rhythmia HDx and DirectSense Technology |
|---|---|---|
| Participants analysed | 62 | |
| Age, Continuous | years | 62 (SD 11) |
| Sex: Female, Male: Female | Participants | 28 |
| Sex: Female, Male: Male | Participants | 33 |
| Race and Ethnicity Not Collected | Participants | — |
| Region of Enrollment: United Kingdom | participants | 19 |
| Region of Enrollment: France | participants | 1 |
| Region of Enrollment: Germany | participants | 12 |
| Region of Enrollment: Spain | participants | 30 |
| Height | cm | 172 (SD 9) |
| Weight | kg | 80 (SD 12) |
| Resting Heart Rate | bpm | 66 (SD 15) |
| Systolic Blood pressure | mmHg | 126 (SD 16) |
| Diastolic Blood Pressure | mmHg | 72 (SD 9) |
6. Primary Endpoint
The registry lists the primary outcome as Local Impedance and Local Impedance Change at Day Zero and PVI Gaps at the Month 3 Assessment, measured over Day 0 and 3 months.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | ohm |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint concerns the association between DirectSense local impedance measures recorded at the index ablation procedure and pulmonary vein segment status at the 3-month assessment. The measures are baseline local impedance and local impedance change, recorded per anatomical segment. Segment status is described in terms of blocked versus reconnected segments, with the number of ablation gaps assessed at the follow-up procedure. The registry defines each pulmonary vein pair as 8 segments, based on tags placed on the left atrium geometry created with the Rhythmia system.
The endpoint is useful for characterizing whether local impedance measurements correspond to later segment-level findings in this particular procedural setting. It addresses a measurement and mapping question, rather than a randomized comparison of clinical treatment strategies. A segment-level association, if demonstrated, would describe correspondence between the recorded measurement and the later classification; by itself, it would not establish that the measurement caused the segment status or that it predicts outcomes in other populations.
The endpoint is summarized using medians and interquartile ranges, with impedance measured in ohms. In general, the median describes the middle of a distribution, while the interquartile range describes the spread of its central portion. The registry record does not report the numerical medians, interquartile ranges, or a numerical estimate of the comparison. Therefore, the size, direction, and precision of the endpoint findings cannot be assessed from the information reported.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry describes a focused measurement question: whether local impedance recorded at the index ablation procedure differs between pulmonary vein segments classified as blocked and segments classified as reconnected at the 3-month assessment. This is a within-study comparison among segments, not a randomized comparison between separate treatment arms. The single-group design is consistent with the stated objective of characterizing DirectSense technology during ablation, but it does not provide a concurrent control group for comparing treatment strategies.
The primary endpoint analysis included 51 subjects. The registry states that 7 subjects were removed because their electro-anatomical maps were not technically usable for the specific endpoint analysis. The enrollment total was 62. Since the record does not provide a complete disposition of all enrolled subjects, the reason every enrolled subject is or is not represented in the endpoint analysis is not fully described. The analysis population is therefore important context for interpreting the endpoint, especially because technical map usability determined inclusion for that analysis.
Numerical results for the primary endpoint are not reported in the registry record. The posted information does not give medians or interquartile ranges for the impedance measures, a numerical comparison between blocked and reconnected segments, or a measure of uncertainty such as a confidence interval. It also does not report a p-value for this comparison. Without those results, it is not possible to describe whether the measurements differed, how large any difference was, or how precisely it was estimated.
General statistical interpretation: a confidence interval, when reported, conveys a range of values compatible with the data under the analysis assumptions; its width gives information about precision. A p-value addresses compatibility with a specified null hypothesis under a statistical model, but does not describe the size or practical importance of an association. Neither can substitute for the estimated effect itself. The registry does not report these quantities for the primary endpoint, so no inference about statistical significance or precision can be made.
The registry’s stated objective includes generating usage guidance and supporting future development of a lesion-indexing feature. Those aims are not the same as demonstrating that the technology improves a clinical outcome. The endpoint as described concerns local impedance metrics and segment-level findings at follow-up. It does not, by itself, establish a causal effect of the mapping technology, an effect on patient outcomes, or performance in settings beyond the population and procedures studied. The registry record does not report enough outcome results to judge the strength or consistency of any association.
9. Statistical Methods Explained
What does the endpoint compare?
The primary endpoint connects measurements made at two stages. Local impedance and local impedance change were recorded for anatomical segments during the index procedure on Day 0. At the 3-month assessment, segments were classified according to whether they were blocked or reconnected, with ablation gaps assessed at that procedure. The endpoint therefore asks whether the earlier impedance measurements correspond to the later segment classification.
The registry says each pulmonary vein pair is divided into 8 segments using tags placed on the left atrium geometry created with the Rhythmia system. This matters because the analysis is described at the segment level, while the study enrolled subjects. Multiple segments can belong to one subject. In general, observations from the same subject may be related rather than statistically independent. The registry record does not report whether or how the analysis accounted for this potential clustering.
Why report a median and interquartile range?
The endpoint’s summary measure is the median, with interquartile range as the measure of dispersion. In general, the median is the middle value after observations are ordered. The interquartile range describes the interval between the lower and upper quartiles and gives a sense of how spread out the central observations are. These summaries can be informative when a distribution is skewed or contains extreme observations, because the median is less affected by those values than the arithmetic mean.
Here, those summaries would describe the distributions of local impedance measures in the segment groups being compared. They do not, on their own, quantify a modeled association or adjust for differences among subjects or segments. The registry does not report the numerical median or interquartile range values, nor does it describe a model or adjustment strategy for the primary endpoint. No adjusted estimate should therefore be inferred.
What can the comparison establish?
General statistical explanation: an observed difference between groups of segments can describe how the measurements vary with their later classification in the studied data. It does not by itself establish that the measurement caused the classification, that the relationship is predictive in new patients, or that using the measurement changes clinical outcomes. The prospective timing is relevant to the sequence of measurement and assessment, but timing alone does not remove confounding or other sources of bias.
The study was non-randomized and had a single group. Its primary comparison is between segment classifications within that group rather than between randomized interventions. Accordingly, the primary endpoint should be read as a characterization of measurement patterns in the study setting. It cannot be interpreted as a randomized treatment effect. The registry record does not report a statistical model, a confidence interval, a p-value, or other inferential details for the primary comparison.
How should uncertainty be assessed?
In general, a confidence interval communicates the uncertainty around an estimate, conditional on the analysis method and its assumptions. A narrow interval indicates more precision than a wide interval, while both the point estimate and the interval are needed to understand the magnitude and range of plausible values. A p-value answers a different question: how compatible the observed data are with a specified null model. It does not measure the probability that a hypothesis is true, and it does not indicate clinical importance.
The registry record does not report a numerical effect estimate, confidence interval, or p-value for the primary endpoint. Thus there is no basis in the posted information for describing either the magnitude or statistical uncertainty of the endpoint comparison. The fact that the endpoint is described and an analysis population is stated does not supply the missing numerical results.
What does over-dispersion mean in general?
General statistical explanation: for count outcomes, over-dispersion means the observed variability is greater than the variability assumed by a basic model. If it is ignored, standard errors may be too small and inferential results may appear more precise than they are. This concept is relevant in some analyses of counts, such as numbers of gaps, but the registry record does not report a count model or state whether over-dispersion was assessed. It would be inappropriate to assume that a particular model was used.
The registry lists secondary outcomes relating to local impedance, local impedance change, and gaps at Day Zero, as well as segment-level impedance measures. However, it does not provide statistical-analysis details for these outcomes in the registry record described. The sample-size justification, any interim analysis plan, and the statistical methods used for secondary outcomes are not reported in the registry record. General statistical considerations can clarify what such methods would address, but they cannot establish which methods this study actually used.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary endpoint and five secondary outcome titles, for six outcome measures in total. The secondary outcomes cover local impedance and local impedance change at Day Zero, the number of gaps at Day Zero, maximum gaps per pulmonary vein segment, and impedance measures in segments with the maximum number of gaps. Considering multiple outcomes can create multiplicity: when many hypotheses are tested, the chance of at least one apparently unusual result may increase. General approaches include identifying a hierarchy of outcomes or adjusting interpretation for multiple testing.
The registry record does not report a multiplicity plan, a testing hierarchy, or any adjustment procedure. It also does not report analysis entries for the outcomes. Because numerical results and statistical tests are not reported in the registry information described, it is not possible to determine how multiplicity was handled or whether any reported inference was adjusted.
For the primary endpoint, the record states that 51 subjects were included and 7 were removed because their electro-anatomical maps were not technically usable for that specific analysis. This identifies one endpoint-specific exclusion reason, but it is not a complete account of missingness. The registry does not report the amount or reasons for missing data at each assessment, how unavailable measurements were handled, or whether any imputation was performed. It also does not state whether exclusions were determined before outcome data were reviewed.
These omissions matter because analysis populations and missing-data handling can affect which observations contribute to an estimate. The full analysis population definitions, per-outcome denominators, and sensitivity analyses are not reported in the registry record. Consequently, the extent to which results could be affected by unavailable maps or other missing information cannot be assessed.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Rhythmia HDx and DirectSense Technology | 8 | 62 | 12.9% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Rhythmia HDx and DirectSense Technology | 0 of 62 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Rhythmia HDx and DirectSense Technology | 4 of 62 |
Most frequent serious adverse event terms
| Event term | Organ system | Rhythmia HDx and DirectSense Technology |
|---|---|---|
| Infection | Surgical and medical procedures | 2 of 62 |
| Stroke (ischemic) | Surgical and medical procedures | 2 of 62 |
| Adverse reaction - Neurological (non-TIA, non-stroke) | Surgical and medical procedures | 1 of 62 |
| Atrial Tachycardia/Other SVT (eg AVRT, AVNRT, EAT) | Cardiac disorders | 1 of 62 |
| Pulmonary | Respiratory, thoracic and mediastinal disorders | 1 of 62 |
| Sinus Bradycardia | Cardiac disorders | 1 of 62 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Rhythmia HDx and DirectSense Technology |
|---|---|---|
| Hemoptosis | Surgical and medical procedures | 1 of 62 |
| Left Atrial (type II) Flutter | Surgical and medical procedures | 1 of 62 |
| NSVT (Non Sustained Ventricular Tachycardia) | Surgical and medical procedures | 1 of 62 |
| Pseudoaneurysm | Surgical and medical procedures | 1 of 62 |
| Visual blurring/disturbances | Surgical and medical procedures | 1 of 62 |
| Atrial Flutter, not specified | Surgical and medical procedures | 1 of 62 |
Serious events with the highest arm-level rate: infection (3.2%), stroke (ischemic) (3.2%), adverse reaction - neurological (non-tia, non-stroke) (1.6%), atrial tachycardia/other svt (eg avrt, avnrt, eat) (1.6%), pulmonary (1.6%).
The registry reports serious adverse-event figures for the Rhythmia HDx and DirectSense technology group. The serious adverse-event figure is 8 among 62 at risk; the other adverse-event figure is 4 among 62 at risk. The record reports 0 deaths. These are safety summaries for the study group and should not be read as comparisons with another treatment group, because the study had no randomized control arm.
The listed serious-event terms include Infection and Stroke (ischemic), each reported as 3.2%. Adverse reaction - Neurological (non-TIA, non-stroke), Atrial Tachycardia/Other SVT (eg AVRT, AVNRT), Pulmonary, and Sinus Bradycardia are each listed as 1.6%. These term-specific percentages describe the registry’s reported safety listing; the record does not explain whether people could contribute to more than one term or how terms were grouped. They should not be added together to create a total.
In general, adverse-event summaries describe events recorded during a study and do not, by themselves, establish that an event was caused by the intervention. The registry information does not provide event narratives, timing, severity details beyond the serious-event classification, or a causal assessment for each term. The figures should therefore be read as reported safety counts and terms, not as evidence of comparative risk or causation.
12. What the Result Does, and Does Not, Mean
The study addresses whether DirectSense local impedance measurements recorded during the index procedure correspond to pulmonary vein segment status assessed at 3 months. It is a prospective, non-randomized, single-group study with an endpoint analysis involving 51 subjects. The registry’s stated purpose is to characterize the technology’s use and local impedance data during pulmonary vein ablation, inform usage guidance, and support development of a future lesion-indexing feature.
The registry record does not report numerical primary endpoint results. There are no reported medians or interquartile ranges for the impedance measures, no numerical estimate comparing blocked and reconnected segments, and no reported confidence interval or p-value for that comparison. It is therefore not possible to say from the posted information whether the measurements differed, in what direction, or by how much. Nor can the precision of an estimated association be evaluated.
Even if a segment-level association were reported, its interpretation would remain specific to the study design and setting. A within-study association would not establish that impedance measurements caused a later segment classification. It would not demonstrate that use of the technology changes patient outcomes, and it would not establish that findings apply to populations or procedures outside those studied. Those conclusions require evidence suited to those questions.
The study also lacks a randomized comparison between treatment groups. Its design is appropriate to describing the measurement context stated in the registry, but it cannot provide a randomized estimate of a treatment contrast. The reported safety figures likewise have no concurrent randomized comparator and do not establish that events were caused by the device or procedure.
The registry record does not report the sample-size justification, detailed statistical plan, multiplicity handling, full missing-data approach, or inferential results. Those omissions limit assessment of precision, robustness, and the scope of the conclusions. The most defensible reading is that the study was intended to characterize local impedance data and its relationship to segment findings; the posted information does not establish the magnitude or statistical certainty of that relationship.
13. Why This Trial Matters Statistically
This trial is statistically notable for the distinction between the study’s overall design and its primary comparison. It is a single-group, non-randomized study, yet the primary endpoint compares measurement patterns across pulmonary vein segments classified as blocked or reconnected at follow-up. Recognizing that distinction prevents the segment comparison from being mistaken for a randomized comparison of treatments.
The endpoint also links data at different levels: subjects contribute measurements for anatomical segments, and those segments are classified at a later assessment. In general, observations nested within the same subject may be correlated. If an analysis treats correlated observations as independent, uncertainty can be understated. The registry does not report the method used to address this issue, making the analysis approach important information for interpreting any segment-level estimate.
Another important feature is endpoint-specific analysis eligibility. The registry states that 51 subjects were included in the primary endpoint analysis and that 7 were removed because their maps were not technically usable for that analysis. This makes technical usability part of the evidence base, not merely a procedural detail. Without a fuller account of missing information and exclusions, readers cannot determine how representative the analyzed subjects are of all enrolled subjects for the endpoint.
Finally, the registry states an objective of characterizing a measurement feature and generating guidance, but numerical endpoint findings and inferential details are not reported. This illustrates why an outcome definition and a study objective are not substitutes for results. The measurement question is clear; the strength, direction, and precision of any observed relationship are not available from the registry record.
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 primary limitation for interpreting the endpoint is the absence of numerical results in the registry record. The endpoint definition and analysis population are described, but the impedance summaries and the comparison of blocked with reconnected segments are not reported. No estimate of the association, confidence interval, or p-value is given. This prevents evaluation of magnitude, direction, and precision.
The primary endpoint analysis excluded subjects whose electro-anatomical maps were technically unusable for that endpoint. The record reports 51 subjects in the analysis and 7 removed for this reason, but does not provide a complete participant disposition or explain all differences between enrollment and analysis counts. It does not report whether map usability was associated with subject characteristics or endpoint status.
The endpoint is defined at the anatomical-segment level, while subjects contribute the study data. The registry does not describe how within-subject dependence among segments was handled. It also does not report the statistical model, adjustment strategy, handling of repeated or clustered observations, or assessment of model assumptions. Those details are necessary to understand how uncertainty would be estimated.
Further limitations include the non-randomized, single-group design and lack of a separate control arm. The endpoint concerns association between measurements and later segment classifications, not a randomized effect of an intervention. The registry does not report a multiplicity plan, a complete missing-data strategy, a sample-size justification, or interim-analysis details. These elements are not reported in the registry record, so their presence or absence in the study protocol cannot be inferred.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Electrical Coupling Information From The Rhythmia HDx System And DirectSense Technology In Subjects With Paroxysmal Atrial Fibrillation — NCT03232645.
- Registry record last updated 2021-09-05; status last verified 2021-08.
- Results first posted 2021-08-09.
- 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.
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18. Record Summary
NCT03232645 is a completed, prospective, non-randomized, single-group study of Rhythmia HDx mapping with DirectSense technology during ablation for de-novo paroxysmal atrial fibrillation. Enrollment was 62. The primary endpoint examined Day 0 local impedance and local impedance change in relation to pulmonary vein segment findings at the 3-month assessment.
The primary endpoint analysis included 51 subjects; the registry says 7 were removed because their maps were not technically usable for that analysis. The endpoint was summarized using medians and interquartile ranges, but numerical results and inferential statistics are not reported in the registry record. Safety figures include 8 serious adverse-event entries among 62 at risk, 4 other adverse-event entries among 62 at risk, and 0 deaths. The study’s stated aim was to characterize local impedance data and inform use of the technology, rather than to provide a randomized treatment comparison.