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 Using Non-Fluoroscopic Imaging Devices to Decrease Radiation Exposure During Ablation of Supraventricular Tachycardia (NCT00979303), a randomized na study. The primary outcome is Total Fluoroscopy Time.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00979303 |
| Phase | NA |
| Condition | Supraventricular Tachycardia |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 74 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Boston Children's Hospital |
| Results posted | Yes |
2. Clinical Question
Population
Children with supraventricular tachycardia undergoing ablation procedures. Eligibility criteria, age distribution, and other participant characteristics are not reported in the registry record.
Intervention
Ablation with intracardiac echocardiography and a 3D navigational system, used in addition to radiation. The study asks whether adding these non-fluoroscopic imaging devices can reduce radiation exposure during standard ablation procedures.
Comparator
Ablation procedures using radiation or fluoroscopy only. The registry describes a randomized comparison between this control approach and the added imaging-device approach.
Primary question
What was the total fluoroscopy time during the ablation procedure in each group? The primary endpoint is reported in minutes as a median with a full range. The registry record does not report an inferential estimate of the difference between groups.
The clinical question concerns the use of fluoroscopy during the procedure, rather than a clinical outcome after ablation. Total radiation exposure is listed as a secondary outcome, but a result for that outcome is not reported in the registry record. The posted primary results describe the distribution of fluoroscopy time in each randomized group; they do not establish whether any observed difference is statistically reliable or whether radiation dose itself differed.
3. Trial Design
The registry identifies this as a randomized, parallel-group trial with no masking. The control group underwent ablation procedures with radiation or fluoroscopy only. The study group underwent ablation with intracardiac echocardiography and a 3D navigational system in addition to radiation. The record lists the intervention as a device and the condition as supraventricular tachycardia.
The registry reports enrollment of 74 and lists 37 participants in each group for the posted primary outcome. The trial is marked completed. Its listed start date is 2009-01-09, and its primary completion date is 2009-09-28. The phase is recorded as NA. Boston Children's Hospital is listed as the sponsor.
Random assignment is intended, in general, to make treatment groups comparable on average with respect to factors that could influence outcomes. It does not guarantee that every characteristic is balanced in a particular trial. Because masking is listed as none, participants and study personnel were not masked according to the registry description. The record does not report additional details about allocation concealment, randomization procedures, procedural standardization, or who collected the endpoint.
The registry gives no eligibility criteria, baseline characteristics, or participant flow details. It does not report the trial's own sample-size justification or describe interim analyses. The analysis population and handling of participants who did not complete the procedure are not reported in the registry record. These omissions limit assessment of how closely the reported outcome groups correspond to the randomized groups and how broadly the findings may apply.
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 | Control Group | Study Group |
|---|---|---|
| STARTED | 37 | 37 |
| COMPLETED | 37 | 37 |
| NOT COMPLETED | 0 | 0 |
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 | Control Group | Study Group | Total |
|---|---|---|---|---|
| Participants analysed | 37 | 37 | 74 | |
| Age, Categorical: <=18 years | Participants | 37 | 35 | 72 |
| Age, Categorical: Between 18 and 65 years | Participants | 0 | 2 | 2 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 |
| Age, Continuous | years | 14.2 (8.0 to 20.5) | 14.7 (8.6 to 22.3) | 14.5 (8.0 to 22.3) |
| Sex: Female, Male: Female | Participants | 20 | 18 | 38 |
| Sex: Female, Male: Male | Participants | 17 | 19 | 36 |
| Region of Enrollment: United States | participants | 37 | 37 | 74 |
| Weight | kg | 57.9 (27.4 to 92.2) | 59.1 (26.8 to 104.0) | 58.5 (26.8 to 104.0) |
| Height | cm | 162 (126 to 190) | 162.2 (134 to 184) | 162.1 (126 to 190) |
| Chest circumference | cm | 17.4 (12.5 to 24.5) | 17.5 (12 to 27) | 17.4 (12 to 27) |
| BSA | m^2 | 1.6 (1.0 to 2.2) | 1.6 (1.0 to 2.2) | 1.6 (1.0 to 2.2) |
| BMI | kg/m^2 | 21.4 (15.0 to 31.3) | 22.3 (14.9 to 41.7) | 21.9 (14.9 to 41.7) |
6. Primary Endpoint
The registry lists the primary outcome as Total Fluoroscopy Time, measured over During the Ablation procedure.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Full Range |
| Unit | minutes |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is total fluoroscopy time, measured in minutes during the ablation procedure. Fluoroscopy uses X-ray imaging to guide a procedure, so time under fluoroscopy is a measure of how long this imaging method is used. It is not itself a direct measure of radiation dose: dose can depend on factors beyond time, and the registry lists total radiation exposure separately as a secondary outcome.
Fluoroscopy time is relevant to the trial's stated question because the intervention adds non-fluoroscopic imaging devices while retaining radiation. A reduction in the amount of time fluoroscopy is used would be consistent with less reliance on fluoroscopy during the procedure. That interpretation should remain specific to this endpoint; it does not by itself describe total radiation exposure, procedural success, complications, or later health outcomes.
The registry reports the primary endpoint as a median and gives the full range for each group. A median describes the middle of the ordered observations and is less affected by extreme values than a mean. The full range gives the lowest and highest reported values, but it does not show how observations are distributed between those endpoints. The registry record does not report a confidence interval or an inferential comparison for the primary endpoint.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The control group had a reported median total fluoroscopy time of 18.3 minutes, with a full range of 5.4 to 74.4. The study group had a reported median of 7.5 minutes, with a full range of 0.0 to 52.9. The study group's reported median is lower than the control group's median. These are descriptive summaries; they do not quantify the uncertainty in the between-group comparison.
The ranges show that fluoroscopy time varied within each group. The full range is sensitive to the most extreme observations and does not indicate how many participants had values near either endpoint. It also cannot show the shape of the distribution or provide the precision of a group comparison. The reported medians and ranges therefore offer a limited description of the outcome, not a complete account of its distribution.
No p-value, confidence interval, standard error, or adjusted effect estimate for the primary comparison is reported in the registry record. The number of analyses is listed as zero, and the record indicates that values are missing or not estimable for a two-arm comparison for the other endpoint. Consequently, the posted data do not support a statement about statistical significance or a precise estimate of the difference between groups. A lower descriptive median should not be treated as evidence that a difference is unlikely to be due to chance.
The primary endpoint is fluoroscopy time, not total radiation dose. Although total radiation exposure is named as a secondary outcome, its result is not reported in the registry record. The time summaries therefore cannot establish how much radiation participants received or whether the groups differed in dose. Nor do these summaries address ablation success, recurrence, length of follow-up, or other clinical outcomes.
The randomized design is relevant to interpreting a group comparison, but design alone does not resolve the lack of an inferential result. The record does not describe the analysis population, missing-outcome handling, adjustment strategy, or a statistical analysis plan. It is therefore not possible to determine whether the posted descriptive summaries reflect all randomized participants, a subset with measured procedures, or another analysis set. The most direct reading is limited to the recorded medians and ranges in the two groups.
In general, a confidence interval would express the uncertainty around an estimated group contrast, while a p-value would evaluate compatibility with a specified null hypothesis under stated assumptions. Neither is available for the primary outcome in the registry record. No conclusion about the size, precision, or statistical reliability of a between-group effect should be inferred from the medians alone.
9. Statistical Methods Explained
The registry reports the primary outcome using a median and full range, rather than a mean and standard deviation. This is a descriptive choice. A median identifies the central observation after values are ordered, while the full range reports the endpoints of the observed values. The median can be useful when a distribution is asymmetric or contains unusually high observations, because extreme values have less influence on it than they would on a mean. The registry record does not state why this summary was selected.
What does the median tell us?
The control group's median fluoroscopy time is 18.3 minutes, and the study group's median is 7.5 minutes. Each median describes the center of its own group's observed values. Comparing these medians gives a descriptive view of how the group centers differ, but it does not provide a measure of uncertainty. In particular, it does not say whether the observed separation is compatible with a range of possible underlying group differences.
A median is not an estimate of every participant's experience. It does not show how concentrated or dispersed values are around the center, and it does not describe the frequency of values in any interval. Two groups can have different medians while their individual observations overlap substantially. The registry gives ranges, but not the participant-level values or other distribution summaries needed to characterize that pattern fully.
How should the ranges be read?
The control group's full range is 5.4 to 74.4 minutes, and the study group's full range is 0.0 to 52.9 minutes. A range records the lowest and highest values observed in a group. It is not a confidence interval: it does not describe the precision of an estimated effect, and it does not give a plausible interval for the population value. Because the endpoints depend on the most extreme observations, ranges can be strongly influenced by a small number of values.
The record does not report a standard deviation, interquartile range, or distribution plot in the registry record for the primary outcome. Without such summaries or participant-level data, the degree and pattern of within-group variability cannot be evaluated in detail. The median and full range remain useful descriptive information, but they should not be mistaken for an inferential comparison.
What would an inferential comparison add?
An inferential analysis would estimate a contrast between groups and quantify uncertainty around it, using a method suited to the outcome distribution and trial design. A confidence interval would show the precision of that estimate. A hypothesis test could report a p-value under a specified null hypothesis and model. The registry record reports neither for total fluoroscopy time. The result cannot therefore be classified as statistically significant or not statistically significant from the posted summaries.
General statistical practice also considers whether an outcome is skewed, whether observations are independent, and whether the analysis follows the randomized allocation. These considerations matter because a method's assumptions affect how its estimate and uncertainty should be interpreted. The registry does not report the distributional diagnostics, model, or testing procedure used for the primary comparison. It would not be appropriate to assume that a particular test or model was used.
Over-dispersion is a general issue for some count outcomes when observed variability exceeds what a simple model expects. It is not a stated feature of this continuous time endpoint, and the registry does not report a model for which over-dispersion was assessed. More generally, statistical methods should match the type and distribution of the measured outcome; the record does not provide enough analysis detail to assess that match.
What do the planning assumptions mean?
The registry describes sample-size illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation between groups, and a normal approximation. It also describes the effect to detect as a stated fraction of the observed effect. These are planning assumptions, not results from the trial and not evidence of the probability that the trial detected an effect. The registry record does not report the trial's own sample-size justification. Any sample-size illustration should be understood as a planning exercise rather than observed power.
The record does not report a sponsor analysis for the primary comparison or a recalculated inferential result. There is therefore no competing inferential estimate to reconcile. The posted group summaries remain descriptive, and no new test statistic or effect estimate can be recovered from the reported medians and ranges alone.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists total fluoroscopy time as the primary outcome and total radiation exposure as a secondary outcome. It reports two outcome measures, but a result for total radiation exposure is not reported in the registry record. No multiplicity strategy is reported. When multiple outcomes or statistical tests are considered, multiplicity can increase the chance of at least one apparently notable result; methods for addressing this depend on the analysis plan and the questions being tested. The record does not describe such a plan, so the handling of multiple outcomes cannot be assessed.
Missing-data procedures are not reported in the registry record. The record does not state whether any primary endpoint observations were missing, how missing values were handled, or whether sensitivity analyses were conducted. It also does not describe whether participants who did not complete a procedure were included in any analysis.
The analysis population is not reported. Although the trial is listed as randomized and the primary results give group counts, the registry does not specify whether the analysis followed intention-to-treat principles, included only participants with measured fluoroscopy time, or used another population definition. These details matter because exclusions after randomization can affect how well a comparison preserves the benefits of random assignment.
No interim analyses or prespecified statistical analysis plan are reported. The absence of these details does not establish that such procedures were or were not used; their status is not reported in the registry record. The posted information is insufficient to evaluate multiplicity control, missing-data assumptions, or the choice of analysis population.
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 |
|---|---|---|---|
| Control Group | 0 | 37 | 0.0% |
| Study Group | 0 | 37 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Control Group | 0 of 37 |
| Study Group | 0 of 37 |
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 |
|---|---|
| Control Group | 8 of 37 |
| Study Group | 6 of 37 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Control Group | Study Group |
|---|---|---|---|
| Hematoma | Skin and subcutaneous tissue disorders | 5 of 37 | 3 of 37 |
| Headache | Nervous system disorders | 1 of 37 | 1 of 37 |
| bronchospasm | Respiratory, thoracic and mediastinal disorders | 0 of 37 | 1 of 37 |
| Vasovagal syncope | Nervous system disorders | 0 of 37 | 1 of 37 |
| Neuropathy | Nervous system disorders | 0 of 37 | 1 of 37 |
| Mechanical trauma to pathway | Cardiac disorders | 0 of 37 | 1 of 37 |
| Groin Pain | Skin and subcutaneous tissue disorders | 1 of 37 | 0 of 37 |
| Skin abrasion | Skin and subcutaneous tissue disorders | 1 of 37 | 0 of 37 |
The registry reports no serious adverse events among the 37 participants at risk in the control group and no serious adverse events among the 37 participants at risk in the study group. It reports zero deaths in each group. The listed counts are the registry's recorded figures for the stated groups; they do not establish that every possible adverse event was captured or that the groups have equivalent safety profiles.
For other adverse events, the registry reports 8 affected among 37 at risk in the control group and 6 affected among 37 at risk in the study group. These are counts, not adjusted comparisons. The record does not provide event-specific terms for serious adverse events, and the list of top serious terms is empty. It does not report an inferential safety analysis or explain the event-collection and classification procedures.
In general, safety counts should be interpreted in light of how events were defined, collected, and followed. A zero count means no event was recorded in the stated category for that group in the registry result; it is not proof that the true risk is zero. The available figures do not support a conclusion that one approach is safer than the other.
12. What the Result Does, and Does Not, Mean
The posted primary results describe total fluoroscopy time during ablation. The median is 18.3 minutes in the control group and 7.5 minutes in the study group, with full ranges of 5.4 to 74.4 and 0.0 to 52.9, respectively. This is a descriptive pattern in which the study group has the lower reported median. The registry record does not provide an inferential comparison or a confidence interval to show the uncertainty around a group contrast.
The trial's design asks whether adding intracardiac echocardiography and a 3D navigational system to radiation-based ablation can reduce radiation exposure. The primary outcome measures fluoroscopy time, which captures duration of fluoroscopy use rather than radiation dose itself. Total radiation exposure is listed as a secondary outcome, but its result is not reported in the registry record. The posted primary summaries therefore do not answer the full question about radiation exposure.
The results do not establish statistical significance, the magnitude or precision of an underlying effect, or whether any difference is clinically important. They also do not establish effects on ablation outcomes, later health, or other endpoints. The record gives no analysis population, missing-data method, or statistical analysis plan, further limiting interpretation of the reported summaries.
Randomization is a strength of the design in general, but it does not replace transparent outcome analysis. The absence of an inferential result means the descriptive group summaries should be read as the evidence available in the registry record, not as a definitive comparison. These data neither demonstrate nor rule out a meaningful difference in fluoroscopy time or radiation exposure.
13. Why This Trial Matters Statistically
This trial addresses a statistical distinction that is important in procedural research: the difference between measuring how long a technology is used and measuring the exposure or outcome that the technology is intended to affect. Fluoroscopy time is the primary endpoint, while total radiation exposure is a separate secondary outcome. The distinction prevents an interpretation of time as though it were a direct dose measurement.
The randomized parallel-group design creates a framework for comparing procedural approaches. The reported medians provide a concise description of the typical observed fluoroscopy time in each group, and the ranges show that values varied. Yet a descriptive contrast is not a substitute for an estimate of effect with uncertainty. Without a confidence interval or inferential result, the precision of the comparison remains unknown.
The record also illustrates why outcome reporting and analysis details matter. The secondary outcome is named but lacks a reported result, and the analysis population, missing-data procedures, and multiplicity approach are not reported. These gaps make it difficult to judge the completeness and robustness of the evidence from the registry record alone.
Statistically, the trial is useful as an example of how a randomized design and descriptive summaries can coexist with limited inferential reporting. Readers can identify the measured endpoint, the intervention contrast, and the group-level summaries, while also recognizing what cannot be concluded. Clear separation of endpoint, dose, precision, and analysis population is essential when interpreting procedural studies.
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 results are limited to medians and full ranges. The registry record does not report an effect estimate for the group contrast, a confidence interval, a p-value, or another measure of inferential precision. The distribution of individual fluoroscopy times cannot be reconstructed from these summaries, and the range alone does not show how values are distributed.
The primary endpoint measures fluoroscopy time rather than radiation dose. Although total radiation exposure is listed as a secondary outcome, its result is not reported in the registry record. The record also does not give additional clinical outcomes or follow-up results. As a result, the posted primary data address only a limited part of the study's stated question.
Important analysis details are absent: the analysis population, missing-data handling, statistical model or test, multiplicity procedures, and any prespecified analysis plan are not reported in the registry record. The record does not provide eligibility criteria, baseline characteristics, participant flow, or details of how fluoroscopy time and adverse events were collected. These omissions restrict assessment of comparability, completeness, and potential sources of bias.
The trial is listed as having no masking. The registry record does not describe allocation concealment or procedural safeguards that might affect measurement or conduct. The reported group counts and summary values should therefore be interpreted within the limited context available, rather than as a complete account of trial conduct or all outcomes.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Using Non-Fluoroscopic Imaging Devices to Decrease Radiation Exposure During Ablation of Supraventricular Tachycardia — NCT00979303.
- Registry record last updated 2018-03-08; status last verified 2018-02.
- Results first posted 2018-03-08.
- 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
NCT00979303 is a completed, randomized, parallel-group trial sponsored by Boston Children's Hospital. It compares ablation using radiation or fluoroscopy only with ablation using intracardiac echocardiography and a 3D navigational system in addition to radiation. The trial concerns supraventricular tachycardia in children and is listed as unmasked.
The primary endpoint is total fluoroscopy time in minutes during the ablation procedure, summarized by group as a median and full range. The control group median is 18.3, with a range of 5.4 to 74.4; the study group median is 7.5, with a range of 0.0 to 52.9. Total radiation exposure is listed as a secondary outcome, but its result is not reported in the registry record.
No inferential comparison is reported for the primary endpoint. The registry also does not report the analysis population, missing-data procedures, or multiplicity approach. The posted summaries are descriptive and do not establish the precision or statistical reliability of a difference between groups.