Assessment of the Sphere-9™ Catheter and Affera Mapping and Ablation System for Treatment of Atrial and Ventricular Arrhythmias: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Assessment of the Sphere-9™ Catheter and Affera Mapping and Ablation System for Treatment of Atrial and Ventricular Arrhythmias (NCT04211441), a na na study. The primary outcome is Percentage of Subjects With a Primary Safety Event.

2. Clinical Question

The registry also lists percentage of subjects free from documented recurrence and the number of patients with durable ablation lesions at remapping procedure as secondary outcomes. Their presence indicates additional areas of assessment, but does not establish that results for those outcomes were reported or analyzed. The record lists four outcome measures overall, while no outcome analysis records are listed.

Because this is a single-group assessment, the clinical question is descriptive: what safety and performance observations were recorded among people treated with the device system? Without a comparator, differences from another treatment or from usual care cannot be estimated from this record. The listed conditions also span atrial and ventricular arrhythmias; the registry description does not provide outcome results broken down by condition. Consequently, the record does not support a condition-specific interpretation of the primary safety endpoint.

3. Trial Design

The registry describes a prospective, single-arm, multi-center safety and performance assessment of the Sphere-9™ Catheter and the Affera Mapping and RF Ablation System. The intervention is recorded as a device, and the arm description identifies subjects treated with the Sphere-9™ Catheter. The study is marked completed. Its recorded enrollment is 74.

The design is single-group, with allocation listed as NA and masking listed as NONE. No comparator arm is described. The registry lists the phase as NA. The sponsor is Medtronic Cardiac Ablation Solutions. The recorded start date is 2018-06-01, and the primary completion date is 2019-09-02.

The primary outcome is titled “Percentage of Subjects With a Primary Safety Event,” uses participants as its unit, and has a recorded timeframe of 90 days. Its population is subjects who underwent a procedure with the investigational device. The outcome description specifies serious adverse events occurring from Day 0 through the Day 10 post-treatment assessment, with atrio-esophageal fistula included through the Day 90 assessment. This distinction matters when interpreting the recorded timeframe: the description does not define every listed event as being observed over the same window.

The listed secondary outcomes concern documented recurrence and durable ablation lesions at remapping. The registry record does not report a detailed schedule for those assessments, eligibility criteria, a sample-size justification, or the study’s statistical analysis plan. Those details should not be inferred from the prospective or multi-center design labels. The design supports description of observations within the treated group, but not a like-for-like comparison with an untreated or alternative-treatment group.

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.

Before assignment: 74 subjects were enrolled in the study. Of these, five were excluded or withdrew prior to treatment with the study devices. 69 patients underwent the procedure.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Subjects who underwent a procedure with the investigational device

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

Population: Baseline subject demographics for all subjects treated with the investigational device.

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Subjects With a Primary Safety Event, measured over 90 days.

The primary endpoint is the percentage of subjects with a primary safety event. It is defined by the occurrence of specified serious adverse events in subjects who underwent a procedure with the investigational device. The listed events include neurological, bleeding, cardiac, pulmonary-vein, pericardial, diaphragmatic, esophageal, valvular, vascular, device-related, and fatal events. The description gives an occurrence window from Day 0 through the Day 10 post-treatment assessment, except that atrio-esophageal fistula is included through the Day 90 assessment.

Safety endpoints of this kind are used to make potentially serious harms a central part of an initial assessment of a device and procedure. A composite endpoint can capture several types of serious event under a single outcome, but its interpretation depends on the event definitions, observation windows, and rules for counting participants and events. The registry record does not explain how overlapping events were handled or whether the primary endpoint was adjudicated.

Although the outcome is titled as a percentage, the registry record does not report the primary endpoint result, a confidence interval, or an analysis. The serious adverse-event counts listed elsewhere in the record should not automatically be treated as the primary endpoint result: the record does not state that those counts correspond exactly to the primary endpoint definition and its specified time windows.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods need to match the design and the form of the outcome. This study is recorded as single-group, and its primary outcome is binary at the participant level: whether a participant met the specified primary safety event definition. The registry describes the result as a percentage, but does not report the primary endpoint estimate or an analysis. The statistical meaning of such an endpoint can be explained generally, while the analysis actually used in this study cannot be reconstructed from the record.

What does a participant-level percentage represent?

In general, a participant-level percentage is a count of participants meeting an outcome definition relative to the eligible analysis population, expressed as a proportion. The numerator and denominator need to refer to the same clearly defined population and observation rules. For a composite safety outcome, the event definitions and time windows determine which participants qualify. If a participant experiences more than one event, the analysis plan must specify whether the participant is counted once for the composite or whether events are counted separately. That rule is not reported in the registry record.

The adverse-event summary includes a group with 69 at risk and 5 affected by serious adverse events. Those counts are not identified as the primary endpoint numerator and denominator. They should not be converted into a primary endpoint percentage without confirmation that the population, event definition, time window, and counting rules match. No recalculated primary estimate is available from the registry record.

Why does a confidence interval matter?

In general, a confidence interval describes the statistical uncertainty around an estimate under a specified method and its assumptions. For a proportion, an interval helps readers assess how compatible the observed data are with a range of underlying event rates. A point estimate alone does not communicate that precision. The registry record does not report a confidence interval for the primary endpoint, so its precision cannot be evaluated using an interval from this record. No interval should be inferred from the adverse-event counts, especially because their connection to the primary endpoint is not stated.

With a single-group design, an interval around an event proportion would describe uncertainty about the measured group outcome under the chosen model. It would not address confounding or provide the missing comparison with another treatment. Statistical precision and causal interpretation are separate issues: an estimate can be precise as a description and still not establish a comparative effect.

What can the absence of analyses tell us?

The registry lists zero outcome analyses. This means analysis results are not recorded in the analysis listing; it does not establish why no analyses are present or whether analyses were conducted outside the registry record. The record does not specify a statistical model, confidence-interval method, hypothesis test, covariate adjustment, or handling of repeated or overlapping events. Each of these details can affect how a safety endpoint is summarized, so none should be assumed.

The primary outcome is a composite of serious events with different clinical descriptions and, for one event type, a distinct observation window. In general, a composite can make a broad safety summary possible, but the overall result can be influenced by which event types occur and how they are counted. A combined endpoint does not show that each component has the same frequency or meaning. The registry does not report component-specific primary endpoint results.

How should planning calculations be read?

General sample-size calculations answer a design question: how much information might be needed to detect a specified effect under stated assumptions. The registry-associated planning illustration is described as based on a fraction of the observed effect, with two-sided significance level 0.05, equal allocation between two arms, and a normal approximation. It is not the trial’s own design justification. The study itself is single-group, so the two-arm assumptions in that illustration do not describe the recorded trial design. Such planning quantities are not observed power and do not demonstrate that the study had a particular probability of detecting an effect. The sample-size justification for the actual study is not reported in the registry record.

General statistical interpretation also depends on the analysis population. The primary outcome names subjects who underwent a procedure with the investigational device, while the adverse-event summary reports a separate at-risk group. The record does not explain population derivation, exclusions, missing observations, or whether every enrolled participant contributed to each outcome. Without those details and the actual endpoint estimate, a fuller statistical assessment is not possible.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Sphere-9™ Catheter")
n      <- c(69)
events <- c(2)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Sphere-9™ Catheter  69  2  2.9  0.4  10.1  0.8  10.0  0.9  9.9

11. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures, including the primary safety outcome and secondary outcomes concerning documented recurrence and durable ablation lesions at remapping. It records zero outcome analyses. The record does not state whether a hierarchy among outcomes was prespecified, whether any multiplicity adjustment was planned, or how multiple comparisons would be interpreted. These features are not reported in the registry record.

In general, testing multiple outcomes can increase the chance of obtaining at least one apparently notable result by chance if each is interpreted independently. A prespecified testing strategy or an explicit descriptive interpretation can help readers understand that issue. No such strategy is recorded here, and no statistical test results are listed. It is therefore not possible to assess multiplicity control or to characterize the results as confirmatory from this information.

Missing-data methods are also not reported in the registry record. The recorded enrollment is 74, while the adverse-event summary gives 69 at risk. The record does not explain the difference, state whether outcome observations were missing, or describe any exclusions or imputation. No reason for the denominator distinction should be inferred.

The primary outcome population is described as subjects who underwent a procedure with the investigational device. The registry does not specify further analysis populations, such as whether the primary analysis included all treated subjects or required complete follow-up. It also does not explain how participants with incomplete observation were handled. These omissions limit assessment of potential selection and missing-data effects. No analysis population or missing-data assumption beyond the stated primary population can be established from the record.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: pericarditis (1.4%), esophogeal thermal injury (1.4%), septic shock (1.4%), diaphragmatic paralysis (1.4%), cerebrovascular accident (1.4%).

The serious adverse-event summary for the Sphere-9™ Catheter group records 69 at risk and 5 affected. It records 0 affected by other adverse events and 0 deaths. The event-term listing includes Pericarditis, Esophogeal thermal injury, Septic Shock, Diaphragmatic paralysis, and Cerebrovascular accident, each shown as 1.4%. These are the figures recorded for the adverse-event summary.

These counts should not be conflated with the primary safety endpoint. The primary endpoint has its own serious-event definition and specified observation windows, including the distinct Day 90 window for atrio-esophageal fistula. The registry does not confirm that the adverse-event count and term listing use exactly the primary endpoint’s population, definitions, and timing. The primary endpoint result is not reported in the registry record.

Event terms and affected-participant counts are not necessarily interchangeable. The registry does not explain whether a participant could contribute more than one term or how the listed terms relate to the 5 affected by serious adverse events. The percentages are quoted as recorded and are not independently recalculated. These descriptive observations do not establish comparative risk or prove that unlisted events did not occur.

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

The record documents an assessment of the Sphere-9™ Catheter and Affera Mapping and Ablation System in a prospective, single-arm, multi-center study that is marked completed. It records serious adverse events among the treated group and names several event terms. Those observations are relevant to describing the safety experience captured in the registry, but the information does not amount to a comparative evaluation.

The principal limitation for interpreting the primary safety question is that the primary endpoint result is not reported in the registry record. The adverse-event summary gives 5 affected by serious adverse events among 69 at risk, but the registry does not state that this is the primary endpoint result under its detailed event definition and observation windows. No primary endpoint confidence interval or analysis is recorded. The event-term percentages add detail to the adverse-event listing but do not resolve that distinction.

Because there is no comparator group, the study cannot estimate how the recorded event experience compares with another device, another procedure, or a different care strategy. A single-group description also cannot separate the influence of the device system from other factors associated with the procedure or the participants. The registry does not report condition-specific outcome results, so the listed conditions cannot be interpreted as separate efficacy or safety findings.

The record lists recurrence and durable lesions as secondary outcomes, but does not include their results or analyses in the information available. It therefore does not establish those outcomes’ measured frequency or provide a basis for comparing them with another approach. The study’s status as completed means its registry status is completed; it does not substitute for an endpoint result or a detailed statistical report.

Overall, the record supports a limited descriptive reading of the reported safety counts and study design. It does not establish a treatment effect, a comparative safety advantage, or an efficacy conclusion. Those questions require outcome results, clear analysis populations and methods, and an appropriate comparison where comparative claims are intended.

14. Why This Trial Matters Statistically

This trial is statistically important as an example of how design and reporting shape the meaning of safety data. A single-group study can describe recorded events in a treated population, but it cannot supply the direct comparison that a randomized or concurrent-control design would permit. The distinction is essential when readers encounter event counts and percentages: a descriptive value is not a treatment contrast.

The primary outcome is a composite safety measure with several serious event types and a defined observation period. Composite outcomes can provide a broad summary, but their interpretation depends on component definitions, timing, and counting rules. Here, the description distinguishes the general Day 0 through Day 10 period from the Day 90 assessment for atrio-esophageal fistula. The registry does not report component-level results or the primary endpoint estimate, leaving those details unavailable for statistical interpretation.

The adverse-event summary also illustrates why denominators and populations matter. Recorded enrollment is 74, while the serious adverse-event summary lists 69 at risk. Without an explanation of the difference, readers cannot assume that the populations are interchangeable or determine the reason for the denominator used. Likewise, the 5 serious-event count should not be substituted for the primary endpoint numerator without a recorded link between the two.

Finally, the registry lists no outcome analyses. This makes the record useful for understanding the stated design and identifying reported safety counts, while limiting assessment of statistical precision, missingness, multiplicity, and the planned analysis. These are not minor presentation details: they determine what can responsibly be inferred from observed data. The study’s statistical contribution in this record is therefore primarily descriptive, with important uncertainties about endpoint reporting and analysis left unresolved.

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 endpoint estimate, confidence interval, and statistical analysis are not reported in the registry record. The serious adverse-event summary cannot be assumed to be the primary endpoint result because the record does not explicitly connect its event count to the endpoint’s population, definition, and observation windows.

The study has no recorded comparator group. Its single-group design limits interpretation to description of the treated group and does not support an estimate of comparative effect. The registry also does not report outcome results by condition, despite listing atrial fibrillation, atrial flutter, and ventricular tachycardia.

The recorded enrollment is 74, whereas 69 are listed as at risk in the adverse-event summary. The registry does not explain this difference or report whether it reflects eligibility, treatment, follow-up, missing observations, or another reason. Missing-data handling and detailed analysis-population rules are not reported.

The primary endpoint combines serious events with different characteristics and observation windows. The record does not describe component-specific endpoint results, event adjudication, handling of multiple events in a participant, or the rule used to classify events against the composite. These omissions limit assessment of how the endpoint was constructed and whether the adverse-event listing maps onto it.

The registry lists four outcome measures and zero analyses, but does not report a statistical analysis plan, multiplicity approach, or sample-size justification for the actual study. Planning assumptions associated with an illustration do not establish the study’s design rationale or observed power. The available record therefore leaves key details needed to assess precision and robustness unreported.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Assessment of the Sphere-9™ Catheter and Affera Mapping and Ablation System for Treatment of Atrial and Ventricular Arrhythmias — NCT04211441.
• Registry record last updated 2025-05-16; status last verified 2025-05.
• Results first posted 2025-05-16.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

The registry record describes a completed, prospective, single-arm, multi-center assessment of the Sphere-9™ Catheter and Affera Mapping and Ablation System. Recorded enrollment is 74; the study is listed as phase NA, with allocation NA and masking NONE. The sponsor is Medtronic Cardiac Ablation Solutions.

The primary outcome is the percentage of subjects with a primary safety event. Its description specifies serious adverse events from Day 0 through the Day 10 post-treatment assessment, with atrio-esophageal fistula included through the Day 90 assessment. The primary endpoint result and analysis are not reported in the registry record.

The adverse-event summary lists 69 at risk, 5 affected by serious adverse events, 0 affected by other adverse events, and 0 deaths. Five serious event terms are listed at 1.4% each. The record does not explain the denominator difference from enrollment or establish that these adverse-event figures equal the primary endpoint result. It lists secondary outcomes for documented recurrence and durable lesions at remapping, but no outcome analyses are recorded.