A Post-market Clinical Evaluation of St. Jude Medical™ MR Conditional ICD System on Patients Undergoing Magnetic Resonance Imaging: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Post-market Clinical Evaluation of St. Jude Medical™ MR Conditional ICD System on Patients Undergoing Magnetic Resonance Imaging (NCT02877693), a non-randomized na study. The primary outcome is Number of Participants With Freedom From MRI-scan Related Complications* Related to St. Jude Medical™ MR Conditional ICD System.

2. Clinical Question

3. Trial Design

This was a completed, non-randomized, single-group post-market clinical evaluation sponsored by Abbott Medical Devices. The registry lists 205 participants and identifies ICD and tachycardia as conditions. Its stated purpose was to assess clinical performance of the St. Jude Medical™ MR Conditional ICD System during elective thoracic MRI. The intervention is a thoracic MRI scan; the arm descriptions specify 1.5 Tesla and 3 Tesla scans.

According to the arm descriptions, participants were enrolled at least 60 days after successful implantation and underwent an elective MRI within 30 days after enrollment. Follow-up was scheduled at 1 month after the MRI visit. The primary endpoint timeframe runs from the scan visit through 1 month post-MRI. These details define the intended observation period, but the registry record does not report adherence to each timing requirement or the number of participants followed in each MRI-strength group.

The record identifies no masking and no randomized allocation. It says that primary endpoint analyses would be performed separately for each study phase, while the phase field is listed as NA. The relationship between that phase-specific statement and the MRI-strength groups is not explained. The record lists 7 outcome measures and 0 analysis entries. A detailed statistical analysis plan, including any prespecified models or inferential procedures, is not reported in the registry record.

The primary safety population contains 177 participants who completed through the 1-month post-MRI visit, stated as 86.3% of enrolled participants. This is the population specified for the primary endpoint, not necessarily the population used for every other outcome. Group-specific enrollment, exclusions, and reasons for not completing the visit 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

Analysis population for the primary outcome, as defined in the registry: 177 subjects (86.3% of enrolled subjects) completed through the 1-month post-MRI scan visit and are included in the primary safety 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.

Population: The baseline analysis population consisted of study participants that provided and signed acknowledgement of informed consent and were enrolled in the study.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Freedom From MRI-scan Related Complications* Related to St. Jude Medical™ MR Conditional ICD System, measured over from MRI scan visit to 1 month post-MRI scan visit.

The primary endpoint is the number of participants with freedom from MRI-scan-related complications related to the St. Jude Medical™ MR Conditional ICD System. The registry defines a complication as a serious adverse device effect that requires an invasive intervention or leads to death. The observation period extends from the MRI scan visit to 1 month after the scan.

A participant count is a direct way to describe how many people met a defined safety criterion during a specified follow-up period. This endpoint focuses on a narrowly defined, consequential device-related complication, rather than counting every symptom or event. Its interpretation depends on the stated definition, the follow-up period, and the population included in the analysis. It should not be treated as a complete account of all adverse events, because events outside the definition may not qualify as primary-endpoint complications.

The registry states that 177 subjects who completed through the 1-month post-MRI visit were included in the primary safety endpoint analysis. However, it does not report the number who were free of complications or the number who experienced a qualifying complication. Thus, the endpoint definition and analysis population are available, but the primary endpoint result is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The available registry information supports a descriptive reading of the study, not a reconstruction of a full inferential analysis. The record lists a participant-count primary outcome and identifies the population included in that analysis. It does not report the primary endpoint count, an uncertainty interval, or a model-based estimate. A statistical method should not be inferred merely from the fact that an outcome is expressed as a count.

What does a participant count tell the reader?

A count states how many people meet a defined outcome. For a safety endpoint, the definition determines which events qualify, and the follow-up window determines when events are considered. Here, a qualifying complication is a serious adverse device effect requiring invasive intervention or leading to death, assessed from the MRI scan visit through 1 month post-MRI. This is narrower than a count of all adverse experiences. The count is most interpretable when read alongside the number of participants assessed, the endpoint definition, and the handling of participants without complete follow-up.

The record identifies 177 participants as completing through the 1-month visit and being included in the primary safety analysis. It does not report the endpoint count for these participants. Without the outcome count, the registry information cannot show the observed frequency of the primary event or the precision of that frequency. The fact that the primary endpoint is a count does not license calculation of an unreported percentage or interval.

Why does the design affect interpretation?

Random allocation can help make groups comparable at baseline, while masking can limit some forms of measurement or conduct bias. This study is listed as non-randomized, with no masking and a single-group model. As a result, its design does not support treating MRI-strength groups as exchangeable randomized arms. The two MRI descriptions identify different scan strengths, but the record does not describe a randomized allocation or a controlled comparison. Any difference between groups, if reported elsewhere, could reflect differences in who entered each group or other factors; the registry entries do not establish a causal contrast.

The record says the primary endpoint analysis would be performed for each study phase separately, but lists the phase as NA. It does not explain how study phases correspond to the described MRI groups. This leaves the intended analytic grouping unclear. The registry record does not report a statistical analysis plan with details such as model choice, covariate adjustment, or rules for handling incomplete observations. These omissions should be treated as missing documentation, not as evidence that a particular method was or was not used.

How should uncertainty be considered?

A confidence interval is a statistical range expressing uncertainty around an estimate under a specified method and assumptions. It helps distinguish a precise estimate from one that remains compatible with a wide range of values. No confidence interval for the primary endpoint is reported in the registry record. Consequently, neither the primary result's precision nor the range of values reasonably compatible with the observed data can be judged from the registry information.

Counts of serious events can also be sparse. With few events, estimates are often imprecise, and conventional approximations may perform poorly. This is a general statistical consideration, not a finding about the unreported primary endpoint. The registry lists 1 serious event affected and 1 other event affected for the 1.5 Tesla group, along with 2 deaths, but it does not report uncertainty intervals or the event-level relationships needed to interpret those counts fully.

What do planning calculations mean?

Sample-size illustrations are planning exercises, not observed study outcomes. The assumptions recorded for the illustrations include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is expressed as a stated fraction of the observed effect. For time-to-event illustrations, the stated quantity is total events; for other outcomes, it is participants per arm. Those assumptions describe the illustrations, not necessarily the design or analysis of this non-randomized single-group evaluation. They do not establish that the study was designed around those assumptions or that the assumptions were used prospectively.

Planning calculations also should not be described as observed power. Power is a design quantity tied to assumed effects and analysis conditions; calculations based on an observed effect are particularly dependent on the estimate used. The registry record does not report the trial's sample-size justification, and no planning calculation can fill in the missing primary endpoint result. The illustrations should be understood only as hypothetical planning information under their stated assumptions.

What does the analysis record establish?

The record lists 7 outcome measures and 0 analysis entries. That does not by itself show that no analyses were performed; it indicates that no analysis entries are listed in the registry. The registered endpoint definitions and safety counts remain descriptive registry information. No inferential result, adjustment strategy, or multiplicity procedure should be attributed to the study unless it is reported in the registry record.

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("Thoracic MRI Scan With 1.5 Tesla MRI")
n      <- c(177)
events <- c(177)
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  Thoracic MRI Scan With 1.5 Tesla MRI  177  177  100.0  97.9  100.0  97.9  100.0  97.9  100.0

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 7 outcome measures, but does not report how statistical testing across outcomes was handled. A multiplicity procedure addresses the increased chance of false-positive findings that can arise when several hypotheses are tested. Without a stated testing hierarchy, adjustment method, or distinction between confirmatory and exploratory outcomes, the status of any individual inferential finding cannot be determined. The record lists 0 analysis entries, so it does not provide test results that could be reviewed for such procedures.

Missing-data handling is also not described. The registry identifies 177 subjects, or 86.3% of enrolled subjects, as having completed through the 1-month post-MRI visit and being included in the primary safety endpoint analysis. It does not state why other enrolled participants were absent from that population, whether outcome information was available for them, or how any incomplete follow-up was handled. A completed-visit population can differ from all enrolled participants; the direction or effect of that difference cannot be assessed without further information.

The record does not report whether the primary analysis used an intention-to-treat approach, a per-protocol approach, or another rule for defining the analysis population. Nor does it describe imputation, sensitivity analyses, or assumptions about participants with missing outcome data. These details matter because safety conclusions may depend on who was observed and how unavailable outcomes are treated. No particular approach should be assumed from the stated population count alone.

The registry says that the primary endpoint analysis would be performed separately for each study phase, while the phase field is NA. It does not explain how this relates to the two MRI-strength descriptions. This limits clarity about the intended analysis populations as well as the potential multiplicity structure. The registry record does not report interim analyses, stopping boundaries, or a statistical plan addressing multiplicity.

12. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0.5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: breathlessness (0.5%), refractory cardiogenic shock, recurrent ventricular tachycardia, ventricular fibrillation (0.5%), ventricular arrhythmia (0.5%), serious adverse device effect: acute pulmonary edema (0.5%).

The serious-event figures are listed for the group titled “Thoracic MRI Scan With 1.5 Tesla MRI.” The registry reports 205 participants at risk and 1 affected for serious events, 205 at risk and 1 affected for other events, and 2 deaths. These are registry counts and should be kept distinct from the primary endpoint, which is freedom from a specifically defined MRI-scan-related complication. The primary endpoint count itself is not reported in the registry record.

The serious terms list includes breathlessness; refractory cardiogenic shock, recurrent ventricular tachycardia, ventricular fibrillation; ventricular arrhythmia; and serious adverse device effect: acute pulmonary edema. Each term is reported at 0.5%. The record does not state whether these terms occurred in separate participants, whether one participant could contribute multiple terms, or whether all are considered device-related. It also does not establish whether the 2 deaths were related to the MRI scan, device, or listed events.

“At risk” is the denominator label in the adverse-event information; it should not be assumed to be the same analysis population as the primary safety endpoint population without clarification. The adverse-event information does not provide a complete account of event timing, severity beyond the labels, or causal assessment. These counts describe what the registry lists, not a causal comparison or a standalone measure of the primary endpoint.

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

The registry record describes a post-market evaluation of a specified ICD System in patients undergoing elective thoracic MRI. It provides the primary endpoint definition, its follow-up window, and the size of the population included in the primary safety endpoint analysis. It also reports selected adverse-event counts and serious-event terms. These details establish what the study intended to assess and offer limited descriptive safety information.

The record does not report the number of participants who met the primary endpoint of freedom from MRI-scan-related complications. Therefore, the primary result cannot be quantified from the posted information. No primary endpoint estimate or confidence interval is reported, so its precision cannot be evaluated. The reported completion count is not a substitute for the missing outcome count.

The adverse-event information should not be interpreted as proof of a causal relationship with MRI or the device. The registry does not clarify the relationship of the listed deaths and serious terms to the scan, nor whether event categories overlap. Nor does it provide a randomized control group. The record's non-randomized, single-group classification means that the information does not establish comparative effects between MRI strategies or against no MRI.

Likewise, the distinction between 1.5 Tesla and 3 Tesla descriptions does not, on its own, establish a valid treatment comparison. The registry does not report group-specific outcome results or a comparative statistical analysis. Any conclusions should be limited to the registered population, defined outcomes, and documented follow-up, while recognizing that important results and methods are not reported in the registry record.

In general, a safety evaluation is interpreted by considering the seriousness and definition of events, the number of participants observed, follow-up completeness, and uncertainty around the estimates. The record supplies some of this context but not the primary endpoint result or uncertainty measure. It therefore supports a description of the study's scope and reported event information, rather than a definitive statement about comparative safety or clinical performance.

14. Why This Trial Matters Statistically

This trial is statistically notable because it illustrates the difference between a clearly defined endpoint and a reported endpoint result. The registry specifies what constitutes an MRI-scan-related complication, the relevant follow-up window, and the population included in the primary analysis. Yet the number of participants free from qualifying complications is not reported in the registry record. Without that result, readers cannot assess the observed primary outcome or its precision.

The design also matters. A post-market evaluation can describe events observed in clinical use, but a non-randomized, single-group design does not automatically provide a controlled estimate of the effect of MRI or compare MRI field strengths causally. The record's 1.5 Tesla and 3 Tesla descriptions do not replace randomization or a clear comparative analysis. Recognizing this distinction prevents descriptive event counts from being treated as evidence of a between-group difference.

Follow-up completion is another important part of the statistical interpretation. The primary safety population includes 177 subjects, reported as 86.3% of enrollment. That makes the population definition visible, while the absence of reasons for non-completion leaves uncertainty about how representative the analyzed participants are of everyone enrolled. Missing outcomes can matter even when a study's endpoint is simple to define.

Finally, the record includes several outcome measures and separate safety-event information, but no listed analysis entries. The multiplicity strategy, missing-data methods, and inferential procedures are not reported. This makes the registry a useful example of why endpoint definitions, analysis populations, uncertainty, and transparent methods must be read together. The available information allows a bounded account of what was planned and which events were listed, but not a complete statistical evaluation of the primary safety finding.

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 central limitation is that the registry record does not report the primary endpoint count. The outcome is defined, and the primary analysis population is identified, but the result needed to describe the proportion of participants free from qualifying complications is absent. No uncertainty interval or statistical estimate is reported for that endpoint.

The primary analysis population consists of 177 subjects who completed through the 1-month post-MRI scan visit, stated as 86.3% of those enrolled. The record does not give reasons for the other participants' absence from this population or describe how incomplete outcome information was handled. This prevents assessment of potential bias related to follow-up or analysis-population selection.

The design is non-randomized, unmasked, and classified as single-group. The registry does not establish a like-for-like control comparison, and the field-strength descriptions do not by themselves support causal comparisons. The relation between the statement about separate study phases and the phase field listed as NA is not explained.

Safety details are limited. The adverse-event group lists 1 serious event affected, 1 other event affected, and 2 deaths, but the record does not clarify overlap, participant-level attribution, timing, or causality. The serious terms are listed without enough context to connect each one to the primary endpoint. The registry also does not report a detailed analysis plan, multiplicity handling, missing-data methods, or the sample-size justification. These gaps constrain interpretation of both the primary outcome and the broader safety profile.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Post-market Clinical Evaluation of St. Jude Medical™ MR Conditional ICD System on Patients Undergoing Magnetic Resonance Imaging — NCT02877693.
• Registry record last updated 2023-12-08; status last verified 2023-03.
• Results first posted 2023-12-08.
• 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.

19. Record Summary

NCT02877693 is a completed, non-randomized, single-group post-market evaluation sponsored by Abbott Medical Devices. Its stated aim was to assess the clinical performance of the St. Jude Medical™ MR Conditional ICD System in patients undergoing elective thoracic MRI. The registry describes 1.5 Tesla and 3 Tesla scans and follow-up at 1 month after MRI.

The primary endpoint is the number of participants free from MRI-scan-related complications, defined as serious adverse device effects requiring invasive intervention or leading to death, from the scan visit through 1 month post-MRI. The primary safety population included 177 subjects, reported as 86.3% of 205 enrolled participants. The endpoint result is not reported in the registry record.

For the listed 1.5 Tesla group, adverse-event information reports 1 serious event affected, 1 other event affected, and 2 deaths. The registry lists 7 outcome measures and 0 analysis entries. Comparative results, uncertainty estimates, and details of missing-data and multiplicity methods are not reported in the registry record.