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 Clinically Indicated Magnetic Resonance Imaging in Patients With Cardiac Devices (NCT01130896), a registered phase not stated study. The primary outcome is Device Malfunction.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01130896 |
| Phase | Phase not stated |
| Condition | Arrhythmias, Cardiac |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 1509 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Johns Hopkins University |
| Results posted | Yes |
2. Clinical Question
Population
Patients with implanted permanent pacemakers or implantable defibrillators who met appropriate entrance criteria and underwent clinically indicated MRI. The condition listed in the registry is cardiac arrhythmias; further eligibility details and characteristics of the enrolled participants are not reported in the registry record.
Intervention
Clinically indicated MRI, described as all types, performed in patients with implanted cardiac devices using an established safety protocol. The protocol’s specific procedures and device-management requirements are not reported in the registry record.
Comparator
No like-for-like control group is described. The registry lists a single study group, and allocation is not stated. This record therefore does not describe a randomized comparison of MRI with a control condition.
Primary question
The primary outcome was the number of participants with a change in device testing after MRI or during follow-up, using specified device measurements and a threshold defined relative to baseline. The registry lists assessment immediately after MRI, up to 2 hours, and long-term follow-up, up to 6 months. It does not report the number of participants meeting this primary outcome, so the primary question cannot be answered from the reported outcome information.
3. Trial Design
The registry describes a completed study of clinically indicated MRI in patients with permanent pacemakers and implantable defibrillators. The listed group received clinically indicated MRI of all types under an established safety protocol. The record reports enrollment of 1509 participants and identifies Johns Hopkins University as the sponsor. The study start is recorded as 2003-05, with primary completion on 2015-01-22.
The design information does not describe a randomized allocation or a control group. Allocation is not stated, and the listed study group is not a like-for-like comparison arm. These details matter because an outcome observed in a single group can describe what was recorded among those participants, but does not by itself estimate a contrast against participants who did not undergo MRI or who received another intervention.
Participants were described as meeting appropriate entrance criteria. The registry record does not report the criteria themselves, how the clinically indicated scans were selected, or the specific protocol procedures. It also does not report participant characteristics that would allow readers to assess how closely the enrolled group represents other patients with implanted devices.
The primary outcome was defined as a count of participants with a specified change in device testing. Its stated assessment windows were immediately post MRI, up to 2 hours, and long-term follow-up, up to 6 months. The registry records three outcome measures, but the full outcome list and results are not available in the information. The study status is COMPLETED; completion status does not establish that results for every registered outcome were posted.
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 | MRI and Cardiac Devices |
|---|---|
| STARTED | 1509 |
| COMPLETED | 1509 |
| NOT COMPLETED | 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 | MRI and Cardiac Devices |
|---|---|---|
| Participants analysed | 1509 | |
| Age, Continuous | years | 69.3 (57.7 to 78.1) |
| Sex: Female, Male: Female | Participants | 548 |
| Sex: Female, Male: Male | Participants | 961 |
| Region of Enrollment: United States | participants | 1509 |
6. Primary Endpoint
The registry lists the primary outcome as Device Malfunction, measured over immediately post MRI (up to 2 hours) and long-term follow-up (up to 6 months).
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is a participant count: the number of patients with a change in device testing. The registry defines a qualifying change using any of the following measurements: impedance, battery life, P and R wave sensing, and atrial and ventricular capture thresholds. The stated criterion is that the change not exceed 50 percent from baseline. The assessment timeframe includes immediately after MRI, up to 2 hours, and long-term follow-up, up to 6 months.
Using a count of participants gives a direct description of how many people met the endpoint definition, rather than reporting a group average across device measurements. This can be useful when the clinical question concerns whether a participant experienced a change meeting a prespecified threshold. In general, a threshold-based endpoint simplifies a set of measurements into a defined event, but the interpretation depends on the exact definition, measurement procedures, and follow-up completeness.
The endpoint definition is reported, but its observed count and any uncertainty estimate are not reported in the registry record. Therefore, readers cannot determine from this record how many participants met the definition at either assessment period. Nor does the entry clarify how a participant with changes in multiple measurements or at multiple timepoints would be counted beyond describing the outcome as a number of patients.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record gives the primary endpoint definition but not its result. It therefore does not establish how many participants experienced a qualifying device-testing change, how often such a change occurred across the assessment windows, or how precisely any observed count was estimated. No primary endpoint analysis is listed. A completed study status and an enrolled population of 1509 do not substitute for a reported endpoint count.
The available safety counts are distinct from the primary endpoint. The record lists 0 participants with serious adverse events among 1509 at risk, 8 participants with other adverse events among 1509 at risk, and 0 deaths among 1509 at risk. These are descriptive counts in the registry record. The serious-event terms are not listed, and the record does not describe the other adverse events. The entries do not establish whether an event was caused by MRI or by another circumstance.
Because no control group is described, the counts cannot be interpreted as a comparative estimate of risk. A single-group count describes what was recorded in the enrolled group under the study conditions; it does not show what would have occurred in a comparable group without MRI. The registry also does not provide the details needed to assess how participants were selected, whether all enrolled participants contributed to each outcome, or whether follow-up was complete.
In general, estimates are easier to interpret when the event definition, time at risk, follow-up, and analysis population are clear. A count alone does not convey uncertainty in the way a confidence interval does. A confidence interval, as a general statistical concept, describes a range of values compatible with the data and a specified method, but no interval for the primary endpoint is reported in the registry record.
The record identifies the study’s intended topic and endpoint, but the information available does not answer the primary statistical question. The safety counts should be read as reported counts, not as evidence of a comparative effect or as a complete account of all outcomes. The registry does not report a sponsor analysis of device malfunction, an adjusted analysis, or a statistical test for the primary endpoint.
9. Statistical Methods Explained
Statistical interpretation begins with identifying the study design and the quantity the analysis is intended to estimate. This registry entry describes clinically indicated MRI in one listed study group. It does not describe randomized allocation or a like-for-like control group. In general, random assignment can support comparisons by balancing measured and unmeasured factors on average, while a single-group study describes outcomes among participants who received the intervention under the observed conditions. Here, allocation is not stated, and the record does not support a randomized treatment comparison.
What does a participant count represent?
The primary outcome is a count of participants meeting a threshold-based definition of device-testing change. This is a binary outcome at the participant level: a participant either meets the stated event definition or does not, according to the recorded measurements and the endpoint rule. The registry describes the measurements used—impedance, battery life, P and R wave sensing, and atrial and ventricular capture thresholds—and specifies that the change is not to exceed 50 percent from baseline.
In general, a binary endpoint can be summarized as an event count and as the number of participants assessed. The count is interpretable only alongside a clear denominator and a clear definition of who was assessed. The registry record does not report the primary endpoint count, the denominator analyzed, or a confidence interval. The listed enrollment of 1509 is not necessarily the analysis denominator for every outcome; the analyzed population and outcome-specific completion are not reported in the registry record.
Why do the assessment windows matter?
The endpoint includes assessment immediately after MRI, up to 2 hours, and long-term follow-up, up to 6 months. In general, an outcome may differ according to when it is measured. An immediate assessment and a later follow-up answer related but not identical questions, and the handling of repeated measurements should be specified when the same participant can contribute information at more than one time. The registry record does not report separate primary endpoint results by window or explain how observations across the windows were combined.
Timing also matters for the denominator. Participants may have different amounts of observed follow-up, and missing measurements can affect which participants contribute to a result. In general, an analysis should make clear who was eligible for each assessment and how unavailable measurements were handled. Those details are not reported in the registry record.
What can a confidence interval add?
In general, a confidence interval expresses the precision of an estimate under a stated statistical method. A narrow interval indicates greater precision than a wide interval, while neither interval alone resolves biases in study design or measurement. For a participant count, uncertainty is usually considered in relation to the number of participants assessed and the event count. No confidence interval for the primary endpoint is reported, so its precision cannot be evaluated from this record.
A statistical test and a confidence interval serve different but related purposes. A test evaluates compatibility with a specified null hypothesis under its assumptions; an interval presents a range of estimates compatible with the data and method. Neither can be reconstructed from a definition alone. Because the registry does not report the primary outcome results or an analysis, no test result or interval should be inferred.
How should planning assumptions be read?
General sample-size planning asks how many participants would be needed to detect a specified effect under assumptions about the significance level, allocation, outcome variability, and statistical method. The listed planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They also describe the effect to detect as a stated fraction of an observed effect. These assumptions are planning illustrations, not a description of the enrolled study design. The registry record does not report a trial-specific sample-size justification.
The assumptions of equal allocation and two arms do not match the listed single-group experience and are not evidence that the study enrolled a randomized comparator group. Any sample-size illustrations should therefore be interpreted only as hypothetical planning scenarios under their stated assumptions, not as analyses of the registry study. Planning calculations are not observed power. Observed power is not a substitute for reporting an effect estimate and its uncertainty, and no primary endpoint estimate is available in this record to interpret.
In general, over-dispersion matters when observed variation exceeds what a statistical model assumes; ignoring it can make standard errors too small and confidence intervals too narrow. The primary outcome is presented as a participant count, but the registry record does not report a fitted model or an analysis that would permit assessment of over-dispersion. It would be inappropriate to assume that such a model was used.
What can be inferred from the posted analysis information?
The record lists 0 analyses. This means the information available does not include a reported analysis for the primary outcome. The endpoint definition and the adverse-event counts are not substitutes for a prespecified statistical analysis plan. The plan for covariate adjustment, handling of repeated observations, subgroup analyses, and any interim analyses is not reported in the registry record. General statistical principles can explain why these decisions matter, but cannot establish which decisions were made for this study.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists three outcome measures, but the information available does not include a complete account of all outcome names, their results, or the analysis plan. It identifies a primary outcome and lists noise artifacts as a secondary outcome, defined by participants with a greater-than-50-percent change in lead impedance. The names and results of any other outcome measures are not reported in the registry record.
Multiplicity arises in general when several outcomes, timepoints, subgroups, or statistical tests are examined. Each additional analysis can increase the chance of finding an apparently notable result by chance if the analyses are treated as independent opportunities for discovery. A prespecified hierarchy or adjustment method can address some of this concern. The registry record does not report whether multiplicity was addressed, whether outcomes were adjusted for repeated measurements, or whether any secondary outcome was designated for confirmatory interpretation.
Missing data can also affect interpretation. In general, if some participants lack an outcome assessment, the result among those assessed may differ from the result that would have been observed had everyone been measured. The registry record does not report the number with available primary endpoint measurements, reasons for missing assessments, follow-up completion, or methods for handling missing data. It also does not identify the analysis population used for the primary endpoint.
These omissions prevent assessment of whether the reported enrollment and the endpoint denominator would coincide. They also prevent evaluation of any sensitivity analysis for missing outcomes. The registry record does not report an interim-analysis plan, stopping rules, or an adjustment for interim looks. No such procedures should be inferred from the study’s duration or completed status.
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 |
|---|---|---|---|
| MRI and Cardiac Devices | 0 | 1509 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| MRI and Cardiac Devices | 0 of 1509 |
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 |
|---|---|
| MRI and Cardiac Devices | 8 of 1509 |
Most frequent non-serious adverse event terms
| Event term | Organ system | MRI and Cardiac Devices |
|---|---|---|
| Power on reset | Surgical and medical procedures | 8 of 1509 |
The registry lists 0 participants with serious adverse events among 1509 at risk, 8 with other adverse events among 1509 at risk, and 0 deaths among 1509 at risk. These are reported counts for the study group. The serious adverse-event terms are not listed, and the nature and timing of the other adverse events are not reported in the registry record.
Serious adverse events and other adverse events are separate registry categories. The count of 0 for serious events should not be treated as a description of all adverse events, since the record separately lists 8 participants with other adverse events. Likewise, the count of 0 deaths is a distinct entry and does not describe the primary device-malfunction endpoint.
In general, safety counts need context about event definitions, follow-up duration, ascertainment, and attribution. The registry record does not report whether events were considered related to MRI, how they were collected, or whether the same participant could contribute to more than one event category. The counts are therefore descriptive and do not establish causation or comparative safety.
12. What the Result Does, and Does Not, Mean
The registry record documents a study of clinically indicated MRI in patients with implanted pacemakers and defibrillators, with a stated safety protocol and a defined device-malfunction endpoint. It also reports enrollment of 1509 and safety counts of 0 serious adverse events, 8 other adverse events, and 0 deaths. Those details describe the recorded study entry.
The primary endpoint result is not reported in the registry record. As a result, the record does not show how many participants had a qualifying change in device testing, either immediately after MRI or during the stated long-term follow-up. It also does not provide an estimate of uncertainty for that outcome. The primary question therefore remains unanswered by the outcome results available in this record.
The safety counts do not establish that MRI caused or did not cause an event. Without a comparison group, the record cannot quantify a difference against another care strategy or against what would have happened without MRI. Counts from a selected group meeting entrance criteria also do not, on their own, establish how the findings would apply to people who would not meet those criteria.
In general, a result is most informative when readers can assess the endpoint definition, analyzed denominator, follow-up, missingness, and uncertainty together. Those elements are not all reported for the primary outcome. The listed planning assumptions describe hypothetical sample-size illustrations; they are not evidence of the study’s design, its observed power, or an effect estimate.
The appropriate statistical reading is limited: the registry describes the intended question and some safety counts, but does not supply the primary endpoint result or an analysis that answers the question. This distinction avoids treating study completion, enrollment, or the absence of reported serious events as a substitute for the missing primary outcome estimate.
13. Why This Trial Matters Statistically
This study raises an important statistical distinction between a clinically relevant question and a reported result. The registry defines a device-testing outcome tied to specific measurements and baseline change, with immediate and longer-term assessment windows. That level of endpoint description helps readers understand what investigators intended to count. However, without the observed endpoint count, denominator, and uncertainty, the endpoint cannot be evaluated quantitatively.
The study also illustrates why design context matters when interpreting counts. A single listed group can describe the participants who underwent clinically indicated MRI, but it does not provide a randomized contrast. In general, a comparison requires a suitable comparator and an analysis that accounts for how participants entered each group. Here, allocation is not stated and the registry explicitly does not describe a like-for-like control comparison.
Another statistical issue is the separation of primary outcomes from safety summaries. The primary device-malfunction endpoint and the reported adverse-event counts are different measures. Reading the safety counts as if they answered the primary question would conflate distinct outcomes. The record’s completed status and enrollment figure likewise do not fill the gap in the primary result.
Finally, the planning assumptions underline the importance of distinguishing hypothetical design calculations from the study that actually took place. Equal allocation between two arms is an assumption for the illustrations, not a feature of the listed study group. Clear reporting of analysis populations, follow-up, missing data, and uncertainty would be needed for a fuller statistical assessment. The record makes these reporting limits visible without permitting conclusions beyond the counts and definitions it contains.
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 main limitation for interpretation is that the registry record does not report the primary endpoint result or any analysis of it. The endpoint’s count, analyzed denominator, and precision are unavailable. Although the assessment windows are stated, separate results by timepoint and the method for combining repeated measurements are not reported.
The record lists one study group and does not describe a randomized comparison. Allocation is not stated, and there is no like-for-like control arm. Consequently, the reported safety counts cannot be used to estimate a comparative effect or to isolate the contribution of MRI from other circumstances.
Details needed to judge applicability are also not reported, including the entrance criteria, participant characteristics, and the specific procedures in the established safety protocol. The registry record does not report outcome-specific follow-up completion, missing data, reasons for missing assessments, or the analysis population. These omissions limit assessment of selection, measurement, and attrition.
The safety information is limited to counts. The serious-event terms are not listed, and descriptions, timing, and attribution for the other adverse events are not reported in the registry record. The record also does not report an analysis plan, sample-size justification, interim analyses, or methods for handling multiplicity. The planning assumptions described for hypothetical calculations should not be mistaken for the actual study design or a trial-specific justification.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Clinically Indicated Magnetic Resonance Imaging in Patients With Cardiac Devices — NCT01130896.
- Registry record last updated 2021-05-13; status last verified 2021-04.
- Results first posted 2018-12-12.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
The registry record describes a completed study sponsored by Johns Hopkins University, with enrollment of 1509. It concerns clinically indicated MRI of all types in patients with implanted pacemakers and implantable defibrillators who met appropriate entrance criteria and underwent MRI under an established safety protocol. The recorded start is 2003-05, and primary completion is 2015-01-22.
The primary outcome is a count of participants with a defined change in device testing, assessed immediately after MRI, up to 2 hours, and during long-term follow-up, up to 6 months. The primary result and an analysis of that outcome are not reported in the registry record. The safety entries list 0 serious adverse events, 8 other adverse events, and 0 deaths among 1509 at risk. The record does not describe a randomized control comparison.