EMRI SureScan™ Clinical Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for EMRI SureScan™ Clinical Study (NCT00433654), a randomized na study. The primary outcome is Atrial Pacing Capture Threshold Success.

2. Clinical Question

The study’s stated purpose was to confirm safety and efficacy in the clinical MRI environment for the investigational pacing system. The primary endpoint specifically concerns atrial capture threshold: the energy required from the pacemaker to make the heart’s atrium beat. It is a device-performance measure over the interval around the scan, rather than a direct measure of symptoms or longer-term health outcomes.

The result addresses the analyzed participants who met the endpoint’s measurement and protocol criteria. It does not automatically describe every enrolled participant, and the registry record does not report why each participant was absent from the primary analysis. The comparison is therefore best read as a comparison of the posted endpoint results under those analysis criteria, not as a complete account of every possible consequence of MRI exposure.

3. Trial Design

The EMRI SureScan™ Clinical Study is recorded as a randomized, parallel-group trial with no masking. It is marked completed, and the recorded phase is NA. The registry lists an enrollment of 484. The sponsor is Medtronic Cardiac Rhythm and Heart Failure, and the stated study purpose was to assess safety and efficacy of the investigational EnRhythm MRI™ SureScan™ Pacing System in the clinical MRI environment.

Both groups received an implantable pulse generator and pacing leads. At the 9-12 week post-implant follow-up, the MRI group underwent a one-hour MRI scan, while the control group waited for one hour without MRI. The primary endpoint compared atrial pacing capture threshold between the 9-12 week visit and the 4-month visit, described as one month post-MRI for the MRI group.

Random allocation can help make groups comparable at the point of assignment, but the registry record does not report the method used to generate or conceal the allocation sequence. It records no masking. The record also does not describe whether outcome assessors were masked, so that detail is not reported in the registry record.

The primary analysis was not defined simply by enrollment. Participants were excluded if they lacked the threshold measurement at either required visit; MRI-group participants were also excluded if their scan was not performed according to protocol. The posted primary arm counts are 165 for the MRI group and 164 for the control group. These analysis counts differ from the enrollment figure, but the registry record does not give a full accounting of the reasons for that difference.

The record gives the study start as 2007-02 and primary completion as 2008-11. It does not report the protocol’s sample-size justification, a detailed schedule of analyses, or how missing measurements were handled beyond the stated primary-analysis exclusions.

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: Implant procedure included EnRhythm MRI SureScan pacemaker and 2 CapsureFix MRI 5086MRI leads. Pacemaker function and adverse events were assessed. 17 subjects did not have an implant attempt. 3 subjects received a subset of the 3 system components and were followed for safety. All other subjects were randomized after successful implant.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Subjects who underwent an MRI scan following study protocol-specified instructions are included. Of the 243 subjects who completed a one-month post-MRI (4-month) visit, 32 did not complete the MRI scan according to the protocol instructions, and are not included.

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.

6. Primary Endpoint

The registry lists the primary outcome as Atrial Pacing Capture Threshold Success, measured over 9-12 week visit to 4-month visit.

The primary endpoint is atrial pacing capture threshold success, measured from the 9-12 week visit to the 4-month visit. Capture threshold is described in the registry as the energy sent from the pacemaker needed to make the heart’s atrium beat. A participant was considered successful if the threshold did not increase by 1.0 volt or more over that interval.

This endpoint is used to assess a specific aspect of pacing-system performance around MRI exposure. The pre-scan measurement for the MRI group provides a reference point, and the later measurement allows the study to assess whether the threshold changed by the defined amount. The endpoint reduces a continuous measurement to a success-or-not classification using the stated threshold criterion. That makes the primary comparison a comparison of participant counts rather than a comparison of mean voltage changes.

The definition also determines who contributes to the analysis. Participants without measurements at either visit were excluded, as were MRI-group participants whose scan did not follow protocol. The registry record does not describe an approach to impute missing measurements or classify excluded participants.

Interpretation should remain tied to this endpoint: it concerns the specified atrial threshold change over the stated follow-up interval. It does not, by itself, establish effects on other measures of device function, arrhythmias, complications, symptoms, or outcomes beyond the follow-up described. Those topics require separate outcome data and appropriate analysis.

7. Results Posted in the Registry

• MRI Group: 100.0% (165/165) versus 100.0% (164/164) on control; risk difference 0.0 percentage points (95% CI 0.0 to 0.0), risk ratio 1.00 (1.00–1.00); unadjusted two-proportion z-test p = n/a.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Atrial Lead Impedance Change

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • MRI Group: mean -0.60 versus 7.30 on control; difference -7.90 (95% CI -18.97 to 3.17), standardized effect d = -0.14; z-test p = 0.162.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between MRI Group and the control. The interval gives the range of effects that remain compatible with the data.

Ventricular Lead Impedance Change

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • MRI Group: mean -9.00 versus -5.70 on control; difference -3.30 (95% CI -13.18 to 6.58), standardized effect d = -0.07; z-test p = 0.513.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between MRI Group and the control. The interval gives the range of effects that remain compatible with the data.

Atrial Pacing Capture Threshold

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • MRI Group: mean 0.78 versus 0.77 on control; difference 0.01 (95% CI -0.10 to 0.12), standardized effect d = 0.02; z-test p = 0.854.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between MRI Group and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary outcomes cover additional device measurements and clinical events, including lead impedance, lead handling, complications, adverse device effects, arrhythmias, and threshold-related measures. The continuous comparisons available for recalculation show estimates close to zero relative to their stated measurement scales, with confidence intervals that include zero. Taken together, these results do not present a clear, consistent signal of a group difference across the posted continuous comparisons.

This broad pattern is compatible with the primary result in the limited sense that neither the primary success counts nor the continuous secondary estimates show an obvious separation between groups. It does not independently verify the primary result or demonstrate equivalence across outcomes. The primary endpoint is a binary threshold-change classification; secondary measures have different definitions, units, analysis populations, and follow-up descriptions. Agreement in broad direction does not make them interchangeable evidence.

The registry lists 11 posted secondary outcomes, while the study record also lists 16 outcome measures and 6 analyses. The record does not explain the relationship between those counts, how outcomes were selected for reporting, or whether all planned analyses are included. The secondary results should therefore be read with caution.

Unadjusted secondary results carry less weight because examining many outcomes increases the chance of finding an apparently notable result by chance. No multiplicity adjustment or hierarchy among secondary outcomes is reported in the registry record. These results are most useful as descriptive and exploratory context, not as a collection of separate confirmatory tests. They also do not resolve limitations of the primary analysis, including its exclusions and the absence of the sponsor’s confidence limits and decision margin.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Subjects With System-related Complications
• System Related Adverse Device Effects Due to Labeling Instructions
• Occurrence of Arrhythmias
• Atrial Lead Impedance Change
• Ventricular Lead Impedance Change
• Atrial Lead Handling Rating
• Ventricular Lead Handling Rating
• Atrial Pacing Capture Threshold

9. Statistical Interpretation

10. Statistical Methods Explained

The registry’s primary outcome is binary: each analyzed participant is classified as a success or not under the stated threshold rule. The posted group counts show successes, while the recalculation compares the proportion of participants classified as successful between MRI and control. No failures appear in either posted primary count.

What does a risk difference express?

In general, a risk difference is the proportion with the outcome in one group minus the proportion with the outcome in the comparison group. It describes an absolute contrast on the outcome scale. A value of 0.0 means the observed proportions are the same in the posted analysis. It does not, by itself, say how compatible the data are with other possible underlying differences; that requires an uncertainty measure and attention to how the estimate was obtained.

Here, the recalculated risk difference is 0.0 and its recalculated interval is 0.0 to 0.0, because the posted analysis has no failures in either group. General statistical caution is important when an outcome has no events or failures: standard methods can produce boundary estimates that understate uncertainty or become uninformative. This is why the reported interval should not be interpreted as proof that the population difference must be exactly zero.

What does the sponsor’s method address?

The registry lists a Farrington-Manning analysis for a difference in percentages, marked as a legacy non-inferiority or equivalence analysis. In general, this method can be used to evaluate a difference against a prespecified margin, with a confidence interval and test interpreted in relation to that margin. The registry record reports a point estimate of 0 and a 95% confidence level, but gives no confidence limits, p-value, or non-inferiority/equivalence margin. Without those details, the inferential conclusion of that analysis cannot be reconstructed from the record.

A non-inferiority or equivalence conclusion is not established merely because two observed proportions match. Such a conclusion depends on the prespecified margin and the uncertainty around the difference. The registry record does not report the margin, so the posted primary counts alone cannot establish whether the sponsor’s intended criterion was met.

How should the continuous secondary measures be read?

For the posted continuous secondary outcomes, the record gives group means and standard deviations, along with recalculated mean differences and confidence intervals. A mean difference expresses the contrast between the group averages in the measurement’s units. A standard deviation describes how spread out individual measurements are around a group mean; it is not the uncertainty of the mean itself. The recalculated intervals for these comparisons include zero, so the data do not identify a clear direction of difference at the stated interval level. The intervals also permit differences other than zero, which means a non-significant result is not evidence that the groups are identical.

General statistical reasoning also cautions that unadjusted p-values do not account for the number of outcomes examined. With multiple endpoints, chance alone can produce apparently notable results. The registry record does not report a multiplicity strategy, so the secondary p-values should not be treated as confirmatory without additional context.

What do the planning illustrations mean?

The planning illustrations use the observed effects as hypothetical targets and state assumptions of a two-sided significance level of 0.05, equal allocation, and a normal approximation. They are not observed power and do not describe the trial’s original design justification. In general, a planning calculation asks how many participants per arm might be needed to detect an assumed effect under stated assumptions. It cannot show that a study had a particular probability of finding an effect after the results are known. The registry record does not report whether these assumptions match the original protocol.

Across all methods, analysis choices matter. The endpoint-specific exclusions, the absence of a reported missing-data approach, the unavailable limits and p-value for the sponsor’s primary analysis, and the unreported multiplicity plan limit how far formal conclusions can be taken. The posted recalculations are simple comparisons based on the posted summary statistics; they do not replace the sponsor’s full protocol analysis.

11. Confidence Intervals and Precision

A confidence interval describes a range of values reasonably compatible with the data and the method used to calculate it. In general, a narrower interval indicates greater statistical precision, while a wider interval indicates greater uncertainty. The interval does not give the probability that a fixed true effect lies within its particular bounds.

For the primary endpoint, the recalculated risk-difference interval is 0.0 to 0.0. The point estimate and interval arise from posted counts in which every analyzed participant is classified as a success. This degenerate interval should not be mistaken for strong precision: with no observed failures in either group, the data do not reveal how often failure might occur in a wider population. The sponsor’s listed analysis gives a 95% confidence level but does not provide the interval limits, so its precision cannot be evaluated from the registry record.

The recalculated intervals for the continuous secondary comparisons include zero. They are not all equally informative: their widths depend on the observed variability and the amount of data contributing to each outcome. These intervals leave room for both directions of difference, rather than establishing that a meaningful difference is absent. The registry record does not state a clinically important difference for these measures, so statistical precision cannot be translated into a judgment about clinical importance.

Precision is also affected by who was analyzed. The primary endpoint excluded participants without required measurements and certain MRI-group participants with protocol deviations. The registry record does not provide a complete account of missingness or a sensitivity analysis. Consequently, the intervals characterize the stated analyzed data and methods, not every uncertainty arising from exclusions, protocol conduct, or outcome reporting.

12. Analyses Reported by the Sponsor

The sponsor’s listed primary analysis uses the Farrington-Manning method for a difference in percentages and reports a value of 0 with a 95% confidence level. The recalculation from the posted group counts also gives a risk difference of 0.0. These point estimates agree in substance: the posted primary analysis shows the same success proportion in the MRI and control groups.

The registry record does not include the sponsor analysis’s confidence limits or p-value. It also does not report the non-inferiority or equivalence margin needed to interpret a Farrington-Manning result as evidence meeting a prespecified criterion. The recalculated interval is not a substitute for those missing elements, particularly given that no primary-endpoint failures were observed in either group.

The registry record does not indicate a discrepancy between the posted point estimate and recalculation. The sponsor’s method and its intended criterion remain the relevant basis for the sponsor’s formal analysis, but the information recorded is not sufficient to determine the full inferential conclusion. The shared zero point estimate is descriptive; it does not alone establish non-inferiority, equivalence, or absence of a population-level difference.

13. Multiplicity, Missing Data and Analysis Populations

The registry lists multiple outcome measures and analyses, including a primary endpoint and a range of secondary measures. When several hypotheses are tested, the chance of at least one apparently positive result can increase. General statistical practice addresses this issue through a prespecified testing hierarchy, adjustment of significance thresholds, or a clear designation of secondary results as exploratory. The registry record does not report a multiplicity plan, so it is not possible to determine whether or how the sponsor accounted for multiple comparisons.

Missing data are relevant to the primary endpoint because participants without atrial capture threshold measurements at either required visit were excluded. MRI-group participants whose scan was not performed according to protocol were also excluded. These are the stated primary-analysis rules. The registry record does not report the number of participants excluded for each reason, the distribution of exclusions by group, why measurements were missing, or a sensitivity analysis under alternative assumptions.

The record does not identify the primary analysis as intention-to-treat, per-protocol, or another named population. Because protocol adherence is part of the MRI-group exclusion rule, the posted primary result should not be assumed to represent every randomized participant. The record does not explain how participants were handled in outcomes other than the primary endpoint.

The adverse-event figures use at-risk counts that differ from the primary endpoint analysis counts, and an additional non-randomized group is listed. The registry record does not explain the membership rules or accounting behind these denominators. It is therefore important not to combine those safety figures with the primary analysis or infer a participant flow from them.

The sponsor’s primary analysis reports a point estimate and confidence level but omits the confidence limits, p-value, and decision margin. The registry record also does not report the original sample-size rationale, interim analysis plans, or a full statistical analysis plan. These absences constrain assessment of selective reporting, analysis choices, and the intended evidentiary standard.

14. Safety Results

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

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

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: pneumonia (10.0%), atrial fibrillation (5.0%), lead dislodgement (4.6%), chest pain (3.4%), pneumothorax (3.4%).

The registry reports serious adverse-event figures for the MRI group, control group, and a non-randomized group. The listed at-risk counts are 260, 207, and 20, respectively; the corresponding serious-event affected counts are 117, 77, and 3. For other adverse events, the affected counts are 24, 19, and 0. These are the posted counts; no rates or between-group differences are calculated.

The at-risk counts do not match the primary analysis counts, and the record does not explain the difference. The serious-event counts should not be read as counts of events caused by the MRI scan or pacing system. The registry’s listed serious terms include pneumonia, atrial fibrillation, lead dislodgement, chest pain, pneumothorax, and syncope, with displayed percentages. The record does not specify the denominator or attribution basis for those term percentages, so they should be interpreted as registry listings rather than causal estimates.

Deaths are not reported in the registry record. The event figures are descriptive safety information, not a randomized causal comparison unless the underlying definitions, observation periods, and analysis methods support that interpretation. Those details are not fully reported in the registry record.

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

The primary result means that, among participants included in the posted analysis, every participant in each group met the registry’s stated atrial capture threshold success definition. The recalculated difference in success proportions is zero. This is a direct description of the analyzed counts and the specified endpoint over the stated follow-up interval.

It does not establish that the MRI scan and control condition are equivalent for every possible effect, or that the true difference in the broader population is exactly zero. The absence of primary failures makes the recalculated interval uninformative about the frequency of failures beyond the observed sample. The sponsor’s analysis is identified as a non-inferiority or equivalence-style method, but the registry record lacks its confidence limits, p-value, and margin. A formal non-inferiority or equivalence conclusion cannot be recovered from the reported point estimate alone.

Nor does the primary endpoint speak to all aspects of safety or device performance. It evaluates a particular threshold change, not every complication, adverse device effect, arrhythmia, or longer-term outcome. The registry lists safety and secondary outcomes, but the available results and analysis details do not support a single broad conclusion about all potential effects.

The result also applies to the analyzed population under the stated exclusions. Missing measurements and MRI protocol deviations affected eligibility for the primary analysis, and the registry record does not report a full accounting or missing-data sensitivity analysis. The posted result therefore should not be generalized automatically to all enrolled participants or to settings and follow-up periods not described in the record.

In general, a finding that does not show a clear difference is not the same as proof that no meaningful difference exists. That distinction is especially important when the endpoint has no observed failures, inferential details are incomplete, and multiple secondary outcomes are reported without a stated multiplicity plan.

16. Why This Trial Matters Statistically

This trial is statistically interesting because its primary endpoint is a binary success measure with all analyzed participants classified as successful in both groups. The resulting zero difference is easy to describe but difficult to interpret as evidence of precision. It illustrates why identical observed proportions do not, by themselves, establish equivalence or rule out a difference in the underlying populations.

The record also connects a sponsor-reported non-inferiority or equivalence-style analysis with a simple recalculation from posted counts. The point estimates agree, yet the key information needed to assess the sponsor’s formal conclusion—the margin and confidence limits—is not reported. This distinction matters: a point estimate addresses the observed contrast, while a decision about non-inferiority or equivalence requires the prespecified criterion and uncertainty around that contrast.

The trial also highlights how analysis populations shape interpretation. The primary endpoint excluded participants missing measurements and MRI-group participants with protocol deviations. The safety figures use different at-risk counts and include a non-randomized group. Without a complete participant accounting, these sets of results cannot be treated as though they describe the same population.

Finally, the secondary results show why a set of unadjusted comparisons should not be read as multiple independent confirmations. Different outcomes may offer useful descriptive context, but multiple testing, incomplete analysis details, and differing outcome definitions affect the weight of that evidence. These are general statistical lessons that apply beyond this trial: estimates, intervals, design criteria, and analysis populations must be considered together.

17. 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 registry record leaves important trial-specific details unavailable. It records randomized allocation and no masking, but does not describe the randomization procedure, allocation concealment, or masking of outcome assessors. Those details matter when evaluating possible selection and measurement biases.

The primary endpoint has a restricted analysis population: participants without measurements at either specified visit and MRI-group participants whose scan did not follow protocol were excluded. The record does not quantify exclusions by reason or group, provide a full participant flow, or report sensitivity analyses for missing data and protocol deviations. The posted primary counts therefore cannot be assumed to include every randomized participant.

The sponsor’s Farrington-Manning analysis is missing its confidence limits, p-value, and non-inferiority or equivalence margin. This prevents assessment of the intended decision criterion from the registry record. The protocol’s sample-size justification and statistical analysis plan are also not reported, so the planning illustrations cannot be treated as evidence about the original design.

Follow-up for the primary endpoint is described through the 4-month visit, with the MRI scan at the 9-12 week follow-up. The record does not establish what happened beyond the reported timeframes. The endpoint addresses atrial capture threshold, not every dimension of safety or system performance.

Safety-event denominators differ from the primary analysis counts, and the reason is not reported. The record does not provide enough detail about attribution, observation windows, or the denominator for displayed serious-event term percentages to support causal interpretation. Deaths are not reported in the registry record. Finally, the multiplicity approach and the relationship between listed outcomes and reported analyses are not explained.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: EMRI SureScan™ Clinical Study — NCT00433654.
• Registry record last updated 2025-09-15; status last verified 2011-07.
• Results first posted 2011-08-11.
• 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.

21. Record Summary

The EMRI SureScan™ Clinical Study (NCT00433654) is recorded as a completed, randomized, parallel-group study with no masking and an enrollment of 484. Its purpose was to assess safety and efficacy of the investigational EnRhythm MRI™ SureScan™ Pacing System in the clinical MRI environment.

The MRI group underwent a one-hour MRI scan at the 9-12 week post-implant follow-up; the control group waited for one hour without MRI. The primary outcome was atrial pacing capture threshold success from the 9-12 week visit to the 4-month visit. The posted primary analysis shows success for all analyzed participants in both groups, with a recalculated risk difference of 0.0.

The sponsor’s listed analysis reports a point estimate of 0 but omits confidence limits, a p-value, and the decision margin. Secondary comparisons and adverse-event counts provide additional descriptive context, but their analysis populations and methods are not fully explained. Missing-data handling, multiplicity plans, and the original sample-size justification are not reported in the registry record.