Improve SCA Bridge Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Improve SCA Bridge Study (NCT03715790), a registered phase not stated study. The primary outcome is Percentage of Post-Acute MI Patients Who Are Referred for Sudden Cardiac Death Risk Stratification > Risk (SCD) Stratification and Management.

2. Clinical Question

The study was intended to characterize the care pathway following acute myocardial infarction, including assessment of left ventricular ejection fraction in the acute phase, defined in the study summary as ≤14 days post-acute MI, and in the chronic phase, defined as ≥40-90 days post-acute MI. The primary endpoint concerns referral for risk stratification and management; it is not itself a measure of whether an implant was received or whether a cardiovascular event occurred.

The registry also lists outcomes concerning ICD/CRT-D indication and receipt within 12 months post-MI, referral or implant refusal among ICD-indicated patients, cardiovascular mortality, and evolution of ejection fraction. The record does not provide outcome results for these questions. The primary endpoint description explicitly states that no hypotheses were tested for that endpoint, so the primary question is descriptive rather than a test of a prespecified treatment contrast.

3. Trial Design

The Improve SCA Bridge Study is a completed study sponsored by Medtronic Cardiac Rhythm and Heart Failure. The registry reports a start date of 2018-11-02, a primary completion date of 2021-04-16, and enrollment of 1491. The conditions listed are Sudden Cardiac Arrest and Acute Myocardial Infarction. The study summary describes assessment and characterization of care pathways among post-acute MI patients.

The record lists an EP referred group and a Non-Referred group, both as behavioral interventions. It also clarifies that participants were enrolled in a single arm and that the referred and not-referred groups are results of the referral process within that arm. The record says the groups are not a like-for-like control comparison, and allocation is not stated. Thus, the group labels should not be read as evidence of randomized assignment or as defining treatment and control arms.

For the primary endpoint, the numerator is the number of patients who met the clinician's determination to refer the subject for SCD risk stratification and management at any of the three follow-up visits. The denominator is the number of patients who completed a 3-month follow-up visit. The primary endpoint timeframe is 3-months post-MI to 12-months post-MI. This definition makes the outcome a count of referrals within a follow-up process, using a specified follow-up group as its denominator.

The registry lists 6 outcome measures and 0 analyses. The primary endpoint description says no hypotheses were tested for this endpoint. The record does not report randomization, a protocol-defined comparison between the referral groups, or an inferential analysis plan. Detailed procedures for follow-up, data collection, and adjudication beyond the clinician's referral determination 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.

Before assignment: While the study objective was to categorize patients into those who met referral criteria and those who did not, those two groups were not, strictly speaking, considered to be treatment arms. Rather, subjects in the single enrolled patients arm could, by meeting the required criteria at any of the three follow-up evaluations, be reported in the referral group. Thus the two groups were the result of the collective referral assessments and not separate study arms with a subsequent study flow.

3-months

6-months

12-months

Analysis population for the primary outcome, as defined in the registry: Enrolled subjects who were evaluated at 3-month follow up to determine if they met referral criteria or did not meet referral criteria.

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 Percentage of Post-Acute MI Patients Who Are Referred for Sudden Cardiac Death Risk Stratification > Risk (SCD) Stratification and Management, measured over 3-months post-MI to 12-months post-MI.

The primary endpoint is described as the percentage of post-acute MI patients referred for sudden cardiac death risk stratification and management. Its operational definition identifies a numerator: patients meeting the clinician's determination for referral at any of the three follow-up visits. Its denominator is patients who completed a 3-month follow-up visit. The stated timeframe runs from 3-months post-MI to 12-months post-MI. Although the endpoint title refers to a percentage, the listed parameter is a count of participants, and no observed endpoint count or percentage is reported in the registry record.

This endpoint is used to describe a step in the care pathway: whether patients were determined to meet referral criteria and were referred for further risk stratification and management. It is distinct from downstream outcomes such as receiving an ICD/CRT-D, refusing a referral or implant, or experiencing cardiovascular mortality. Those are listed separately among the outcomes.

General: A referral endpoint can describe how clinical assessment translates into a next step in care, while a device-implant endpoint describes a later action. These outcomes answer different questions and should not be treated as interchangeable. Here, the registry's primary measure is specifically the clinician's referral determination, not a clinical benefit or harm measure. The record says that no hypotheses were tested for this endpoint, and does not report an observed result or a statistical estimate of uncertainty.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a participant count describe?

The primary endpoint is listed with a participant-count parameter. A count describes how many participants meet the endpoint definition. The endpoint's title refers to a percentage, and its description supplies a numerator and denominator: the numerator is patients meeting the clinician's referral determination at any of the three follow-up visits, while the denominator is patients who completed a 3-month follow-up visit. To report a percentage, the numerator and denominator would both need observed values. Those values are not reported in the registry record, so no percentage can be interpreted from the primary endpoint entry.

The endpoint definition also matters for interpretation. A patient meeting the referral determination at any of the specified visits is counted according to that rule. The record does not provide a more detailed account of how clinicians made the determination, how repeated visits were handled in the data, or how missing visit information was treated. Those details are not reported in the registry record.

Why does the group structure matter?

The registry describes a single enrolled arm in which referred and not-referred groups result from the referral process. It specifically says these groups are not a like-for-like control comparison, and allocation is not stated. Therefore, group membership should be understood as a characteristic of the care pathway, not as a randomized assignment. In general, a randomized comparison is designed to make groups comparable through allocation; groups formed by clinical criteria can differ for reasons that also relate to referral. A contrast between them would not by itself isolate the effect of referral or of any intervention.

The arm descriptions refer to ejection fraction and referral criteria: the EP referred group includes subjects with EF ≤ 40% or meeting one of the referral criteria, and the non-referred group includes subjects with 40% < EF < 50%. The record does not set out a complete decision algorithm or explain how these descriptions relate to every patient's classification. No additional operational detail should be inferred from the group names.

What does the registry say about statistical testing?

The primary endpoint description says that no hypotheses were tested for this endpoint. The registry lists 0 analyses. Accordingly, it reports no hypothesis-test result, estimate of association, or confidence interval for the primary endpoint. The record does not report a statistical analysis plan, a model, covariate adjustment, an interim analysis, or a sample-size justification. These items are not reported in the registry record.

General: A hypothesis test evaluates data against a stated null hypothesis using a specified test and assumptions. A p-value, when reported, summarizes how incompatible the observed data are with that null model; it is not the probability that the null hypothesis is true. An interval estimate communicates a range of values compatible with data and model assumptions at a chosen confidence level. Since the registry provides neither an endpoint estimate nor a test for this outcome, these inferential interpretations cannot be applied to the primary endpoint results.

How should counts and proportions be distinguished?

A count is an absolute number of participants or events; a proportion relates a count to a defined denominator. The study's endpoint title uses percentage language, but its parameter is a participant count. Its written definition identifies a denominator based on completing a 3-month follow-up, rather than all enrolled subjects. That distinction is important: changing the denominator changes the population the measure describes. The registry does not provide the observed denominator or numerator, so a rate cannot be reconstructed from the record.

General: A proportion is interpretable only when the event definition, time window, and denominator are clear. A count alone does not show how common an event was in the population at risk. Conversely, a percentage without a clear denominator can conceal which participants were included. Here the registry does define the intended endpoint denominator, but it does not report its observed size in the endpoint results.

What can be concluded from missing analysis details?

The absence of a reported analysis plan does not establish that no analysis was performed outside the registry; it means the plan is not reported in the registry record. The same distinction applies to handling of missing observations, protocol deviations, or analysis populations. The primary endpoint description identifies patients completing a 3-month follow-up as the denominator, but it does not explain how absent follow-up data were handled or whether additional populations were analyzed. The registry's listing of 0 analyses and statement that no hypotheses were tested constrain the interpretation of what is documented, not what may have occurred elsewhere.

General: Over-dispersion is extra variability beyond that expected under a chosen statistical model, and can make standard errors too small if ignored. It is relevant to some count-data analyses, but the record does not report a fitted count model or dispersion estimate for this endpoint. There is therefore no basis for describing an over-dispersion adjustment, or for assuming one was needed. Similarly, the registry does not identify a model for repeated follow-up assessments, despite describing referral determinations at three follow-up visits.

The study summary frames the work as characterization of care pathways following MI and describes acute and chronic phase LVEF assessments. This context clarifies the clinical process under study, but it does not provide a statistical comparison or treatment-effect estimate. Any numerical result beyond the entries stated in the registry is not 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("Referred Subjects", "Not Referred Subjects")
n      <- c(1170, 1170)
events <- c(236, 934)
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  Referred Subjects  1170  236  20.2  17.9  22.6  18.0  22.6  18.0  22.6
ARM  Not Referred Subjects  1170  934  79.8  77.4  82.1  77.4  82.0  77.4  82.0

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 6 outcome measures. The primary endpoint description states that no hypotheses were tested for this endpoint, and the record lists 0 analyses. No multiplicity adjustment, hierarchy among outcomes, or prespecified family of hypothesis tests is reported in the registry record. Because inferential tests are not reported for the primary outcome, the record does not support interpreting it as a statistically significant or nonsignificant finding. The listed secondary outcomes should be read as outcome definitions, not as evidence that each was tested or produced a result.

The primary endpoint denominator is defined as patients who completed a 3-month follow-up visit. This makes completion of that visit part of the described analysis population. The record does not state how many patients completed follow-up, how missing visits were handled, whether values were imputed, or whether sensitivity analyses were conducted. These details are not reported in the registry record. No other analysis population is described for the primary endpoint.

General: Missing outcome data can affect descriptive proportions as well as model-based estimates, particularly if the availability of follow-up information is related to the outcome or to patient characteristics. The direction and size of any effect depend on why data are missing and how the analysis handles them. The registry does not provide enough information to assess those possibilities for this study. The defined denominator limits the endpoint to 3-month follow-up completers, but does not explain the characteristics or outcomes of those who did not complete that visit.

The record also does not report an analysis plan, interim analyses, or a sample-size justification. Their absence from the registry record should not be taken as proof that none existed elsewhere; their methods and rationale cannot be assessed from the reported information.

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% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: cardiac failure acute (1.7%), acute myocardial infarction (1.6%), death (1.5%), coronary artery disease (1.1%), sudden cardiac death (0.9%).

For enrolled subjects, the registry lists 1491 at risk for serious adverse events and 180 under serious adverse events affected. It lists 1491 at risk for other adverse events and 18 under other adverse events affected, along with 88 deaths. These are registry counts; the record does not give a safety observation timeframe or additional definitions that would clarify how the entries were collected and summarized. No percentage should be inferred from these counts.

The listed serious adverse-event terms and percentages are Cardiac Failure Acute, 1.7%; Acute Myocardial Infarction, 1.6%; Death, 1.5%; Coronary Artery Disease, 1.1%; Sudden Cardiac Death, 0.9%; and Cardiac Failure, 0.6%. These terms describe entries in the serious-event listing. The record does not explain whether terms can overlap within a participant or provide further detail about event timing, severity criteria, or causal assessment.

General: Adverse-event counts describe events or affected participants as defined by a registry record; they do not, by themselves, establish that an event was caused by an intervention. Interpretation of event frequency also depends on the observation window and the population at risk. The registry describes a single enrolled population and does not report a randomized safety comparison. The safety entries therefore should not be treated as comparative evidence between the referral groups or as estimates of a treatment effect.

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

The study is framed as a description of how post-acute MI patients move through assessment and referral for sudden cardiac death risk stratification and management. Its primary endpoint is a referral determination during follow-up, with patients completing a 3-month follow-up visit defining the denominator. This makes the endpoint relevant to understanding a care pathway, rather than directly measuring the effect of an assigned treatment.

The registry record does not report the observed primary endpoint count or percentage, and it states that no hypotheses were tested for this endpoint. It therefore cannot establish from the reported endpoint entry how frequently patients were referred or how precisely that frequency was estimated. It also cannot establish whether referral was associated with later ICD/CRT-D receipt, refusal, cardiovascular mortality, or changes in ejection fraction. Those outcomes are listed, but their numerical results are not reported in the registry record.

The group labels do not create a randomized comparison. The registry says they reflect the referral process in the single enrolled arm and are not a like-for-like control comparison. Any difference between referred and non-referred patients would need to be interpreted in light of how referral criteria and clinical decisions formed those groups. The record does not report an analysis that addresses such differences.

General: A descriptive care-pathway study can provide information about observed clinical processes, but an outcome's presence in a registry is not itself evidence of a result. A count or percentage describes what was recorded in a defined population; a causal claim requires a design and analysis capable of supporting that interpretation. The information does not supply a causal estimate.

The safety entries are also descriptive registry data. Without the reported observation period, definitions, and a comparative design, they do not establish the cause of an event or comparative safety. The study's completed status and enrollment figure describe the registry record, but do not fill in the missing outcome estimates or analysis details.

14. Why This Trial Matters Statistically

This study is statistically useful as an example of why the design and endpoint definition must be read together. The primary endpoint sounds like a percentage, but the registry lists a participant count and defines a denominator based on completion of a 3-month follow-up. That distinction highlights how the analysis population is determined and why a reader needs both observed numerator and denominator to interpret a rate. Neither observed value is reported for the primary endpoint.

The referral groups also illustrate the difference between groups created by clinical processes and groups formed through randomized assignment. The registry describes referred and not-referred patients as the result of the referral process within one enrolled arm, and explicitly says they are not a like-for-like control comparison. Statistical comparisons between groups formed in this way require caution because the process that determines group membership can also be related to outcomes.

Another important lesson is that a registry may list multiple outcome measures without reporting inferential analyses for them. This record lists six outcome measures, while the primary endpoint description states that no hypotheses were tested and the registry lists zero analyses. Knowing the outcome definitions is not the same as knowing the outcome results, their precision, or whether any prespecified comparisons were made.

General: Transparent reporting of denominators, missing follow-up, statistical models, uncertainty, and multiplicity helps readers assess how much confidence to place in an estimate. These details are especially important when a study's aim is descriptive and the groups are not randomized. In this record, several such analysis details are not reported, so interpretation appropriately remains limited to the stated design and endpoint definitions.

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 limitation for interpreting the main question is that the registry record does not report an observed primary endpoint count, percentage, or uncertainty estimate. Although the endpoint title refers to a percentage and the description defines its numerator and denominator, the corresponding results are not reported in the registry record. The statement that no hypotheses were tested further indicates that no inferential test result is available for this endpoint in the record.

The group structure limits comparative interpretation. The registry describes referral groups arising within one enrolled arm, says they are not a like-for-like control comparison, and does not state allocation. As a result, the groups cannot be treated as randomized treatment and control arms. The record does not report adjusted comparisons or an analysis designed to account for the process that determined referral.

Information about follow-up and missing data is incomplete. The primary endpoint denominator is based on completing a 3-month follow-up visit, but the number completing that visit and the handling of unavailable follow-up information are not reported in the registry record. Details of the three follow-up visits, data collection, and the referral decision process beyond the clinician's determination are also not reported.

The registry lists 6 outcome measures and 0 analyses, but does not report a statistical analysis plan, sample-size justification, interim analyses, multiplicity approach, or model assumptions. Safety entries lack a stated observation period and further event-definition details. The study summary describes acute and chronic phase LVEF assessments, but detailed results for those assessments are not reported in the registry record. These omissions restrict assessment of precision, completeness, and the scope of conclusions that can be drawn.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Improve SCA Bridge Study — NCT03715790.
• Registry record last updated 2024-01-16; status last verified 2023-04.
• Results first posted 2024-01-16.
• 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 Improve SCA Bridge Study (NCT03715790) is listed as completed, sponsored by Medtronic Cardiac Rhythm and Heart Failure, with enrollment of 1491. Its reported start date is 2018-11-02 and its primary completion date is 2021-04-16. The conditions listed are Sudden Cardiac Arrest and Acute Myocardial Infarction.

The study summary describes characterization of post-acute MI care pathways following LVEF assessments in the acute and chronic phases. The primary endpoint concerns referral for sudden cardiac death risk stratification and management from 3-months post-MI to 12-months post-MI. The record defines its numerator and denominator but does not report the observed endpoint result. It states that no hypotheses were tested for the primary endpoint and lists 0 analyses.

Referred and non-referred groups are described as arising within a single enrolled arm, not as a like-for-like control comparison. Other listed outcomes concern ICD/CRT-D indication and receipt, refusal, cardiovascular mortality, and ejection fraction evolution. Safety entries include 180 serious adverse events affected, 18 other adverse events affected, and 88 deaths among the enrolled-subject group. The registry record does not report the additional analysis and follow-up details needed for broader comparative interpretation.