Improving Mitral Repair for Functional Mitral Regurgitation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Improving Mitral Repair for Functional Mitral Regurgitation (NCT03366649), a non-randomized na study. The primary outcome is Change in FMR Severity.

2. Clinical Question

The clinical rationale is that the investigators sought to evaluate whether a geometric measure could help identify recurrence after UMA and whether adding PMA could reduce regurgitation severity. These are distinct questions: the first concerns a potential predictor among patients receiving UMA, while the second concerns outcomes after a combined procedure compared with UMA alone. Because treatment allocation was non-randomized, observed differences between groups could reflect differences in the patients or circumstances leading to each procedure as well as any procedural effect. The registry record does not report numerical primary-outcome results, so the stated questions cannot be answered from the posted results alone.

3. Trial Design

The study, registered as NCT03366649 and titled “Improving Mitral Repair for Functional Mitral Regurgitation,” is described as a parallel, non-randomized, unmasked study. Emory University is the sponsor. The registry lists enrollment of 34, phase as NA, and status as terminated. The start date is 2018-03-20, and the primary completion date is 2023-12-31. The reason for termination is not reported in the registry record.

The study description has two related components. The investigators planned to measure lateral inter-papillary muscle separation (IPMS) before surgery and relate it to post-surgery functional mitral regurgitation severity at discharge/30 days, 6 months, and 12 months. They also planned to perform PMA together with UMA and assess regurgitation severity at those follow-up times. These are the stated aims; whether all planned assessments were completed is not reported in the registry record.

The listed groups include UMA alone, UMA plus PMA, and retrospectively identified patients who had already undergone standard-of-care surgery at Emory. The record says the retrospective patients were identified within 6 months (± 1 month) after surgery and were suitable for recruitment for postoperative research. It does not report the number of participants in each group or explain how the retrospective group was incorporated into each outcome analysis.

Allocation was not randomized, and masking was listed as none. Consequently, the registry itself warns that the arms are not a like-for-like control comparison. Details about how treatment choice was made, whether any adjustment was planned to account for group differences, and how the retrospective patients were analyzed are not reported in the registry record. The record lists 11 outcome measures and 0 analyses. Although it identifies the primary measure and the intended follow-up, it does not provide a numerical primary-outcome estimate or a statistical comparison between groups.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Data is available only for the 12-month follow-up, as other data was unavailable due to many follow-ups occurring during the COVID pandemic.

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 Change in FMR Severity, measured over Pre-Intervention and Post-Intervention (12 Months).

The primary endpoint is change in functional mitral regurgitation (FMR) severity, expressed as a mean score on a scale and measured before intervention and at 12 months after intervention. Severity is assessed using cardiac echocardiography and/or MRI, at the physician’s discretion. The scale ranges from grade 0, none, through grade 4, severe. Intermediate grades describe increasing regurgitation severity and its potential effects on heart function.

A change in this measure is intended to describe whether the degree of regurgitation differs between the pre-intervention assessment and the 12-month assessment. It is a continuous outcome in the registry’s analysis description, with the mean and standard deviation identified as the summary statistics. For a continuous outcome, a mean describes the central level of the measured scores, while a standard deviation describes how spread out scores are around that mean. These summaries can help characterize the observed group data, but they do not by themselves establish that a difference is caused by a procedure.

The registry record states that data are available only for the 12-month follow-up because other data were unavailable due to many follow-ups occurring during the COVID pandemic. It does not report the numerical means, standard deviations, change estimates, confidence intervals, or a statistical test for the primary endpoint. Thus, the endpoint’s definition and intended timing are available, but the magnitude and precision of any observed change are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical interpretation depends first on the outcome scale and study design. FMR severity is graded from 0 to 4+, and the registry identifies the primary outcome as a mean of a continuous measure, summarized with a standard deviation. Treating a graded score as a mean can provide a concise group summary, but interpretation still depends on the underlying distribution and on how the scale is used. The record describes the scoring categories, but does not report the observed score distributions or numerical summaries.

What does a mean and standard deviation describe?

In general, a mean is a measure of the central level of observed values. A standard deviation describes their spread around that mean. They answer different questions: the mean indicates the average score, while the standard deviation conveys how variable the scores are. Neither quantity alone shows the uncertainty in an estimated group difference. A confidence interval is a general way to express uncertainty around an estimate: it gives a range of values compatible with the data and the statistical assumptions used. No confidence interval for the primary outcome is reported in the registry record.

What would a comparison between procedures require?

The registry describes a parallel, non-randomized study with UMA and UMA plus PMA groups. In general, random assignment helps balance measured and unmeasured characteristics across groups on average. Without randomization, the groups can differ for reasons connected to treatment choice. A raw comparison may therefore mix the association of treatment with those pre-existing differences. Statistical adjustment can sometimes address measured differences, but it cannot automatically remove bias from unmeasured factors. Whether adjustment was planned or used is not reported in the registry record.

The registry explicitly cautions that the arms are not a like-for-like control comparison. That warning matters when interpreting a potential difference in average 12-month scores. Even if an estimate were available, its meaning would depend on group comparability, outcome ascertainment, follow-up completeness, and the analysis approach. In this record, no numerical comparison or analysis is reported, so there is no effect estimate to interpret.

Why does missing follow-up matter?

In general, missing outcome data reduce the information available and can introduce bias if the chance of being observed is related to patient characteristics or the outcome. The record says only 12-month data are available, because many follow-ups occurred during the COVID pandemic. It does not report how many measurements were missing, whether missingness differed between groups, or whether missing values were handled using a particular method. Without those details, the possible influence of incomplete follow-up cannot be assessed.

How should planning calculations be read?

The registry’s sample-size assumptions describe a planning illustration computed from an observed effect, rather than the trial’s own design. The illustration assumes a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. Such calculations estimate the participants per arm that would be required under those assumptions for a target power. They are planning illustrations, not observed power and not evidence that the trial was designed or conducted to meet those targets. The underlying observed effect and resulting values are not reported in the registry record, so the illustration cannot be interpreted as a substitute for a primary-outcome result.

More generally, statistical power is a design concept: it concerns the chance that a study would detect an effect of a specified size under stated assumptions if that effect were present. It is not a measure of whether a result is true, nor does it describe the strength of evidence after the data have been collected. A small or imprecise estimate can arise for many reasons, including limited information, variability, or missing outcomes. Conversely, a nominally small p-value would not resolve confounding in a non-randomized comparison. No p-value for the primary endpoint is reported in the registry record.

What does the outcome schedule allow?

The study description lists assessments at discharge/30 days, 6 months, and 12 months for the planned FMR evaluation, but the primary endpoint specifies pre-intervention and post-intervention at 12 months. The record says only the 12-month data are available. As a result, the registry does not provide the repeated follow-up information needed to describe the pattern of outcome change over the full stated schedule. The measure is also obtained using echocardiography and/or MRI at physician discretion; the record does not report how often each modality was used or whether measurement procedures differed by group.

Finally, the registry lists 11 outcome measures and 0 analyses. Outcome definitions and planned timing help identify what investigators intended to assess, but do not establish which analyses were completed or how multiplicity was managed. The statistical analysis plan, any interim analyses, and any prespecified adjustment strategy are not reported in the registry record. Statistical methods should therefore be read as general context, not as a description of unreported analyses.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 11 outcome measures, including the primary change in FMR severity and secondary outcomes covering mortality, major adverse cardiac events, quality of life, functional status, readmission, and left ventricular volume. When a study evaluates multiple outcomes or multiple comparisons, the chance of obtaining an apparently notable result by chance can increase. General approaches to multiplicity include prespecifying a primary outcome, adjusting tests, or interpreting secondary findings as exploratory. The registry record does not report a multiplicity strategy, a hierarchy of secondary outcomes, or which analyses were performed; it lists 0 analyses.

Missingness is especially relevant because the record states that data are available only for the 12-month follow-up. Other data were unavailable due to many follow-ups occurring during the COVID pandemic. The number of missing assessments, their distribution across study groups, and the reasons for missingness at the participant level are not reported in the registry record. Nor does the record state whether the analysis used complete cases, imputation, or another approach. In general, conclusions from observed follow-up can be biased if those with available data differ systematically from those without it.

The record does not describe analysis populations, such as whether participants were analyzed according to the procedure received, the group originally intended, or eligibility for a particular follow-up. It also does not report exclusions from outcome analyses or a statistical analysis plan. Therefore, the population represented by any primary-outcome estimate cannot be established from the available record, and no such estimate is reported.

11. 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

Serious events with the highest arm-level rate: atrial fibrillation + congestive heart failure (chf) (3.8%), atrial flutter (3.8%), acute cholecystitis with perforated gallbladder (3.8%), syncope (3.8%).

The safety entry for UMA (Group 1) lists 26 participants at risk, 4 with serious adverse events, 0 with other adverse events, and 0 deaths. The serious-event terms listed are atrial fibrillation + congestive heart failure (CHF), atrial flutter, acute cholecystitis with perforated gallbladder, and syncope; each is reported as 3.8%. These are registry entries, not a comparative estimate between the procedures.

The record does not provide corresponding safety figures for UMA plus PMA in the adverse-event information. It also does not explain whether the serious-event terms refer to separate participants or how multiple events in the same participant were handled. The percentages should therefore be read as recorded for each listed term, not added together or treated as a comprehensive rate. The record does not report event timing, severity grading beyond the serious-event classification, or attribution to a procedure.

Zero deaths in this entry means no deaths are listed for this reported group and safety record; it does not establish that the procedures carry no mortality risk. Likewise, these figures alone do not show whether one procedure is safer than another. The small amount of comparative information and the non-randomized design limit what can be concluded from the safety entries.

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

This record is useful for understanding the investigators’ questions and the outcome they intended to study. It describes a comparison involving UMA alone and UMA with PMA, a proposed predictor role for lateral IPMS, and a primary endpoint based on FMR severity before intervention and at 12 months. It also gives the broad measurement scale and notes that echocardiography and/or MRI were used at physician discretion.

What it does not establish is the magnitude or direction of change in FMR severity. The registry record does not report a numerical primary-outcome result, group summaries, a confidence interval, or a statistical test. The record lists 0 analyses. Accordingly, there is no posted estimate from which to judge how much the scores changed, how variable the observations were, or how precisely any group difference was estimated.

Even if a group difference were reported, this non-randomized study would not support the same interpretation as a randomized comparison. The registry warns that the arms are not a like-for-like control comparison. Patient and clinical characteristics associated with procedure selection could also be associated with outcomes. The record does not report an adjusted comparison that would address measured differences, and adjustment would not in general eliminate possible confounding from unmeasured factors.

The safety entries are also limited in scope. They report serious adverse events for the UMA group, but do not present a comparative safety summary across the procedural groups. These entries cannot be used to determine whether one approach has a more favorable safety profile.

The most defensible reading is therefore descriptive: the record documents an intended clinical and statistical evaluation, reports that only 12-month follow-up data were available, and contains limited safety information for UMA. It does not provide sufficient outcome results to draw conclusions about the procedures’ comparative effects or the predictive value of IPMS. This is a statement about what the registry record reports, not a claim that the study questions are unimportant or that an effect is absent.

13. Why This Trial Matters Statistically

The statistical importance of this study lies in how it frames two different research questions around the same clinical condition. One concerns whether a preoperative geometric measure, lateral IPMS, is associated with later FMR severity after UMA. The other concerns whether outcomes differ when PMA is added to UMA. Separating prediction from comparative treatment evaluation is important: a measure may be associated with outcome without establishing that changing the measure through a procedure changes the outcome.

The design also highlights the limits of non-randomized procedural comparisons. In routine clinical settings, the choice of procedure may reflect patient characteristics, clinical judgment, or other circumstances. Those factors can also relate to the outcome. Clear group descriptions, baseline information, adjustment methods, and transparent reporting of uncertainty are therefore important for interpreting any observed comparison. The registry record cautions that the arms are not a like-for-like control comparison, while the analysis details and numerical primary results are not reported.

Follow-up completeness is another central issue. The record states that only 12-month data are available, with other data unavailable because many follow-ups occurred during the COVID pandemic. This limits the ability to describe change over the planned follow-up schedule and raises questions about who contributed outcome data. Reporting the number and pattern of missing measurements, and the approach used to handle them, would help readers judge the reliability of estimates.

Finally, the record distinguishes an intended endpoint from evidence about that endpoint. Defining a score, timing, and assessment approach is necessary for analysis, but does not reveal the observed effect or its precision. With 0 analyses listed and no numerical primary result reported, the record supports careful methodological interpretation rather than a conclusion about comparative outcomes.

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.

Several limitations are specific to the information recorded for this study. Allocation was non-randomized and masking was listed as none. The registry itself says the arms are not a like-for-like control comparison, so differences between groups would require cautious interpretation. The record does not report the treatment-selection process, baseline characteristics by group, or any adjusted comparison.

Although enrollment is listed as 34, the number of participants in each group and the number contributing primary-outcome data are not reported in the registry record. The primary outcome is defined, but the group means, standard deviations, change estimates, uncertainty intervals, and statistical tests are absent. The record lists 0 analyses. The reason for study termination is not reported in the registry record.

The record states that only 12-month data are available because many follow-ups occurred during the COVID pandemic. It does not report how much follow-up information is missing, whether missingness differs across groups, or how missing data were handled. The outcome may be assessed by echocardiography and/or MRI at physician discretion, but the distribution of assessment methods and any consistency checks are not reported.

The study description includes retrospectively identified patients, but does not explain their contribution to the primary analysis. The registry record also does not report the statistical analysis plan, a multiplicity approach, analysis populations, interim analyses, or sample-size justification for the trial’s own design. These gaps prevent a full assessment of the planned and completed analyses from the registry record alone.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Improving Mitral Repair for Functional Mitral Regurgitation — NCT03366649.
• Registry record last updated 2025-01-16; status last verified 2024-12.
• Results first posted 2025-01-16.
• 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.

18. Record Summary

NCT03366649 is a parallel, non-randomized, unmasked study sponsored by Emory University, with enrollment listed as 34 and status listed as terminated. It examines UMA alone and UMA combined with PMA for functional mitral regurgitation, alongside a question about lateral IPMS as a predictor of post-UMA outcome. The primary endpoint is change in FMR severity from pre-intervention to 12 months, using a grade 0 to 4+ scale.

The record states that only 12-month data are available because many follow-ups occurred during the COVID pandemic. It lists 11 outcome measures and 0 analyses, and does not report a numerical primary-outcome result. The safety entry for UMA lists 4 serious adverse events among 26 at risk, 0 other adverse events, and 0 deaths. The registry cautions that the non-randomized groups are not a like-for-like control comparison.