Optimize RV Follow-up Selective Site Pacing Clinical Trial: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Optimize RV Follow-up Selective Site Pacing Clinical Trial (NCT00949715), a non-randomized na study. The primary outcome is Difference in Mean Left Ventricular Ejection Fraction (LVEF) Between RV Pacing Sites at 24 Month.

2. Clinical Question

The study asks whether the location of a pacing lead in the right ventricle is associated with a difference in left ventricular ejection fraction (LVEF) at 24 months. Its primary comparison is the mean LVEF for right ventricular mid-septal pacing minus the mean LVEF for right ventricular apical pacing, measured using the 4 chamber view. The primary outcome applies to subjects with LVEF measurements at both baseline and 24 months.

The two pacing locations are described anatomically. In the mid-septal group, the lead is located in the middle of the muscle separating the right and left sides of the heart. In the apical group, the lead is located at the bottom of the right ventricle, in its apex. The study’s stated purpose is to determine the long-term effect of selective site pacing; selective site pacing refers to the area of the right ventricle where the lead is placed.

The registry also lists comparisons of change in LVEF from the 2 Week visit, collected in a prior study, to the 24 Month follow-up; change in left ventricular end systolic volume after 24 months; and AT/AF burden from baseline to 24 months. These are secondary outcomes, not the primary endpoint.

The clinical question is comparative, but the allocation is non-randomized. Accordingly, the comparison describes outcomes in the two pacing groups and does not, by itself, establish that pacing location caused any observed difference. The registry record does not report the numerical primary result, group-specific outcome estimates, or an uncertainty interval for the comparison.

3. Trial Design

The Optimize RV Follow-up Selective Site Pacing Clinical Trial is recorded as a completed, parallel, non-randomized study with no masking. Its listed enrollment is 67. The record lists the study start as 2009-09 and primary completion as 2011-04. The phase is recorded as NA. These design details describe the registry entry; they do not establish how participants were selected for each pacing site or what factors guided allocation.

The two groups are defined by the right ventricular location of the pacing lead: mid-septal or apical. The listed devices are a Medtronic or Vitatron Dual-Chamber Pacemaker and a Medtronic SelectSecure 3830 Lead. The record does not give device use by group or additional procedural details. The study description frames selective site pacing as a question about where the lead is placed and its long-term effect.

The primary endpoint is the difference in mean LVEF between the pacing sites at 24 months, using the 4 chamber view. The endpoint description specifies a population with measurements at both baseline and 24 months. The registry record gives 95% confidence interval as the dispersion measure for the primary endpoint, but does not report the interval’s values or the primary effect estimate.

Four outcome measures and four analyses are listed. The secondary outcomes include change in LVEF between the 2 Week visit, collected in a prior study, and 24 Month follow-up; change in left ventricular end systolic volume after 24 months; and AT/AF burden from baseline to 24 months. The record does not specify the detailed analytic methods for these outcomes.

Because allocation was non-randomized, the groups are not a like-for-like control comparison. Differences between groups may reflect factors associated with allocation as well as any relationship with pacing site. The registry record does not report randomization, masking, or an adjustment strategy that would address such differences.

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: Two of 67 subjects were excluded due to non-compliant programming.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Subjects who had LVEF measurements from both baseline and 24 month timepoints

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 Difference in Mean Left Ventricular Ejection Fraction (LVEF) Between RV Pacing Sites at 24 Month, measured over 24 months.

The primary endpoint is mean left ventricular ejection fraction (LVEF) at 24 months, compared between right ventricular mid-septal and right ventricular apical pacing. The specified contrast is mid-septal minus apical, and the measurement uses the 4 chamber view. The record defines the primary-outcome population as subjects with LVEF measurements at both baseline and 24 months.

LVEF is a continuous measure, so the endpoint compares group means rather than event counts or the proportion of participants meeting a threshold. In general, a mean describes the central value of measurements in a group, while a between-group difference expresses how far apart the two group means are on the measure’s scale. The registry identifies the unit as percentage of LVEF.

In general, LVEF is used to describe left ventricular function, making it relevant to a study whose stated purpose concerns the long-term effect of pacing-site selection. That rationale does not determine what the observed comparison means; interpretation depends on the actual estimates, their precision, and the study design.

The registry record lists a 95% confidence interval as the dispersion measure for the primary outcome, but the interval and the mean difference are not reported in the record. Therefore, the direction, magnitude, and precision of the primary comparison cannot be characterized from the registry information. The endpoint definition alone is not evidence of an observed difference between pacing sites.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous, and the registry identifies its parameter as a mean. A mean is the arithmetic average of measured values within a group. The primary contrast is defined as the mean for right ventricular mid-septal pacing minus the mean for right ventricular apical pacing. This order matters: a positive contrast would indicate a higher mean in the mid-septal group, while a negative contrast would indicate a higher mean in the apical group, if such an estimate were reported. The registry record does not report an estimate, so its direction cannot be stated.

What does a confidence interval communicate?

In general, a confidence interval gives a range of values compatible with an estimate under the statistical method and its assumptions. It conveys precision: intervals that are narrower represent more precise estimates than wider intervals. It does not describe the range of individual participants’ measurements, and it does not by itself resolve whether a difference is clinically important. The registry specifies a 95% confidence interval for the primary endpoint, but its limits are not reported in the registry record. It is therefore not possible to evaluate the primary estimate’s precision or whether the interval includes no difference.

Why does the design affect interpretation?

The trial is recorded as non-randomized and unmasked. In general, random allocation can reduce systematic differences between comparison groups at the point of assignment. When allocation is not randomized, group membership may be associated with participant characteristics, clinical circumstances, or other factors that also relate to the outcome. A comparison of group means can then combine the association with pacing site and differences between the groups. This is a limitation on causal interpretation, not a reason to assume that any particular bias occurred.

Adjustment methods can sometimes account for measured differences, but they cannot automatically eliminate unmeasured confounding. The registry record does not report an adjustment method, the variables used in an adjusted analysis, or group-specific baseline characteristics. No claim can therefore be made about whether confounding was addressed in the analysis. The lack of masking is part of the recorded design; the record does not describe any procedures used to limit its influence on measurement or analysis.

How should a planning illustration be read?

The record describes sample-size assumptions as a planning illustration based on the observed effect, not as the trial’s own design justification. It specifies a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. For continuous outcomes, the illustration is expressed as participants per arm for 80% power or for other stated power levels. In general, such figures describe how a hypothetical study might be planned under those assumptions. They are not observed participant counts, and they are not observed power for this completed study.

The record does not report the trial’s original sample-size justification or say that these planning assumptions governed enrollment. In particular, an illustration derived from an observed effect depends on the effect estimate used and the assumptions stated for the illustration. It cannot establish whether the study was adequately planned or whether its results are conclusive. No planning output values are reported in the registry entries described for this analysis.

What can be said about the secondary outcomes?

The registry lists change in LVEF from the 2 Week visit, collected in a prior study, to the 24 Month follow-up; change in left ventricular end systolic volume after 24 months; and AT/AF burden from baseline to 24 months. These outcomes concern different measurements or time comparisons from the primary endpoint. In general, analyzing multiple outcomes can raise a multiplicity concern: the more statistical comparisons made, the greater the chance that at least one appears notable by chance if each is interpreted without regard to the others. The record does not report a multiplicity adjustment, a hierarchy among secondary outcomes, or detailed results that could be used to assess this issue.

The primary endpoint includes participants with measurements at baseline and 24 months. In general, missing outcome data can affect both precision and validity, especially if the availability of measurements is related to participant characteristics or outcomes. The registry record does not report group-specific completion counts, reasons for missing measurements, imputation, or sensitivity analyses. The consequences of missing data therefore cannot be evaluated from the recorded information.

Four outcome measures and four analyses are listed, but these counts do not identify the statistical model, covariates, handling of repeated observations, or analysis population for each comparison. Those details are not reported in the registry record. Any more specific description of the analysis would go beyond what the record states.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary LVEF comparison and secondary outcomes concerning LVEF change, left ventricular end systolic volume, and AT/AF burden. It also records four outcome measures and four analyses. The registry record does not report whether the primary outcome was formally distinguished from secondary analyses for inferential purposes, whether a testing hierarchy was specified, or whether any multiplicity adjustment was used.

In general, multiplicity arises when several hypotheses are tested. If each is evaluated independently using the same significance criterion, the chance of at least one chance finding across the set can increase. Methods for controlling that risk depend on the analysis plan and the intended interpretation of the outcomes. Without a reported plan or the numerical findings, it is not possible to determine how multiplicity affects interpretation of this trial’s results.

The primary-outcome population is described as subjects with LVEF measurements from both baseline and 24 months. The registry record does not report the number with measurements in each group, the amount or pattern of missing data, reasons for missingness, or how missing values were handled. It also does not report whether the analysis used imputation, a complete-case approach, or sensitivity analyses. These methods are not interchangeable, and the appropriate interpretation depends on details that are not reported in the registry record.

The record does not specify an analysis population beyond the primary endpoint’s measurement requirement. It does not describe exclusions, adherence-related criteria, or whether all enrolled participants were included in each analysis. The listed enrollment cannot be treated as the number analyzed for the primary endpoint. The implications of missing outcomes and analysis-population choices therefore remain uncertain.

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

The registry record establishes the study question and endpoint, but it does not report the primary estimate or its 95% confidence interval. It therefore does not show the size, direction, or precision of the mean LVEF difference between right ventricular mid-septal and apical pacing at 24 months. The endpoint description should not be mistaken for a result, and no conclusion about the comparative outcome can be drawn from the information recorded.

Even when a group difference is reported, a non-randomized comparison should be interpreted as an association unless the analysis and design support stronger causal conclusions. In general, participants in the two groups may differ in factors that are related to both pacing-site selection and outcome. The registry record does not report sufficient allocation details, group characteristics, or adjustment methods to assess that possibility.

The primary endpoint concerns LVEF at a specified follow-up and in a defined measurement population. It does not, on its own, describe every aspect of cardiac function, other clinical outcomes, or the experience of participants outside that analysis population. The secondary outcomes address additional measures, but their numerical results are not reported in the registry record.

Nor does the planning illustration establish observed power or demonstrate that the study was designed around a particular effect. It is described as a planning calculation based on an observed effect, with stated assumptions; it is not a substitute for the estimates and uncertainty intervals from the actual analyses. Those outcomes and their analytic details are not reported in the registry record.

The appropriate statistical conclusion is limited: the record describes a completed, non-randomized comparison and defines its primary outcome, but does not report the numerical primary result needed to judge what the observed data show. This absence of a reported estimate is not evidence of no difference, nor evidence of a difference. The comparison’s magnitude, precision, and causal interpretation cannot be determined from the record.

12. Why This Trial Matters Statistically

This study illustrates why a clearly stated comparison and a reported result are both necessary for statistical interpretation. The primary contrast is explicitly ordered as mid-septal minus apical mean LVEF at 24 months, and the endpoint specifies a 95% confidence interval. Yet the registry record does not report the estimate or interval. Without them, readers cannot assess direction, magnitude, or precision, regardless of how clearly the endpoint is defined.

It also illustrates the distinction between a comparative question and a randomized comparison. The two pacing sites provide a clinically framed contrast, but allocation is recorded as non-randomized. In general, this means observed group differences may reflect factors associated with group assignment as well as any relationship with pacing site. Statistical interpretation must account for that design rather than treating the groups as interchangeable by default.

The record further distinguishes the primary endpoint from related outcomes. LVEF change, left ventricular end systolic volume, and AT/AF burden broaden the set of questions, but multiple outcomes require clarity about which comparisons were primary and how multiplicity was addressed. The record does not report those methods or the secondary estimates.

Finally, planning illustrations and completed-study evidence answer different questions. A sample-size illustration using an observed effect and specified assumptions can inform hypothetical planning; it does not supply the trial’s observed estimates, establish observed power, or explain the original design rationale. Here, the record states that distinction, while the primary numerical results remain not reported in the registry record.

13. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The central limitation for interpreting this trial from the registry record is that the primary result is not reported. The record defines mean LVEF at 24 months and specifies a 95% confidence interval, but gives neither the mean difference nor the interval. There is consequently no basis in the registry information to describe the observed primary outcome’s direction, size, or precision.

The non-randomized allocation limits causal interpretation. The record does not explain how participants came to receive mid-septal or apical pacing, report group-specific characteristics, or describe an adjustment strategy. It is not possible to assess the balance of potential confounders or how any differences were handled. The absence of masking is recorded, but its practical effects on measurement or analysis are not described.

The primary analysis population requires LVEF measurements at both baseline and 24 months. The registry record does not report how many participants in each group met this requirement, what data were missing, or how missingness was addressed. It also does not report the analysis population for secondary outcomes. This prevents assessment of selection arising from availability of follow-up measurements.

Although secondary outcomes are listed, their estimates and inferential methods are not reported. The record does not describe how multiple comparisons were handled, whether a prespecified hierarchy was used, or which statistical models and covariates were applied. The original sample-size justification and detailed protocol-level statistical plan are not reported in the registry record.

14. Related Tutorials

15. Related Statistical Calculators

16. Sources

• ClinicalTrials.gov: Optimize RV Follow-up Selective Site Pacing Clinical Trial — NCT00949715.
• Registry record last updated 2018-02-15; status last verified 2018-01.
• Results first posted 2013-10-01.
• 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.

17. Record Summary

The registry record describes the Optimize RV Follow-up Selective Site Pacing Clinical Trial as a completed, parallel, non-randomized study with no masking. Enrollment is listed as 67, the phase as NA, the start as 2009-09, and primary completion as 2011-04.

The study compares right ventricular mid-septal pacing with right ventricular apical pacing. Its primary outcome is the difference in mean LVEF at 24 months, calculated as mid-septal minus apical, using the 4 chamber view. The primary population is defined as subjects with LVEF measurements at both baseline and 24 months.

Secondary outcomes concern change in LVEF from the 2 Week visit collected in a prior study to 24 Month follow-up, change in left ventricular end systolic volume after 24 months, and AT/AF burden from baseline to 24 months. The primary estimate, confidence interval, secondary estimates, missing-data methods, and detailed statistical plan are not reported in the registry record. The non-randomized design also limits causal interpretation of group comparisons.