A Comparison of the Pacemaker Automatic Features in Reduction of Ventricular Pacing: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Comparison of the Pacemaker Automatic Features in Reduction of Ventricular Pacing (NCT01039467), a randomized na study. The primary outcome is Number of Participants With Decreased Percent of Ventricular Pacing Compared to MVP Using Search AV+.

2. Clinical Question

The question concerns a device’s automatic pacing feature, not a comparison between different pacemaker models. The registry describes a randomized, multicenter, prospective study. Its stated purpose also included observing atrial fibrillation burden and the clinical profile of Adapta pacemaker patients. The primary endpoint, however, is a count of participants meeting the described decrease criterion at the 1 month visit. It is not a direct summary of each participant’s full pacing history, and it does not by itself describe how large any individual decrease was.

The posted endpoint counts were 1 of 167 participants in the Managed Ventricular Pacing group and 4 of 163 in the Search AV+ group. Those counts are the basis for the simple binary re-calculation. The registry also reports a Wilcoxon (Mann-Whitney) analysis with p < 0.001. Because the registry does not give a test statistic, effect estimate, or further details for that analysis, the numerical contrast from the re-calculation and the sponsor-reported analysis should be read as distinct statistical summaries rather than assumed to be interchangeable.

3. Trial Design

The registry describes COMPARE-Adapta as a randomized, multicenter, prospective study conducted in China. It is listed as a parallel-group study with no masking. The intervention was the Medtronic Adapta dual-chamber pacemaker, with participants assigned to a group in which either Managed Ventricular Pacing or Search AV+ was programmed on. The study is marked completed. The registry lists an enrollment of 385.

The primary endpoint was assessed at 1 month post-implantation. Its stated population includes participants who completed the 1 month visit and had %VP data available. The arm counts used for the endpoint comparison were 167 for Managed Ventricular Pacing and 163 for Search AV+. Those endpoint denominators do not match the overall enrollment count; the reasons for the difference, including the contribution of missing visits or unavailable %VP data, are not reported in the registry record.

The study is listed as phase NA. The registry identifies bradycardia as the condition and records no masking. It does not report the original sample-size justification, the planned allocation ratio, details of the randomization procedure, or the protocol’s full analysis plan. It also does not report whether interim analyses were planned or conducted. These omissions mean that the design can be described from the recorded features, but the rationale for the chosen enrollment and all operational details cannot be reconstructed from the registry record.

Several secondary outcomes are listed, including percent ventricular pacing, changes in percent ventricular pacing, a lower-level pacing threshold, atrial fibrillation burden, and results stratified by baseline atrioventricular block status. The available posted outcome summaries should be interpreted according to their own stated populations and measures. In particular, subgroup counts apply only to the relevant stratum and are not direct replacements for the overall primary endpoint result.

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: 6 patients withdrawn from study pre-randomization for not meeting inclusion/exclusion criteria.

Overall Study

Analysis population for the primary outcome, as defined in the registry: all participants who completed the 1 month visit with %VP data available.

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 Number of Participants With Decreased Percent of Ventricular Pacing Compared to MVP Using Search AV+, measured over 1 month post-implantation.

The primary endpoint counts participants whose percent ventricular pacing decreased when Search AV+ was used, compared with the MVP group, at 1 month post-implantation. The registry describes the outcome as a number of participants and defines the analysis population as those who completed the 1 month visit with %VP data available. The posted counts are 1 participant among 167 in the MVP group and 4 among 163 in the Search AV+ group.

A binary participant count is useful when the clinical question is whether a specified event or criterion occurred, rather than the size of a continuous measurement. It allows the groups to be compared in terms of how many participants met the endpoint. However, the endpoint’s title and description do not give a detailed operational definition of “decreased,” such as the precise reference measurement or threshold used to classify an individual. That definition is not reported in the registry record.

The endpoint also does not capture the complete distribution of %VP values or the magnitude of change for each participant. A participant-level count can therefore answer a narrower question than a continuous comparison of pacing percentages. Other registry outcomes separately address percent ventricular pacing and change in percent ventricular pacing, but they should not be substituted for the primary endpoint. The 1 month time frame is important: this result describes the specified post-implantation visit and does not, on its own, establish what happened at later times.

Because the primary endpoint is binary, an unadjusted risk difference can express the contrast between the observed proportions in the two arms. Its confidence interval describes uncertainty in that contrast. The posted results also include a sponsor-reported Wilcoxon (Mann-Whitney) test. The registry does not explain how that test was applied to this participant-count endpoint, so its reported result needs to be kept separate from the simple binary comparison.

7. Results Posted in the Registry

• Search AV+: 2.5% (4/163) versus 0.6% (1/167) on control; risk difference 1.9 percentage points (95% CI -0.8 to 4.5), risk ratio 4.10 (0.46–36.28); unadjusted two-proportion z-test p = 0.168.

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.

Number of Participants With Percent Ventricular Pacing Reduced to Lower Levels (<10%VP)

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Search AV+: 55.8% (91/163) versus 79.0% (132/167) on control; risk difference -23.2 percentage points (95% CI -33.0 to -13.4), risk ratio 0.71 (0.60–0.83); unadjusted two-proportion z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically lower for Search AV+ than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Number of Participants With Decreased Percent Ventricular Pacing Stratified by Baseline Atrioventricular Block Status (No AVB - nAVB)

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • nAVB: 0.9% (1/110) versus 1.0% (1/105) on control; risk difference -0.0 percentage points (95% CI -2.6 to 2.5), risk ratio 0.95 (0.06–15.06); unadjusted two-proportion z-test p = 0.974.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between nAVB and the control. The interval gives the range of effects that remain compatible with the data.

The registry lists several secondary questions covering ventricular pacing percentages, changes in those percentages, a lower-level pacing threshold, atrial fibrillation burden, and analyses by baseline atrioventricular block status. They extend the study’s focus from the primary participant-count endpoint to different measurement scales and subpopulations. They should be viewed as complementary descriptions rather than interchangeable tests of a single claim.

The posted secondary results include an additional participant-count comparison based on a lower-level threshold and subgroup information for baseline block status. These measures do not directly reproduce the primary endpoint: a threshold asks whether participants fall into a specified category, whereas the primary endpoint concerns whether percent ventricular pacing decreased. The listed continuous or percentage-based outcomes address other aspects of pacing and cannot be inferred from the binary counts alone. The registry record does not report numerical results for every listed secondary outcome in the available outcome summaries.

Secondary results can help describe the broader pattern of outcomes, but they carry less weight as confirmatory evidence when many endpoints and subgroup comparisons are examined. Unless a multiplicity plan is reported, nominal p-values do not account for the increased opportunity to find a seemingly notable result across several analyses. Selection among many outcomes for emphasis can also make a pattern appear more consistent than the complete record warrants.

The secondary outcomes should therefore be read as supporting context for the primary question, not as a substitute for resolving the difference between the sponsor-reported primary test and the binary re-calculation. The registry does not report a multiplicity adjustment or a hierarchy identifying which secondary outcomes were confirmatory. Nor does it provide a reported interaction analysis to establish that the results differ according to baseline block status. The overall pattern is necessarily limited by what is posted: the endpoint list signals the breadth of questions, but it does not by itself establish consistent effects across them.

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

• Percent of Ventricular Pacing
• Percentage of Reduced Percent of Atrial Fibrillation (AF) Burden 1-month Post-Implant
• Change in Percent of Ventricular Pacing
• Number of Participants With Percent Ventricular Pacing Reduced to Lower Levels (<10%VP)
• Number of Participants With Decreased Percent Ventricular Pacing Stratified by Baseline Atrioventricular Block Status (No AVB - nAVB)
• Percent of Ventricular Pacing Stratified by Baseline AV Block Status (1st Degree - 1AVB)
• Percent of Ventricular Pacing Stratified by Baseline AV Block Status (2nd Degree Type I & II - 2AVB)
• Percent of Ventricular Pacing Stratified by Baseline AV Block Status (3rd Degree Episodic - e3AVB)

9. Statistical Interpretation

10. Statistical Methods Explained

What does a risk difference represent?

A risk difference compares the proportion of participants with an event in one group with the proportion in another group. For this endpoint, the event is being counted as a participant with decreased percent ventricular pacing. The re-calculated contrast is unadjusted: it uses the posted counts and denominators without adjustment for other participant characteristics. A positive or negative value depends on the order used for the two groups. It is an absolute contrast in proportions, not a ratio and not a measure of the magnitude of each participant’s pacing change.

The posted re-calculation gives a risk difference of 0.019. That value should be interpreted alongside its confidence interval, rather than alone. The event counts are sparse, so the estimate can be sensitive to a small number of participants. The risk difference is not the same quantity as the Wilcoxon test result reported by the registry.

What does a confidence interval add?

A confidence interval gives a range of values compatible with the data and the statistical procedure used to form it. In repeated use of the same procedure under its assumptions, intervals constructed in this way have a stated coverage property. The interval does not assign a probability to the true effect being within this particular realized range. It also does not remove uncertainty about whether the endpoint was defined or analyzed as intended.

For the primary re-calculation, the interval runs from -0.008 to 0.045. It includes zero, which represents no risk difference on this scale. Its span signals limited precision: the posted counts do not sharply pin down the direction or size of the binary contrast. The sponsor-reported test has no associated confidence interval in the reported analysis, so the precision of that analysis cannot be assessed from a corresponding effect interval in the registry record.

What does the p-value test?

A p-value describes how unusual the observed data, or data more extreme under a specified test statistic, would be if the test’s null hypothesis and assumptions held. It is not the probability that the null hypothesis is true, and it does not measure clinical importance. A smaller p-value is not automatically evidence of a larger effect. Interpretation also depends on whether the test matches the endpoint, analysis population, and prespecified plan.

The registry reports a Wilcoxon (Mann-Whitney) p-value of < 0.001 for the primary comparison. The re-calculation based on binary counts gives an unadjusted p-value of 0.168. The registry does not report enough detail about the Wilcoxon analysis to determine what data or statistic produced its value. Since the discrepancy flag is true, the sponsor’s analysis takes precedence, but the two results should not be presented as though they came from the same test or the same calculation.

What are the reported tests?

For the primary comparison, the registry names Wilcoxon (Mann-Whitney). This is a rank-based test generally used to compare the distributions of measured values between two groups. In general, a rank-based test evaluates how values in one group tend to compare with values in the other; it is not inherently a test of a difference in binary event proportions. The registry supplies no test statistic, parameter, or details about how the method was applied to the primary participant-count endpoint. That limits interpretation of the reported p-value.

For the secondary threshold count, the registry names a chi-squared test. In general, a chi-squared test can assess whether categorical outcome proportions differ between groups, subject to its assumptions. The reported test result is p < 0.001. The registry does not include the test statistic or a confidence interval for that analysis. The re-calculated comparison for that endpoint is a simple unadjusted comparison based on the posted counts and denominators, and it is distinct from the sponsor’s named test.

Why does over-dispersion matter in general?

Over-dispersion is a general issue for count outcomes when their variability is greater than assumed by a statistical model. If a model assumes less variability than the data contain, standard errors can be too small and confidence intervals too narrow. That concern is relevant in general to count analyses, but the primary endpoint is recorded as a count of participants with an event, rather than a rate of repeated events. The registry does not report a dispersion estimate or a model-based count analysis for this primary endpoint. It would therefore be inappropriate to infer that over-dispersion was assessed or present in the trial analysis.

What is the role of unadjusted re-calculation?

The re-calculated estimates are simple, unadjusted calculations from the posted summary counts. They can serve as a transparent check of the group contrast using the information recorded in the registry, but they are not a substitute for a complete participant-level analysis or for the sponsor’s specified analysis. They do not account for covariates, missing data mechanisms, repeated measures, or design features unless those are explicitly built into the calculation. No such adjustment is reported for these re-calculations.

The re-calculated p-values should likewise be treated as unadjusted. They do not account for the number of endpoints or comparisons examined. The registry lists multiple secondary outcomes and stratified results, so selective emphasis on a single nominal result can exaggerate how much certainty the record supports. Multiplicity handling is not reported in the registry record.

How should subgroup results be understood?

A subgroup analysis restricts attention to a specified part of the population, such as participants classified by baseline atrioventricular block status. Such results may be less precise because fewer participants contribute to each comparison. A difference in statistical significance between a subgroup and the overall population would not, by itself, establish that the treatment-feature effect differs across subgroups. That requires an appropriate interaction assessment, which is not reported in the registry record.

For a subgroup result to support a broader claim, the subgroup definition, analysis plan, and interaction method matter. The posted subgroup counts are narrow summaries for their named strata. They do not demonstrate that a feature performs differently across all atrioventricular block categories, and they should not be read as independent confirmation of the primary comparison.

How does the analysis population affect interpretation?

The primary population is described as participants who completed the 1 month visit and had %VP data available. This is a visit-completer, data-available population rather than an explicitly stated intention-to-treat population. The registry does not provide the number or characteristics of people missing from that endpoint population, nor does it describe a missing-data method. If inclusion depends on attendance or data availability, the analyzed groups may not represent all randomized participants in the same way. The extent and direction of any such effect cannot be determined from the registry record.

11. Confidence Intervals and Precision

The primary binary re-calculation estimates a risk difference of 0.019, with a 95% confidence interval from -0.008 to 0.045. Because the interval includes zero, the posted binary data are compatible with no difference under the calculation’s assumptions. The interval also extends to values on either side of zero, so the estimate is not precise enough to establish a clear direction for the primary contrast. The interval’s width reflects the uncertainty arising from the observed data and the method used; it is not a guarantee that the true effect lies within the limits.

The small event counts are important to that interpretation. There were 1 participants counted in the Managed Ventricular Pacing group and 4 in the Search AV+ group, with endpoint denominators of 167 and 163. When only a few participants meet a binary criterion, the estimated contrast can change noticeably with small changes in the event counts. The confidence interval conveys more about this uncertainty than a point estimate alone.

The sponsor-reported primary analysis gives p < 0.001 but does not include a reported effect estimate or confidence interval. A small p-value without an accompanying effect estimate does not show how large the contrast is, and without an interval it does not show its precision. The reported Wilcoxon result and the binary re-calculation are discrepant; the registry does not report enough detail to reconcile them. The sponsor analysis takes precedence in the presence of that discrepancy, but its missing estimate and interval remain limitations for assessing precision.

Precision is also distinct from statistical significance. An interval can be wide even when a test reports a small p-value if the analysis targets a different quantity or uses different information. The registry record does not establish that this explains the difference in these results, so it should not be assumed. The available information supports describing the two analyses separately and noting that the precision of the sponsor’s primary analysis is not reported.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning display gives illustrative participants per arm for the binary comparisons, not total events. For the primary and secondary participant-count outcomes, each entry is the number of participants needed in each of two equally allocated arms under the stated planning assumptions. These figures are not the number enrolled in this trial and do not describe the trial’s original design justification, which is not reported in the registry record. This is not observed power.

The planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect used for each row is a stated fraction of the observed effect. The displayed 80% power column means the planned chance of detecting the chosen effect under those assumptions if that effect were the true effect and the model assumptions held. The 90% power column uses a higher target chance of detecting it, which generally requires more participants than the 80% target.

The rows consider planning for 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. The smaller the effect to be detected, the more participants are needed, because a smaller contrast is harder to distinguish from random variation. The figures are mathematical illustrations based on observed effects, not recommendations and not evidence that the study had a particular probability of success. The original sample-size assumptions, including whether the investigators planned around these effects or used another basis, are not reported in the registry record.

For time-to-event outcomes, a planning display would instead give total events under the stated event-based method. The outcomes considered in these planning entries are participant counts, so the relevant unit is participants per arm. These planning quantities should not be confused with observed group sizes or with the number of participants whose endpoint data were available.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.006; treatment proportion p₁ = 0.025; average p̄ = 0.015.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.1734 = 0.3398.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.1729 = 0.1455.
4. n = (0.3398 + 0.1455)² / (0.0186)² = 684.4, rounded up to 685 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
p0 <- 0.00598802395209581                          # control proportion
p1 <- 0.0245398773006135                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(1039467)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 685 (80% power), 916 (90% power)
 75% of observed effect: n per arm = 1,035 (80% power), 1,385 (90% power)
 50% of observed effect: n per arm = 1,917 (80% power), 2,566 (90% power)
power.prop.test: 684.4 
Simulated power at n = 685 per arm: 0.833 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Analyses Reported by the Sponsor

The registry’s own primary analysis is a Wilcoxon (Mann-Whitney) comparison with p < 0.001. The simple re-calculation uses the posted binary counts and gives an unadjusted p-value of 0.168, with a risk difference of 0.019 and a 95% confidence interval from -0.008 to 0.045. The results differ, and the discrepancy flag is true. Under the stated interpretation rule for such a discrepancy, the sponsor’s own analysis takes precedence over the re-calculation.

Precedence does not mean the registry record explains the result. It does not include a test statistic, a sponsor-reported effect estimate, a confidence interval, or enough analysis detail to reproduce the Wilcoxon result from the participant counts. The outcome is described as a count of participants with decreased %VP, while the named test is rank-based; the record does not describe the data used to produce the test. There is no basis in the registry record to attribute the disagreement to a particular method choice, data transformation, or population difference.

The re-calculation remains useful as a transparent unadjusted comparison of the posted counts, but it is not a replacement for the sponsor analysis. Readers should keep the two results distinct and avoid combining the sponsor p-value with the re-calculated confidence interval as if they summarized one analysis. The sponsor’s result is the registry-reported analysis; its effect size and precision are not reported in the registry record.

15. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary outcome and multiple secondary outcomes, including several analyses stratified by baseline atrioventricular block status. Testing many outcomes can increase the chance of observing at least one apparently unusual result even when no underlying differences exist. This is a general statistical concern called multiplicity. Whether and how it should be addressed depends on the study’s prespecified objectives and analysis plan.

A multiplicity strategy might define a hierarchy of outcomes, adjust significance thresholds, or identify analyses as exploratory. The registry record does not report a multiplicity adjustment, a testing hierarchy, or which secondary comparisons were confirmatory. The posted secondary p-values should therefore be treated as unadjusted unless the record states otherwise. A nominal p-value should not be read as if it accounted for every other outcome and subgroup examined.

The primary result also has an analysis discrepancy: the registry reports a Wilcoxon (Mann-Whitney) p-value of < 0.001, while the simple binary re-calculation gives an unadjusted p-value of 0.168. Because the discrepancy flag is true, the sponsor’s own analysis takes precedence, but the record does not include sufficient details to reconcile the two analyses. This issue is distinct from multiplicity; resolving one would not automatically address the other.

The primary endpoint population is described as participants who completed the 1 month visit and had %VP data available. The registry does not report the number of participants excluded from that population, why endpoint data were unavailable, or how missing data were handled. It also does not state whether the primary analysis was intention-to-treat, per-protocol, or another specified population. These details matter because the analyzed population may differ from all randomized participants, and missingness can affect the interpretation of a group comparison.

The allocation is recorded as randomized, but details of sequence generation, concealment, and implementation are not reported in the registry record. The registry also does not report an interim-analysis plan or whether any such analyses occurred. These are unknowns, not evidence that the procedures were absent. Without the protocol and a detailed statistical plan, it is not possible to determine how the posted analyses compare with the original prespecified approach.

16. 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 1% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: sudden cardiac death (chd) (1.1%), non-cardiac death (cancer) (1.1%), death (unknown reason) (0.5%), non-cardiac death (cerebrovascular accident） (0.5%), dislodgement of rv lead and reposition of the lead (0.5%).

The registry lists serious adverse events for 2 of 196 participants at risk in the Managed Ventricular Pacing group and 7 of 189 at risk in the Search AV+ group. It also lists other adverse events for 2 of 196 and 3 of 189, respectively. These are descriptive counts in the registry record; they are not adjusted comparisons, and the record does not provide a statistical test or confidence interval for the safety counts.

The listed serious-event terms include sudden cardiac death (CHD) and non-cardiac death (cancer), each reported as 1.1%; death for an unknown reason and non-cardiac death (cerebrovascular accident), each reported as 0.5%; dislodgement of RV lead and reposition of the lead at 0.5%; and pocket infection at 0.5%. These entries describe reported terms and percentages, not a complete assessment of the causes, timing, or comparative risk of each event. The registry does not report deaths as a separate numeric field for the arms.

Differences in raw counts should be interpreted with the group denominators and reporting context in mind. The registry does not provide enough detail to assess exposure time, event adjudication, or whether multiple events could occur in one participant. The figures therefore support a description of the listed serious and other adverse events, but not a definitive comparative safety conclusion.

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

The posted results answer a narrow question about the number of participants meeting a defined decrease criterion for percent ventricular pacing at 1 month post-implantation. In the available primary endpoint counts, 1 participant in the Managed Ventricular Pacing group and 4 in the Search AV+ group met that criterion. The simple binary re-calculation has a confidence interval that includes zero, indicating substantial uncertainty about the direction and size of the contrast on that scale.

The registry’s own analysis reports p < 0.001 using a Wilcoxon (Mann-Whitney) method. Because that result differs from the unadjusted binary re-calculation, the sponsor analysis takes precedence under the stated discrepancy rule. Yet the registry record does not give the sponsor’s effect estimate, confidence interval, test statistic, or enough detail to reproduce its analysis. A p-value alone cannot show how large the group difference is or how precisely it has been estimated.

The result does not establish how the pacing feature performs outside the 1 month endpoint population, whether the same pattern holds over longer follow-up, or how much any individual participant’s pacing changed. The endpoint is a participant count, and the registry’s other outcomes concern related but different measures. The available records do not justify treating one endpoint as a proxy for all aspects of pacing or atrial fibrillation burden.

Nor do the posted statistics establish that a device feature should be selected for an individual. They are study summaries, with important unresolved questions about the primary analysis, missing endpoint data, multiplicity, and the original statistical plan. This interpretation is statistical rather than medical: it describes the recorded counts and their uncertainty without making a treatment recommendation or asserting a clinical effect.

18. Why This Trial Matters Statistically

This trial illustrates why a result should be interpreted at the level of its actual endpoint. A count of participants meeting a decrease criterion is not the same as a comparison of mean or median pacing percentages, a continuous change score, or a measure of atrial fibrillation burden. Several of those related outcomes appear in the registry’s outcome list, but their distinct definitions mean that no single measure automatically answers all the others.

It also shows why effect estimates and confidence intervals matter alongside p-values. The registry-reported primary p-value is small, while the simple binary re-calculation produces a different unadjusted result and an interval spanning zero. The registry does not provide enough details to reconcile the analyses or a sponsor effect estimate with which to assess the magnitude and precision of the reported result. Reporting the test, estimand, data population, and uncertainty together would make the finding easier to evaluate.

The endpoint population is restricted to people who completed the 1 month visit and had %VP data available. Without a fuller accounting of missing outcome data and analysis populations, readers cannot determine how the available analysis relates to all randomized participants. The record also lists multiple secondary and subgroup questions but does not report a multiplicity plan. These are general issues of transparency and confirmatory interpretation, not evidence that any specific analysis was mishandled.

Finally, the study’s stated purpose includes observing more than one aspect of pacemaker performance. A careful statistical reading keeps the primary endpoint, secondary outcomes, and adverse-event counts separate, while recognizing where the record leaves questions unanswered. That approach avoids turning one test result into a broader conclusion than the available data can support.

19. 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 available registry record. First, the primary endpoint is titled as the number of participants with decreased %VP, but its detailed classification rule is not described. The record does not specify the exact baseline reference, threshold, or measurement procedure used to decide that a participant’s %VP decreased. That makes it difficult to assess whether the binary endpoint captures a small change, a clinically meaningful change, or another prespecified criterion.

Second, there is a clear difference between the registry-reported primary analysis and the unadjusted binary re-calculation. The sponsor’s analysis takes precedence because the discrepancy flag is true, but the record omits the information needed to understand the Wilcoxon result or reproduce it. There is no reported sponsor effect estimate or confidence interval for that test.

Third, the primary analysis population includes only those who completed the 1 month visit and had %VP data available. The reasons for the difference between the overall enrollment and endpoint denominators are not reported in the registry record. There is no reported missing-data analysis or account of how people without endpoint data were handled. The consequences of those exclusions cannot be quantified from the posted summaries.

Fourth, the registry lists multiple secondary outcomes and strata without reporting how multiplicity was addressed or which comparisons were planned as confirmatory. The available numerical summaries do not include every listed secondary outcome. For subgroup results, no interaction test is reported, so the record cannot establish that the comparison differs across baseline atrioventricular block categories.

Finally, the original sample-size justification, full statistical analysis plan, randomization details, and interim-analysis information are not reported in the registry record. These omissions constrain assessment of prespecification and design adequacy. They should be understood as limitations of what is recorded, not as proof that the study team did not have procedures or analyses in place.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: A Comparison of the Pacemaker Automatic Features in Reduction of Ventricular Pacing — NCT01039467.
• Registry record last updated 2020-02-05; status last verified 2020-01.
• Results first posted 2020-02-05.
• 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.

23. Record Summary

The registry describes a completed randomized, multicenter, prospective, parallel-group study in China comparing Adapta pacemaker programming with Search AV+ versus Managed Ventricular Pacing. It records no masking and an enrollment of 385. The primary endpoint counts participants with decreased percent ventricular pacing at 1 month post-implantation among those completing the visit with available %VP data.

The posted primary counts are 1 of 167 for Managed Ventricular Pacing and 4 of 163 for Search AV+. The registry reports a Wilcoxon (Mann-Whitney) p-value of < 0.001. A simple unadjusted binary re-calculation gives p = 0.168 and a 95% confidence interval for the risk difference from -0.008 to 0.045. The discrepancy means the sponsor’s analysis takes precedence, although the registry does not report enough detail to reconcile the results or assess the sponsor analysis’s effect size and precision.

Secondary outcomes address other pacing measures, atrial fibrillation burden, and baseline block subgroups. Serious adverse events and other adverse events are also listed. The registry record does not report the original sample-size rationale, multiplicity handling, or missing-data methods.