Femoral Vein Hemostasis After Ablation for Atrial Fibrillation With Manual Pressure Versus a Figure of 8 Suture: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Femoral Vein Hemostasis After Ablation for Atrial Fibrillation With Manual Pressure Versus a Figure of 8 Suture (NCT03040661), a randomized na study. The primary outcome is Time Required to Achieve Hemostasis.

2. Clinical Question

The study also lists groin complications as a secondary outcome, comparing the Figure of 8 Suture technique with manual hemostasis. A result for that secondary outcome is not reported in the registry record. Thus, the main posted comparison concerns the time endpoint, not a complete accounting of the trial's stated outcomes. The central statistical question is a comparison of group averages; it does not by itself describe every participant's experience or establish how consistently the approaches perform across settings.

3. Trial Design

This was a randomized, parallel-group trial with no masking. It enrolled 70 participants and is listed as completed. The registry record identifies Inova Health Care Services as the sponsor and gives a start date of 2017-03-01 and a primary completion date of 2018-03-01. The record identifies atrial fibrillation as the condition under study.

The two groups were Figure of 8 Suture and Manual Hemostasis Group, with 35 participants in each group for the primary outcome. Both groups underwent ablation for atrial fibrillation; the assigned difference concerned the hemostasis technique after the procedure. The registry describes the suture approach as achieving hemostasis as the sheaths are removed. In the manual approach, the record describes ACT assessment, protamine administration, and manual pressure after sheath removal.

Random allocation is intended to make the groups comparable, on average, with respect to factors that could affect outcomes. It does not guarantee that every prognostic feature is balanced in a particular trial, and the registry record does not report baseline characteristics or details of the randomization procedure. With no masking, participants and clinical staff were not masked to group assignment according to the registry listing. The record does not say whether outcome assessment was masked.

The reported primary endpoint is time from sheath removal until hemostasis is achieved. The trial also lists groin complications as a secondary outcome, but its results are not reported in the registry record. The record lists three outcome measures, while no analysis entries are posted. The particular analysis population, handling of missing data, and prespecified statistical methods are not reported in the registry record. Those omissions limit how fully the posted group summaries can be connected to a complete account of the trial's original analysis plan.

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

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 Time Required to Achieve Hemostasis, measured over Time (minutes) from sheath removal till hemostasis achieved.

The primary endpoint is the time, in minutes, from removal of the venous sheaths until hemostasis is achieved. It measures the duration of the hemostasis process after sheath removal, which is the practical interval that distinguishes the approaches in the stated research question. The registry reports this endpoint as a mean with a standard deviation.

A continuous time measure retains information about the length of the interval rather than reducing each participant's result to a yes-or-no outcome. Comparing group means gives a summary of the average recorded time in each arm. The measure is useful for comparing duration, but the mean alone does not show the distribution of individual times, whether there were unusual observations, or how the process varied among participants.

The posted mean was 0.0 minutes in the Figure of 8 Suture group, with a standard deviation of 0.0 minutes. In the Manual Hemostasis Group, the mean was 15.0 minutes and the standard deviation was 6.0 minutes. The time origin and endpoint are defined in the registry as sheath removal and hemostasis achieved, respectively. Further operational details about how achievement of hemostasis was assessed are not reported in the registry record. The registry also lists groin complications as a secondary outcome, but its result is not reported there.

7. Results Posted in the Registry

• Manual Hemostasis Group: mean 15.00 versus 0.00 on control; difference 15.00 (95% CI 13.01 to 16.99), standardized effect d = 3.54; z-test p = <0.001.

8. Statistical Interpretation

9. Statistical Methods Explained

What does a mean summarize?

The mean is the arithmetic average of the measured times within a group. It provides one summary of the group's central value, but it does not reveal the full distribution of observations. The posted results report a mean of 0.0 minutes for Figure of 8 Suture and 15.0 minutes for Manual Hemostasis Group. Their corresponding standard deviations are 0.0 minutes and 6.0 minutes. These are group summaries; they do not show the individual observations or the shape of the distribution.

General statistical explanation: the standard deviation describes how spread out observations are around their group mean. A standard deviation of 0.0 means no spread is represented in that reported group summary. When one arm has no reported variability, usual comparisons of means can be sensitive to how measurements were made, how the outcome was recorded, and whether the observed pattern is representative. The registry record does not provide participant-level data or details that would resolve those questions.

What does the mean difference express?

The reported mean difference is 15.0 minutes, with the group means reported as 0.0 minutes for the suture group and 15.0 minutes for the manual group. In plain terms, the manual group's reported mean is higher by the amount of the reported difference. This estimate summarizes the contrast in group averages; it is not an estimate of the time for every participant and does not describe the range of individual responses.

The record also reports a pooled standard deviation of 4.243 and a standardized difference of 3.536. These are statistical summaries related to the comparison, not separate clinical outcomes. A standardized difference expresses a mean contrast relative to a measure of variability. In this trial, the reported zero variability in one arm is particularly relevant to how such a standardized summary should be interpreted. The registry does not report the detailed method used to derive the pooled spread or standardized difference.

How should the p-value be read?

The reported unadjusted p-value is <0.001. General statistical explanation: a p-value describes how unusual data at least as incompatible with a stated null model would be if that model and the test assumptions were correct. It does not give the probability that the null hypothesis is true, and it does not measure the size or practical importance of an effect. The registry does not report the specific statistical test, its assumptions, or any adjustment for multiple comparisons. Therefore, the p-value is best treated as the unadjusted value posted for the primary comparison.

What does the confidence interval add?

The reported confidence interval for the mean difference extends from 13.01 to 16.99 minutes. General statistical explanation: a confidence interval conveys uncertainty in an estimated quantity, conditional on the method and its assumptions. It helps distinguish the precision of the estimate from the amount of variation among individuals. A confidence interval for a mean difference is not an interval for individual participant outcomes. Details of the interval procedure are not reported in the registry record.

What analysis details are absent?

The registry lists zero analysis entries. It does not report whether the primary comparison was prespecified in the same form as the posted calculation, which statistical test was used, whether any covariate adjustment was undertaken, or how missing values and protocol deviations were handled. The original sample-size justification and the trial's own design assumptions are also not reported in the registry record. These are distinct from the planning illustrations based on the observed effect.

General statistical explanation: conclusions from a randomized comparison depend not only on the group summaries but also on the analysis population, how outcomes are defined and measured, and how incomplete observations are handled. A transparent analysis plan makes it easier to assess whether the reported comparison follows the intended approach and whether additional analyses were considered. Without those details, the posted mean difference and interval remain interpretable as the registry's reported summary, but the analytic pathway cannot be fully audited from the record alone.

10. Confidence Intervals and Precision

The registry reports a mean difference of 15.0 minutes, with a confidence interval from 13.01 to 16.99 minutes. The interval describes the precision of the estimated difference under the method used to calculate it. Its endpoints are not bounds on the times experienced by all participants, and the interval does not describe individual variation. The trial's group standard deviations provide a separate description of spread: 0.0 minutes for Figure of 8 Suture and 6.0 minutes for Manual Hemostasis Group.

General statistical explanation: a confidence interval combines an estimate with uncertainty arising from sampling and the statistical method. A narrower interval indicates greater precision for the quantity being estimated, conditional on the method's assumptions. It does not account automatically for possible bias, measurement problems, missing data, or unreported analytic choices. The registry record does not identify the interval-construction method or provide enough detail to evaluate all of its assumptions.

The reported interval lies above 0 minutes, and the unadjusted p-value is <0.001. Those summaries express the reported comparison's statistical uncertainty under the analysis used; they do not make the result immune to limitations in design, measurement, or reporting. In particular, the suture group's reported standard deviation of 0.0 minutes is unusual as a summary of a continuous measure and deserves consideration when judging the stability and interpretation of the comparison. Participant-level observations and further measurement details are not reported in the registry record.

Precision should also be considered alongside the size of the study. There were 35 participants in each arm for the primary outcome. The reported interval is a statement about the mean difference, not a guarantee that a new study would produce the same estimate or interval. The record does not report a prespecified target for the interval's width or a design-based precision goal.

11. 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 figures are participants per arm, not total events. They are illustrations computed from the observed effect, rather than the trial's own original sample-size justification. The planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is the stated fraction of the observed effect. The trial's original design assumptions and sample-size justification are not reported in the registry record.

For planning at 100% of the observed effect, the illustration gives 2 participants per arm for 80% power and 2 participants per arm for 90% power. At 75% of the observed effect, it gives 3 participants per arm for 80% power and 3 participants per arm for 90% power. At 50% of the observed effect, it gives 6 participants per arm for 80% power and 7 participants per arm for 90% power. These figures are planning outputs under the stated assumptions, not a recommendation for a future study.

In plain terms, the 80% power column gives the illustrated number of participants per arm for a design with an 80% chance of detecting the specified effect under its assumptions, if that effect is real. The 90% column gives the corresponding planning number for a design targeting 90% power. Smaller effects need more participants to detect them with the same power, which is why the illustration calls for more participants per arm when planning for 50% of the observed effect than for 100%.

This is not observed power. The illustrations use the observed effect as a planning input and do not measure the probability that this completed trial's result is true or reliable. The figures are especially sensitive to the very large observed contrast and the reported zero spread in one arm, so they should be read as mathematical illustrations under their assumptions, not as a substitute for a prospective design rationale.

12. 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, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 15.000; pooled standard deviation σ = 4.243.
2. n = 2 × (1.96 + 0.842)² × 4.243² / 15.000² = 1.3, rounded up to 2 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
delta <- 15                      # observed difference in means
sigma <- 4.24264068711928                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^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 (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(3040661)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 2 (80% power), 2 (90% power)
 75% of observed effect: n per arm = 3 (80% power), 3 (90% power)
 50% of observed effect: n per arm = 6 (80% power), 7 (90% power)
power.t.test: 2.6 
Simulated power at n = 2 per arm: 0.485 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-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.

13. Multiplicity, Missing Data and Analysis Populations

The registry lists three outcome measures and identifies time required to achieve hemostasis as the primary outcome. It lists percent groin complications in the Figure of 8 Suture group compared with the Manual Hemostasis Group as a secondary outcome. A result for that secondary outcome is not reported in the registry record. No analysis entries are posted, and the record does not describe a multiplicity strategy, such as whether or how the statistical interpretation was adjusted across outcomes or comparisons.

Multiplicity matters because considering several outcomes or analyses can increase the chance of at least one apparently notable result, even when each individual test is conducted at a conventional threshold. General statistical explanation: prespecifying a primary outcome and controlling how multiple tests are interpreted can help distinguish confirmatory findings from exploratory ones. Here, the designation of a primary time endpoint is recorded, but the full analysis plan and any adjustment procedures are not reported in the registry record. The posted p-value is explicitly unadjusted.

Missing-data methods and the analysis population are not reported in the registry record. It is therefore not stated whether every randomized participant contributed to the primary endpoint, how any unavailable measurements were handled, or whether the analysis followed an intention-to-treat or another population definition. The listed group sizes are 35 per arm for the primary outcome, but those counts alone do not establish how the analysis population was defined or whether any measurements were missing.

The record does not report exclusions after randomization, protocol deviations, sensitivity analyses, or interim analyses. It also does not give details about the statistical test, adjustment for baseline variables, or any prespecified approach to handling outliers. These absences do not change the posted descriptive values, but they limit independent assessment of whether the reported comparison reflects the planned analysis and how robust it is to alternative choices.

For these reasons, the primary result can be described as the registry's reported unadjusted comparison of mean times, while broader claims about all endpoints or analysis populations cannot be verified from the record. The unreported secondary result is especially important to distinguish from evidence of no difference: the record does not establish what that outcome showed.

14. 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 non-serious adverse event terms

The registry reports serious adverse events in 0 of 35 participants at risk in the Figure of 8 Suture group and 0 of 35 at risk in the Manual Hemostasis Group. It reports 0 deaths in each group. The listed other adverse-event counts are 2 of 35 at risk in each group. These are counts as recorded; the registry does not provide further event terms in the serious-event list.

These summaries should be read as reported counts within the stated groups, not as proof that an event could not occur. A count of zero means no event was recorded in that group under the registry's reporting, but the record does not provide additional detail about event definitions, collection procedures, duration of safety follow-up, or attribution. The serious-event terms list is empty, and descriptions of the other adverse events are not reported in the registry record.

The equal counts for other adverse events do not establish that event types or severity were the same across groups, because those details are not provided. Nor do these counts alone support a broad safety comparison. The safety information is limited to the posted group counts and does not replace the unreported details about event definitions, follow-up, and assessment.

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

The posted data show a difference in mean time to hemostasis between the randomized groups: 0.0 minutes for Figure of 8 Suture and 15.0 minutes for Manual Hemostasis Group. The reported mean difference is 15.0 minutes, with a confidence interval from 13.01 to 16.99 minutes and an unadjusted p-value of <0.001. These figures describe the recorded primary endpoint and quantify the reported comparison and its statistical precision.

They do not establish what every participant experienced. A mean is a group-level summary, and the registry does not provide participant-level times. The standard deviation of 0.0 minutes in the suture group indicates no spread in that reported summary; further information about how the times were measured or recorded is not available. The observed pattern should therefore be interpreted with attention to how the endpoint was defined and assessed, details that are not fully reported.

The result does not answer the listed secondary question about groin complications, because that result is not reported in the registry record. The adverse-event listing reports no serious adverse events and no deaths in either group, with 2 other adverse events recorded in each group, but provides limited detail about event definitions and follow-up. Those counts are not a complete characterization of safety.

Random allocation gives the design a basis for comparing assigned approaches, but important analysis details are missing from the registry record. The specific statistical test, missing-data handling, analysis population, and any multiplicity approach are not reported. The record also does not report baseline characteristics or the original sample-size rationale. These limitations mean the posted statistics should be understood as a reported comparison, not as a complete reconstruction of the trial's analysis or evidence about performance in every clinical setting.

General statistical explanation: a statistically notable result and a clinically important result are related but different judgments. The p-value addresses compatibility with a statistical null model, while clinical interpretation requires context about the endpoint, measurement, workflow, and consequences that the registry statistics alone do not supply. The result should not be extended beyond the time outcome and the study population described in the record.

16. Why This Trial Matters Statistically

This trial is statistically interesting because its primary endpoint is continuous and the posted group summaries show a stark contrast: a mean of 0.0 minutes with a standard deviation of 0.0 minutes for Figure of 8 Suture, compared with a mean of 15.0 minutes and a standard deviation of 6.0 minutes for manual hemostasis. The reported mean difference is 15.0 minutes. Those values make it important to examine not only the contrast but also the pattern of variability underlying it.

General statistical explanation: group averages can make a comparison easy to communicate, but they can conceal variation in individual observations. A zero standard deviation in one group may make usual assumptions and calculations particularly consequential. The registry record does not include the participant-level data or measurement details needed to investigate why the reported spread is zero. This is a useful reminder that statistical interpretation depends on data structure and measurement as well as on a p-value.

The record also illustrates why a reported estimate, a confidence interval, and a p-value answer different questions. The estimate describes the direction and size of the average contrast; the interval conveys precision under its method; the p-value gives a test-based summary under a null model. None alone captures the full design, analysis, or clinical context. The unadjusted p-value and the absence of a reported analysis plan make careful wording especially important.

Finally, the registry identifies a secondary outcome of groin complications but does not report its result. The missing outcome information, alongside unreported methods for missing data, analysis populations, and multiplicity, illustrates why a notable primary result should not be treated as a complete account of a trial. Statistical reporting is most informative when it connects estimates to definitions, analysis choices, and all outcomes specified in the record.

17. Limitations

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

Several trial-specific limitations affect interpretation of the posted comparison. The Figure of 8 Suture group has a reported mean time of 0.0 minutes and standard deviation of 0.0 minutes. Without participant-level observations, it is not possible to inspect the distribution, determine how recorded times were rounded or coded, or clarify why no spread is reported. The registry record does not provide additional measurement details to resolve this issue.

The design is randomized and parallel, but the record lists no masking. It does not report whether outcome assessment was masked, how allocation was generated or concealed, or baseline characteristics by group. These details matter when assessing comparability and the potential for measurement or other bias. The record also does not report the specific statistical test or the method used to construct the confidence interval.

Although the registry lists three outcome measures, only the primary time outcome has posted results in the information described. Groin complications are identified as a secondary outcome, but that result is not reported in the registry record. Missing-data procedures, analysis populations, exclusions, protocol deviations, sensitivity analyses, and multiplicity handling are also not reported. Thus, the posted statistics cannot be checked against a complete account of the planned analysis.

The trial's original sample-size rationale and design assumptions are not reported. The planning figures based on the observed effect are not a substitute for that rationale. Safety reporting is limited to group counts, with no serious-event terms listed and limited detail about the other adverse events or follow-up. The record's enrollment and outcome summaries therefore support a focused description of the reported time comparison, but they leave important questions about measurement, analysis, secondary outcomes, and completeness of reporting unresolved.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Femoral Vein Hemostasis After Ablation for Atrial Fibrillation With Manual Pressure Versus a Figure of 8 Suture — NCT03040661.
• Registry record last updated 2022-01-11; status last verified 2021-12.
• Results first posted 2022-01-11.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

21. Record Summary

The registry record identifies NCT03040661 as a completed, randomized, parallel-group trial with no masking and enrollment of 70 participants. The sponsor is Inova Health Care Services. The study concerns atrial fibrillation ablation and compares Figure of 8 Suture with manual hemostasis.

The primary outcome is time in minutes from sheath removal until hemostasis is achieved. There were 35 participants per group in the posted primary outcome summaries. The mean was 0.0 minutes in the Figure of 8 Suture group and 15.0 minutes in the Manual Hemostasis Group; the reported mean difference was 15.0 minutes, with a confidence interval from 13.01 to 16.99 minutes and an unadjusted p-value of <0.001.

The registry also lists groin complications as a secondary outcome, but a result is not reported in the registry record. Serious adverse events and deaths are listed as 0 in both groups; other adverse events are listed as 2 in each group. The statistical test, analysis population, missing-data approach, and original sample-size justification are not reported.