Femoral Arterial Access With Ultrasound Trial: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Femoral Arterial Access With Ultrasound Trial (NCT00667381), a randomized na study. The primary outcome is Participants With Successful Common Femoral Artery Cannulation, as Determined by Femoral Angiography.

2. Clinical Question

The question concerns the placement of the femoral arterial sheath, not a broad comparison of all possible benefits and harms of the procedures. Successful cannulation was defined by the sheath lying above the common femoral artery bifurcation and below the origin of the inferior epigastric artery. Insertion outside those landmarks was classified as unsuccessful.

The registry also lists immediate procedural outcomes, including time to successful sheath insertion and accidental femoral venipunctures, as well as vascular complications recorded immediately and up to 1 month after the procedure. Those outcomes offer additional information about procedural performance and complications, but they are secondary to the angiographic cannulation outcome. The registry record does not report a broader primary question about long-term outcomes.

3. Trial Design

The Femoral Arterial Access With Ultrasound Trial was a randomized, parallel-group study. The registry lists single masking, but does not report who was masked. The study was sponsored by the University of California, Irvine, and its status is completed. The recorded start was 2008-04 and the primary completion was 2009-02.

Participants were assigned to control or ultrasound guidance. Control access was guided by anatomic landmarks and fluoroscopic localization of the femoral head. In the ultrasound group, anatomic landmarks were checked and real-time ultrasound guidance was used to aid access. The named device was a Site-Rite 5 or 6 machine. The registry classifies the phase as NA.

The primary outcome was assessed immediately during the procedure. Femoral angiography was performed in 490 control participants and 499 ultrasound participants. Angiography was not performed or was inadequate for analysis in 11 control and 4 ultrasound participants; these participants were excluded from the primary outcome analysis but included for other analyses. The record does not report further detail on the analysis population for each secondary outcome.

The posted primary outcome counts are 408 successful cannulations among 490 control participants and 431 among 499 ultrasound participants. The posted randomized enrollment is 1014. These figures describe different aspects of the record: enrollment, availability of angiography for the primary endpoint, and successful cannulation among those assessed. The registry does not report the original sample-size justification, the detailed allocation procedure, or the responsibilities of masked personnel. It also does not provide a protocol or a full statistical analysis plan in the record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: 10 patients (6 control, 4 US) were excluded after randomization but before procedure for no longer meeting the inclusion criteria, including cancellation of the procedure, lack of a dual-trained operator, or change in access site. Baseline and procedural data were not recorded in this group, and these were not included in any analysis.

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 Participants With Successful Common Femoral Artery Cannulation, as Determined by Femoral Angiography, measured over Immediately, during procedure..

The primary endpoint counts participants whose sheath insertion was positioned within the specified common femoral artery landmarks. Femoral angiography was used to assess the location. A sheath placed above the bifurcation and below the origin of the inferior epigastric artery met the definition of successful cannulation; a sheath outside those markers did not.

This endpoint is a procedural measure: it records whether access was obtained at the intended anatomical location. A binary outcome makes the result interpretable as the number of participants meeting the definition in each group, alongside a comparison of the groups’ event proportions. The outcome is therefore directly connected to the trial’s stated question about using ultrasound to aid sheath placement.

The endpoint does not, by itself, describe every aspect of the access procedure or establish what happened after the immediate angiographic assessment. Other listed outcomes address timing, accidental venipunctures, and vascular complications. Those outcomes complement rather than replace the primary endpoint, because they represent different dimensions of the procedure.

Angiographic assessment was unavailable or inadequate for some participants, and those participants were excluded from this primary analysis. The registry states that they remained included for other analyses. The record does not report further details about how missing primary endpoint information was handled beyond this exclusion.

7. Results Posted in the Registry

• Ultrasound: 86.4% (431/499) versus 83.3% (408/490) on control; risk difference 3.1 percentage points (95% CI -1.4 to 7.6), risk ratio 1.04 (0.98–1.09); unadjusted two-proportion z-test p = 0.173.

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.

Time to Successful Sheath Insertion.

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Ultrasound: mean 185.00 versus 213.00 on control; difference -28.00 (95% CI -50.88 to -5.12), standardized effect d = -0.15; z-test p = 0.016.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Ultrasound than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Number of Patients With Accidental Femoral Venipunctures.

• 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:
  • Ultrasound: 2.4% (12/502) versus 15.8% (79/500) on control; risk difference -13.4 percentage points (95% CI -16.9 to -9.9), risk ratio 0.15 (0.08–0.27); 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 Ultrasound than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Number of Participants With Vascular Complications

• 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:
  • Ultrasound: 1.4% (7/503) versus 3.4% (17/501) on control; risk difference -2.0 percentage points (95% CI -3.9 to -0.1), risk ratio 0.41 (0.17–0.98); unadjusted two-proportion z-test p = 0.038.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically lower for Ultrasound than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The secondary outcomes cover different dimensions of femoral access: time to successful sheath insertion, accidental femoral venipunctures, and vascular complications recorded immediately and up to 1 month after the procedure. Their overall pattern is that the posted unadjusted comparisons differ across outcomes and should be interpreted separately rather than compressed into a single judgment about the intervention.

These outcomes add context to the primary angiographic endpoint. Time and venipunctures relate to how access was achieved, while vascular complications address events after or during the procedure. Their definitions and observation windows are not interchangeable with the primary endpoint’s anatomical success definition. A result on one endpoint therefore does not determine the result on another.

The secondary p-values are unadjusted. When several outcomes are examined, the chance of at least one apparently notable result can rise, depending on the number and relationship of tests and the analysis plan. This general issue is called multiplicity. It does not mean that a secondary result is necessarily spurious; it means that the strength of evidence should be weighed in light of the full set of outcomes and whether they were prespecified. The registry does not report a multiplicity adjustment, hierarchy, or full analysis plan.

The secondary findings do not overturn or settle the primary result. They may be useful as separate descriptions of procedural measures and complications, but their evidential weight is limited by the absence of reported multiplicity handling and detailed analysis methods. The registry lists no reported analyses beyond the posted outcome results. Further interpretation would require information about outcome definitions, analysis populations, and prespecification that is not reported in the registry record.

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

• Time to Successful Sheath Insertion.
• Number of Patients With Accidental Femoral Venipunctures.
• Number of Participants With Vascular Complications

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is binary: each assessed participant either met the registry definition of successful common femoral artery cannulation or did not. For a binary outcome, a group’s event proportion is the number meeting the definition divided by the number assessed. The comparison can then be expressed as an absolute difference between the group proportions or as a relative measure, such as a risk ratio or odds ratio. These measures answer related but distinct questions: an absolute difference describes the separation in event proportions, while relative measures describe the comparison in relation to the control group’s event level.

The posted primary comparison uses a risk difference. The estimated direction is ultrasound minus control, as indicated by the comparison of the ultrasound arm with the control arm. A value of zero for a risk difference corresponds to no separation in the proportions. The confidence interval crosses zero, so it includes possibilities in both directions. The posted unadjusted p-value is 0.173. A p-value describes how compatible the observed data are with a specified no-difference model under the analysis assumptions; it is not the probability that the no-difference model is true, and it does not measure the size or clinical importance of an effect.

For continuous outcomes, such as time to successful sheath insertion, the registry reports group means and standard deviations and compares them with a mean difference. A mean summarizes the arithmetic center of the observations, while the standard deviation describes how spread out observations are around that mean. The time outcome has means of 213.0 seconds in control and 185.0 seconds with ultrasound, with standard deviations of 194.0 and 175.0 seconds. Its posted mean difference is -28.0 seconds, with a confidence interval from -50.88 to -5.12 and an unadjusted p-value of 0.016. The negative sign represents a lower mean time in the ultrasound group under the stated comparison direction.

Standard deviations and standard errors describe different forms of variability. A standard deviation characterizes variation among individual observations. A standard error describes uncertainty in an estimated quantity, such as a group mean, and is affected by both the variability of observations and the amount of information available. The registry lists standard errors for the group means, but the posted comparison is expressed as a mean difference and its confidence interval.

Confidence intervals provide a range of estimates compatible with the data under the method used. For a difference, an interval containing zero does not rule out no difference at the interval’s confidence level; an interval wholly on one side of zero indicates that the range excludes zero under that method. This statistical interpretation does not establish clinical importance. The registry does not report a threshold for a clinically important difference.

Some general statistical methods are relevant to procedural outcomes. Binary outcomes can be analyzed with methods based on binomial variation, but the registry record does not specify which model or test generated the sponsor’s original analyses. Counts can also be more variable than a basic model assumes; this is called over-dispersion. In general, ignoring over-dispersion can make uncertainty appear too small, while an appropriate model can account for extra variation. The record does not report whether over-dispersion was assessed or whether such a model was used.

Randomization supports comparison between groups by assigning participants to approaches without using the outcome to determine assignment. It does not guarantee that every feature is balanced, and it does not eliminate uncertainty from missing measurements or analytic choices. The registry identifies the study as randomized and single-masked, but does not report the allocation concealment method or who was masked. Those details should not be inferred from the design labels.

The registry lists unadjusted p-values for the posted comparisons and no reported analyses. It does not report a complete statistical analysis plan, the exact test or model used for each result, covariate adjustments, subgroup analyses, interim analyses, or a multiplicity procedure. Without those details, the displayed recalculated comparisons are best interpreted as simple unadjusted comparisons from the posted summary statistics, not as a replacement for a prespecified sponsor analysis.

11. Confidence Intervals and Precision

Precision concerns how narrowly an effect is estimated. A confidence interval expresses this uncertainty by giving a range of values compatible with the data under the method used. A narrow interval indicates a more concentrated estimate; a wide interval leaves more uncertainty about the size and possibly the direction of an effect. Confidence intervals should be read with the point estimate and the outcome definition, rather than as a stand-alone verdict.

For the primary risk difference, the interval spans zero. That means the posted interval includes no difference as well as estimates in either direction. The point estimate alone should not be treated as a definitive effect, and the interval does not establish that the approaches are equivalent. The primary p-value is 0.173, but the interval is especially useful for showing the range of uncertainty that the p-value alone cannot convey.

The continuous time outcome has a confidence interval for the mean difference from -50.88 to -5.12 seconds. This interval lies below zero under the registry comparison direction. Its width conveys uncertainty about the magnitude of the difference, even though the range does not cross zero. The risk-difference intervals for accidental venipunctures and vascular complications also lie below zero, while their estimates remain subject to the limitations of secondary, unadjusted analyses.

Precision depends on the amount of information and the variability of the outcome, as well as the analysis method. A larger sample does not automatically make every estimate precise if the outcome is highly variable or incompletely observed. For the primary endpoint, some angiograms were missing or inadequate and were excluded from that analysis. The registry does not report additional precision analyses or sensitivity analyses for those missing assessments.

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 figures describe hypothetical future studies based on fractions of the observed effect, not the trial’s original design. The registry’s planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each planning row uses the stated fraction of the observed effect as the effect to detect. The original design assumptions and original sample-size justification are not reported in the registry record.

For these outcomes, the figures are participants per arm. They are not totals across both arms. The 80% power column gives the number of participants per arm that the planning calculation estimates would be needed for an 80% chance of detecting the chosen effect, assuming the stated model and significance level when that effect is present. The 90% power column gives the corresponding planning estimate for a 90% chance. These are design probabilities under assumptions, not guarantees about a future study.

The rows distinguish planning for 100%, 75%, and 50% of the observed effect. The smaller the effect a study aims to detect, the more participants it generally needs, because a smaller signal is harder to distinguish from random variation. For example, the accidental venipuncture planning estimates range from 71 participants per arm for 80% power at 100% of the observed effect to 380 participants per arm for 80% power at 50% of the observed effect. The corresponding 90% figures are 95 and 508. The other outcomes have their own estimates because their observed effects and variability differ.

On a sample-size curve, the same principle is represented visually: planning for a smaller effect moves the required sample size upward, and targeting higher power also requires more participants under the stated assumptions. These are planning illustrations computed from the observed effects. This is not observed power and does not describe the probability that the completed trial detected its results.

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 = 0.833; treatment proportion p₁ = 0.864; average p̄ = 0.848.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.5075 = 0.9946.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.5070 = 0.4267.
4. n = (0.9946 + 0.4267)² / (0.0311)² = 2,092.1, rounded up to 2,093 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 <- 0.83265306122449                          # control proportion
p1 <- 0.86372745490982                          # 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(667381)
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 = 2,093 (80% power), 2,801 (90% power)
 75% of observed effect: n per arm = 3,798 (80% power), 5,084 (90% power)
 50% of observed effect: n per arm = 8,720 (80% power), 11,673 (90% power)
power.prop.test: 2092.1 
Simulated power at n = 2,093 per arm: 0.797 (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. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when more than one outcome or statistical comparison is examined. Even if each test is considered individually, testing a collection of outcomes can make it more likely that at least one result appears notable by chance. Whether and how to address this depends on the study’s aims, outcome hierarchy, and analysis plan. The registry record does not report a multiplicity adjustment or a prespecified hierarchy for the primary and secondary outcomes.

The primary endpoint is identified in the record, and three secondary outcomes are posted. However, the registry does not explain whether the secondary outcomes were prespecified in a protocol, whether additional analyses were planned, or how the family of comparisons was defined. The unadjusted p-values should therefore not be read as if a multiple-testing procedure had been applied. No adjustment should be inferred.

Missing primary outcome information is described: femoral angiography was not performed or was inadequate for analysis for 11 control and 4 ultrasound participants. Those participants were excluded from the primary outcome analysis and included for other analyses. The registry does not report a sensitivity analysis for these exclusions, imputation, or another method to assess the effect of missing primary endpoint information. It also does not provide a full account of missingness for each secondary outcome.

The analysis populations are only partly described. The primary outcome denominators are reported, and the record explains the angiography-related exclusions. Further details about whether each analysis followed an intention-to-treat approach, how protocol deviations were handled, or how participants were included in each secondary analysis are not reported in the registry record.

The registry lists no reported analyses. It does not report a complete statistical analysis plan, interim analyses, the original sample-size justification, or the precise analysis methods used for each posted result. These absences limit the ability to assess whether the analyses followed a prespecified plan and how missing data and multiple comparisons were handled.

15. 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 0% reporting threshold.

Most frequent non-serious adverse event terms

The adverse-event record lists serious adverse events as 0 among 501 control participants at risk and 0 among 503 ultrasound participants at risk. No serious adverse event terms are listed. The registry also reports other adverse events: 17 in control and 7 with ultrasound, among the stated groups at risk. These are registry categories and should not be assumed to describe a specific type of event without further detail.

The figures are counts, not a complete narrative of each event, its severity, timing, or relationship to the procedure. The record does not report deaths for these groups. A zero count in the posted serious-event field means no serious events were reported there; it does not establish that the risk is absent. Safety interpretation also depends on follow-up, ascertainment, definitions, and the completeness of reporting, details that are not fully described in the registry record.

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

The primary result describes angiographically assessed sheath placement among participants with an adequate angiogram. The posted counts and unadjusted comparison do not yield a precise estimate that resolves whether the proportion of successful cannulations differed between groups. The confidence interval spans zero, and the p-value is 0.173. This is uncertainty, not proof that the approaches are identical and not evidence of equivalence.

The secondary outcomes add information about time, accidental venipunctures, and vascular complications. Their estimates and unadjusted p-values describe the posted comparisons, but they represent distinct outcomes and are subject to the uncertainty and multiplicity concerns already noted. They do not establish an overall treatment effect or a complete balance of benefit and harm.

The record does not establish how results would generalize beyond the participants and procedures represented in this trial. It gives a brief description of cardiac catheterization and peripheral arterial angiography, but does not report detailed eligibility criteria or enough population characteristics to assess applicability across settings. It also does not provide long-term outcomes beyond the stated vascular complication follow-up of up to 1 month.

Statistical significance and clinical importance are different questions. The registry does not report a threshold for a clinically meaningful change in cannulation success, procedural time, venipunctures, or complications. The estimated differences therefore should not be labeled clinically important or unimportant based on the posted statistical results alone.

The study’s completed status indicates that the trial is no longer listed as ongoing in the registry, but it does not add details about the conduct or completeness of reporting. The registry record supports a narrow interpretation of the posted outcomes and their uncertainty; it does not, by itself, settle broader decisions about femoral access methods.

17. Why This Trial Matters Statistically

This trial illustrates why the endpoint definition matters. “Successful access” is not left as an informal judgment: the primary outcome is tied to an angiographic location bounded by named anatomical landmarks. A precise definition makes the measured event more interpretable and helps distinguish technical placement from other procedural or clinical outcomes.

It also illustrates how a randomized comparison can produce a primary estimate that remains uncertain. The group counts and p-value are not enough on their own; the confidence interval shows that the data remain compatible with effects in either direction. A result that does not exclude no difference is not proof of equality, just as a result that excludes zero does not by itself establish clinical importance.

The registry’s secondary outcomes demonstrate that the statistical story can vary by endpoint. Timing, accidental venipuncture, and vascular complications measure different aspects of a procedure. Their unadjusted results should be read with attention to multiplicity and the lack of a reported analysis plan, rather than treated as a single composite conclusion.

Finally, the angiography-related exclusions show how outcome availability shapes the analysis population. The registry identifies the excluded participants and states that they remained included for other analyses, but does not report sensitivity analyses. This is a useful reminder that randomized assignment and complete outcome measurement are separate issues in interpreting trial evidence.

18. 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 registry record leaves important design and analysis details unreported. It identifies the trial as randomized and single-masked, but does not say who was masked or describe the allocation procedure. It does not report detailed eligibility criteria, baseline characteristics, or a full description of the enrolled population. These omissions limit assessment of how broadly the results may apply.

The primary endpoint was unavailable or inadequate for some participants, who were excluded from that analysis. Although the record explains their inclusion in other analyses, it does not report sensitivity analyses or a detailed account of missing data across outcomes. The primary finding therefore needs to be understood in relation to the assessed analysis population.

The registry does not report a full statistical analysis plan, the original sample-size justification, multiplicity handling, interim analyses, or adjusted analyses. The exact methods used for the sponsor’s analyses are not reported. The posted p-values are unadjusted, especially relevant when considering several outcomes, and should not be interpreted as if a multiplicity procedure had been applied.

The secondary outcomes also differ in measurement and follow-up: some are immediate procedural outcomes, while vascular complications are recorded immediately and up to 1 month after the procedure. The record does not provide further detail about event definitions, ascertainment, or missingness for each outcome. Adverse-event counts are reported without a full event narrative, and deaths are not reported in the registry record.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Femoral Arterial Access With Ultrasound Trial — NCT00667381.
• Registry record last updated 2010-11-16; status last verified 2010-10.
• Results first posted 2010-11-16.
• 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.

22. Record Summary

The Femoral Arterial Access With Ultrasound Trial was a completed randomized, parallel-group trial sponsored by the University of California, Irvine. The registry records enrollment of 1014 and a study period beginning 2008-04, with primary completion in 2009-02. The intervention was real-time ultrasound guidance to aid femoral arterial access; control access used anatomic landmarks and fluoroscopic localization of the femoral head.

The primary outcome was angiographically assessed successful common femoral artery cannulation, defined by sheath insertion within specified anatomical landmarks. The posted primary comparison is uncertain, with a confidence interval that spans zero and an unadjusted p-value of 0.173. The registry also reports three secondary outcomes and adverse-event counts. Detailed analysis methods, multiplicity handling, the original sample-size justification, and several aspects of missing-data handling are not reported in the registry record.