Effects of Losartan Versus Atenolol on Aortic and Cardiac Muscle Stiffness in Adults With Marfan Syndrome: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effects of Losartan Versus Atenolol on Aortic and Cardiac Muscle Stiffness in Adults With Marfan Syndrome (NCT00723801), a randomized phase 3 study. The primary outcome is Aortic Biophysical Properties - Pulse Wave Velocity.

2. Clinical Question

The registry describes a clinical rationale focused on aortic stiffness and left ventricular diastolic function in adults with Marfan syndrome. The primary endpoint was a change in pulse wave velocity, a measure derived from the travel of the pulse between carotid and femoral arteries. A lower velocity is generally consistent with less stiffness, but interpreting this trial's result requires attention to the direction in which change was calculated and to the fact that both group means were negative.

The registry also lists change in ejection fraction as a secondary outcome. That measure addresses a different aspect of cardiac function and should not be treated as interchangeable with the primary measure. The comparison is between randomized groups, not a test of whether either group's mean change alone differs from zero. The posted results describe the observed means and an unadjusted between-group estimate; they do not establish the clinical importance of a difference or provide an account of all analyses that may have been planned.

3. Trial Design

The registry classifies this as a Phase 3, randomized, parallel-group trial sponsored by Brigham and Women's Hospital. Its structured design information lists quadruple masking. The brief summary calls the study double-blind, so the record uses different masking descriptions; which specific people were masked is not reported in the registry record. The trial is marked completed. The recorded start is 2007-10 and the primary completion is 2012-12.

The intervention arms were losartan and atenolol. The arm descriptions specify losartan 100 mg by mouth once daily and atenolol 50 mg by mouth once daily. The summary describes treatment over 6 months, with assessments at the beginning and end of treatment. It describes arterial tonometry for aortic stiffness and echocardiography for diastolic function, as well as blood draws for serum markers. The posted outcomes include pulse wave velocity and ejection fraction; the registry record does not post results for the serum markers.

The enrollment field records 40 participants. The brief summary describes a plan involving 50 adults, whereas the posted primary and secondary outcome summaries each report 17 participants per arm. These are distinct entries in the record and should not be silently reconciled: the reason for the difference is not reported in the registry record. The trial's original sample-size justification, intended analysis population, and detailed protocol are not reported in the registry record. The observed outcome counts describe participants contributing to those posted results, not necessarily every person enrolled.

The primary comparison is losartan versus atenolol for mean change in pulse wave velocity between baseline and 6 months. Random allocation supports a between-group comparison, but details such as the allocation method, concealment procedures, follow-up completeness, and handling of missing measurements are not reported in the registry record. Those omissions limit assessment of how closely the posted result reflects the originally intended trial analysis.

4. Participant Flow and Accounting

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

Overall Study

Reasons for not completing this period:

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 Aortic Biophysical Properties - Pulse Wave Velocity, measured over Baseline and 6 months.

The primary endpoint is the change in aortic pulse wave velocity, expressed in meters per second, from baseline to 6 months. Pulse wave velocity is the speed at which a pressure pulse travels along an artery. In general, it is used as an indicator of arterial stiffness: the measure connects a physical property of the arterial system to a quantifiable signal that can be compared across participants and treatment groups.

The registry describes measurement by applanation tonometry, using carotid and femoral pulse recordings. Participants lay supine in a quiet environment while a handheld probe recorded pulses at the two sites. The distance from the sternal notch to the pulse acquisition sites was measured and entered into the device. The device calculated velocity using distance and the time between pulse upstrokes, with the QRS upstroke on a three-lead surface electrocardiogram serving as a timing reference. The record states that recorded measurements met the manufacturer's software quality-control standards.

Using change from baseline aims to describe how the measure shifted over the treatment period rather than reporting only an end-of-treatment value. In general, a change score is interpretable only with a clear direction convention; the registry gives the group means and their difference but does not explain a broader clinical threshold for meaningful change. The endpoint is a physiological measurement, not a direct measure of symptoms, clinical events, or long-term outcomes. Its interpretation should therefore stay within what the six-month measurement and posted group summaries can establish.

7. Results Posted in the Registry

• Subjects Randomized to Losartan: mean -0.22 versus -1.15 on control; difference 0.93 (95% CI 0.08 to 1.78), standardized effect d = 0.74; z-test p = 0.031.

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.

Diastolic Function - Ejection Fraction

• 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:
  • Subjects Randomized to Losartan: mean 1.57 versus 1.31 on control; difference 0.26 (95% CI -4.13 to 4.65), standardized effect d = 0.04; z-test p = 0.908.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Subjects Randomized to Losartan and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary endpoint is change in ejection fraction from baseline to 6 months. Its group means are close, but the spread is broad and the confidence interval for the difference includes values on both sides of zero. This pattern adds a separate, uncertain description of cardiac function alongside the primary pulse wave velocity result; it does not independently confirm or overturn that primary comparison.

In general, secondary outcomes can provide context about other dimensions of a trial's question, but they may have less evidential weight than a prespecified primary outcome. The record does not identify a multiplicity strategy, outcome hierarchy, or adjustment for multiple comparisons. When several endpoints or analyses are considered, unadjusted p-values do not account for the increased chance of finding an apparently notable result by chance across the full set. The registry record lists one secondary outcome and two outcome measures overall, but does not report whether additional outcomes were measured or analyzed.

The secondary result should be read on its own scale and with its own uncertainty. Ejection fraction and pulse wave velocity measure different physiological properties, so their numerical estimates cannot be combined or interpreted as interchangeable evidence. The registry's secondary result is not a formal equivalence test, and the absence of a small p-value does not establish that the treatments have the same effect. The registry does not report a clinically important difference for ejection fraction or a planned rule for interpreting the secondary result.

In general, a coherent pattern across outcomes can be informative, but interpretation depends on prespecification, measurement quality, analysis completeness, and the relationship between outcomes. Those details are not reported in the registry record. The posted secondary findings therefore provide limited additional context, and should not be treated as a definitive test of a broader cardiac-function claim or as a correction to the primary result.

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

• Diastolic Function - Ejection Fraction

9. Statistical Interpretation

10. Statistical Methods Explained

The registry reports continuous outcomes as means with standard deviations. For pulse wave velocity, the analysis compares the average change from baseline to 6 months between the atenolol and losartan groups. The reported mean difference is 0.93 meters per second, with the losartan group minus the atenolol group as the direction indicated by the posted group means. The ejection-fraction result is also presented as a difference in group means. These summaries answer a between-group question; they do not test each group's change against zero.

What does a mean difference represent?

In general, a mean is the arithmetic average of the observations in a group. A mean difference subtracts one group's mean from the other group's mean, so its sign depends on which group is subtracted from which. A positive difference does not automatically mean improvement: interpretation also depends on the measure, how change is defined, and which direction is clinically favorable. Here, the pulse wave velocity means are both negative, and the reported between-group difference is positive because the losartan mean is less negative than the atenolol mean. The record does not state a clinical threshold that would translate the numerical difference into a meaningful change for an individual.

What does the standard deviation describe?

In general, a standard deviation describes how spread out individual observations are around their group mean. It is not the same as the uncertainty in the estimated mean or in the difference between means. The pulse wave velocity standard deviations are 1.68 meters per second for atenolol and 0.59 meters per second for losartan. For ejection fraction, the corresponding standard deviations are 4.07 and 8.29 percentage points. The different spreads matter: a group mean alone does not show how varied individual changes were. The registry reports standard deviations, but it does not provide participant-level measurements or distributions that would allow further assessment of shape, outliers, or unusual observations.

How should the confidence interval be read?

In general, a confidence interval gives a range of values compatible with the data and the statistical procedure used, under its assumptions. It communicates uncertainty around an estimate, rather than a range containing a known proportion of individual participant outcomes. For the primary mean difference, the reported range runs from just above zero to 1.776 meters per second. Because the range is close to zero at its lower end and reaches considerably higher values at its upper end, the direction is more certain than the exact magnitude. For ejection fraction, the interval extends from -4.13 to 4.65 percentage points and includes zero, indicating that the posted data are compatible with differences in either direction.

What does the p-value add?

In general, a p-value measures how unusual the observed data, or data more extreme, would be under a specified null model and the assumptions of the test. It does not measure effect size, the probability that a result is due to chance, or the probability that a treatment is effective. The primary unadjusted p-value is 0.031; the secondary unadjusted p-value is 0.908. These values describe the posted comparisons without any reported adjustment for multiple testing. The record does not provide enough information to establish the full analysis plan, including whether the test was prespecified, what model was used beyond the posted summary, or how any deviations from assumptions were handled.

The posted comparison is labelled a mean difference and the provided group summaries include sample sizes, means, and standard deviations. A straightforward summary comparison can be useful, but the registry does not report whether the primary result was adjusted for baseline values or other characteristics. It also does not state whether all randomized participants were included in the outcome analysis, how missing values were handled, or whether there were protocol deviations. Such details can affect interpretation, particularly when analysis counts do not match the overall enrollment field.

Why do spread and sample size affect precision?

In general, estimates become less precise when observations vary more or when fewer participants contribute information. The standard error describes the expected variability of an estimate across repeated samples under a statistical model; it differs from the standard deviation, which describes participant-level spread. The registry does not present its own detailed analysis plan or explain all assumptions behind the reported confidence intervals. The intervals and p-values should therefore be read as the uncertainty summaries attached to the posted results, rather than as a substitute for unavailable methods details.

The record's planning illustrations use the observed effect as their starting point and vary the fraction of that effect to be detected. They assume a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. In general, planning for a smaller effect requires more participants to achieve the same target power, because a smaller signal is harder to distinguish from random variation. Those illustrations are not evidence that the trial was designed with those assumptions. The original sample-size justification and analysis assumptions are not reported in the registry record.

11. Confidence Intervals and Precision

Precision is about how tightly the data estimate a quantity, not whether the estimated quantity is important. For pulse wave velocity, the mean difference is 0.93 meters per second, and its confidence interval runs from just above zero to 1.776 meters per second. The interval does not include zero, but its lower end is close to zero and its upper end is substantially larger. That span leaves uncertainty about the magnitude of the between-group difference, even though the estimated direction is positive on the posted losartan-minus-atenolol scale.

In general, a confidence interval is interpreted as a range generated by a method that would cover the fixed underlying parameter at its stated long-run rate if the assumptions and procedure were repeated across many comparable studies. It is not a probability statement about the specific parameter after observing these data. The registry does not provide a clinically meaningful threshold for pulse wave velocity, so the interval cannot be classified as wholly clinically important or unimportant from the posted information alone.

For ejection fraction, the mean difference is 0.26 percentage points and the interval ranges from -4.13 to 4.65. Because the interval includes zero and extends in both directions, the secondary result is compatible with either a lower or higher mean change under losartan relative to atenolol. The point estimate alone should not be used to claim the groups are alike. A formal equivalence or noninferiority conclusion would require an appropriate margin and design, neither of which is reported in the registry record.

Both posted endpoints have 17 participants per arm. In general, estimates based on limited numbers of observations can remain uncertain, especially when individual outcomes vary. The pulse wave velocity and ejection-fraction standard deviations differ across arms, and the ejection-fraction results show notably wider reported individual variation in the losartan group. These summaries help explain why point estimates should be read alongside their intervals. The record does not report missing-data patterns or the number of participants with incomplete measurements, which further limits assessment of precision and representativeness.

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 are participants per arm for 80% power or participants per arm for 90% power, not total events. The calculation assumptions listed in the registry are a two-sided significance level of 0.05, equal allocation between the two arms, a normal approximation, and an effect to detect set to the stated fraction of the observed effect. The original trial's own sample-size assumptions and justification are not reported in the registry record; these planning values are illustrations based on the observed effect, not a reconstruction of the original design.

In general, power is the probability that a statistical test will detect an effect of a specified size under the assumptions used in the planning calculation. The 80% column means the illustrated number of participants per arm for a design with an 80% chance of detecting the effect used in that row, if the assumptions hold. The 90% column gives the corresponding planning target for a 90% chance. These are prospective planning interpretations, not probabilities that the observed trial result is correct.

For pulse wave velocity, planning for 100% of the observed effect gives 29 participants per arm for 80% power and 39 per arm for 90% power. Planning for 75% of the observed effect gives 52 and 69 participants per arm, respectively; planning for 50% gives 116 and 155. For ejection fraction, the corresponding values are much larger: 9,903 and 13,257 for 100% of the observed effect; 17,605 and 23,568 for 75%; and 39,611 and 53,028 for 50%.

As a general principle, smaller effects require more participants to distinguish them from random variation at a fixed power target. These planning calculations use the observed effects, so they should not be mistaken for evidence about the probability that the completed trial had a significant result. This is not observed power.

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

Worked calculation for this trial

1. Observed difference Δ = 0.930; pooled standard deviation σ = 1.259.
2. n = 2 × (1.96 + 0.842)² × 1.259² / 0.930² = 28.8, rounded up to 29 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 <- 0.93                      # observed difference in means
sigma <- 1.25906711497045                     # 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(723801)
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 = 29 (80% power), 39 (90% power)
 75% of observed effect: n per arm = 52 (80% power), 69 (90% power)
 50% of observed effect: n per arm = 116 (80% power), 155 (90% power)
power.t.test: 29.8 
Simulated power at n = 29 per arm: 0.785 (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.

14. Multiplicity, Missing Data and Analysis Populations

The registry record does not report a multiplicity plan, such as a rule for controlling the chance of false-positive findings across multiple outcomes or analyses. It also does not report a hierarchy identifying which outcome would be tested first or how secondary results would be interpreted relative to the primary endpoint. The posted p-values are unadjusted. In general, testing multiple outcomes can increase the chance that at least one result appears statistically notable even when there is no corresponding underlying effect. That general concern does not establish that any posted finding is false; it means the unadjusted values do not address the full family of possible tests.

The primary endpoint is identified as pulse wave velocity, and ejection fraction is listed as a secondary outcome. The registry reports no additional secondary posted outcome result beyond ejection fraction. It does not state whether all intended outcomes are included in the record, whether analyses were prespecified, or whether any analyses were changed after data collection. The original statistical analysis plan and protocol details are not reported in the registry record.

Missing-data handling is also not reported in the registry record. The endpoint summaries each report 17 participants in each arm, whereas overall enrollment is recorded as 40. The record does not explain the difference, specify whether every randomized participant had an outcome measurement, describe reasons for missing measurements, or state whether any imputation or other missing-data method was used. It is therefore not possible to assess from these summaries alone whether the observed endpoint participants represent all randomized participants or whether missingness could have influenced the estimates.

The analysis population is not reported in the registry record. The posted outcome counts should not be assumed to represent an intention-to-treat population, a per-protocol population, or another defined group without an explicit description. The record also does not report how protocol deviations, treatment discontinuation, adherence, or participants who did not complete follow-up were handled. In general, these choices matter because they define which participants contribute to an estimate and what treatment comparison the estimate represents. Their absence limits evaluation of the robustness of the posted results.

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.

The adverse-event summary lists 20 participants at risk in each arm for serious adverse events and 20 in each arm for other adverse events. It records zero affected participants in both categories for atenolol and for losartan. No serious adverse-event terms are listed. These are the figures recorded in the safety summary; they should be read with their stated denominators rather than assumed to cover all enrolled participants.

Deaths are not reported in the registry record. The safety entries do not provide event descriptions, timing, severity categories beyond serious versus other, or a narrative explaining how events were collected. The record also does not reconcile the 20 participants at risk per arm in the safety summary with the 17 participants per arm in the posted efficacy outcomes. The reason for that difference is not reported in the registry record.

In general, a zero count in a posted summary means no affected participants were recorded in that category for the stated group and denominator; it does not prove that an event is impossible or establish a complete safety profile. The registry's safety figures do not by themselves support a broad comparison of overall safety, particularly without details of ascertainment, follow-up, and the completeness of reporting.

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

The primary estimate describes a between-group difference in mean change in pulse wave velocity over the period from baseline to 6 months. The losartan group had a less negative mean change than the atenolol group, and the reported mean difference was 0.93 meters per second. Its confidence interval begins just above zero and extends to 1.776 meters per second; the unadjusted p-value is 0.031. This is evidence about the posted comparison under the analysis assumptions, not a direct statement about an individual's response.

The result does not establish the clinical importance of the observed difference. The registry record does not provide a threshold for a meaningful change in pulse wave velocity, and the interval leaves uncertainty about the magnitude. Nor does a difference in this physiological measure establish a difference in symptoms, clinical complications, or long-term outcomes. The posted trial results concern aortic pulse wave velocity and ejection fraction, not every consequence of Marfan syndrome.

The secondary ejection-fraction comparison is uncertain: its estimate is small relative to the broad interval, which includes zero and values in either direction. This is not proof of equivalence. The two outcomes measure different properties and the record does not give a multiplicity plan or a rule for combining them into an overall conclusion.

The trial's randomized design is relevant to the comparison, but important details remain unavailable, including the original analysis plan, missing-data handling, and analysis population. The posted endpoint counts are 17 participants per arm, while overall enrollment is recorded as 40; the reason is not reported in the registry record. Therefore, the numerical results should be understood as reported summaries from the outcome groups, not as a complete account of all participants or all possible analyses.

In general, statistical evidence, clinical importance, and certainty are separate questions. The p-value addresses compatibility with a null model, the confidence interval conveys uncertainty about the estimated difference, and clinical relevance requires context not stated in the record. The results should not be converted into medical advice or a claim that either treatment works or does not work.

17. Why This Trial Matters Statistically

This trial illustrates why the difference between a point estimate and its precision matters. The primary result has a positive mean difference and an unadjusted p-value of 0.031, but its confidence interval begins close to zero and extends to a larger difference. A single estimate can therefore suggest a direction without fixing the magnitude with comparable certainty. Reporting the interval alongside the p-value gives a fuller account of what the data support.

It also illustrates the importance of keeping primary and secondary outcomes distinct. Pulse wave velocity is the primary endpoint, while ejection fraction is secondary. The latter has a broad interval including zero, and the registry does not report a multiplicity plan. Reading an unadjusted secondary p-value as if it were an isolated confirmatory test would overlook the wider context of multiple outcomes and possible analyses.

The registry entries demonstrate why trial enrollment and analyzed endpoint counts should be read separately. Overall enrollment is 40, while 17 participants per arm appear in each efficacy summary and 20 per arm are listed in the safety summary. The record does not explain these differences. Without a participant flow account and missing-data details, readers cannot fully determine how the posted analyses relate to all randomized participants.

Finally, the sample-size illustrations are based on observed effects and explicit planning assumptions, whereas the original design justification is not reported. The projections show how much planning requirements depend on the effect size chosen, especially for an endpoint with a small observed difference relative to its variability. These calculations help interpret the limitations of a small outcome sample, but they are not retrospective proof that a study was adequately or inadequately designed.

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 posted outcomes have 17 participants per arm, while the enrollment field records 40 overall. The safety summary lists 20 participants at risk per arm. The registry record does not explain these differences or provide a participant flow description. It is consequently unclear from the posted summaries how many enrolled or randomized participants contributed to each analysis and why other participants may not appear in the endpoint counts.

The original sample-size justification, protocol, and statistical analysis plan are not reported in the registry record. The available planning figures are illustrations based on the observed effects and should not be treated as the trial's original design calculations. The record also does not report whether the primary comparison was adjusted for baseline values, how the estimates were calculated in full, or whether sensitivity analyses were conducted.

Missing-data methods and the analysis population are not reported in the registry record. There is no posted account of adherence, treatment discontinuation, protocol deviations, or reasons for incomplete endpoint measurement. These gaps make it difficult to judge the possible influence of missing information or to establish exactly which population the estimates represent.

The registry lists quadruple masking in its structured design fields, but the brief summary describes a double-blind trial. Which participants, investigators, assessors, or other personnel were masked is not reported in the registry record. Details of allocation concealment and the randomization procedure are also not reported.

The primary result is a physiological endpoint observed over 6 months. The record does not give a threshold for clinical importance or post longer-term clinical outcomes. The secondary endpoint result is imprecise, and no multiplicity strategy is reported. Finally, the adverse-event summary reports zero affected participants for its stated categories but provides little detail about event ascertainment; deaths are not reported in the registry record. These are limitations of the available record, not evidence that unreported procedures or analyses did or did not occur.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Effects of Losartan Versus Atenolol on Aortic and Cardiac Muscle Stiffness in Adults With Marfan Syndrome — NCT00723801.
• Registry record last updated 2014-09-09; status last verified 2014-09.
• Results first posted 2014-09-01.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

22. Record Summary

The registry record describes a completed Phase 3, randomized, parallel-group trial sponsored by Brigham and Women's Hospital. It compares losartan with atenolol in adults with Marfan syndrome; the arm descriptions specify 100 mg and 50 mg by mouth once daily, respectively. The structured design field lists quadruple masking, while the brief summary calls the study double-blind.

The primary outcome is mean change in aortic pulse wave velocity from baseline to 6 months. The posted mean difference, losartan minus atenolol, is 0.93 meters per second, with a confidence interval from just above zero to 1.776 and an unadjusted p-value of 0.031. The secondary ejection-fraction comparison is imprecise, with a mean difference of 0.26 percentage points and a confidence interval from -4.13 to 4.65.

Overall enrollment is recorded as 40, while efficacy results report 17 participants per arm. The reason for this difference and key analysis details are not reported in the registry record. The safety summary records zero serious and zero other adverse events among 20 participants at risk in each arm; deaths are not reported.