BACKGROUND: Regulation of vascular permeability in hereditary angioedema due to C1 inhibitor deficiency (HAE-C1INH) is key to understanding the disease, but the role of the autonomic nervous system (ANS) in this mechanism remains unclear.
PURPOSE: The aim of this study was to compare the cardiovascular autonomic response to the head-up tilt test (HUTT) in HAE-C1INH patients and matched healthy controls (HCs).
METHODS: HAE-C1INH patients were evaluated during a 1-week symptom-free period. Electrocardiogram (ECG) and beat-to-beat non-invasive arterial blood pressure (BP) were recorded in the supine position (REST) and during 70° tilt (TILT). Heart rate and systolic BP (SBP) variability indices were derived. Variance (σ2 SBP) and low-frequency power (LFSBP) of SBP variability were used as markers of sympathetic vascular control.
RESULTS: Twenty-five HAE-C1INH patients [13 male individuals, 44 (28.8-57.5) years] and 25 HCs [13 male individuals, 44 (30.8-54.3) years] were enrolled and divided into <45 and ≥45 age groups. Eighteen patients were on long-term prophylaxis (LTP). In the younger group, LFSBP increased from REST to TILT in both groups, with no differences. In older subjects, HAE-C1INH patients showed higher σ2 SBP [21.2 (9.3-59.2) vs. 7.5 (1.9-14.6) mmHg2] and a greater LFSBP increase [9.4 (4.6-22.4) vs. 0.9 (0.2-7.6) mmHg2] than HCs during TILT, suggesting sympathetic hyperactivation. No significant group differences in cardiac autonomic control were observed during REST or TILT, regardless of age. Findings in the LTP subgroup mirrored those of the full cohort.
CONCLUSION: Older HAE-C1INH patients display altered vascular autonomic regulation, with an exaggerated sympathetic response during orthostatic stress. Further studies are needed to assess the role of LTP in these alterations.
CLINICAL TRIAL REGISTRATION: https://clinicaltrials.gov/study/NCT06408805?cond=Hereditary%20Angioedema&term=autonomic&rank=1.
Older HAE-C1INH patients display altered vascular autonomic regulation, with an exaggerated sympathetic response during orthostatic stress.
small age strata and 57–70% vascular-outcome power make the age-specific signal hypothesis-generating
No significant group differences in cardiac autonomic control were observed during REST or TILT, regardless of age.
standardized HUTT measurements were consistent across analyses, although enrollment fell below the planned sample
The LTP might not modify the behavior of the cardiovascular neural control of HAE-C1INH patients.
only seven untreated patients prevented a direct treatment comparison and medication effects remain inseparable from disease effects
The selective vascular involvement becomes more pronounced with longer disease exposure.
cross-sectional age stratification does not identify disease-duration effects
Derived from the full evaluation — not a separate score.
Strengths
The study examines an androgen-free population and directly contrasts its treatment context with the attenuated-androgen exposure in the closest prior HUTT study.
↳ Background, final paragraph; Discussion, paragraph 2
ECG, beat-to-beat blood pressure, and respiration were recorded under standardized REST and 70° TILT conditions, with explicit artifact correction and segment-selection rules.
↳ Experimental Protocol; Methods, Signals Pre-processing
The Discussion connects low power to replication needs, BMI imbalance to future control matching, and the age cutoff to the constraints of rare-disease sampling.
↳ Discussion, limitations
Limitations
The analyzed sample fell below the planned target, and post-hoc power was 70% for σ²SBP and 57% for LFSBP. The older-group comparison further divides the cohort into approximately 12 participants per arm.
↳ Population; Results, Cardiovascular Neural Control During HUTT; Figure 3
The Conclusion states that vascular involvement increases with longer disease exposure, but the reported analysis stratifies by age and does not analyze disease duration.
↳ Methods, Statistical Analysis; Conclusion
The autonomic indices are not tied to attacks, prognosis, treatment response, diagnostic thresholds, or a current clinical decision. The paper consequently supports follow-up research rather than implementation.
↳ Aim; Discussion; Conclusion
The study’s main value is its standardized HUTT characterization of an androgen-free contemporary HAE-C1INH cohort and its direct engagement with the closest prior study. Methodological confidence is reduced because the analyzed sample missed its target, vascular outcomes had only 57–70% post-hoc power, and the central age strata contained roughly 12 participants per arm. The paper reports its principal limitations clearly and verifies respiratory frequency for interpretation of high-frequency HRV. Its strongest wording should nevertheless be revised because age-stratified cross-sectional findings do not establish increasing vascular involvement with longer disease exposure.
Nabu’s assessment, alongside the field’s view.
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Sound3.2
Confidence mediumThe study provides a real but narrow update to the sparse HUTT literature by examining an androgen-free contemporary cohort and adding age-stratified findings. It does not resolve whether autonomic differences arise from disease, treatment, aging, or disease duration.
“the contributions of aging and disease duration in HAE-C1INH have never been considered”
Age- and sex-matched controls, standardized HUTT acquisition, artifact handling, and respiratory monitoring support the physiological comparisons. Methodological Rigour is constrained by an achieved sample below target, 57–70% vascular-outcome power, small balanced-cutoff age strata, and an unsupported inference from age to disease exposure.
“The selective vascular involvement becomes more pronounced with longer disease exposure.”
The research question, protocol, results, and limitations are presented in a followable sequence with generally cautious wording. The Conclusion nevertheless converts an age-stratified association into a longer-disease-exposure claim that was not directly analyzed.
“In this study, this point is not directly addressed.”
The Discussion directly engages the closest conflicting HUTT study and explains why historical androgen treatment may matter, while tracing power, BMI, medication, and age-cutoff limitations to interpretation. Positioning remains below the highest band because the final disease-duration statement is stronger than that contextual caution permits.
“our analyses do not allow discrimination of medication and disease effects”
Caveats4 of 4 checks
The reported results are numerically interpretable, but precision and claim alignment warrant caution. The central vascular finding relies on small age strata with 57–70% post-hoc power, while the Conclusion infers longer disease exposure from age rather than a reported duration analysis.
Ethics approval, informed consent, trial registration, and an author-provided data-availability statement are declared. The data statement identifies no repository, and no conflict-of-interest statement is visible in the supplied text.
Flags: 3 declared / 5 total
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No retraction or expression of concern found in Crossref (includes Retraction Watch).
Sources: Crossref (incl. Retraction Watch) ✓
Where this paper’s evidence sits on the path from initial observation to real-world use.
The study characterizes autonomic indices during a controlled orthostatic challenge but provides no validated diagnostic threshold, intervention, prognostic association, or implementation guidance. Readiness therefore remains at an early observational stage.
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