Physiology and Clinical Manifestations of Pathologic Cranial Suture Widening

Cranial sutures are complex structures integrating mechanical forces with osteogenesis which are often affected in craniofacial syndromes. While premature fusion is frequently described, rare pathological widening of cranial sutures is a comparatively understudied phenomenon. This narrative review aims to bring to light the biologically variable underlying causes of widened sutures and persistent fontanelles leading to a common outcome. The authors herein present four syndromes, selected from a literature review, and their identified biological mechanisms in the context of altered suture physiology, exploring the roles of progenitor cell differentiation, extracellular matrix production, mineralization, and bone resorption. This article illustrates the gaps in understanding of complex craniofacial disorders, and the potential for further unification of genetics, cellular biology, and clinical pillars of health science research to improve treatment outcomes for patients.

Initial UK series of endoscopic suturectomy with postoperative helmeting for craniosynostosis: early report of perioperative experience

BACKGROUND

Endoscopic suturectomy with postoperative helmeting (ESCH) has emerged as a successful treatment for craniosynostosis, initially in North America. We report early outcomes from the first cohort of ESCH patients treated in the United Kingdom (UK).

METHODS

Retrospective cohort study with electronic chart review.

RESULTS

18 consecutive patients from the first ESCH procedure in UK (May 2017) until January 2020 identified. 12 male and 6 female infantsd, with a mean age of 4.6 months (range 2.5-7.8 months) and weight of 6.8 kg (range 4.8-9.8 kg). Diagnoses were metopic (n = 8), unicoronal (n = 7), sagittal (n = 2) and multi-sutural (n = 1) synostoses. Median incision length was 3 cm (range 2-10 cm). 16/18 received no blood products, with 2 (both metopics) requiring transfusion (1 donor exposure). Mean operative time (including anaesthesia) was 96 min (range 40-127 min). Median length of hospital stay was 1 night. 1 surgical complication (superficial infection). All patients are currently undergoing helmet orthosis therapy. So far, no patients have required revisional or squint surgery.

CONCLUSION

Early experience from the first UK cohort of ESCH suggests that this is a safe and well tolerated technique with low morbidity, transfusion and short hospital stay. Long-term results in terms of shape, cosmetic and developmental outcome are awaited.

AB0752 HOW DOES TIME TO DIAGNOSIS AND GENDER AFFECT TREATMENT OUTCOMES IN PATIENTS WITH ANKYLOSING SPONDYLITIS OR PSORIATIC ARTHRITIS? – REAL WORLD DATA FROM THE GERMAN AQUILA STUDY WITH SECUKINUMAB

Background

In both, ankylosing spondylitis (AS) and psoriatic arthritis (PsA), women typically have a longer delay in diagnosis.1,2 There is scientific evidence that prognosis for AS and PsA improves when diagnosed early. The German non-interventional study AQUILA provides real-world data on the influence of time to diagnosis and gender on treatment outcomes under secukinumab, a fully human monoclonal antibody that selectively inhibits interleukin-17A.

Objectives

The aims of this interim analysis are to describe selected baseline (BL) demographics of AS and PsA patients (pts) and to evaluate the impact of time to diagnosis and gender on secukinumab treatment outcomes, such as disease activity and global functioning and health.

Methods

AQUILA is an ongoing, multi-center, non-interventional study including up to 3000 pts with AS or PsA. Pts were observed from BL up to week (w) 52 according to clinical routine. Real-world data were assessed prospectively and analyzed as observed. Validated questionnaires were used to collect data on disease activity (Bath Ankylosing Spondylitis Disease Activity Index, BASDAI), global functioning and health (Assessment of SpondyloArthritis-Health Index, ASAS-HI) in AS, and skin and joint-related disease activity (Psoriasis Area and Severity Index, PASI; tender/swollen joint counts, TJC/SJC) and impact of disease (Psoriatic Arthritis Impact of Disease - 12 items, PsAID-12 score) in PsA pts. This interim analysis focused on the subgroups of male and female AS and PsA pts stratified by time to diagnosis after disease onset (˂1 year [y] and ≥1y for early and late diagnosis, respectively).

Results

At BL, 609 AS and 1145 PsA pts were included with information on time to diagnosis (Table 1); only 18.7% of AS and 25.8% of PsA pts were diagnosed within one year. Of interest, both female AS and PsA pts as well as male PsA pts with increased BMI tended to be diagnosed later (Table 1). Regarding BASDAI scores, male AS pts diagnosed late had increased disease activity at BL and throughout the study (Figure 1A); female AS pts diagnosed late showed reduced total treatment effect with increasing time to diagnosis (Figure 1B). Similarly, both male and female AS pts diagnosed late had slightly increased ASAS-HI at BL and throughout the study (Table 1). For PsA pts, there was no difference in skin- (PASI, Figure 1C/D) and joint-related (Figure 1E/F) disease activity with respect to time to diagnosis. Furthermore, there was no difference in PsAID scores (data not shown) between early- and late-diagnosed PsA pts.

Table 1.

Overview of selected BL characteristics in AS and PsA pts stratified by time to diagnosis

AS (N=609)Time to diagnosis ˂1 year (n=114)Time to diagnosis ≥1 year (n=495)Male (n=63)Female (n=51)Male (n=301)Female (n=194)Age, years43.146.345.947.7BMI27.725.927.327.8BASDAI4.75.05.35.2ASAS-HI6.78.07.48.2PsA (N=1145)Time to diagnosis ˂1 year (n=295)Time to diagnosis ≥1 year (n=850)Male (n=126)Female (n=169)Male (n=363)Female (n=487)Age, years50.151.852.353.1BMI28.729.429.328.8PASI6.56.27.07.2PsAID4.65.24.85.3TJC/SJC5.9/3.37.3/3.27.0/3.77.3/3.8

All variables given as mean

Figure 1.

Disease activity in early- and late-diagnosed AS and PsA pts

Conclusion

In a real-world setting, secukinumab improved disease activity and global functioning in both AS and PsA pts. Both, male and female AS pts had a higher treatment response when diagnosed early. Interestingly, delay in diagnosis appeared to be BMI-dependent in female AS pts and PsA pts of both genders. However, in contrast to AS, treatment response of early- and late-diagnosed PsA pts did not differ in the further course.

References

[1]Rusman, T., van Bentum, R.E. & van der Horst-Bruinsma, I.E. Rheumatology59, iv38-iv46 (2020). 2. Passia, E., et al. OP0057. Annals of the Rheumatic Diseases79, 38-39 (2020).

Disclosure of Interests

Karolina Benesova Speakers bureau: Abbvie, BMS, Gilead/Galapagos, Janssen, Lilly, Medac, MSD, Novartis, Roche, Viatris, Consultant of: Gilead/Galapagos, Novartis, Grant/research support from: Abbvie, Novartis, Oliver Hansen Grant/research support from: Novartis, Uta Kiltz Consultant of: AbbVie, Amgen, Biogen, Chugai, Eli Lilly, Gilead, GSK, Grünenthal, Hexal, Janssen, MSD, Novartis, Pfizer, Roche, UCB, Grant/research support from: AbbVie, Amgen, Biogen, Chugai, Eli Lilly, Gilead, GSK, Grünenthal, Hexal, Janssen, MSD, Novartis, Pfizer, Roche, UCB, Jan Brandt-Juergens Consultant of: Abbvie, Affibody, BMS, Gilead, Janssen, Lilly, Medac, MSD, Novartis, Pfizer, Roche, Sanofi-Aventis, UCB, Peter Kästner Consultant of: Chugai, Novartis, Elke Riechers Consultant of: AbbVie, Chugai, Novartis, UCB, Grant/research support from: AbbVie, Chugai, Novartis, UCB, Pfizer, Daniel Peterlik Employee of: Novartis, Christina Budden Employee of: Novartis, Annika Boas Employee of: Novartis, Stefanie Welle Employee of: Novartis, Hans-Peter Tony Consultant of: AbbVie, Astra-Zeneca, BMS, Chugai, Janssen, Lilly, MSD, Novartis, Pfizer, Roche, Sanofi

AB0751 HOW DOES BODY MASS INDEX AFFECT SECUKINUMAB TREATMENT OUTCOMES AND SAFETY IN PATIENTS WITH ANKYLOSING SPONDYLITIS? – REAL WORLD DATA FROM THE GERMAN AQUILA STUDY

Background

Obesity is a risk factor for worse overall health in people with ankylosing spondylitis (AS)1. The German non-interventional study AQUILA provides real-world data in AS on the influence of body mass index (BMI) on therapeutic effectiveness and safety under treatment with secukinumab, a fully human monoclonal antibody that selectively inhibits IL-17A.

Objectives

The aims of this interim analysis are to describe selected baseline (BL) demographics and to evaluate secukinumab treatment outcomes on disease activity and global functioning and health and to report safety profile depending on the BMI of AS patients (pts).

Methods

AQUILA is an ongoing, multi-center, non-interventional study including up to 3000 pts with active AS or psoriatic arthritis. Pts were observed from BL up to week (w) 52 according to clinical routine. Real-world data were assessed prospectively and analyzed as observed. Validated questionnaires were used to collect data on disease activity (Bath Ankylosing Spondylitis Disease Activity Index, BASDAI) and global functioning and health (Assessment of SpondyloArthritis-Health Index, ASAS-HI). For calculation of proportion of pts that experienced (serious) adverse events ((S)AEs), all AS pts were included that received at least one dose of secukinumab. This interim analysis focuses on BMI subgroups ≤25 kg/m2 (normal weight), >25 to ≤30 kg/m2 (overweight) and >30 kg/m2 (obese) in AS pts.

Results

At BL, BMI data were available for 667 AS pts: 33.6% (n=224) normal weight, 39.9% (n=266) overweight and 26.5% (n=177) obese AS pts (Table 1). In all BMI subgroups the proportion of men was higher, even doubled among overweight AS pts. As BMI increased, so did age and comorbidities/extraarticular manifestations (EAMs, Table 1).

Table 1.

Overview of baseline characteristics in AS pts depending on BMI

DemographicsBMI ≤25 kg/m2 (N=224)BMI >25 to ≤30 kg/m2 (N=266)BMI >30 kg/m2 (N=177)Male*123 (54.9)178 (66.9)94 (53.1)Age, years**43.3 (12.1)47.5 (12.3)49.2 (11.0)BASDAI**4.8 (2.0)5.5 (1.8)5.5 (2.0)ASAS-HI**7.4 (3.7)7.7 (3.3)8.1 (3.6)Comorbidities/EAMs*Heart-related disease4 (1.8)12 (4.5)12 (6.8)Coronary heart disease4 (1.8)10 (3.8)8 (4.5)Stroke1 (0.4)0 (0.0)2 (1.1)Heart insufficiency1 (0.4)4 (1.5)8 (4.5)Uveitis11 (4.9)17 (6.4)13 (7.3)Depression88 (55.3)121 (58.2)73 (54.9)

*variables are given as n (%); **variables given as mean (SD)

Mean BASDAI developed similarly over time with lowest scores for normal weight and highest scores for obese AS pts (Figure 1A). Mean improvement from BL to w52 was 1.3 (27.1%) for normal weight, 1.5 (27.2%) for overweight, and 1.2 (21.8%) for obese AS pts.

Figure 1.

Disease activity and global functioning under secukinumab treatment in AS pts stratified by BMI

Mean ASAS-HI at BL was similar for all BMI subgroups (≤25: 7.4; >25-≤30: 7.7; >30: 8.1); the best improvement was observed in normal weight, the least in obese AS pts (Figure 1B). Mean improvement from BL to w52 was 2.1 (28.4%) for normal weight, 1.3 (16.9%) for overweight, and 0.6 (7.4%) for obese AS pts.

The occurrence of AEs/SAEs with or without suspected relationship to secukinumab increased with increasing BMI. For example, the percentage of SAEs in normal weight was 21%, in overweight 26.7% and in obese AS pts 30.9% (data not shown). There were no events with fatal outcome or unexpected safety signals in either subgroup.

Conclusion

In a real-world setting, secukinumab improved disease activity and global functioning and health in all BMI subgroups of AS pts; normal weight AS pts had numerically better ASAS-HI and BASDAI scores than obese AS pts. Altogether, real-world data of this interim analysis show that secukinumab is an effective treatment with a favorable safety profile up to 52 weeks in AS pts in all BMI subgroups.

References

[1]Chen, C.-H., et al. International Journal of Rheumatic Diseases23, 1165-1174 (2020).

Disclosure of Interests

Uta Kiltz Consultant of: AbbVie, Amgen, Biogen, Chugai, Eli Lilly, Gilead, GSK, Grünenthal, Hexal, Janssen, MSD, Novartis, Pfizer, Roche, UCB, Grant/research support from: AbbVie, Amgen, Biogen, Chugai, Eli Lilly, Gilead, GSK, Grünenthal, Hexal, Janssen, MSD, Novartis, Pfizer, Roche, UCB, Jan Brandt-Juergens Consultant of: Abbvie, Affibody, BMS, Gilead, Janssen, Lilly, Medac, MSD, Novartis, Pfizer, Roche, Sanofi-Aventis, UCB, Peter Kästner Consultant of: Chugai, Novartis, Elke Riechers Consultant of: AbbVie, Chugai, Novartis, UCB, Grant/research support from: AbbVie, Chugai, Novartis, UCB, Pfizer, Daniel Peterlik Employee of: Novartis, Christina Budden Employee of: Novartis, Hans-Peter Tony Consultant of: AbbVie, Astra-Zeneca, BMS, Chugai, Janssen, Lilly, MSD, Novartis, Pfizer, Roche, Sanofi

POS1013 HOW DOES BODY MASS INDEX AFFECT SECUKINUMAB TREATMENT OUTCOMES AND SAFETY IN PATIENTS WITH PSORIATIC ARTHRITIS? – REAL WORLD DATA FROM THE GERMAN AQUILA STUDY

Background

There is a higher prevalence of obesity in patients (pts) with psoriatic disease1. The German non-interventional study AQUILA provides real-world data on the influence of body mass index (BMI) of pts with psoriatic arthritis (PsA) on therapeutic effectiveness and safety under treatment with secukinumab, a fully human monoclonal antibody that selectively inhibits IL-17A.

Objectives

The aims of this interim analysis are to describe selected baseline (BL) demographics and to evaluate secukinumab treatment outcomes on disease activity and impact of disease on health and to report safety profile depending on the BMI of PsA pts.

Methods

AQUILA is an ongoing, multi-center study including up to 3000 pts with active PsA or ankylosing spondylitis. Pts were observed from BL up to week (w) 52. Real-world data were assessed prospectively and analyzed as observed. Data were collected on Psoriatic Arthritis Impact of Disease-12 items (PsAID-12 score) and Patient’s Global Assessment (PGA). For calculation of proportion of pts that experienced (serious) adverse events ((S)AEs), all PsA pts were included that received at least one dose of secukinumab. This interim analysis focuses on BMI subgroups ≤25 kg/m2 (normal weight), >25 to ≤30 kg/m2 (overweight) and >30 kg/m2 (obese) in PsA pts.

Results

At BL, BMI data were available for 1228 PsA pts: 26.5% (n=325) normal weight, 35.0% (n=430) overweight and 38.5% (n=473) obese PsA pts. Proportion of men was lower in normal weight and obese PsA pts. As BMI increased, so did age and comorbidities/extraarticular manifestations (EAMs; Table 1); e.g. percentage of PsA pts with heart-related disease increased from 5.2% in normal weight to 9.3% in obese PsA pts.

Table 1.

Overview of baseline characteristics in PsA pts depending on BMI

DemographicsBMI ≤25 kg/m2(N=325)BMI >25 to ≤30 kg/m2(N=430)BMI >30 kg/m2(N=473)Male*105 (32.3)219 (50.9)188 (39.7)Age, years**49.5 (±12.7)53.2 (±11.0)54.1 (±10.6)PsAID**4.7 (2.4)4.9 (2.2)5.4 (2.0)PGA**4.8 (2.6)5.4 (2.4)5.5 (2.4)Comorbidities/EAMs* Heart-related disease17 (5.2)29 (6.7)44 (9.3) Coronary heart disease10 (3.1)25 (5.8)35 (7.4) Stroke1 (0.3)9 (2.1)11 (2.3) Heart insufficiency9 (2.8)15 (3.5)15 (3.2) Uveitis5 (1.5)6 (1.4)10 (2.1) Depression137 (53.5)190 (55.2)231 (58.5)

*variables are given as n (%); **variables given as mean (SD)

Mean PsAID at BL was similar for all BMI subgroups (≤25: 4.7; >25-≤30: 4.9; >30: 5.4; Figure 1A). Mean improvement from BL to w52 was 1.9 (40.4%) for normal weight, 1.8 (36.7%) for overweight, and 1.7 (31.5%) for obese PsA pts.

Figure 1.

Impact of disease and PGA in PsA pts stratified by BMI.

Note: p-values are of exploratory nature. Wilcoxon tests were used to show significant subroup differences.

Mean PGA developed in a similar way over time with lowest scores for normal weight and highest scores for obese PsA pts (Figure 1B). Mean improvement from BL to w52 was 2.0 (41.6%) for normal weight, 2.2 (40.7%) for overweight, and 1.8 (32.7%) for obese PsA pts.

The occurrence of AEs/SAEs with or without suspected relationship to secukinumab was most frequent in overweight and obese PsA pts. For example, the percentage of SAEs in normal weight PsA pts was 21.6%, in overweight 26.3% and in obese 25.9%. There were no unexpected safety signals in either subgroup. One male obese PsA patient died. Cause of death was not reported, however, treating physician did not suspect a causal relationship to secukinumab.

Conclusion

In a real-world setting, secukinumab improved impact of disease and patient´s global assessment of disease activity in all BMI subgroups of PsA pts. However, normal weight PsA pts had numerically better PsAID and PGA scores than obese PsA pts. Altogether, real-world data of this interim analysis show that secukinumab is an effective treatment with a favorable safety profile up to 52 weeks in PsA pts in all BMI subgroups.

References

[1]Queiro, R., Lorenzo, A., Tejón, P., Coto, P. & Pardo, E. Medicine (Baltimore) 98, e16400 (2019).

Disclosure of Interests

Uta Kiltz Consultant of: AbbVie, Amgen, Biogen, Chugai, Eli Lilly, Gilead, GSK, Grünenthal, Hexal, Janssen, MSD, Novartis, Pfizer, Roche, UCB, Grant/research support from: AbbVie, Amgen, Biogen, Chugai, Eli Lilly, Gilead, GSK, Grünenthal, Hexal, Janssen, MSD, Novartis, Pfizer, Roche, UCB, Jan Brandt-Juergens Consultant of: Abbvie, Affibody, BMS, Gilead, Janssen, Lilly, Medac, MSD, Novartis, Pfizer, Roche, Sanofi-Aventis, UCB, Peter Kästner Consultant of: Chugai, Novartis, Elke Riechers Consultant of: AbbVie, Chugai, Novartis, UCB, Grant/research support from: AbbVie, Chugai, Novartis, UCB, Pfizer, Daniel Peterlik Employee of: Novartis, Christina Budden Employee of: Novartis, Hans-Peter Tony Consultant of: AbbVie, Astra-Zeneca, BMS, Chugai, Janssen, Lilly, MSD, Novartis, Pfizer, Roche, Sanofi

Peripheral nerve surgical competency in plastic surgery and neurosurgery residents

OBJECTIVE

To assess the case volume and self-perceived competence of current mandatory skills in peripheral nerve surgery.

DESIGN

Cross sectional survey based study examining case volume and self-reported competence in peripheral nerve surgery.

SETTING

Canadian Neurosurgery and Plastic Surgery accredited residency programs PARTICIPANTS: All Canadian Neurosurgery and Plastic Surgery senior trainees (PGY 3+) invited to participate RESULTS: Much variability exists in both exposure to cases and perceived senior resident competence for both plastic and neurosurgery residents. Confidence in surgical ability as perceived competency is lower in trainees for more advanced peripheral nerve procedures. Self- reported confidence increased with post-graduate experience.

CONCLUSIONS

Overall, the findings in this study highlight the importance of increasing operative experience in complex peripheral nerve surgery among surgical residents.

Peri-Operative Outcomes Comparison of General Anaesthesia and Brachial Plexus Block for Open Reduction Internal Fixation of Metacarpal Fractures

INTRODUCTION

Brachial plexus blockade (BPB) is a procedure of growing popularity amongst surgeons and anaesthesiologists involved with upper limb surgery. The safety and benefit in hand surgery is unclear.

METHODS

A retrospective chart review was performed examining all operative hand cases over a 2-year period. All cases of metacarpal open reduction internal fixation (ORIF) were included. Cases were excluded if paediatric patient, additional procedures performed, and/or a decreased LOC. Parametric statistical tests were performed.

RESULTS

In total, 54 cases with general anaesthesia (GA) and 48 cases with BPB were identified for the study (n = 102). The average total time from operating theatre to discharge was 245 ± 72 minutes in GA group and 195 ± 54 minutes in BPB (P < .001). Of those who had a GA, 47/54 patients required analgesia post-operatively versus 12/48 in the BPB (P < .001). Of all, 25/52 and 5/48 patients required anti-emetics post-operatively in the GA and BPB groups, respectively (P < .001). Need for any parenteral medication post-operatively was also significantly different (P < .001).

CONCLUSION

This is the first study to specifically examine anaesthetic techniques for ORIF of hand fractures; adding to the body of literature establishing BPB as a safe and efficient method of anaesthesia.

Mechanical and morphological properties of parietal bone in patients with sagittal craniosynostosis

Limited information is available on the effect of sagittal craniosynostosis (CS) on morphological and material properties of the parietal bone. Understanding these properties would not only provide an insight into bone response to surgical procedures but also improve the accuracy of computational models simulating these surgeries. The aim of the present study was to characterise the mechanical and microstructural properties of the cortical table and diploe in parietal bone of patients affected by sagittal CS. Twelve samples were collected from pediatric patients (11 males, and 1 female; age 5.2 ± 1.3 months) surgically treated for sagittal CS. Samples were imaged using micro-computed tomography (micro-CT); and mechanical properties were extracted by means of micro-CT based finite element modelling (micro-FE) of three-point bending test, calibrated using sample-specific experimental data. Reference point indentation (RPI) was used to validate the micro-FE output. Bone samples were classified based on their macrostructure as unilaminar or trilaminar (sandwich) structure. The elastic moduli obtained using RPI and micro-FE approaches for cortical tables (E_RPI 3973.33 ± 268.45 MPa and E_micro-FE 3438.11 ± 387.38 MPa) in the sandwich structure and diploe (E_RPI1958.17 ± 563.79 MPa and E_micro-FE 1960.66 ± 492.44 MPa) in unilaminar samples were in strong agreement (r = 0.86, p < .01). We found that the elastic modulus of cortical tables and diploe were correlated with bone mineral density. Changes in the microstructure and mechanical properties of bone specimens were found to be irrespective of patients' age. Although younger patients are reported to benefit more from surgical intervention as skull is more malleable, understanding the material properties is critical to better predict the surgical outcome in patients <1 year old since age-related changes were minimal.

Monobloc Distraction and Facial Bipartition Distraction with External Devices

Monobloc and bipartition advancement by external distraction plays a major role in the treatment of syndromic craniosynostosis. They can reverse the associated facial deformity and play a role in the management of ocular exposure, intracranial hypertension, and upper airway obstruction. Facial bipartition distraction corrects the intrinsic facial deformities of Apert syndrome. Both procedures are associated with relatively high complication rates principally related to ascending infection and persistent cerebrospinal fluid leaks. Modern perioperative management has resulted in a significant decline in complications. External distractors allow fine tuning of distraction vectors and improve outcome but are less well tolerated than internal distractors.

Effect of heart rate on regulative features of the cortical activity-flow coupling

OBJECTIVE

Heart rate plays an important role in compensatory conditions of arterial pressure changes. Very little information, however, exists on its role in the dynamic adjustment of stimulated organ perfusion. We studied the influence of heart rate on the activity-flow coupling mechanism which adapts local cerebral blood flow in accordance with cortical activity. Since it does not affect heart rate or arterial blood pressure by itself, the commonly observed heart rate variability in test conditions was used to compare the flow response between different heart rate groups. For evaluation under stable heart rate conditions we performed a short test paradigm with a transcranial Doppler technique with the necessary high time resolution.

METHODS

168 healthy young volunteers (24 +/- 3 years of age) were grouped according to their heart rate in decade steps from 60 to 100 beats/min (mean: 82 +/- 9 beats/min). The visually evoked flow velocity responses in the posterior cerebral artery were evaluated according to a control system approach. Peak systolic and end diastolic data were evaluated separately.

RESULTS

A correlation analysis between heart rate and baseline flow velocity as well as each of the control system parameters, i.e. gain, attenuation, rate time and natural frequency, revealed no significance. The flow responses did not differ among the heart rate groups as concluded from an ANOVA test.

DISCUSSION

The increase in heart rate and the possible stress factors responsible for this seem to be of no relevance in regulative features of the activity-flow coupling. The almost identical time course of flow velocity responses among the groups showing a heart rate difference of up to 50% indicates an integrative principle in flow regulation supporting simplified concepts of flow adaptation.