Original Article
Can the Windkessel Hypothesis Explain Delayed Intraparenchymal Haemorrhage After Flow Diversion? A Case Report and Model-Based Analysis of Possible Mechanisms

https://doi.org/10.1016/j.hlc.2015.02.001Get rights and content

Background

Delayed ipsilateral intraparenchymal haemorrhage is a recently recognised complication after endovascular flow diversion for intracranial aneurysms. Although the mechanism of this phenomenon is not understood, one proposed explanation (the windkessel hypothesis) is that removal of aneurysmal compliance increases distal pulse pressure.

Methods

We present a case of delayed haemorrhage after placement of a Pipeline stent, discuss the proposed mechanisms, and describe a novel electrical analogue model that was used to evaluate the likely haemodynamic effect of stent placement.

Results

Model-based analysis suggests that stenting is not likely to produce a significant change in distal pulse pressure. Moreover, basic fluid dynamics principles suggest that a local reduction in disturbed flow in the region of the aneurysm could produce only a minor increase in distal pressure (a few mmHg), which is unlikely to be the main cause of the observed haemorrhage.

Conclusion

The windkessel hypothesis is unlikely to explain the occurrence of delayed ipsilateral intraparenchymal haemorrhage after flow diversion; however, other mechanisms involving altered haemodynamics distal to the treated aneurysm may play a role. Further studies involving the assessment of haemodynamic changes after flow diversion would be useful to understand, and eventually mitigate, this currently unpredictable risk.

Introduction

Recently, several reports have surfaced demonstrating delayed ipsilateral intraparenchymal haemorrhage (IPH) as a potential complication of flow diversion treatment of intracranial aneurysms [1], [2], [3]. Common to these reports is that all patients awoke from general anaesthetic at baseline condition, then experienced delayed neurological deterioration (hours to days post-procedure) related to the development of IPH in a vascular distribution ipsilateral, but distal to the treated aneurysm. Although uncommon, the pathophysiology of this process is unknown; hence, we are unable to predict which patients are more susceptible to this potentially severe complication.

In this paper, we report another case of delayed ipsilateral IPH following flow diversion occurring at our institution. Our case is among the most severe examples reported to date, and resulted in death. After describing the case, we critically assess possible mechanisms that have been advanced to explain delayed intraparenchymal haemorrhages in this setting, making use of a novel electrical analogue model based on fundamental fluid dynamics principles.

Section snippets

Case Report

The patient was a 48 year-old woman with a past history of hypertension, hypothyroidism and a known left cavernous internal carotid artery (ICA) fusiform aneurysm of 1.5 cm maximum diameter (Figure 1A). The patient was diagnosed with the initially incidental aneurysm in 2004 following a magnetic resonance imaging (MRI) scan investigating unrelated symptoms of right-sided hearing loss, dizziness, and chronic headaches. At the time of initial diagnosis, the decision was made to follow the aneurysm

Model Analysis

One hypothesis that has been advanced as a possible mechanism of delayed ipsilateral IPH is that replacing the relatively compliant segment of the aneurysm and blood vessel wall with a relatively rigid stent alters pressure transmission across this segment [1], [3]. This has been described as a reduction in the windkessel effect, which refers to a decrease in blood vessel elasticity that leads to an increase in distal pulse pressure [1]. While this hypothesis has not yet been tested in-vivo,

Discussion

Flow diverting stents are relatively new devices in the treatment armamentarium for intracranial aneurysms. These devices are designed to reduce flow into the aneurysmal portion of the artery in order to promote thrombosis within the aneurysm, while maintaining patency of the parent and branch vessels. Flow diverters have also been observed to promote endothelial regrowth across the neck of the aneurysm, further reducing the potential for aneurysm recurrence or recanalisation. The Pipeline

Conclusion

Delayed intraparenchymal haemorrhage after flow diversion is increasingly being recognised as a potentially significant complication and may result in death. Proper counselling of patients prior to treatment should include a discussion of this possible risk. A number of considerations based on established fluid dynamics theory suggest that haemodynamic changes caused by the presence of a flow diverting stent, in place of a compliant aneurysm, are likely to be small and may not provide an

Acknowledgements

Author JPM was supported by a CJ Martin Early Career Fellowship from the National Health and Medical Research Council of Australia.

References (22)

  • R.W. Barnes

    Hemodynamics for the vascular surgeon

    Arch Surg.

    (1980)
  • Cited by (20)

    • Reversible Brain Edema Associated with Flow Diverter Stent Procedures: A Retrospective Single- Center Study to Evaluate Frequency, Clinical Evolution, and Possible Mechanism

      2019, World Neurosurgery
      Citation Excerpt :

      Decreased arterial elasticity could be considered a quick removal of the Windkessel effect: increased pressure transmitted to distal territories after FDS could be considered correlated to with disruption and brain edema.9 This viewpoint was considered in a literature report wherein a decrease in the Windkessel effect could partially explain BBB disruption and intra-parenchymal hematoma after FDS.10 Considering perfusion tests, PWI is not a quantitative examination, and it is necessary to compare the result with the opposite hemisphere or previous PWI performed before treatment to precisely confirm a status of hyperperfusion.11

    • The profile of blunt traumatic infratentorial cranial bleed types

      2019, Journal of Clinical Neuroscience
      Citation Excerpt :

      The cerebellum is one of the most common locations for a spontaneous hypertensive hemorrhage [49]. The reason why these patients had long ICU stays is because IPHs are unpredictable thus requiring intensive monitoring; this usually means multiple CT scans during their ICU stay [50,51]. These hemorrhages can blossom.

    • Validation of parametric mesh generation for subject-specific cerebroarterial trees using modified Hausdorff distance metrics

      2018, Computers in Biology and Medicine
      Citation Excerpt :

      Even small changes in vascular network configuration or geometry can substantially alter WSS in arteries [7]. Therefore, surgical interventions inducing geometrical changes may inadvertently induce undesired wall shear stress, which can lead to further lesions both local and distal to the site of intervention [8–11]. Hence, accurate reconstruction of large-scale cerebral arterial trees topology can be of significance to anticipate the endovascular lesion-prone sites.

    • Large-scale subject-specific cerebral arterial tree modeling using automated parametric mesh generation for blood flow simulation

      2017, Computers in Biology and Medicine
      Citation Excerpt :

      The automatic PRM method enables detailed hemodynamic analysis for a large portion of the arterial tree, including small downstream vessels. A large-scale approach of assessing hemodynamic risk factors for regions far away from the site of intervention, could aid in elucidating poorly understood phenomena such as delayed hemorrhage (DH) [51,52]. Moreover, automation of the workflow presented here would address an important clinical need, because it enables image segmentation and dynamic simulation of patient-specific images on the same day.

    View all citing articles on Scopus
    1

    Equal first author

    View full text