Aneurysm size and the Windkessel effect: An analysis of contrast intensity in digital subtraction angiography

Abstract

<jats:p> Large cerebral aneurysms are considered more dangerous than their smaller counterparts, with higher risk of subarachnoid hemorrhage. Understanding the hemodynamics of large aneurysms has potential to predict their response to treatment. </jats:p><jats:p> Digital subtraction angiography images for patients with intracranial aneurysms over a seven-year period were reviewed. Unruptured solitary aneurysms of the internal carotid artery (ICA) proximal to the terminus and posterior communicating artery were included. Contrast intensity over time was analyzed at the center of the M1 segment of the middle cerebral artery distal to the aneurysm and compared to the contralateral side. Analysis included time to peak (TP)<jats:sub>10%–100%</jats:sub> (time needed for contrast to change from 10% intensity to 100%), washout time (WT)<jats:sub>100%–10%</jats:sub> (time for 100% intensity to 10%), and quartile time (QT)<jats:sub>25%–25%</jats:sub> (time for 25% intensity during vessel filling to 25% during emptying). </jats:p><jats:p> Fifty patients met the inclusion criteria. Analysis over the ipsilateral M1 segment revealed a significant increase in QT<jats:sub>25%–25%</jats:sub> (8.5 vs 7.6 seconds, p = 0.006) compared to the contralateral side. There was a correlation between TP<jats:sub>10%–100%</jats:sub> and QT<jats:sub>25%–25%</jats:sub> with aneurysm size (Pearson’s r = 0.37, p = 0.007 and r = 0.43, p = 0.001, respectively). </jats:p><jats:p> Larger ICA aneurysms were associated with delayed contrast intensity times . A plausible mechanism is that large aneurysms act as a capacitance chamber (Windkessel effect) that slow the arrival of contrast distal to the aneurysm. This may be of significance for large aneurysms after treatment, where the loss of the Windkessel effect places the distal circulation at greater risk for hemorrhage, and warrants further study. </jats:p>

Clinical application of pulsatility index

“…It has been described that in arterial aneurysms, a Windkessel effect takes place, where the aneurysm acts as a reservoir for blood during systole and releases it during diastole. This results in lower pulse pressure, because of increased vascular resistance distally [9,10]. This was supported by a study by Hussein et al [9], where the authors demonstrated the relationship between the size of internal carotid artery aneurysms and distal intracranial hemodynamics.…”

“…With the loss of elasticity, there is an increase in pulsatile load of the heart, which has detrimental effects on the left ventricle through increasing its mass and thus the myocardial oxygen demand [9]. Additionally, the increased pulsations resulting from the stiffness of large vessels are believed to affect the capillary networks, resulting in microvascular complications, as they allow the harmful pulsations to be conducted into end-organ microcirculation [10]. This is particularly important when it comes to organs characterized by high flow and low resistance, such as the brain and the kidneys [6].…”

Effects of low-dose intravenous heparin therapy in aneurysmal subarachnoid hemorrhage: a randomized controlled clinical trial protocol

“…The cerebral venous system in uences intracranial pressure by affecting the absorption of cerebral uid. The cerebral venous system regulates blood out ow in various ways, including Starling resistance modepassive regulation [27], the active regulation mode controlled by sympathetic nerves [28], and the Windkessel effect [29]. Several studies have demonstrated that insu cient cortical venous lling and constrained venous out ow are correlated with elevated cerebral edema [30,31], although these ndings were observed in patients with ischemic stroke.…”

Hyperperfusion Syndrome Detected by 15O-Gas Positron Emission Tomography after Clipping of a Large Unruptured Internal Carotid Artery Aneurysm: A Case Report

“…In the area distal to a large aneurysm, chronic hypoperfusion may exist preoperatively because the aneurysm acts as a reservoir. [9][10][11] This phenomenon, reported as "Damping effect" or "Windkessel effect" causes drop in cerebrovascular reactivity (CVR). 11) In addition, the maximum flow rate increased after clipping of an aneurysm lead to hyperperfusion.…”

“…[9][10][11] This phenomenon, reported as "Damping effect" or "Windkessel effect" causes drop in cerebrovascular reactivity (CVR). 11) In addition, the maximum flow rate increased after clipping of an aneurysm lead to hyperperfusion. 9) As well as neck clipping, flow-diverting stents for large aneurysms can also reduce blood flow into the aneurysmal sac by directing flow to the distal vessel, leading to hyperperfusion.…”