Angioarchitecture and hemodynamics of microvascular arterio-venous malformations

Abstract

IntroductionArteriovenous malformations (AVMs) are characterized by pathological high flow, low resistance connections between arteries and veins. Treatment is critically dependent on correct interpretation of angioarchitectural features. However, some microfistular AVMs do not match the characteristics described in current AVM classification systems. Therefore, we propose a new subgroup of microfistular AVMs, composed of enlarged, fistulous paths on the venous half of capillaries and/or dilated draining venules (hyperdynamic, capillary-venulous malformation [CV-AVM]). CV-AVMs still ensure arterial flow to the periphery and fistulous venous drainage is less pronounced than in classical AVMs such that these lesions are often misinterpreted as venous malformations.Materials and methodsWe developed a computational model to study the effects of microvascular anomalies on local hemodynamics, as well as their impact on angiographic contrast propagation. Flow rates and pressures were computed with a lumped parameter description, while contrast propagation was determined by solving the 1D advection-diffusion equation.Results and conclusionsFor the newly proposed CV-AVM angioarchitecture, the computational model predicts increased arterio-venous contrast agent transit times and highly dispersive transport characteristics, compared to microfistular, interstitial type IV AVMs and high flow type II and III AVMs. We related these findings to time-contrast intensity curves sampled from clinical angiographies and found that there is strong evidence for the existence of CV-AVM.

Preoperative embolization of high-flow peripheral AVMs using plug and push technique with low-density NBCA/Lipiodol

“…In our report, we examined the type IV AVM according to Yakes classification. Yakes developed a new classification of these lesions [ 4 , 5 ]. NBCA was widely used because of these benefits, and the patient could accept it easier for a low-cost price, especially in a developing country.…”

Capillary-venule malformation is a microfistulous variant of arteriovenous malformation

“…Those 398 patients where retrospectively reviewed to identify patients with CV-AVM. Criteria to define a CV-AVM were: 1. hyperdynamic AVM characteristics using duplex ultrasound and/or magnetic resonance imaging, 2. delayed venous shunting defined as an occurrence after arterial contrast transit using DSA (Figures 1;3;4) 13,14 .…”

“…shows no typical early venous shunting. Venous drainage is considerably delayed and dispersed as compared to other types of AVM 14 , and even can be missed with insufficient angiographic technique as it becomes obvious only with long DSA sequences after disappearance of arterial contrast flow.…”

“…Frey et al were the first to describe the hypothesis that the structural pathology of this subgroup of AVM probably is at the level of capillary venules after assessing multiple types of AVM with an analyzing program developed for this purpose 13 . The model was robust to simulate different types of AVM and to differentiate classical types in patients 13,14 . It was shown that CV-AVM show a particularly slow and dispersive venous shunting behavior that is different from other high flow AVM and that the anatomical change mathematically should be on the venule side following the capillary bed.…”

A Computational Framework for Pre-Interventional Planning of Peripheral Arteriovenous Malformations

“…The majority of numerical works described in the literature employed simplified approaches to model the intricate geometry of AVMs, such as the exclusive use of electric networks to reproduce the vasculature, [9][10][11][12][13] or their combination with a porous medium to represent the nidus. 13 A similar approach was employed by Orlowski et al, in which the haemodynamics of cerebral AVMs were studied by means of patient-derived computational fluid dynamics (CFD).…”