Editing Arteriovenous malformation (section)

==Pathophysiology==
In the [[circulatory system]], arteries carry blood away from the heart to the [[lung]]s and the rest of the body, where the blood normally passes through [[capillaries]]—where oxygen is released and waste products like [[carbon dioxide]] ({{CO2}}) absorbed—before veins return blood to the heart.<ref>{{Cite web |date=2021-09-21 |title=Circulatory System: Anatomy and Function |url=https://my.clevelandclinic.org/health/body/21775-circulatory-system |access-date=2023-03-08 |website=[[Cleveland Clinic]] |language=en}}</ref> An AVM interferes with this process by forming a direct connection of the arteries and veins, bypassing the [[capillary bed]].<ref name=":0" /> AVMs can cause intense pain and lead to serious medical problems. Although AVMs are often associated with the brain and spinal cord, they can develop in other parts of the body.<ref name=":0">{{Cite journal |last1=Schimmel |first1=Katharina |last2=Ali |first2=Md Khadem |last3=Tan |first3=Serena Y. |last4=Teng |first4=Joyce |last5=Do |first5=Huy M. |last6=Steinberg |first6=Gary K. |last7=Stevenson |first7=David A. |last8=Spiekerkoetter |first8=Edda |date=2021-08-21 |title=Arteriovenous Malformations—Current Understanding of the Pathogenesis with Implications for Treatment |journal=International Journal of Molecular Sciences |volume=22 |issue=16 |pages=9037 |doi=10.3390/ijms22169037 |issn=1422-0067 |pmc=8396465 |pmid=34445743|doi-access=free }}</ref>

As an AVM lacks the dampening effect of capillaries on the blood flow, the AVM can get progressively larger over time as the amount of blood flowing through it increases, forcing the heart to work harder to keep up with the extra blood flow. It also causes the surrounding area to be deprived of the functions of the capillaries. The resulting tangle of [[blood vessel]]s, often called a ''nidus'' ([[Latin]] for 'nest'), has no capillaries. It can be extremely fragile and prone to bleeding because of the abnormally direct connections between high-pressure arteries and low-pressure veins.<ref>{{Cite journal |last1=Mouchtouris |first1=Nikolaos |last2=Jabbour |first2=Pascal M. |last3=Starke |first3=Robert M. |last4=Hasan |first4=David M. |last5=Zanaty |first5=Mario |last6=Theofanis |first6=Thana |last7=Ding |first7=Dale |last8=Tjoumakaris |first8=Stavropoula I. |last9=Dumont |first9=Aaron S. |last10=Ghobrial |first10=George M. |last11=Kung |first11=David |date=February 2015 |title=Biology of cerebral arteriovenous malformations with a focus on inflammation |journal=Journal of Cerebral Blood Flow and Metabolism|volume=35 |issue=2 |pages=167–175 |doi=10.1038/jcbfm.2014.179 |pmc=4426734 |pmid=25407267}}</ref> One indicator is a pulsing 'whoosh' sound caused by rapid blood flow through arteries and veins, which has been given the term ''bruit'' ([[French language|French]] for 'noise'). If the AVM is severe, this may produce an audible symptom which can interfere with hearing and sleep as well as cause psychological distress.<ref name="NINDS" />