The factors influencing haematoma volume due to arteriovenous malformations

Haemorrhage due to cerebral arteriovenous malformations (AVMs) varies from massive, requiring urgent operations, to clinically silent. The present stu dy was designated to identify factors influencing haematoma size, and the p athophysiological mechanisms of massive haemorrhage were studied. 55 patien ts with intracerebral haematomas due to supratentorial AVMs were included i n this study. Angiographic and clinical findings were retrospectively evalu ated in relation to haematoma size. Statistical analysis demonstrated that small size and the presence of only one draining vein were high risk factors for massive haemorrhage. The haema toma volume in small AVMs (30 +/- 4 cm(3)) was significantly larger than in other AVMs (7 +/- 3 cm(3)) (p = 0.0005). AVMs with only one draining vein were associated with massive haematoma volume as compared to AVMs with two or more draining veins (30 +/- 4 versus 11 +/- 3 cm(3), p = 0.0023). Our previous study demonstrated that feeding artery pressure (FAP) was sign ificantly higher in AVMs with haemorrhage than in those without, as was dra ining vein pressure (DVP), and FAP and DVP were inversely related to the nu mber of draining veins and the size of the AVMs. Thus, in small AVMs and AV Ms with only one draining vein, local increase in DVP may thus contribute t o massive haemorrhage.