Kondziolka et al developed a simple risk equation to help predict the lifetime risk of hemorrhage from an arteriovenous malformation. This can help a patient make informed decisions about management. The authors are from the University of Pittsburgh and the University of British Columbia.


(1) age of the patient

(2) life expectancy of the patient (from life insurance tables)

(3) annual risk of hemorrhage expected (usually 2-4%)


expected years of remaining life =

= (life expectancy for the patient) - (current age)


risk of no hemorrhage =

= 100% - (annual risk of hemorrhage)


probability of no hemorrhage during the remaining years of life =

= ((risk of no hemorrhage) ^ (expected years of remaining life))


probability of hemorrhage for the patient =

= 100% - ((risk of no hemorrhage) ^ (expected years of remaining life))



• The model assumes that the risk of hemorrhage every year is constant. The actual risk may be affected by changing risk factors such as a previous hemorrhage.

• The model also assumes that the risk each year is independent.

• Although the model may not be rigorous, it is simple and may be good enough for convey the degree of risk.

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