What is the critical value for mean pulmonary arterial pressure, above which the right ventricle fails and death may ensue?

a. 30 mm Hg
b. 40 mm Hg
c. 50 mm Hg
d. 60 mm Hg

ANS: B
When the mean pulmonary arterial pressure increases to greater than 40 mm Hg during an acute first pulmonary embolism, the right ventricle fails, and hemodynamic collapse and death occur.