Examples of right-to-left shunting are congenital cyanotic heart disease and pulmonary arteriovenous malformations (PAVMs) 1) 2) ,which form the basis of current recommendations for prophylactic antibiotics in patients with such conditions and for prophylactic closure of PAVMs 3).

1)
Kawamata T, Takeshita M, Ishizuka N, Hori T. Patent foramen ovale as a possible risk factor for cryptogenic brain abscess: report of two cases. Neurosurgery 2001;49:204-206; discussion 206-207.
2)
Sung CW, Jung JH, Lee SH, Choi S, Cho JR, Lee N, et al. Brain abscess in an adult with atrial septal defect. Clin Cardiol 2010;33:E51-E53.
3)
Trerotola SO, Pyeritz RE. PAVM embolization: an update. AJR Am J Roentgenol 2010;195:837-845.