The exact mechanism by which the risk factors produce PH has not been established. Given the fact that the absolute risk is generally low, factors of individual susceptibility are likely to play an important role. Risk factors and associated conditions for PAH are presented in the table below .
A "deﬁnite" association is deﬁned as an epidemic, such as occurred with appetite suppressants in the 1960s, or large, multicenter epidemiologic studies demonstrating an association between a drug and PAH.
A "likely" association is deﬁned as a single-center, case-control study demonstrating an association or a multiple-case series. "Possible" is deﬁned as drugs with similar mechanisms of action as those in the "deﬁnite" or "likely" categories but which have not yet been studied (e.g., drugs used to treat attention-deﬁcit disorder).
An "unlikely" association is deﬁned as one in which a drug has been studied in epidemiologic studies and an association with PAH has not been demonstrated.
Table: Updated risk factors for and associated conditions of PAH
|Dexfenfluramine||St. John's Wort|
|Toxic rapeseed oil||Chemotherapeutic agents|
PAH = pulmonary arterial hypertension; SSRI = selective serotonin reuptake inhibitor
Ref. Simmoneau G et al. JACC 2009; 54: Suppl S, S43-54