Why acute pulmonary embolism becomes chronic thromboembolic pulmonary hypertension: clinical and genetic insights.

PURPOSE OF REVIEW: Chronic thromboembolic pulmonary hypertension (CTEPH) is a life-threatening complication that affects a small but appreciable percentage of patients after acute pulmonary embolism. The cause of CTEPH is under investigation, but no single causative mechanism has yet been identified. RECENT
FINDINGS: CTEPH is likely a complication of residual thrombotic material in the pulmonary arteries that becomes transformed into intravascular scars. Pulmonary artery residua are relatively common after acute pulmonary embolism, and CTEPH may be an extreme manifestation of this phenomenon. Several intriguing observations have been made in patients with CTEPH that give insights into the mechanisms responsible for its formation. Two general pathways have been investigated: resistance of thromboemboli to lysis and attenuation of cellular processes involved in thrombus resolution. This review discusses the evidence supporting each pathway as a mechanism for CTEPH formation, as well as the interaction between the two.
SUMMARY: CTEPH may be due to a complex interaction between thrombotic/thrombolytic processes and angiogenic cellular remodeling of organized thrombi. The factors involved may, in fact, vary among CTEPH patients. An understanding of the interplay between the factors that cause CTEPH may help quantify the risk of its occurrence and provide insights into how it can be prevented.