CTPA beyond pulmonary embolism- the pulmonary arterial obstruction index

Abstract

Pulmonary thromboembolism (PTE) and deep vein thrombosis (DVT) are different manifestations of the same condition, venous thromboembolism (VTE), which is the third most common cardiovascular disease after the ischemic heart and cerebrovascular diseases. Thus, we have to be mindful that acute pulmonary embolism (APE) is a medical emergency and a very serious clinical manifestation of VTE, that occurs due to discharge of emboli in the pulmonary arterial system which leads in subsequent arterial occlusion and an increase in the pulmonary vascular resistance, an increase in the right heart afterload and acute right ventricular failure, which is a life- threatening condition. Taking into account the fact that patients with right heart dysfunction have a high mortality rate, timely diagnosis and prompt management are the basis for the reversibility of the condition. The significantly improved image quality and upgraded diagnostic performance of CT pulmonary angiography are essential in acknowledging this diagnostic modality as the imaging technique of choice in suspected pulmonary embolism. The last decade has shown a dramatic improvement in the CTPA depiction quality of the pulmonary vasculature, and through additional enabling of the PAOI calculation, offers a quantitative value to the severity of APE, as well as detailed assessment of RV function. The objective of this lecture is not only to confirm the importance of CTPA in the prompt diagnosis of APE, but also to help radiologists conduct a detailed assessment of the CTPA’s in patients with APE, and by evaluating the relationship between the pulmonary arterial obstruction index (PAOI) and several CT cardiovascular markers of right heart dysfunction, to determine its prognostic value in the risk stratification of potential RHD. Besides confirming the prognostic value of CTPA in predicting possible complications, we also want to make a meaningful contribution into the decision making of the APE management, in forming an interdisciplinary consensus regarding follow up CTPA protocols in patients with PTE, and through the evaluation of PAOI and PAOI- associated right ventricular dysfunction, to optimize the duration of therapy and avoid unnecessary imaging examinations, i.e., over- diagnosis.