Effect of platelet inhibitors on thrombus burden in patients with acute pulmonary embolism

Abstract

Venous thromboembolism (VTE) whether provoked or not can be life-threatening due to an acute increase in load on the right ventricle (RV) from obstruction of the pulmonary artery (PA). Treatment for and prevention of VTE involves anti-thrombotic agents; more specifically, medications targeting the anticoagulation cascade. In spite of the widespread acceptance of anticoagulants in the treatment of VTE, there appears to be an ongoing belief that platelet reactivity contributes to thrombus burden in patients with acute pulmonary embolism (PE). This investigation of 398 patients presenting with acute PE evaluated whether anti-platelet medication use, which consisted mostly of aspirin therapy, at the time of presentation, affects PA thrombus burden, RV load, or short-term patient outcomes. We conclude that platelets may have been erroneously incriminated as direct thrombotic mediators in patients with acute PE since aspirin neither decreased PA thrombus burden, nor did aspirin improve short-term mortality following acute PE.

Keywords: Aspirin; platelet; pulmonary embolism; thrombus.

Figure 1. The modified Qanadli Score for PA Thrombus Burden:

A. In this patient, the minimum score in the setting of bilateral pulmonary artery partial obstructions (red) would be 20. Embolism in the truncus anterior (blue) adds at least two more points for complete blockage of the distal right A1 and A3 segmental branches. B. Positive association of Qm (thrombus burden) and RV/LV ratio (measure of RV strain) by Spearman’s correlation, P < 0.0001 (n=153 paired data sets available).

Figure 2. Patient Characteristics: † Thrombus in the pulmonary trunk or R or L pulmonary artery.

‡ Bleeding with decrease in the hemoglobin at least 2 g/dL or transfusion of at least 2 units of packed red cells, occurring at the following sites (intracranial, intraocular, intraspinal, intraarticular, intramuscular with compartment syndrome, pericardial, retroperitoneal), or death as a consequence of bleeding with 4 months. * p<0.05 anti-platelet agents on presentation vs. no anti-platelet agents on presentation. ** P < 0.0001 mQ vs. RV/LV ratio (taking anti-platelet agents) and †† P=0.02 mQ vs. RV/LV ratio (no anti-platelet agents).