Lipoprotein (a) is not associated with thrombus burden derived from CT pulmonary angiography in patients with acute pulmonary embolism

Abstract

Lipoprotein (a) [Lp(a)] is suspected to have antifibrinolytic effects, however, its relevance for the severity of venous thromboembolic events remains unclear. We studied the association of Lp(a) levels with thrombus load in pulmonary embolism (PE). 90 patients (40% female, median age 70 [56-79] years) at our tertiary care hospital with a diagnosis of acute PE, available Lp(a) levels and CT pulmonary angiography (CT-PA) performed between April 2017 and December 2019 were included. All CT-PA scans were reanalyzed and thrombus load was determined via Qanadli CT obstruction index (CTOI) and most proximal thrombus location. Median Lp(a) levels were 11.4 [9.3-29.1] mg/dL, median D-dimer levels were 4.6 [2.1-9.8] mg/L, median CTOI was 23 [8-50], central PE was present in 27 (30%) patients. Lp(a) did not correlate with CTOI (r = 0.02, p = 0.922) and was not associated with thrombus location (p = 0.369). CTOI significantly correlated with D-dimer (r = 0.43, p < 0.001) and right to left ventricular diameter ratio (r=-0.49, p = < 0.001). Our findings showed that Lp(a) is not associated with thrombus burden in PE, which suggests that a relevant effect of Lp(a) on the extent of venous thromboembolism is unlikely.

Figure 1

Classification of proximal thrombus location. Schematic overlay of the left pulmonary artery tree on a CT-PA reformation (coronal maximum intensity projection). Not all segmental arteries are visible.

Figure 2

Scatter plot of CTOI versus Lipoprotein(a) levels. The dashed line represents the ordinary least squares line of linear best fit for all data, and the solid line the corresponding line of best for for all data excluding the three patients with Lp(a) levels ≥ 100 mg/dL (i.e. datapoints with very high leverage). Abbreviations: CTOI – CT obstruction index, Lp(a) – Lipoprotein(a).

Figure 3

Box-and-whiskers-plots of Lipoprotein(a) levels by PE anatomical extent. The upper and lower boundaries of the boxes represent the 25th and 75th percentile, and the solid line within the box represents the median. The upper and lower adjacent line on the whiskers represent the most extreme value within 1.5x the interquartile range. Values outside the whiskers are outliers.