Pulmonary thrombi are not detected by 3D magnetic resonance angiography in adults with sickle cell anemia and an elevated triscuspid regurgitant jet velocity

Abstract

An elevated tricuspid regurgitant jet (TRJ) velocity is present in more than 30% of adults with sickle cell anemia (SCA) and is associated with a risk of death [1][2][3][4]. The contribution of pulmonary thrombi to an elevated TRJ velocity is not well defined. To evaluate the relationship between an elevated TRJ velocity and pulmonary thrombi, we performed 3D, contrast-enhanced magnetic resonance angiography (3D MRA) in nine adults with SCA. Of the six participants with an elevated TRJ velocity, 5 (83%) did not have thrombi in their pulmonary arteries. No individuals with a normal TRJ velocity had pulmonary thrombi. Based on this pilot study using 3D MRA images, thrombi are not present in large vessels in most individuals with a TRJ 2.5 m/sec, providing evidence thrombi may not significantly contribute to the pathogenesis of an elevated TRJ velocity in individuals with SCA.Pulmonary thrombi are a common etiology of pulmonary hypertension in the general population, and several autopsy studies of individuals with SCA and pulmonary hypertension have reported pulmonary thrombi [5][6][7]. Of individuals with SCA and pulmonary thrombi, 66% involve large pulmonary arteries, indicating an embolic event; however, an autopsy study of individuals with SCA and histological evidence of pulmonary hypertension (n = 20) noted thrombi in the small pulmonary arteries of 33% of individuals [6]. These autopsy studies were published prior to reports describing the risk of mortality associated with an elevated TRJ velocity and thus they examined individuals with SCA and either symptomatic pulmonary hypertension or without a diagnosis of pulmonary hypertension, but with hypertensive changes on autopsy. There have been no autopsy studies examining the pulmonary vasculature of individuals based on the mild elevations in TRJ velocity that are now recognized to be clinically significant. Therefore, the contribution of pulmonary thrombi to the pathogenesis of a TRJ velocity 2.5 m/sec has not been thoroughly evaluated.3D MRA is a technology that allows detailed visualization of the pulmonary arteries. The sensitivity and the specificity of 3D MRA imaging for detecting thromboemboli in the pulmonary vasculature is 81% and 100%, respectively [8]. The sensitivity of 3D MRA is high for the segmental arteries (87%), but decreases to 55% for the subsegmental arteries [8]. Prior imaging studies of the pulmonary vasculature in individuals with SCA using conventional CT methods have demonstrated evidence of thrombi during episodes of acute chest syndrome (ACS), consistent with the process of vasoocclusion [9]. Only one study, however, has evaluated the lung vasculature in individuals with SCA and an elevated TRJ velocity. Using CT angiography to examine the pulmonary vasculature of individuals with SCA and an elevated TRJ velocity, Linguraru et al. found no thrombi or large vessel disease [10].In this study, we used 3D, contrast-enhanced MRA with a parallel imaging to evaluate the pulmonary vasculature of adults with SCA with and without an elevated...

Venous Thromboembolism in Adults with Sickle Cell Disease: A Serious and Under-recognized Complication

“…15, 37, 38 Prior studies have concluded that chronic thromboembolic disease as defined by V/Q scan 39 or magnetic resonance angiography 40 is not common in sickle cell disease patients with tricuspid regurgitant jet velocity ≥ 2.5 m/s. However, studies in sickle cell disease patients with catheterization-confirmed pulmonary hypertension will be needed to definitively determine the contribution of chronic thromboemboli to pulmonary hypertension and to evaluate the relationship between venous thromboembolism and high pulmonary pressures.…”