We read the recent article by Doukky et al. with great interest. This prospective study indicated that commonly used diastolic function parameters are associated with left atrial appendage (LAA) thrombus, independent of clinical risk factors encompassed in the CHA 2 DS 2 -VASc score. According to their investigation, E/e′ and e′ velocity are useful and provide incremental value in assessing LAA thrombus risk in patients with nonvalvular atrial fibrillation (NVAF). We fundamentally appreciate their work in terms of screening patients with high-risk factors for LAA thrombus, but several issues should be considered when interpreting their results.
First, although the table of demographic characteristics contained a description of antithrombotic and antiplatelet therapy, some influential factors such as the average international normalized ratio of those on warfarin and the mean duration of anticoagulation treatment before transesophageal echocardiography, which are associated with LAA hemodynamic status, were not included. Furthermore, as discussed in the article, reduced left ventricular ejection fraction and elevated brain natriuretic peptide levels are associated with LAA thrombus; however, these baseline characteristics were significantly different between the two subgroups, which weakens the predictive value of E/e′ and e′ velocity for LAA thrombus, especially when the sample size is small. Second, as mentioned in the latest American Society of Echocardiography and European Association of Cardiovascular Imaging guidelines, left ventricular diastolic function is always comprehensively evaluated using multiple parameters along with other echocardiographic parameters such as the mitral E-wave deceleration time, pulmonary vein systolic-to-diastolic velocity ratio, and mitral E/Vp. It is unfortunate that these indicators were not reflected in this study. Third, the investigators claimed that the study was prospective; however, they only enrolled the cohort prospectively. No follow-up observation was performed to confirm the impact of left ventricular diastolic function on the risk for LAA thrombus and to determine whether patients with abnormal E/e′ ratios are more susceptible to LAA thrombus. Therefore, follow-up information will make the results more convincing.
Additionally, thromboembolic events are the most feared complication of NVAF, and the causes for these events are multiple and complex. The LAA is a crucial site of thrombus formation, because of its unique structural and functional characteristics. Thus, the association between LAA parameters and thrombus formation also must be considered when assessing thrombus risk. Recent studies have demonstrated that LAA morphometric or volumetric parameters such as the cauliflower phenotype, orifice, and volume are associated with the thromboembolic risk of patients with NVAF. These parameters provide additional value for stratifying thromboembolic risk in patients with NVAF.
Therefore, because confounding factors exist, further well-designed, large-scale longitudinal investigations are urgently needed to confirm these relationships between diastolic function indices and LAA thrombus. More important, there may be an additional benefit to combining diastolic function indices, LAA parameters, and the traditional CHA 2 DS 2 -VASc scoring system to evaluate stroke risk.