Left atrial appendage depth (LAAD) and tachycardia bradycardia syndrome (TBS) are associated with left atrial appendage thrombus (LAAT) in patients with non-valvular atrial fibrillation (NVAF).


 

“Although the incidence of valvular atrial fibrillation (AF) has decreased in recent years due to less streptococcal infections, the incidence of nonvalvular AF (NVAF) has risen annually,” explains Yujie Zhao, MD. “NVAF is independently linked with an increase in ischemic stroke, and the formation of thrombosis in the left atrial appendage (LAA) is the primary source of stroke and systemic embolism in patients with NVAF. Our study team sought to determine risk factors for left atrial appendage thrombus (LAAT) in this patient population.”

In addition, Dr. Zhao notes that the link between AF and impaired sinus syndrome has long been acknowledged and is believed to serve as the basis of tachycardia bradycardia syndrome (TBS). “AF promotes structural abnormalities and electrical remodeling in the form of fibrosis in atrium and sinus node, which is believed to be a critical mechanism for the incidence of TBS in AF,” she says. “Based on prior research, my colleagues and I hypothesized that patients with AF with TBS have worse atrial fibrosis, which can lead to more serious atrial dysfunction and LAAT. Therefore, it was important to include TBS in this study to investigate whether it is a risk factor for LAAT.”

LAAT Found in 9.2% of Total Patient Population

For a paper published in Computational and Mathematical Methods in Medicine, Dr. Zhao and colleagues retrospectively analyzed left atrial computed tomography angiography (CTA) features of patients (N=480) evaluated between January 2020 and January 2021. To identify predictors of LAAT, the researchers utilized logistic regression analysis, t-tests, chi-square tests, and receiver operating characteristics (ROC) curves.

“We observed that LAAT was found in approximately 9.2% of total patients in the study,” Dr. Zhao says. “Predictors of LAAT in patients with NVAF included TBS, left atrial appendage depth (LAAD), non-paroxysmal atrial fibrillation (non-PAF), left atrium top and bottom diameter (LTD), and CHA2DS2-VASc score. We believe that this is the first study showing that LAAD and TBS are associated with LAAT in patients with NVAF.”

 Patients With LAAT Tended to Be Older and Had Hypertension

Dr. Zhao and colleagues also found that patients with LAAT tended to be older and have a greater prevalence of hypertension and massive regurgitation of mitral valve, among other factors. “However, we observed no difference in gender, renal insufficiency, diabetes, and coronary heart disease,” Dr. Zhao notes (Table).

The researchers acknowledged that this study has some limitations. “We did not examine the history of peripheral embolism because the data were incomplete,” Dr. Zhao says. “In addition, most patients with acute cerebral infarction are treated in the neurology department. Therefore, for some of those patients, screening for AF was not conducted. Finally, LAAT measured by CTA lacks 100% sensitivity.”

More Predictors for LAAT Should Be Added to CHA2DS2-VASc System

These findings suggest that cardiologists should incorporate more predictors for LAAT into the CHA2DS2-VASc scoring system, Dr. Zhao says, such as data on left atrial appendage size and TBS, which are associated with atrial fibrosis and the risk for thrombosis.

In the future, Dr. Zhao and colleagues would like research focused on how to make thrombotic risk scoring systems, such as CHA2DS2-VASc, more accurate in predicting thrombus formation and, therefore, help guide clinicians in the creation of individual anticoagulation treatment. “I think precise and individualized anticoagulation solutions will always be needed,” Dr. Zhao adds.