Predictors of left atrial appendage thrombus despite NOAC use in nonvalvular atrial fibrillation and flutter

Objective: A small but significant proportion of patients with atrial fibrillation or atrial flutter (AF) develop left atrial appendage thrombus (LAAT) despite non-vitamin K antagonist oral anticoagulant (NOAC) prescription. This study examines clinical and echocardiographic risk factors associated with LAAT by transesophageal echocardiogram (TEE) despite NOAC use in patients with non-valvular AF, to inform the decision whether a TEE should be performed prior to cardioversion.

Methods: We compared clinical and echocardiographic characteristics of patients with LAAT despite NOAC prescription for >3 weeks (n = 38) with a consecutive sample of patients on NOAC without LAAT (n = 101).

Results: The prevalence of LAAT despite NOAC prescription was 2.6%. Left atrial dilation (adjusted odds ratio [aOR] 3.310, 95% CI 1.144-9.580, p = 0.02) and greater CHA₂DS₂-VASC score (per-point increase, aOR 1.293, 1.027-1.628, p = 0.03) increased the odds for LAAT. Higher LVEF (per 5%, aOR 0.834, 0.704-0.987, p = 0.03) and presence of severe mitral regurgitation (aOR 0.147, 0.048-0.446, p = 0.002) were protective against LAAT. LAA emptying velocities were also independently associated with presence of LAAT (aOR per 10 cm/s, 0.46, 0.27-0.77).

Conclusion: Left atrial dilation, greater CHA₂DS₂-VASC score, absence of severe mitral regurgitation and lower left ventricular ejection fraction are associated with LAAT despite NOAC therapy. In addition to suspected NOAC noncompliance, presence of such high-risk features may warrant pre-cardioversion TEE. Similarly, in patients with LVEF > 50% and CHA₂DS₂-VASC < 2, risk of LAAT was exceedingly low and thus TEE before cardioversion is low-yield.