Left atrial thrombus in heart failure patients undergoing elective electrical cardioversion despite guideline-recommended anticoagulation: prevalence, predictors and prognosis

Abstract Background/Introduction Atrial fibrillation (AF) and heart failure with reduced ejection fraction (HFrEF) frequently coexist and confer a high thromboembolic risk. Guidelines recommend ≥3 weeks of oral anticoagulation before electrical cardioversion (ECV), but the residual risk of left atrial (LA) thrombus or dense spontaneous echo contrast (SEC) in this high-risk population is uncertain. Purpose To determine the prevalence and predictors of LA thrombus or dense SEC in patients with HFrEF undergoing elective ECV for persistent AF or flutter despite guideline-recommended anticoagulation, and to explore their clinical implications. Methods Single-centre retrospective cohort of patients with HFrEF (LVEF ≤40%) scheduled for elective ECV for persistent AF/flutter. All received oral anticoagulation for ≥3 weeks (vitamin K antagonists with INR ≥2.0, or direct oral anticoagulants at label-conforming doses). All underwent pre-ECV transoesophageal echocardiography to detect LA thrombus or dense SEC (grade 3–4). Clinical, echocardiographic and laboratory variables (including NT-proBNP) were compared between patients with and without thrombus/SEC. Independent predictors were assessed by multivariable logistic regression. Clinical outcomes were evaluated during follow-up. Results Seventy-nine patients were included (median age 66 years, 73% male); 87% had AF and 13% flutter. Direct oral anticoagulants were used in 67% and vitamin K antagonists in 33%. LA thrombus or dense SEC was found in 19 patients (24.1%) despite guideline-recommended anticoagulation. Compared with patients without thrombus/SEC, these patients had higher NT-proBNP levels (median 7260 vs 2715 pg/mL, p=0.009), more frequent implantable cardioverter-defibrillator (37% vs 10%, p=0.017) and right atrial dilatation (73% vs 41%, p=0.04), with no differences in age, comorbidities, CHA2DS2-VA score or type of anticoagulant. In multivariable analysis, NT-proBNP >6500 pg/mL independently predicted thrombus/SEC (OR 78.6; 95% CI 1.4–4266; p=0.032). Among 12 patients with initial thrombus/SEC who underwent repeat transoesophageal echocardiography, resolution was documented in 10 (83.3%) after tailored anticoagulation strategies. Over a median follow-up of 15 months (IQR 8–36), baseline thrombus/SEC was associated with higher all-cause mortality (HR 6.0; 95% CI 1.3–26.7; p=0.02) and cardiovascular mortality (HR 6.3; 95% CI 1.1–38.0; p=0.04). Conclusions In patients with persistent AF/flutter and HFrEF, nearly one in four have LA thrombus or dense SEC at pre-ECV imaging despite guideline-recommended anticoagulation, questioning the safety of the standard strategy in this high-risk group. Elevated NT-proBNP identifies patients at particularly high risk. These findings support systematic pre-procedural imaging to rule out LA thrombus in patients with AF and systolic heart failure undergoing elective ECV.