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

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.

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.

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.

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).

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.