Risky Clots May Stick Around for Afib Procedures

Despite widespread anticoagulation for atrial fibrillation (Afib) patients before cardioversion and catheter ablation, a preprocedural transesophageal echocardiogram (TEE) may still be necessary to rule out a left atrial (LA) thrombus, in some people, according to a meta-analysis.

At least 3 weeks of oral anticoagulation (i.e., warfarin or direct oral anticoagulants [DOACs]) was not enough to fully exclude LA thrombi in people with Afib or atrial flutter, who still showed a “non-negligible” 2.73% prevalence of such clots on subsequent TEE, reported Jorge Wong, MD, MPH, of the Population Health Research Institute at McMaster University in Hamilton, Ontario, and colleagues.

Some groups were more likely than others to have an LA thrombus despite anticoagulation:

• Patients with nonparoxysmal Afib or atrial flutter: 4.81% vs 1.03% in paroxysmal patients (P<0.001)

• People undergoing cardioversion: 5.55% vs 1.65% for those undergoing ablation (P<0.001)

• Those with CHA₂DS₂-VASc scores ≥3: 6.31% vs 1.06% in patients with scores ≤2 (P<0.001)

“Overall, these results suggest that TEE may be helpful in select patients with AF/AFL [Afib/atrial flutter] despite guideline-directed anticoagulation before cardioversion or catheter ablation,” Wong’s team concluded in the study online in the Journal of the American College of Cardiology.

“Fortunately, continued oral anticoagulation already yields low peri-procedural stroke rates. Based on this new analysis of existing data, a risk-based use of TEE imaging in anticoagulated patients could enable further improvement in the safe delivery of rhythm control interventions in patients with Afib,” agreed Paulus Kirchhof, MD, and Christoph Sinning, MD, both of the University Heart & Vascular Center Hamburg and the German Centre of Cardiovascular Research, writing in an accompanying editorial.

Regional practice varies substantially, the editorialists noted: Countries such as the U.S. and Germany routinely perform TEE before all catheter ablations, whereas the U.K. and others forego the preprocedural TEE after a few weeks of anticoagulation.

Wong and co-authors had performed a meta-analysis of 35 observational studies. Participants constituted a clinically heterogeneous population of 14,653 people undergoing TEE after anticoagulation therapy.

Guidelines recommend just a minimum of 3 weeks of oral anticoagulation before cardioversion or catheter ablation to exclude the presence of an LA thrombus going into these interventions.

“This minimum anticoagulation duration was chosen empirically based on observational studies from the 1960s, which suggested this approach to be safe and likely to result in the resolution of LA thrombus, if present. However, 3 weeks of anticoagulation may be insufficient to completely resolve LA thrombus in some patients,” Wong and colleagues said.

Even so, they acknowledged that just because an LA thrombus is present doesn’t mean it will lead to a thromboembolic event.

“When a thrombus was found on TEE, clinical judgment led to postponing of the procedure. Thus, the paper cannot demonstrate that presence of a thrombus on TEE is related to peri-procedural ischemic stroke,” said Kirchhof and Sinning.

What’s more, LA thrombi represent only one mechanism for the onset of peri-procedural stroke in Afib patients, Wong’s group noted.

Another major limitation of the meta-analysis, the researchers said, was the potential for confounding given the observational studies included.