Left atrial appendage thrombus may increase the risk of stroke after TAVI

Sonny Palmer

Sonny Palmer (St Vincent’s Hospital, Melbourne, Australia) and others report in JACC: Cardiovascular Interventions that left atrial appendage thrombus, as identified with computed tomography (CT), is a common finding among people who have been referred for transcatheter aortic valve implantation (TAVI). They add that the presence of left atrial appendage thrombus may increase the risk of stroke in these patients.

The authors comment that stroke “remains a feared complication” after TAVI, affecting up to 5% of patients at 30 days post procedure. The causes of post-TAVI stroke, they write, is “likely multifactorial” and include embolisation of calcified material, dislodgement of atheromatous debris during wire and device manipulation, and thrombus formation. “However, embolisation of left atrial appendage thrombus has recently been described during TAVI and may represent additional mechanism of periprocedural stroke,” Palmer et al comment. Noting that the incidence and clinical outcomes of left atrial appendage thrombus “have not been previously reported” in patients undergoing TAVI, they aimed to describe it.

Of 198 patients who were scheduled to undergo TAVI and who underwent CT, between July 2013 and October 2015 at the authors’ institution (The James Cook University Hospital, Middlesbrough, UK), 11% had definite left atrial appendage thrombus. Palmer et al write: “Using transoesophageal echocardiography (TOE) as the reference standard, the overall sensitivity and specificity of CT for the detection of definite left atrial appendage thrombus were 100% and 98%, respectively. The positive and negative predictive values were 75% and 100%, respectively, and the diagnostic accuracy was 98%.” They add that atrial fibrillation was a significant risk factor for left atrial appendage thrombus, which was present in 20 of 63 patients (32%) with atrial fibrillation compared with two of 125 (1.6%) without (p<0.0001).

One hundred and twenty-four patients (63%) subsequently underwent TAVI—8.1% (10) had definite left atrial appendage thrombus and 7.3% (nine) had possible left atrial appendage thrombus. All those with definite thrombus had a history of atrial fibrillation, including eight who were receiving oral anticoagulation, and six patients in the possible thrombus subgroup had such a history.

Six patients (4.8%) had a procedural stroke and two of these had evidence of definite left atrial appendage thrombus, both of whom had atrial fibrillation and were therapeutically anticoagulated were warfarin at the time of the CT. The authors comment: “The remaining four patients who experienced stroke had no left atrial appendage thrombus on CT; none of these patients had atrial fibrillation or were receiving anticoagulation. Therefore, the stroke rate was 20% (two of 10) in patients with left atrial appendage thrombus compared with 3.8% (four of 105) in those without left atrial appendage thrombus.”

Palmer et al add that “although this absolute number of events is small and definite conclusions cannot be drawn”, this finding does “raise the possibility that left atrial appendage thrombus embolisation may represent a clinically important cause of procedural stroke”. Therefore, they recommend that all patients scheduled to undergo TAVI should be screened for left atrial appendage thrombus. If a patient is found to have thrombus—given that in the study, patients already receiving anticoagulation were found to have left atrial appendage thrombus—the authors say that strategies are required to manage such a patient. These strategies, they write, could include postponing TAVI until the thrombus has resolved (with anticoagulation) and considering the use of approaches (eg. cerebral protection devices) for reducing the risk of stroke during TAVI in patients with persistent thrombus.

“Further larger prospective studies are required to confirm whether the presence of left atrial appendage thrombus is an independent risk factor for procedural stroke and to examine the efficacy of potential avoidance strategies,” Palmer et al conclude.

Palmer told Cardiovascular News: “Furthermore, our study identified a large number of patients with AF who were not on anticoagulation. This raises the question as to the utility of left atrial appendage occlusion devices in patients with atrial fibrillation, undergoing TAVI, and who are unable to take long-term anticoagulation.”