Double-contrast, single-phase computed tomography angiography for ruling out left atrial appendage thrombus prior to atrial fibrillation ablation

Abstract

Prior to atrial fibrillation (AF) ablation, computed tomography angiography (CTA) is increasingly used for left atrial appendage (LAA) thrombus detection. LAA filling defects on CTA may represent thrombus or incomplete contrast mixing with blood. A pre-bolus of contrast material with delay before the CTA contrast bolus can help distinguish between thrombus and incomplete contrast mixing. We present results from a double-contrast, single-phase CTA protocol used in our daily clinical practice. In patients who underwent AF ablation between 2011 and 2015, double-contrast, single-phase CTA was performed prior to ablation. Two contrast boluses (30 and 70 ml) with 25-s interbolus delay were administered followed by prospectively triggered cardiac CTA. Only patients with left atrial (LA) or LAA filling defects underwent transesophageal echocardiography (TEE) to rule out thrombus. Prior to ablation, 605 CTA-scans were performed (median radiation dose: 3.1 mSv). In 579 CTA-scans (95.7 %), the LA and LAA completely filled with contrast. In 26 CTA-scans (4.3 %) the LAA showed a filling defect whereby thrombus could not be excluded. In 2 of those 26 patients (7.7 % and 0.3 % of the total population), TEE verified LAA thrombus. Low-risk LAA filling defects on CTA (n = 7/26) with an inhomogeneous aspect, Houndsfield Unit values >100, and an indefinite border were all caused by incomplete contrast mixing. No thromboembolic complications occurred perioperatively or during 6 months follow-up. Prior to AF ablation, incidence of LAA filling defects on double-contrast, single-phase CTA is low. TEE remains warranted in all but low-risk filling defects to rule out thrombus.

A Change of Heart: Yield of Cardiac Imaging in Acute Stroke Workup

“…The LAA thrombus was probably caused by blood stasis during the presence of AF. To detect an intracardiac thrombus, ECG-triggered cardiac CTA has been shown to be of comparable diagnostic value when compared to transesophageal echocardiography [ 7 , 10 ]. However, the specificity of ECG-triggered cardiac CTA for detecting thrombus in the LAA is limited, because hypoattenuation in the LAA may reflect a slow blood flow in that area, which mimics the presence of thrombus.…”

The use of cardiac‐CT alone to exclude left atrial thrombus before atrial fibrillation ablation: Efficiency, safety, and cost analysis

“…In light of that, CCTA has been increasingly used for LAAT detection. Several studies investigated the use of CCTA in the assessment of LAAT in preprocedural evaluation for AF ablation . A challenge with CCTA is that LAA filling defects may represent thrombus or incomplete contrast mixing with blood.…”

Diagnosis of left atrial appendage thrombus in patients with atrial fibrillation: delayed contrast-enhanced cardiac CT

“…Considering the 6-min delayed acquisition, both sensitivity and PPV increased to 100%, while maintaining an optimal delineation of thrombus dimensions and morphology, fully comparable with TEE results. Other options for technical adjustments to improve LAA thrombus detection described in previous studies include a biphasic iodine bolus technique [30]. However, while this method has the advantage of allowing for shorter scan times, it still presents a higher rate of false positives compared to the 6-min delayed acquisition.…”