Dual-Enhancement Cardiac Computed Tomography for Assessing Left Atrial Thrombus and Pulmonary Veins Before Radiofrequency Catheter Ablation for Atrial Fibrillation

Study Questions:

What is the diagnostic accuracy of dual-enhancement cardiac computed tomography (CCT) to identify left atrial appendage thrombus or spontaneous echo contrast (SEC) in patients with atrial fibrillation planned for catheter ablation procedures?

Methods:

This study examined 101 patients with symptomatic atrial fibrillation scheduled for catheter ablation procedures and who underwent both transesophageal echocardiography (TEE) and CCT on the same day. The diagnostic accuracy of a dual-enhancement CCT protocol (first contrast bolus given 3 minutes prior to any imaging, and second contrast bolus started immediately prior to imaging) to detect thrombus, and stasis/SEC was compared to TEE.

Results:

Mean age was 61.8 years, and 70% were male. Mean radiation dose was 4.1 mSv. From the cohort of 101 individuals, TEE identified nine patients with thrombi and 18 patients with SEC. The sensitivity, specificity, and positive and negative predictive values for CCT identification of thrombi were 89%, 100%, 100%, and 99%, respectively. The sensitivity, specificity, and positive and negative predictive values for CCT identification of thrombi or stasis/SEC were each 100%. One case with thrombus on TEE was incorrectly classified as stasis by CCT. The mean left atrial appendage to ascending aorta Hounsfield unit attenuation ratio was significantly different between groups with thrombus (0.17 ± 0.06), SEC/stasis (0.33 ± 0.07), and normal left atrial appendages (0.89 ± 0.08) (p = 0.002).

Conclusions:

The authors concluded that a dual-enhancement CCT protocol has good sensitivity and excellent specificity to identify left atrial appendage thrombus in atrial fibrillation patients as compared to TEE.

Perspective:

As CCT is commonly performed for pulmonary vein mapping in patients undergoing atrial fibrillation ablation procedures, there is interest in using CCT to substitute for TEE assessment of left atrial appendage thrombus. In contrast to many prior studies, this protocol uses two contrast boluses rather than two separate image acquisitions, which increases total contrast volume (120 ml total), but lowers radiation dose. These single-center results are consistent the group’s prior findings using this protocol in patients with stroke, and with other literature using alternative CCT protocols. Nevertheless, while the diagnostic performance is very good, one case of thrombus was missed by CCT; given the serious nature of potential complications such as stroke, this sensitivity may be inadequate. The use of CCT to evaluate the left atrial appendage may be reasonable in atrial fibrillation patients with contraindications to TEE, but the clinical safety of CCT as a routine substitute for TEE is unclear.

Clinical Topics: Arrhythmias and Clinical EP, Noninvasive Imaging, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Computed Tomography, Echocardiography/Ultrasound, Nuclear Imaging

Keywords: Stroke, Atrial Appendage, Thrombosis, Tomography, X-Ray Computed, Pulmonary Veins, Catheter Ablation, Echocardiography, Transesophageal


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