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Utility of Nongated Multidetector Computed Tomography for Detection of Left Atrial Thrombus in Patients Undergoing Catheter Ablation of Atrial Fibrillation

Division of Cardiovascular Diseases and Department of Radiology, Mayo Clinic, Rochester, Minnesota

^_* Reprint requests and correspondence: Dr. Peter A. Brady, Mayo Clinic College of Medicine, 200 First Street Southwest, Rochester, Minnesota 55905 (Email: brady.peter{at}mayo.edu).

Objectives: The aim of this study was to determine whether multidetector computed tomography (MDCT) is able to exclude left atrial appendage (LAA) thrombus in patients referred for catheter ablation of atrial fibrillation (CAAF).

Background: MDCT is commonly used to render pulmonary vein and left atrial anatomy before CAAF. Transesophageal echocardiography (TEE) is also often performed before the ablation to exclude LAA thrombus. Whether MDCT alone is sufficient to exclude LAA thrombus is unknown.

Methods: Patients referred for CAAF at the Mayo Clinic between March 2004 and October 2006 were included. Clinical data, 64-slice MDCT (nonelectrocardiography-gated), and TEE were all analyzed. Image data were independently reviewed by 2 cardiac radiologists blinded to the TEE findings. The appearance of the LAA was defined as normal (fully opacified) or abnormal (underfilled).

Results: Four hundred two patients (mean age 56 ± 10 years; 76% male; ejection fraction 56 ± 10%) were included. Three hundred sixty-two had no evidence of a filling defect by ungated MDCT or left atrial spontaneous echo contrast or thrombus by TEE. In 40 patients, the LAA was "underfilled" with 9 definite thrombi confirmed by TEE. Sensitivity and specificity was 100% and 92%, respectively, with a negative predictive value of 100% and positive predictive value of 23%. In patients with LAA underfilling, Doppler-derived LAA emptying velocities were substantially reduced (mean 19 cm/s; range 6 to 61 cm/s) below the normal range. A higher CHADS² (congestive heart failure, hypertension, age older than 75 years, and diabetes) score (1.6 vs. 1.1) was observed in patients with LAA filling defects. No cases of LAA thrombus were observed in patients age <52 years with CHADS² score <1.

Conclusions: In patients referred for CAAF, MDCT is a sensitive (100% sensitivity) imaging modality that could be used alone especially in patients age <52 years with a CHADS² score <1. Incorporation of these findings could decrease the need for multiple imaging modalities and thereby reduce cost of the procedure.

Key Words: atrial fibrillation • left atrial appendage • thrombus • computed tomography

Abbreviations and Acronyms   AF = atrial fibrillation   CAAF = catheter ablation of atrial fibrillation   CHADS2 = congestive heart failure, hypertension, age older than 75 years, and diabetes   CI = confidence interval   CT = computed tomography   LA = left atrial   LAA = left atrial appendage   MDCT = multidetector computed tomography   OR = odds ratio   SEC = spontaneous echo contrast   TEE = transesophageal echocardiography   TIA = transient ischemic attack

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