Abstract 1580: The Current Diagnostic Accuracy Of Cardiac CT For Left Atrial Appendage Thrombus Is Poor
Background: Cardiac CT is being extensively used prior to atrial fibrillation ablation (AFA) procedures in order to help guide the AFA. Since exclusion of atrial thrombi is important prior to AFA, we sought to determine the diagnostic accuracy of CT in detecting left atrial appendage thrombus (LAAT), as compared to transesophageal echocardiography (TEE).
Methods: A total of 200 patients underwent Cardiac CT scans with 64-detectors (MDCT) and TEE prior to AFA. All patients were on chronic anticoagulation with warfarin, and were transitioned to enoxaparin (1mg/kg BID) prior to the procedure. We intensively examined a subset of 43 of these, who were at high risk for LAAT (a prior history of CVA, low LAA emptying velocity, spontaneous echo contrast in the LA, or a very enlarged LA (>6cm) with a depressed LV ejection fraction (<40%)). MDCT scans were read by three independent clinical cardiac MDCT readers. All MDCT readers have more than 10 years experience with cardiac imaging.
Results: During MDCT scan, 51% of the patients were in AF and the mean HR was 72±24 bpm. The clinical read of the TEE was positive for LAAT in 5 patients. MDCT was read as positive for LAAT in 2, 8 and 25 studies by the three MDCT readers. The table⇓ shows the sensitivity, specificity, and positive and negative predictive values (PPV, NPV) for each MDCT reader, as compared to the clinical TEE read.
Conclusions: Our results demonstrate that detection of LAAT by cardiac MDCT is inconsistent even among experienced observers, and often discrepant with the current ‘gold standard’ of TEE. Potential reasons for this include image quality, the difficulty of distinguishing thrombus from pectinate muscle, and the small size of some thrombi. MDCT is likely not the optimal method to detect LAAT using current techniques and standards of interpretation. Given that many AFA patients have a MDCT prior to their procedure, further investigation and standards of interpretation of the LAA should be pursued.