CT protocols and image analysis
CT was performed within the 3 weeks before CA. Early and late-phase
cardiac CT was conducted in the prone position using a 128-section
helical CT scanner (Somatom Definition AS, Siemens Healthcare GmbH,
Erlangen, Germany). Contrast material (Iopamiro®, 370 mg of iodine/ml,
Bracco Imaging, Milan, Italy) was injected intravenously at a dose of
25.9 mg/kg body weight/s for 12-14 s. Early-phase prone-position CT
(early-pCT) was initiated 5 s after the region of interest in the
ascending aorta reached 160 Hounsfield units. Late-pCT was started 30 s
later. Once the contrast was visualized, a breath-hold instruction was
provided to the patient, and CT was initiated. After CT, the patients
were observed for at least 15 min for the detection of any contrast
medium-related side effects, such as a rash, nausea, or abnormal blood
pressure. Three-dimensional CT images were reconstructed for the left
atrium (LA) and LAA. All CT images were reviewed by two experienced
cardiologists and one radiologist.
If no contrast defect (CD) was observed in the LAA by late-pCT, CA was
performed as planned. If CDs were detected only during early-pCT but not
late-pCT, CA was performed on schedule. The performance of CA was
postponed in patients with CDs who were found on late-pCT; in these
patients, we changed or increased the anticoagulant dose and performed a
careful follow-up at our outpatient clinic. CT angiography was repeated
after several months of altered anticoagulation therapy. If the
subsequent late-pCT revealed the absence of CDs in the LAA, CA was
performed.