History
A 71-year-old female patient, suffering from paroxysmal atrial fibrillation (AF), had undergone an uneventful transcatheter pulmonary vein radiofrequency catheter ablation (PVRCA) in all 4 pulmonary veins (PVs) along with left atrium appendage closure (LAAC). 58 days later, a contrast-enhanced ECG-triggered cardiac CT was performed as a follow-up evaluation.
Diagnosis
CT images showed no structural abnormalities of the left atrium (LA) and the PVs. The LA was enlarged. All four PVs were patent without any signs of stenosis, thrombosis or dissection. A LAAC device was seen, without any deformation, seated in the left atrium appendage (LAA) in which no contrast material opacification was visible. Two small hyperdense areas were visualized in the distal part of the device, adjacent to the inner and outer surface, suggesting fabric leaks. There were no signs of device-related thrombosis, and no evidence of pleural or pericardial effusions. The coronary arteries were free from any plaque or stenosis. Based on CT findings, the patient remained under surveillance with continued anticoagulation treatment.
Fig. 1: MPR images (Fig. 1a and 1b) and three-dimensional LA epicardial (Fig. 1c) and endocardial (Fig. 1d) views show the enlarged LA with four patent PVs without any signs of stenosis.
Fig. 2: MIP (Fig. 2a) and cinematic volume rendering images (Figs. 2b–2d) show two small hyper-dense areas in the distal part of the device, adjacent to the inner and outer surface, suggesting fabric leaks (arrows).
Fig. 3: A thin MIP image (Fig. 3a, RCA) and two curved MPR images (Fig. 3b, LAD; Fig. 3c, Cx) show normal coronary arteries without plaque or stenosis.
Comments
AF is a common cardiac rhythm disturbance with over 90% of ectopic beats originated in the PVs. PVRCA is widely used in the treatment of AF. One of the major complications is post-procedural PV stenosis. [1]
In nonvalvular AF, 90% of thrombi are formed in the LAA. [2] Oral anticoagulants are usually the first-line of therapy to prevent a stroke. However, patients with a higher bleeding risk are not eligible for long-term anticoagulation therapy. LAAC is performed as an alternative, to prevent a cardioembolic stroke. CT imaging is used for pre-procedural planning as well as post-procedural assessment of potential complications, such as peri-device leaking, incomplete closure, device-related thrombus and device dislodgement. [3]
In this case, the patient underwent both PVRCA and LAAC interventions. Post-procedural assessment is performed on a newly introduced Dual Source CT scanner, SOMATOM Pro.Pulse. It provides an ECG triggered, high-pitch spiral scan mode (Flash mode) that allows for a high acquisition speed of 372 mm/s at a pitch value of 3.2. The scan range of 161 mm is acquired in approximately 0.4 seconds with a radiation dose of 2.5 mGy. Additionally, an optimal tube voltage setting (80 kV) for this patient is automatically selected by a fully integrated feature, CARE kV. This low kV setting contributes to the radiation dose reduction due to the increased contrast enhancement compared to a more conventional 120kV acquisition setting. It is worth noting that despite the use of 80 kV, there are no device-related metal artifacts present. To further improve the image contrast-to-noise ratio (CNR), an Advanced Modeled Iterative Reconstruction (ADMIRE) is applied. Owing to the optimal image quality, the post-procedural assessment is successfully completed. The most feared complication, PV stenosis after PVRCA, can be ruled out whereas two small fabric leaks after LAAC are depicted. Although not initially required, the coronary arteries are also evaluable. The diagnostic image quality benefits from a combination of a high temporal resolution of 86 ms and a patient with a very low heart rate of 50 bpm, enabling a complete acquisition within one cardiac cycle in a diastolic rest phase.
Post-procedural assessment for patients after LAAC can be performed using transesophageal echocardiography (TEE) and/or CT imaging. TEE can provide real-time assessment and actual flow velocity of the leak, however, the need for patients to undergo conscious sedation or general anesthesia prevents frequent follow-ups. CT imaging has the advantages of high sensitivity and easy repeatability. [4] The Flash mode is unique for dual source CT and can provide fast scan speed at low dose. For patients who need to undergo CT follow up scans on a regular bases, low dose scan is beneficial.
Examination Protocol
