Using DSCT for Visualizing Pulmonary Veins

Compared to other cardiac applications, motion artefacts are a minor issue in the examination of pulmonary veins. The University of Tuebingen recommends using the DSCT scanner in a non-gated single source mode for the visualization of the ostia and the distal veins.

The role of CT in AF treatment

When it comes to treating Atrial Fibrillation (AF) patients with radio-frequency catheter ablation (RFCA), CT has proven to be of major importance – prior to as well as after the intervention. The underlying rationale is threefold:

• As the effectiveness of RFCA is based on accurate mapping, detailed knowledge of the pulmonary venous anatomy is required. CT is more accurate and time-saving in defining it than fluoroscopy.
• CT is excellent in identifying various veins and, thus, possible sources of AF recurrence. At the same time, atrial thrombi being an absolute contraindication to RFCA can be excluded.
• Post-interventional CT is essential to rule out potential complications of RFCA such as pulmonary vein dissection or perforation.

Defining the venous anatomy with DSCT

With its temporal resolution of a heart rate independent 83 msec, DSCT has the potential to provide superior visualization of the ostia and the distal veins. However, at the University of Tuebingen, we think that the translation of such unparalleled images quality into a gain of diagnostic accuracy is questionable. Whilst most 4- or 16-slice CT still required ECG-gating for elimination of motion artefacts, most investigators considered the temporal resolution of 64-slice systems to be high enough to provide accurate depiction of the atrium in a non-gated mode. Heart beat induced motion artefacts are a less significant issue and, thus, the examination may be performed in a non-gated single source mode.

In view of the difference between radiation dose of non-gated and gated DSCT-protocols, at the University of Tuebingen, we propose to primarily examine pulmonary veins in a non-gated single source mode. In this case, the scanner operates like a 64-slice system. For precise visualisation of the atrial anatomy, we suggest

• Reconstructing between 0.75 to 2 mm MPRs in thee orthogonal planes. Epicardial volume rendering as well as oblique coronal thin MIPs focused on the long axes of each pulmonary vein are valuable in the visualisation of complex venous anatomy and the exact assessment of the ostia.
• Measuring the latter in two perpendicular plains. In our institution, the Marom classification of venous drainage pattern has been adopted for reports and greatly facilitated communication with the referring electrophysiologists.

In our view, gated exam should be reserved to patients with severe tachycardia and sinus rhythm or regular conduction. With irregular conduction non-gated scan should be preferred, irrespective of patients’ heart rate.

See corresponding case: Minor pulmonary vein stenosis post RFCA
See corresponding case: Significant pulmonary vein stenosis
See corresponding protocol: Pulmonary veins