Magnetic Resonance angiography of the pulmonary veins before and after radiofrequency ablation for atrial fibrillation.

PURPOSE

To study the usefulness of magnetic resonance angiography (MRA) in imaging of the pulmonary veins (PV) before and after radiofrequency ablation procedures in patients with atrial fibrillation.

MATERIALS AND METHODS

Between July 2002 and April 2003, 50 patients with atrial fibrillation underwent MRA prior to ablation; 18 patients also underwent post-procedure MRA. Images were acquired with 3D-spoiled gradient echo sequences after intravenous administration of the paramagnetic contrast medium gadopentetate dimeglumine; an automatic triggering device was used to start the angiographic sequence (Smartprep, General Electric Medical Systems). Postprocessing was performed with maximum intensity projection (MIP) and virtual endoscopy (VE) software (Navigator, GEMS).

RESULTS

The venoatrial junction was visualised with MRA VE in 49 of 50 patients (98.0%). Twenty-seven patients out of 49 (55.1%) had two PV ostia on both sides, 13 (26.5%) had two right ostia and a single common left ostium, 5 (10.2%) had supernumerary PV and 4 (8.2%) had both a supernumerary right PV and a single common left ostium. Flythrough navigation showed the number and spatial arrangement of second-order PV branches in 48 out of 49 patients (98.0%). In postablation examinations, mild stenosis was detected with MIP and VE in 17 out of 83 PV examined (20.5%).

CONCLUSIONS

This study confirms the clinical value of magnetic resonance imaging for visualising PV ostia in patients undergoing radiofrequency ablation for atrial fibrillation. Before the ablation procedure, MRA allows an accurate evaluation of PV number, shape and size; after the procedure, MRA is useful in screening for post-ablation stenosis and describing the location and severity of stenosis when present.