Figure 7b. Asymptomatic PV stenoses in a 59-year-old man who underwent two sessions of RF ablation for atrial fibrillation. (a) Coronal maximum-intensity projection image, obtained with a three-dimensional gradient-echo MR angiographic sequence 9 months after the first session of RF ablation for atrial fibrillation in three PVs, shows slight stenosis (arrow) at the origin of the left superior PV. Note the normal origins (arrowheads) of the right superior and inferior PVs. (b) Coronal maximum-intensity projection image obtained with a three-dimensional gradient-echo MR angiographic sequence 3 months after the second session of RF ablation, this time involving all four PVs, shows moderate stenoses (arrows) at the origins of the left superior and right superior and inferior PVs.