A 52-year-old man presented to our institution because of recurrent episodes of atrial fibrillation and counterclockwise atrial flutter, refractory to medical therapy with different regimens including amiodarone, and after several cardioversions to restore in sinus rhythm. Coronary artery stenosis was ruled out invasively. Left and right ventricular function were normal at rest and during bicycle exercise. Preinterventional nuclear magnetic resonance imaging (MRI) and transesophageal echocardiography (TEE) showed 4 pulmonary veins (Figure 1, A) with normal left atrial inflow. The patient underwent radiofrequency (RF) isolation of the 2 left pulmonary veins and the upper right pulmonary vein in combination with a right atrial isthmus ablation in July 2001, and a reintervention because of recurrent atrial fibrillation including reisolation of all 4 pulmonary veins until December 2001. MRI (Figure 1, A) and TEE (Figure 1, B to E) during follow-up demonstrated progressive narrowing of the left upper pulmonary vein until January 2003 with turbulent left atrial inflow (Figure 1, C to E) as compared with the normal inflow pattern (Figure 1, B and C) of the lower left pulmonary vein. Because of normal hemodynamic findings (pulmonary artery mean pressure: 14 mm Hg) on a repeated measurement and absence of any symptoms, the patient is still under close observation without any need for revascularization of the stenosed pulmonary vein. In a similar case, however, venous congestion and recurrent hemoptysis from the upper left pulmonary lobe made surgical reconstruction of the upper left pulmonary vein necessary.