The most likely cause of dyspnea in this patient is pulmonary vein stenosis. He has progressive, unexplained dyspnea and a history of multiple catheter ablation procedures for atrial fibrillation. During catheter ablation of atrial fibrillation, the tissue around each of the pulmonary veins is cauterized to achieve electrical isolation and prevent ectopic foci from triggering recurrent atrial fibrillation. Following this procedure, approximately 1% to 3% of patients can develop symptomatic pulmonary vein stenosis. The risk is higher after multiple procedures, but it can occur after a single procedure. Patients present with progressive dyspnea, but more severe pulmonary vein stenosis can be accompanied by cough, hemoptysis, or chest pain. The image depicts a three-dimensional cardiac magnetic resonance angiogram showing the pulmonary venous return to the left atrium (LA), with stenosis of a pulmonary vein at its ostium where it empties into the LA (arrow).

The most important step in the diagnosis of pulmonary vein stenosis is maintaining a high degree of suspicion when encountering a patient with dyspnea and prior atrial fibrillation ablation. Several diagnostic modalities can be used to make the diagnosis noninvasively, including CT angiography, magnetic resonance angiography, and nuclear lung perfusion scanning. Each method has advantages and disadvantages, and the preferred method of diagnosis often differs from institution to institution.

Chronic thromboembolic disease can cause progressive dyspnea, but it would be unlikely in a patient without prior venous thromboembolism and on chronic anticoagulation.

Although intermittent atrial fibrillation could cause symptoms after ablation, it is not likely to cause progressive dyspnea in the setting of sinus rhythm. Intracardiac shunting is rare after an ablation for atrial fibrillation. Although trans-septal catheterization is performed during ablation procedures, the puncture site usually seals off. The normal oxygen saturation in this patient makes the possibility of a symptomatic shunt unlikely.

Phrenic nerve injury can result from delivery of radiofrequency energy in the vicinity of the right superior pulmonary vein with bystander injury of the right phrenic nerve; however, this injury is observed immediately after ablation and is accompanied by an elevated hemi-diaphragm on chest radiograph.