Pulmonary vein thrombosis is a rare but potentially serious condition. Pulmonary neoplasms, complications of lung transplantation, lobectomy, or radiofrequency ablation, fibrosing mediastinitis, and mitral stenosis with a left atrial clot are known etiology causes of pulmonary vein thrombosis [2]. Thrombosis at the pulmonary vein transection site reportedly occurs in 11.7–30.8% of patients undergoing left upper lobectomy [1, 3, 4]. Care must be taken because cerebral infarction is relatively frequently reported after left upper lobectomy [4, 5], and left pneumonectomy and left upper lobectomy are considered independent risk factors for postoperative stroke [6].

The mechanism of pulmonary vein thrombosis is not fully understood, but it is thought to be related to the fact that the pulmonary vein stump tends to be longer after left upper lobectomy than after other lobectomies despite the surgeon’s efforts to shorten it as much as possible [7]. This leads to decreased blood flow in the left atrium and no blood flow from the bifurcation, which increases the likelihood of turbulent flow and stasis [8]. Additionally, intraoperative pulmonary vein transection damages the vascular endothelium, which causes activation of the extrinsic cascade of coagulation [7].

Most patients with pulmonary vein thrombosis are asymptomatic, but pulmonary vein stenosis can cause nonspecific symptoms such as cough, hemoptysis, and dyspnea [8]. Although our patient had no obvious pulmonary edema, blood flow in the pulmonary veins was greatly impeded. Furthermore, since the patient had no other pulmonary or cardiac disease that could have caused dyspnea, we considered pulmonary vein stenosis to be the probable cause of dyspnea.

In a multicenter observational study, most pulmonary vein thrombosis was detected within the first postoperative week [4]. Although it is unclear whether atrial fibrillation leading to blood stasis is a risk factor for thrombus development and there is also uncertainty regarding the thromboembolic risk associated with left upper pulmonary vein thrombus in atrial fibrillation [8], the pulmonary vein thrombus in this case may have begun to form early in the postoperative period.

Anticoagulant drug therapy is considered in patients with pulmonary vein thrombosis, but its use remains controversial due to the risk of postoperative bleeding. Although 95% of patients with pulmonary vein thrombosis are diagnosed within the first week of surgery [4], the optimal time to begin anticoagulation and the optimal duration of treatment remain unclear. Among patients with pulmonary vein thrombus after lung surgery, 68.5% received anticoagulants, and the thrombus resolved in 94.3% of them [4]. Hemorrhagic complications such as epidural hematoma have not been reported, but caution should be exercised when epidural analgesia is used. There are reports of routine systemic heparin administration for 3 days after left upper lobectomy, during which epidural analgesia is replaced with an intercostal nerve block, but the safety of this has not been confirmed [9]. In addition, recently published European guidelines do not recommend epidural analgesia in patients undergoing VATS but recommend the use of a paravertebral block or spinal erector spinae plane block in combination with general anesthesia [10], because epidural analgesia is more invasive intervention and conveys the risks of hypotension, urinary retention, and potential lower limb weakness, which can delay early rehabilitation and resumption of walking.