Literature regarding etiology and trends of incidence of major thoracic vein thrombosis in the United States is limited. To study the causes, complications, in-hospital mortality rate, and trend in the incidence of major thoracic vein thrombosis which could have led to superior vena cava syndrome (SVCS) between 2010 and 2018. Data from the nationwide emergency department sample (NEDS) that constitutes 20% sample of hospital-owned emergency departments (ED) and in-patient sample in the United States were analyzed using diagnostic codes. A linear p-trend was used to assess the trends. Of the total 1082million ED visits, 37,807 (3.5/100,000) (mean age 53.81 ± 18.07 years, 55% females) patients were recorded with major thoracic vein thrombosis in the ED encounters. Among these patients, 4070 (10.6%) patients had one or more cancers associated with thrombosis. Pacemaker/defibrillator-related thrombosis was recorded in 2820 (7.5%) patients, while intravascular catheter-induced thrombosis was recorded in 1755 (4.55%) patients. Half of the patients had associated complication of pulmonary embolism. A total of 59 (0.15%) patients died during these hospital encounters. The yearly trend for the thrombosis for every 100,000 ED encounters in the United States increased from 2.17/100,000 in 2010 to 5.98/100,000 in 2018 (liner p-trend < 0.001). Yearly trend for catheter/lead associated thrombosis was also up-trending (p-trend 0.015). SVCS is an uncommon medical emergency related to malignancy and indwelling venous devices. The increasing trend in SVCS incidence, predominantly catheter/lead induced, and the high rate of associated pulmonary embolism should prompt physicians to remain vigilant for appropriate evaluation.