Pulmonary thromboembolism is a blood clot that occurs in one of the lungs' arteries. Deep leg vein thrombosis is a blood clot in the leg. The Blast reports that the lung blockage most likely a clot that travelled from Feldstein's leg.
There were also two other factors that contributed to Feldstein's death: obesity and acute bronchopneumonia.
Feldstein, a widely successful music manager, also suffered from heart problems, but he was not being treated for them at the time of his passing.
Substance abuse was previously rumored to have contributed to his death. However, a toxicology report has not been made available.
Feldstein is best known for managing Maroon 5, Miguel, Robin Thicke and Elle King. He also personally negotiated the deal to make Adam Levine a judge on NBC's The Voice.
His successful career was cut short on Dec. 22 when he felt a shortness of breath and later died after receiving medical treatment.
"Unfortunately, last night Jordan called 911 for shortness of breath," Feldstein's family said in a public statement at the time. "When paramedics arrived it was determined he went into full cardiac arrest and passed away shortly thereafter. His family asks for privacy during this difficult and unexpected time."