Garry Shandling Death Certificate

12/27/2016 8:38 AM PST

Garry Shandling had an operation called "inferior vena cava filter" before he died ... according to his death certificate.

TMZ broke the story ... Garry died from pulmonary thrombosis -- a blood clot that traveled from his leg into his lungs. 

Garry officially died at 11:37 AM on March 24 at St. John's Health Center in Santa Monica.