I had the same a few years ago femoral vein DVT and multiple PE's. I was on heperin and then rivaroxaban for 6 months. Came off and then 6 months later, had multiple tiny blood clots that stuck together in my heart, causing a blockage.
I would agree, you need to find the reason for it. I have always had sticky blood. Unfortunately the first hospital did not investigate the reason for the blood clots properly. It turned out it was APS, which a new rheumatologist suggested when talking to me, which causes multiple blood clots. It can be diagnosed by 2 blood test. I am now on warfarin for life. It is likely my femoral vein DVT and PE's were actually tiny blood clots that had stuck together caused by APS.
No blood clots or problems since.