# I was angry

Here "I" refers to Yahweh.

# I defiled my heritage

"I defiled my people, who are my special possession" 

# gave them over into your hand

"I put them under your power" 

# you placed a very heavy yoke on the old people

Yahweh speaks of the Babylonians oppressing the old people as if they had treated the old people like cattle and put heavy yokes on their necks.