Involved in the final steps of cholesterol and steroid degradation (PubMed:28377529). Catalyzes the hydrolytic ring D opening of (7aS)-7a-methyl-1,5-dioxo-2,3,5,6,7,7a-hexahydro-1H-indene-carboxyl-CoA (HIEC-CoA) to (3E)-2-(2-carboxylatoethyl)-3-methyl-6-oxocyclohex-1-ene-1-carboxyl-CoA (COCHEA-CoA) (By similarity). (7aS)-7a-methyl-1,5-dioxo-2,3,5,6,7,7a-hexahydro-1H-indene-carboxyl-CoA + H2O = (3E)-2-(2-carboxylatoethyl)-3-methyl-6-oxocyclohex-1-ene-1-carboxyl-CoA + H(+) Steroid metabolism; cholesterol degradation. Belongs to the enoyl-CoA hydratase/isomerase family.