Volume Replication and Heartbeat on same NIC good?

Hi,

We want to use volume replication.
Each storages has two NICs connected to a SAN; one NIC is directly connected (crossover).
Initially we wanted to use the direct line for heartbeat. To reduce network traffic in the SAN we thought about using the direct line for volume replication as well.

Is it a good idea to have volume replication and heartbeat on the same (direct) line?

Thank you!
hubsif.