Read header data in webrtc Asterisk

Hi Guys,
I am using webrtc with Asterisk but I have a scenario where I want to send some data from Asterisk to Webrtc client when the call is answered at Asterisk. I have tried to use AddSIPHeader application of asterisk and tried to read header data of the response in progress event at webrtc client end but did not get the header data which was set by Asterisk.

Please help me to understand if it is possible or there is any other work around.

Thank You!!