Extrinsic 1389-1

{
  "heartbeat": {
    "blockNumber": 1387,
    "sessionIndex": 23,
    "validatorsLen": 4,
    "authorityIndex": 0
  },
  "signature": "0x72b21c49e5b3a0ba2bc8418dab619892c676c4720d502d683a22ca00984e574059c084dcde6d91b1dd118da89edfde4516462269952dffa7996e019f5bc23780"
}