Cumbria Police said it was thought that the 48-year-old had fallen ill at the wheel of the HGV, which had crossed on to the opposite side of the road before leaving the carriageway.
Mr Ewart was found unresponsive at the scene of the crash, which took place at about 18:10 on Monday evening.
No other vehicle was involved in the incident.
A driver who died after his lorry crashed off the A7 near Longtown has been named as Ian Ewart from Langholm.