This was accomplished back in the early 1980s by Ed Berbari while he was still in Miami (VAMC). An important component in the recording system was the Butterworth filter, enabling a very small signal, the His potential, to be seen once gain was turned up to the max. David Albert, founder and owner of Corazonics, the company that manufactured the recording system, famously invented the Kardia Mobile ECG wearable and app. Michael Simpson from Washington Univ. was also very active in this area.
The technology was long-ago abandoned due to its failure to provide a recording that a physician could make meaningful decisions with.