7 lines (6 with data), 248 Bytes

m251a 0 128 0 11:50:00 15/06/1988
# Start time=11:50
# First beat=12:17:23.695
# <age-range>: 55-59, <sex>: Male, <medication>: None
# <RR-low-limit(sec)>: 0.515,  <RR-high-limit(sec)>: 1.242
# Note: reel-to-reel recording, not flutter-compensated