7 lines (6 with data), 250 Bytes

m218a 0 128 0 10:20:00 26/06/1989
# Start time=10:20
# First beat=10:38:40.382
# <age-range>: 35-39, <sex>: Female, <medication>: None
# <RR-low-limit(sec)>: 0.507,  <RR-high-limit(sec)>: 0.976
# Note: reel-to-reel recording, not flutter-compensated