7 lines (6 with data), 250 Bytes

m276a 0 128 0 16:15:00 17/01/1990
# Start time=16:15
# First beat=16:41:16.835
# <age-range>: 55-59, <sex>: Female, <medication>: None
# <RR-low-limit(sec)>: 0.648,  <RR-high-limit(sec)>: 1.031
# Note: reel-to-reel recording, not flutter-compensated