7 lines (6 with data), 258 Bytes

m257b 0 128 0 11:50:00 27/08/1989
# Start time=11:50
# First beat=11:50:00.765
# <age-range>: 60-64, <sex>: Male, <medication>: Moricizine
# <RR-low-limit(sec)>: 0.515,  <RR-high-limit(sec)>: 1.171
# Note: recording with a timing signal, flutter-compensated