7 lines (6 with data), 250 Bytes

m200a 0 128 0 8:45:00 30/04/1989
# Start time=08:45
# First beat=08:45:00.648
# <age-range>: 55-59, <sex>: Male, <medication>: None
# <RR-low-limit(sec)>: 0.57,  <RR-high-limit(sec)>: 1.328
# Note: recording with a timing signal, flutter-compensated