7 lines (6 with data), 252 Bytes

m142a 0 128 0 10:29:00 10/09/1990
# Start time=10:29
# First beat=10:33:43.609
# <age-range>: 55-59, <sex>: Male, <medication>: None
# <RR-low-limit(sec)>: 0.507,  <RR-high-limit(sec)>: 1.343
# Note: recording with a timing signal, flutter-compensated