7 lines (6 with data), 252 Bytes

m148a 0 128 0 10:57:00 22/04/1991
# Start time=10:57
# First beat=11:04:53.851
# <age-range>: 70-74, <sex>: Male, <medication>: None
# <RR-low-limit(sec)>: 0.726,  <RR-high-limit(sec)>: 1.359
# Note: recording with a timing signal, flutter-compensated