7 lines (6 with data), 252 Bytes

m184a 0 128 0 15:46:00 25/03/1990
# Start time=15:46
# First beat=15:50:30.328
# <age-range>: 70-74, <sex>: Male, <medication>: None
# <RR-low-limit(sec)>: 0.429,  <RR-high-limit(sec)>: 0.726
# Note: recording with a timing signal, flutter-compensated