7 lines (6 with data), 250 Bytes

m166a 0 128 0 10:04:00 29/05/1990
# Start time=10:04
# First beat=10:07:29.273
# <age-range>: 60-64, <sex>: Male, <medication>: None
# <RR-low-limit(sec)>: 0.5,  <RR-high-limit(sec)>: 1.148
# Note: recording with a timing signal, flutter-compensated