7 lines (6 with data), 258 Bytes

m263b 0 128 0 14:15:00 17/02/1991
# Start time=14:15
# First beat=14:23:39.671
# <age-range>: 70-74, <sex>: Male, <medication>: Moricizine
# <RR-low-limit(sec)>: 0.531,  <RR-high-limit(sec)>: 0.921
# Note: recording with a timing signal, flutter-compensated