8Cheng S, Keyes M J, LarsonM G, et al. Long-term outcomes in individuals with prolonged PR interval or first-degree atrioventricular block[J]. JAMA,2009,301 (24) :2571-2577.
9Holm H, Gudbjartsson D F, Amar D O, et al. Several common variants modulate heart rate, PR interval and QRS duration [ J ]. Nature Genetics,2010,42 ( 2 ) : 117-122.