TY - JOUR T1 - Study of cardiac rhythm in healthy newborn infants. JF - British Heart Journal JO - Heart SP - 14 LP - 20 DO - 10.1136/hrt.43.1.14 VL - 43 IS - 1 AU - D P Southall AU - J Richards AU - P Mitchell AU - D J Brown AU - P G Johnston AU - E A Shinebourne Y1 - 1980/01/01 UR - http://heart.bmj.com/content/43/1/14.abstract N2 - Twenty-four-hour electrocardiograms were recorded in the first 10 days of life on 134 healthy full-term infants with birthweights greater than 2.5 kg. The highest heart rate a minute, measured over nine beats, was 175 +/- 19 (SD). The lowest rates, measured over three, five, and nine beats were 82 +/- 12, 87 +/- 12, and 93 +/- 12, respectively. At their lowest rates 109 infants had sinus bradycardia and 25 had junctional escape rhythms. Thirty-three infants showed changes in P wave configuration with or without pronounced variation in PR interval. Atrial premature beats were present in 19 infants but only one had more than 12 per hour. In a randomly selected subgroup of 71 infants sinus pauses were found in 51 (72%). Five (7%) had electrocardiographic patterns and rhythm disturbances that could not be differentiated from those previously described as complete sinuatrial exit block or sinus arrest, eight (11%) had patterns indistinguishable from 2:1 sinuatrial block, and 23 (32%) had pattern indistinguishable from sinuatrial Wenckebach block. This study shows that normal infants have variations in heart rate and rhythm hitherto considered to be abnormal. ER -