Figure 1.

Normal rhythm variants that can be seen in healthy children. (A) Sinus arrhythmia (“respiratory arrhythmia”) in a 14-year-old boy athlete (normal sinus p waves with regular fixed P-R interval and cyclic and gradually lengthening and shortening of P-P intervals causing the heart rate to increase with inspiration, and decrease with expiration, but always within normal limits) with unchanged morphology are seen. (B) Wandering atrial pacemaker activity seen intermittently during daytime in a 4-year-old female patient (R-R distances are generally equal, as in normal sinus rhythm, with gradually changing p-wave morphology). (C) Ectopic atrial rhythm in a 9-year-old female patient at a rate similar to the sinus rate, mainly occurring at night (originates from a different atrial focus than sinus node, with a rate close to the average sinus rate). (D) Intermittent nodal rhythm seen in a 12- year-old male patient at night (the same narrow QRS as sinus rhythm, without any P waves in front of it).