Objective. To asses the heart rhythm disturbances (HRD) in children with palpitations or syncope.

Methods. 504 children aged from 1 to 18 years with complains of palpitations or syncope were investigated by 24 hour ECG-Holter monitoring. There were 235 boys (47%) and 269 girls (53%). Only children with normal echocardiography, somatic and neurological status were included.

Results. Among 504 children HRD were seen in 240 of them (48 %): in 49% of boys and in 46% of girls. Life threatening HRD was found in 1 child (0,4%): in 16 years old girl with LQT syndrome (QTc 560 ms). Intermitent supraventricular tachycardia was found in 5 children (2,1%); WPW in 4 children (1,7%); permanent or intermitent AV block I with occasional Wenckenbach periodicity during the sleep in 14 children (5,8%). Most often HRD were ectopic heart beats: in 123 children (51,3%) supraventricular (SVE) and in 86 (35,8%) ventricular (VE). In 6 children there was intermitent sinus coronarius rhythm (2,5%). One child (0,4%) had 6,5 seconds lasting sinus pause during tilt test.
Most often HRD in girls were SVE (45,2%) and VE (43,5%) and in boys SVE (59,5%). HRD were most often seen in girls aged 15 and 16 years and in boys aged 16. During Holter monitoring only one child had altered consciousness (on tilt test) and 16% of children complained of palpitations.

Conclusion: HRD are seen in approximately half of the children with palpitations or syncope, but life threatenig or tachicardic HRD are rare.