Sympathetic tone and ventricular tachycardia.

Background: The pathogenesis of idiopathic monomorphic ventricular tachycardia is not clear. We suppose that a lack of balance of the sympathetic system could be involved. Frequency domain analyses of the heart rate can be useful to understand autonomic system balance. Therefore we performed this evaluation on a sample of seven children affected by idiopathic monomorphic ventricular tachycardia.

Methods And Results: We performed a Holter recording for palpitations on all the children, with an average age of 12 (range: 7-18 years). In all the patients many episodes of repeated sustained or nonsustained ventricular tachycardia were demonstrated, with an average heart rate of 170 bpm. We excluded any structural heart defect through echocardiography and magnetic resonance imaging studies in all the children. A negative tridimensional electroanatomic mapping was performed on five of them. Holter analysis of ventricular rate variability was performed in the frequency domain. Two main components were distinguished in a spectrum calculated on the basis of 24 h-long recordings. We studied low frequency and high frequency components. We compared the values obtained with those of a control group of 10 healthy children, admitted to our cardiology division, day-care system. Affected patients showed a reduction of average high frequency as a sign of a reduction of vagal activity and an average increase of the low frequency/high frequency ratio.

Conclusions: The data may confirm our hypothesis of the involvement of the sympathetic nervous system in idiopathic monomorphic ventricular tachycardia in children.