Cardiac short circuitsThe presence of abnormal pathways in the sinus node of the heart or between the atria and the ventricles, where the abnormal pathways are shorter than the pathways of the normal pathways, may repeatedly cause arrhythmias. The presence of a short path in the conduction path of the heart is also called preexcitation syndrome. The heart conducts through a short pathway, which is faster and takes less time to reach the ventricles, pre-exciting the ventricular muscle and causing specific ECG changes. The danger of preexcitation syndrome is the formation of refractory tachycardia, which leads to recurrent episodes of ventricular tachycardia and supraventricular tachycardia. Diagnosis of preexcitation syndrome depends mainly on the ECG. The absence of tachycardia episodes does not require treatment. Most tachycardias can be relieved with medication, but medication does not cure preexcitation syndrome. Repeated episodes of tachycardia need to be treated with radiofrequency ablation in the hospital.