Incessant tachycardias.

Incessant tachycardias are some of the rarer forms of normal QRS tachycardias. They are usually diagnosed in infancy or childhood and often present with heart failure secondary to left ventricular dysfunction. Permanent junctional reciprocating tachycardia is a rare type of orthodromic atrioventricular re-entry. Control with drugs is possible but best long-term results are achieved with radio-frequency ablation. Congenital His bundle tachycardia is an automatic arrhythmia characterized by ventriculo-atrial dissociation on the electrocardiogram. The risk of atrio-ventricular block with radiofrequency ablation is high and long-term drug treatment is often effective. Atrial ectopic tachycardia is also automatic and may originate in the left or right atrium. Drug suppression is possible but radiofrequency ablation offers the prospect of cure. All three arrhythmias are likely to persist long term. Drug treatment with class IC or class III drugs is most likely to be effective. Rate control or arrhythmia suppression are likely to lead to improvement or normalization of left ventricular function.