BACKGROUND The so called tachycardia-induced cardiomyopathy may develop as a complication of persistent abnormal high rates. It is especially common in patients who have either a permanent form of junctional reciprocating tachycardia or an ectopic atrial tachycardia. Radiofrequency catheter ablation has become established as an effective and safe treatment to eliminate both arrhythmias. RESULTS Four children aged from 3 months to 8 years, who had incessant tachyarrhythmias and left ventricular dysfunction (shortening fraction of mean +/- SD, 21.7 +/- 1.2%) underwent radiofrequency catheter ablation. The youngest patient had permanent junctional reciprocating tachycardia caused by a left posteroseptal pathway. She was presented with severe heart failure that did not improve with digoxin and amiodarone. The other patients had palpitations and exercise intolerance. Two of them had an ectopic atrial tachycardia caused by a single atrial focus localized in the left atrial appendage apex and the orifice of the right atrial appendage respectively. The other patient had the permanent form of junctional reciprocating tachycardia caused by a right posteroseptal pathway. All four patients underwent one successful ablation. The average procedure mean time was 3.7 hours with an fluoroscopy time of 44 minutes. There were no complications. Subsequently shortening fraction improved progressively. After a mean follow-up of 21.7 months all patients are asymptomatic without medical treatment. CONCLUSIONS Radiofrequency catheter ablation is the therapy of choice in children with either the permanent form of junctional reciprocating tachycardia or ectopic atrial tachycardia refractory to medical treatment. The tachycardia-induced cardiomyopathy is reversible after the elimination of the arrhythmia. The presence of tachycardia-induced cardiomyopathy is an indication for radiofrequency ablation even in small infants.