Background: Supraventricular tachycardias (SVT) are the most common arrhythmia in patients after heart transplantation and there is only limited data about tachycardia mechanisms and the effect of catheter ablation.

Aim: We defined the mechanism of SVT and assessed the acute efficacy and safety of catheter ablation of SVTs in patients with transplanted hearts.

Methods: Consecutive patients and ablation procedures following heart transplantation were analyzed. 3D mapping systems were applied in atrial tachycardias (AT) apart from typical atrial flutter. The mechanism of AT was evaluated by entrainment maneuvers, activation and voltage mapping.

Results: In a total of 6 patients (4 male, 67±7 years, 16±3 years after heart transplantation) 8 procedures were performed revealing cavo-tricuspidal isthmus dependent flutter in 2, peri-mitral flutter in 1, focal atrial tachycardia at the septum in 1, atrioventricular nodal reentry tachycardia in 1, and multiple ATs located at the right free wall as well as cavo-tricuspidal isthmus dependent flutter in 1 patient. Focal or linear lesions resulted in termination and non-inducibility in all procedures. During mapping of the tachycardias, dissociated atrial fibrillation in the recipient LA posterial wall was revealed in one patient and dissociated atrial tachycardia in the recipient right atrium in another patient. Mean procedure duration was 81±17 min with fluoroscopy duration of 11.3±2.7 min and dose area product of 895±642 cGy cm². There was one puncture-related vascular groin site complication occurring in a 78 year old male requiring surgical treatment. No other complications occurred.

Conclusion: SVTs later after heart transplantation are predominantly due to reentry, often in the right atrium and can be amended by safe and effective catheter ablation.