Purpose of the study: Ventricular tachyarrhythmias without structural heart disease (SHD) form a heterogeneous group of unknown mechanism and different clinical and electrophysiological behavior. Purpose of the study was to analyze clinical and electrophysiological characteristics of the arrhythmias, and immediate and long-term results of catheter ablation. Patients: Nineteen consecutive patients without SHD (7 F) aged 44.5 ± 14.1 (18 - 66) years had 23 ablation procedures. Documented arrhythmias varied from incessant ventricular premature beats (1 patient) through paroxysmal nonsustained ventricular tachycardia (5 patients), incessant “repetitive” (non)sustained ventricular tachycardia (4 patients) to paroxysmal sustained ventricular tachycardia (9 patients). Method: Patients underwent standard electrophysiological examination. Mapping of focal arrhyt- hmias was guided by earliest endocardial and epicardial activation, pace-mapping or both. In 1 patient with reentry tachycardia, mapping was guided by late potential during sinus rhythm and low-voltage fractionated diastolic potential during the tachycardia. Results: Catheter ablation was performed in 19 patients and 23 ablation procedures. Mean fluoroscopy time per procedure was 25.4 ± 16.0 (7 - 65) minutes. The arrhythmia was targeted in the right ventricle in 13 patients, and in the left ventricle in 6 patients. All clinically significant ectopic activity was eliminated in 14 patients and significantly reduced in other 2 patients. Ablation procedure failed in 2 patients. In 1 patient sustained monomorphic ventricular tachycardia originating in the epicardial aspect of outflow tract close to the left anterior descending artery was not ablated. During the long-term follow-up 19.2 ± 10.9 (2 - 42) months 14 (73,7 %) patients are free of targered ectopic activity, symptoms, and antiarrhythmic drugs. Other 2 patients experienced significant reduction of ectopic activity and previously ineffective antiarrhythmic therapy could be reduced. Thus, the clinical benefit was enhanced to 16 (84.2 %) patients. Conclusion: Ventricular tachyarrhythmias in patients without SHD form a heterogeneous group of different clinical and electrophysiological behavior and different pathophysiological mechanisms. Majority of the arrhythmias can be eliminated by focal catheter ablation with high efficacy and safety. Deep intramural and epicardial origin of the arrhythmic substrate is common reason for catheter ablation failure.

        Key words: Ventricular tachyarrhythmia - Absence of structural heart disease - Catheter ablation