INTRODUCTION: Several noninvasive risk factors for ventricular arrhythmias have been described in postmyocardial infarction (MI) patients, whose relationships with scar characteristics and modifications by ablation are unknown. METHODS: Twenty-two patients with previous MI referred for ventricular tachycardia ablation were prospectively included. ECG, heart rate variability (HRV), signal-averaged ECG (SA-ECG), and T wave alternans (TWA) were performed before and after radiofrequency ablation. Scar areas were correlated to preablation parameters. Pre and postablation parameters were furthermore compared. RESULTS: Left ventricular ejection fraction and some spectral and time-domain HRV parameters were significantly correlated to the scar areas. QRS duration was larger after vs before ablation (120 +/- 29 vs 105 +/- 22 msec, P = .01). No significant modification in time or spectral domain of HRV was observed. There was no significant change in TWA and SA-ECG before and after ablation. Borderline decreases in quantitative TWA parameters were noted in patients with positive TWA and successful ablation procedure. CONCLUSION: Some noninvasive risk factors were linked to the scar areas, but few were significantly modified after ablation. Larger populations are needed to demonstrate significant differences or correlations.