To evaluate changes in left ventricular diastolic filling patterns resulting from radiofrequency ablation for supraventricular tachycardia (SVT), 44 patients with SVT undergoing radiofrequency ablation (study group), and 16 patients with SVT undergoing electrophysiologic study without ablation (control group) were studied by pulsed Doppler echocardiography. Peak early diastolic filling velocity (E), peak atrial filling velocity (A), and an E/A ratio were obtained from the transmitral flow velocity pattern before and 24-48 h after ablation or electrophysiologic study. In the study group, E and E/A ratio decreased from 67 ± 16 and 1.26 ± 0.42 to 61 ± 16 cm/sand 1.09 ± 0.39 (p < 0.001), respectively. In the control group, only E/A ratio decreased from 1.40 ± 0.47 to 1.26 ± 0.44 (p < 0.001). Heart rate increased from 71 ± 10 to 80 ± 10 beats/ min (p < 0.001) in the study group and from 67 ± 8 to 72 ± 10 beats/min (p < 0.05) in the control group. E and E/A ratio decreased significantly from 73 ± 17 and 1.35 ± 0.49 to 60 ± 18 cm/s and 0.96 ± 0.40 (p < 0.001) in patients with heart rate change of > 20% after ablation. E, A, and E/A ratio did not change significantly in patients with heart rate change of < 10% and of between 10 and 20% after ablation. Blood pressure and left ventricular ejection fraction did not change in either the study or control groups. It was concluded that left ventricular ejection fraction and Doppler diastolic filling patterns are unaffected by radiofrequency ablation. The decrease in E and E/A ratio in patients with SVT resulted from the more than 20% change in heart rate after radiofrequency ablation.