Introduction: During paroxysmal supraventricular tachycardia, atrioventricular(AV) interval is more shorter in AV nodal reentrant tachycardia (AVNRT) compared to AV reentrant tachycardia (AVRT). The aim of this study is to examine whether O2 consumption and homodynamic changes during supraventricular tachycardia may be different between AVNRT and AVRT. Methods: Total 56 patients were studied. Twenty-eight patients were AV nodal reentrant tachycardia, twenty patients were AV reentrant tachycardia, and eight patients were control. Blood pressure, heart rate and right atrial (RA) pressure was measured. O2 saturation in both coronary sinus and femoral vein was compared at baseline, 5 minute after tachycardia induction, and after RF ablation. Results: O2 saturation in coronary sinus was significantly increased during tachycardia in AVNRT compared to AVRT (from 34.1짹11.0% to 45.9짹13.8%, p<0.001). But, O2 saturation in femoral vein was not changed. RA pressure was significantly increased during tachycardia in AVNRT compared to AVRT (from 2.8짹2.4mmHg to 6.3짹2.9mmHg, p<0.001). Systolic BP was significantly decreased during tachycardia in AVNRT compared to AVRT (from 134짹19mmHg to 125짹19mmHg, p=0.03). Conclusions: O2 consumption and homodynamic changes during supraventricular tachycardia may be different between AVNRT and AVRT.