Abstract: AIM: To analyze the changes of vectorcardiogram (VCG) P-loop parameters before and after treatment of paroxysmal atrial fibrallation by segmental pulmonary vein isolation (SPVI), to examine the effect of local electrical still in left atrium by PVI on the vectorcardiogram P-loop parameters in atrial depolarization and to study the size of impaired atrium and the data concerned with atrial fibrillation palindromia. METHODS: Sixty-five patients (45 males, 23 females; average age 57±13 years) with paroxysmal atrial fibrillation were included in the study. Segmental PVI was performed around pulmonary vein ostium and atrial vector was measured by VCG before and after PVI during sinus rhythm. Duration of P-wave loop (Pd), voltage of P-wave loop on frontal, horizontal and sagittal plane (Pfv, Phv, Psv) and direction of P wave loop on frontal, horizontal and sagittal plane (Pfd, Phd, Psd) were recorded and analyzed. RESULTS: No significant changes were observed before and after PVI and the indexes of VCG P-loop parameters were Pd (113.3±1.4) msec and (112.1±1.4) msec; Pfv (0.15±0.01) mV and (0.15±0.01) mV; Phv (0.11±0.00) mV and (0.12±0.00) mV; Psv (0.14±0.01) mV and (0.14±0.01) mV; Pfd (55.2±2.2)° and (53.0±1.7)°; Phd (43.1±2.6)° and (45.9±2.7)°; and Psd (55.4±1.9)° and (54.4±2.0)° (P values were 0.56; 0.77; 0.44; 0.73; 0.87; 0.45 and 0.73, respectively). CONCLUSION: The local electrical still in left atrium induced by paroxysmal atrial fibrillation by pulmonary vein isolation has no effect on the VCG P-loop parameters in atrial depolarization.