Atrial fibrillation and conduction disorders are very common and severe postoperative complications in heart surgery.Retrograde analysis of patients (n=103) who had undergone mitral valve surgery or concomitant mitral and tricuspid valve surgery was performed (from January 2006 to December 2016). Patients from each group were divided into two groups: a subgroup with surgery access through the right atrium and interatrial septum (transseptal access) and a subgroup with surgery access through the left atrium (left atrial access). The following data were recorded for all patients: age, sex, extracorporeal circulation time, aortic clamping time, blood loss after surgery, count of blood transfusions administered, the need for surgical revision because of higher blood loss and postoperative atrial and atrioventricular conduction defect (atrial fibrillation and atrioventricular block with pacemaker implantation).A statistically significant difference in extracorporeal circulation time (p<0.05) and aortic clamping time (p<0.01) was recorded between transseptal access and left atrial and right atrial access separately, if combined surgery of both atrioventricular valves was performed. No other statistically significant differences were recorded between the groups.In general, the choice of surgical access for mitral valve on incidence of postoperative atrial and atrioventricular conduction disorders showed no effect. Both access through the right atrium and interatrial septum and access through the left atrium have a similar incidence of postoperative atrial fibrillation and atrioventricular block.