Background: Transvenous pacemaker lead malposition in the left ventricle is a rare complication of pacemaker implantation, however at the moment of diagnosis poses the serious therapeutic problem.Case Report: The report describes a female with unintentional pacemaker lead placement in the left ventricle through patent foramen ovale. Lead malposition was diagnosed accidentally six years after implantation. Authors analysed this case, in connection with other publicised reports, to find the safe algorithm for intraoperative estimation of correct pacemaker lead fixation.Conclusions: The following algorithm of procedures during pacemaker implantation is proposed to avoid the lead malposition in the left ventricle. First, to obligatory perform 12-lead electrocardiogram in pace mode during surgery or immediately after. Second, in case of RBBB pattern in postimplant ECG, to do ECHO (TTE or TEE if necessary) for precise lead position description.

Keywords: malposition of pacemaker lead, Electrocardiography, Echocardiography