Introduction: Standard pacemaker implantation re-quires venous access to the heart. The venous system is rather frequently predisposed to anomalies. Persis-tent left superior vena cava (PLSVC) is quite frequent, occurring in 0.3-0.5% of general population and has a few variations of its own. Such unusual anatomies can prove extremely challenging in case of pacemaker (PM) implants.

Methods: We hereby present the case of a 72 years-old female patient who was admitted in our hospital with severe bradycardia. She initially underwent cli-nical examination, repeated ECG tracings recording, 24 h Holter monitoring and TTE screening. TEE and 3D contrast CT-scan venous anatomy reconstruction were then deemed as necessary. Finally, she underwent complicated procedure of dual-chamber PM implan-tation.

Results: Clinical history revealed fatigue and constant breathlessness for the past 2 years. Examination of re-peated ECG tracings revealed inferior atrial rhythm alternating with sinus bradycardia with progressive lengthening of PR interval but without blocked P wa-ves and sinoatrial exit block with junctional escape rhythm. QRS morphology was always consistent with sub-Hissian conduction disease (RBBB, LAFB). Thus, she was diagnosed with dual nodal disease and schedu-led for implant. Routine TT echocardiography revea-led a severely dilated CS, severe tricuspid regurgitation (TR) and a right-to-left shunt (during glucose bubble-test – GBT) that could not be localized. The hypothesis of PLSVC was tested by right arm GBT injection and confirmed by TEE. This further revealed interatrial septal aneurysm, important PFO and bi-directional shunt. TTE failed to identify right SVC drainage within RA, while 3D contrast CT-scan reconstruction of the superior venous system determined PLSVC type 2 (no right SVC, left SVC drainage within CS). Such findings were crucial in planning the implant procedure which then underwent uneventfully.

Conclusions: PLSVC is rather frequent, with at least 4 possible subtypes, some of them still allowing commu-nication between the left and right SVCs. PLSVC can be suspected in patients with consistently dilated CSs and sometimes confirmed solely by right arm GBT (for example in type II variations when right SVC is absent). Contrast CT anatomy reconstruction is mandatory in order to have a comprehensive view upon venous ac-cess in such patients. Selection of correct lead lengths can also be guided by anatomical review of the case.