Difficult pacemaker implantation. Detection of a wrong course due to sinus venosus type atrial septal defect.

We present an important cause of wrong pacemaker lead placement in the left ventricle due to atrial septal defect. Early recognition of this error is important to prevent thromboembolic complications. A 62-year-old woman with no history of cardiac disease presented with a chief complaint of dizziness and pre-syncope. During her hospital admission, a long sinus pause of over 3 sec was recorded. On her cardiac exam, the patient had a systolic flow murmur. She was diagnosed with sick sinus syndrome initially treated with a temporary pacemaker lead insertion. Her coronary angiography was unremarkable. She was referred for permanent pacemaker (PPM) insertion. During the procedure, fluoroscopy in the left anterior oblique (LAO) projection showed that the permanent lead was imbedded posterior to the temporary pacing lead (Fig. 1a). In the right anterior oblique (RAO) projection, two different sites of