Introduction
Placement of a pacemaker or an implantable cardioverter-defibrillator (ICD) is a minimally invasive procedure. With access through the left subclavian, cephalic, or femoral vein; the latter usually in the setting of a temporary need for device therapy, the ICD leads are placed into the heart and screwed into position in the right ventricle (Figure 1 ) (1). Misplacement of a pacemaker/defibrillator lead, albeit rare, has been observed in different situations, but a device-lead inside the left ventricular cavity carries a special risk of a thromboembolic event. Hence, prompt identification and early management of misplaced leads inside the left ventricular cavity is essential. The frequency of this complication is unknown, but we believe it is markedly underreported. The most common cause of misplaced right ventricular lead into the left ventricular cavity is lead migration from the right ventricle through the interventricular septum (IVS). Occasionally, an epicardial left ventricular lead inserted into a branch of the coronary sinus can perforate into the endocardium then into the left ventricular cavity in case of cardiac resynchronization therapy (CRT). Rarely, a pacemaker/defibrillator lead may travel via a congenital defect in the interatrial septum (IAS) to the left side of the heart.
Inadvertent pacemaker lead placement can be diagnosed using lateral and antero-posterior (AP) chest X-rays and further confirmed by a twelve-lead electrocardiogram (ECG) exhibiting a right bundle branch block (RBBB) pattern rather than the expected left bundle branch block (LBBB) appearance on ventricular pacing mode. (2, 3). A 12-lead ECG is not helpful if the patient has only atrial pacing or no pacing at baseline like in cases of sinus node dysfunction without atrioventricular node disease or in cases of ICD placed for primary prevention of sudden cardiac death (SCD). Device interrogation at bedside may give a clue of inadvertent lead placement like high pacing threshold or even high impedance. Further imaging including echocardiogram, cardiac computerized tomography (Cardiac CT), or transesophageal echocardiogram (TEE) may be needed to establish the diagnosis and to identify the mechanism of lead migration as clinically indicated.
Diagnosis can occur any time after implantation and approaches differ depending on patient clinical status and time of displacement. In early displacement, surgical repositioning of the lead is possible because the lead has not yet been fixed in the heart. However, with late displacements, repositioning carries unknown and unnecessary risks, and a new lead is often placed in the chamber where displacement occurs to cancel out the previous lead (4). We are presenting a rare case of a dual-chamber lead defibrillator placement where the shock lead was erroneously inserted into the left ventricular cavity via a congenital defect. Unfortunately, this was discovered 6 years after initial implantation; but luckily no thromboembolic complications happened because patient was on chronic anticoagulation throughout that time.