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.