Discussion
Implantation of a pacemaker or defibrillator is the most common surgical
procedure involving the heart. Single lead ICDs are used to prevent
sudden cardiac death in patients at high risk of life-threatening
cardiac arrhythmia by sensing and then delivering electric shock to
restore normal cardiac rhythm. They are typically placed in the right
ventricular cavity. However, 27% of all complications from ICD
insertions are due to lead dislodgment or unsatisfactory position (4).
The migration of a lead occurs in different ways, but passage is most
commonly through an atrial septal defect (ASD) or patent foramen ovale.
Although reported in various cases, misplacement of a lead in the left
ventricle is uncommon, but can lead to dangerous thromboembolic (TE)
events (5). TE events are the result of thrombus formation around the
implantation site and can occur from days to years after implantation
(4). Other complications of inadvertent placement of an ICD lead in the
left ventricle are pericardial effusion, endocarditis, vascular damage,
and peripheral arterial thrombosis (6).
Diagnosis of a misplaced lead in the left ventricle requires high index
of suspicion and immediate action. A misplaced lead in the left
ventricle creates a RBBB-pattern on an ECG and is often the most
important tool in diagnosis (2, 3). Due to the similarity of this
pattern with right ventricle dilatation, coronary pacing, or sinus
pacing, a confirmatory test is typically used; with AP and lateral chest
X-rays being the primary instrument. While a correctly placed lead is
seen with a slight bowing at the right ventricle on an AP view, a
misplaced lead is typically seen to the left and farther superior. On a
lateral projection, a correctly placed ICD lead tip is located
anteriorly, but a misplaced lead’s tip points posteriorly (3). As in our
case, a transesophageal echocardiogram can show a pacemaker lead
crossing from the right atrium to the left atrium, then through the
mitral valve before settling in the left ventricle.
Management of an inadvertent left ventricle lead depends heavily on time
after implantation. Early detection of a misplaced lead allows for lead
extraction, reducing the risk for TE events and avoiding the need for
lifelong anticoagulation (7). If diagnosis is delayed, however, the lead
becomes fixed in the heart and anticoagulation is needed to avoid TE
events. If the patient is young and healthy, surgical extraction can
also be considered, but can lead to inadvertent puncture of the vein
used to access the heart. While the safer option, leaving a pacing lead
in, may also influence function of the aortic valve, leading to heart
failure or cardiac perforation (8).