Discussion
Pacemaker or ICD implantation is one of the most common cardiac
interventions utilized today. They are used to treat cardiac arrythmias,
including bradycardia and tachycardia. As such, indications for
pacemaker implantation are numerous. ICD and pacemakers are most used to
treat Sinus Node Dysfunction (SND) and Atrioventricular block. They can
also treat chronic bifascicular block, hypertrophic cardiomyopathy, or
patients with congenital heart disease.1 The need for
a pacemaker can easily be determined using ECG or EP studies. However,
as manifested by this case, a high degree of skepticism is required,
including situations with young patients or those who have few cardiac
studies.
Pacemaker implantation is a minimally invasive procedure, but still
carries risks. Nearly a third of all complications are due to lead
dislodgement or malposition.2 A proper ventricular
lead is one placed in the right ventricular (RV) cavity; however, leads
can migrate to the left ventricle (LV) through several pathways. Passage
through an atrial septal defect is most common but can also occur
through a patent foramen ovale or a ventricular septal
defect.3 An RV lead in the LV is a serious and likely
under-reported complication of pacemaker implantation. Leads in the LV
can lead to dangerous thromboembolic events, which can occur anywhere
from months to years after lead migration.2
A misplaced ventricular lead must quickly be diagnosed to prevent
adverse events, and thus a high degree of scrutiny is required. The most
important tool to recognize a lead in the LV is an ECG; on ventricular
pacing, a misplaced lead will display a right bundle branch block (RBBB)
morphology rather than the expected left bundle branch block
(LBBB).4 However, this method is limited in cases such
as SND in the absence of AV node disease, as the patient would likely
only have atrial pacing or no pacing at baseline.2Adjunctive imaging is used to further confirm a misplaced lead, with AP
and lateral X-rays as the primary techniques. A correctly positioned RV
lead on an AP chest X-ray should have a smooth right lateral course with
slight bowing at the RV apex (Figure 9). A lateral chest X-ray should
display the tip of an ICD lead projected anteriorly (Figure 10); in a
mispositioned LV lead, this tip is projected
posteriorly.5 It may be difficult to differentiate
between a lead in the LV from those in the middle cardiac vein or
coronary sinuses. Thus, CT imaging or TEE can be used to visualize lead
migration.